Bukidnon State University Food Technology Department Laboratory Manual in Food Chemistry 1 PDF

Bukidnon State University College of Technologies Food Technology Department Laboratory Manual in Food Chemistry 1 Compiled and Prepared by: Dr. Madelaine S. Dumandan, PFT Revised 2024  Table of Contents Content...

Bukidnon State University College of Technologies Food Technology Department Laboratory Manual in Food Chemistry 1 Compiled and Prepared by: Dr. Madelaine S. Dumandan, PFT Revised 2024  Table of Contents Content Page Laboratory Safety Rules and Guidelines 2 Guidelines in Making Laboratory Report 3 Format for Lab Report 5 Laboratory Report Rubric 8 Guidelines Before and After the Laboratory Experiment 10 Exp. No. 1 Water and Water Activity 11 Exp. No. 2 Carbohydrates 15 Exp. No. 3 Carbohydrates: Sugars 20 Exp. No. 4 Benedict’s test – Determination of Reducing Sugar 23 Exp. No. 5 Testing Foods for Starch 25 Exp. No. 6 Lipids 27 Exp. No. 7 Understanding How Food Becomes Rancid 31 Exp. No. 8 Proteins 34 Exp. No. 9 Functional Properties of Proteins 39 Exp. No. 10 Protein Coagulation or Denaturation 43 Exp. No. 11 Enzymes 45 1  LABORATORY SAFETY RULES AND GUIDELINES 1. Come to laboratory prepared. Laboratory experiment should be read before coming to class and be on time. Lab instructions will not be repeated if you are late. Wait for a laboratory introduction by the instructor before starting work. 2. Wear laboratory gown, and closed white laboratory shoes. Tie back long hair. Use disposable surgical gloves in handling chemicals. 3. Keep all tables clear of all personal items. 4. For Handling Chemicals/materials: a. Double-check the label on the container before you remove a chemical. To avoid contamination of the chemical reagents, NEVER insert droppers, pipettes or spatulas into the reagent bottles. Do not return unused chemicals to the original stock containers. b. Do not shake laboratory thermometers. Laboratory thermometers respond quickly to the temperature of their environment. Shaking a thermometer is unnecessary and can cause breakage. c. Clean up spills. Spills of chemicals or water in the work area or on the floor should be cleaned up immediately. Small spills of liquid can be cleaned up with a paper towel. Immediately wash off any chemicals spilled on your skin or clothes. d. Dispose of broken glass immediately. Report to the instructor and laboratory technician for any breakage incident. e. Be very careful of hot objects. Use heat resistant holder/pad. 5. Never put anything into your mouth while in the lab. 6. Keep the lab neat. Return reagent containers and equipment to proper locations. 7. Behave in a responsible manner. 8. Be aware of the location and use of laboratory safety equipment (i.e. fire extinguisher). 9. Immediately report accidents and injuries to your instructor. 10. Thoroughly wash your hands any time you leave the lab. 2  Guidelines in Making Laboratory Report I. Title Page This should be the first (cover) page of the report. When writing the title page of a lab report, the following should be included: 1. The title of the experiment. 2. The students name in full. 3. The instructor or person for whom the lab report is being compiled. 4. The date on which the experiment was performed or the date the lab report was written. II. Introduction Under this heading should be an overview of what the experiment was about. A sound definition of what was learned about the process being carried out during the experiment should be included. Example: “Titration Technique” III. Objectives Write the objectives of your activity IV. Methodology This section should contain a description in the students own words, of the experimental procedure that was followed in the performance of the experiment. The materials and methods section should be complete enough so that another student with the same background, but unfamiliar with the experiment, could perform the same experiment without additional instructions. Procedures and equipment used should be written in a sentence form. Do not list! 1. Materials/Chemicals 3  Write all materials and chemicals that are being used including quantities e.g. 50g sugar. 2. Procedures All procedures should be in past tense. Example: V. Results and Observations The result section should contain raw data. Raw data consist of actual measured values recorded during the experiment. Use pictures, graphs or tables to present this information. All tables should have descriptive titles, and they should show the units of data entries clearly. This is an effective method for communicating experimental results. Example: 4 VI. Analysis and Discussion What took place during the process. Why and how do the results occur. All questions should be answered within this section in a very logical and clear manner. The questions should be put into statement form. You should also include any recommendations that you feel would improve the experimental procedure. If you have any further investigations that might be suggested by the data, you should also include them here. Example: 5 VII. Conclusion How the conduct of the experiment met the objectives. The conclusions should be relevant to the experiment that was performed and should be based on facts learned as a result of the experiment. Example: VIII. References Use APA formatting. Example: 6  Format for Lab Report Student No.: ______________________ Subject/Class Schedule: ___________________ Date Performed: ___________________ Date Submitted: _________________ Experiment No. ___ Experiment Title: Overview: Results and Observations: Discussion and Analysis: Answers to Question: Conclusion: References: 7 Student No.: ____________________ Subject/Class Schedule: ___________________ Date Performed: _________________ Date Submitted: _________________ Experiment No. ___ (Title of Experiment) _______________________________________________________________ Overview: ___________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ _______________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ______________________________________________. Results and Observations: Discussion and Analysis: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ 8 __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ _________________________________________________________________________________. Answers to Question: Conclusion: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ References: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ 9  Laboratory Report Grading Rubric Poor Fair Good Excellent 1 2 3 4 Introduction Introduction Introduction Introduction concisely and/or and/or and procedure describes the procedure are procedure are are complete concepts, objectives missing or incomplete, but unclear, and hypotheses. Introduction provide little or unclear and/or vague or Procedure describes and no clear vague wordy. the equipment and Procedure instruction methods with sufficient detail to reproduce the experiment without non-essential details 0–1 2 3 4 Data tables Data table Data is Data, including units and/or graphs and/or graphs complete and and uncertainties, are are missing, are incomplete. accurate but presented in clear, Data illegible, or some tables, accurate tables and/or Reporting provide little or graphs or graphs. Text is no clear descriptions included when information are unclear necessary to clarify the tables and graphs 0–1 2 3–4 5 Data and error Data and error Data analysis Data and error analysis and analysis are is complete but analysis and discussion are inaccurate, error analysis discussion are missing or incomplete is incomplete. complete and totally provide little or and/or Interpretation accurate. no information. confusing,. is accurate but Discrepancies Discussion is implications between measured incomplete are unclear. and predicted values inaccurate, or Significant are correctly illogical with discrepancies compared with Data little evidence are discussed experimental Analysis of thoughtful but possible uncertainties and and interpretation. explanations identified as Discussion and/or follow- significant or not. The ups are vague. text clarifies and supports the results. Important results are summarized and used to accept or reject hypotheses. Insights are provided into the wider implications of the results. Possible reasons for significant discrepancies are 10  suggested and specific, practical ways to improve or extend the experiment are identified. 0.5 1 1.5 2 None of the Only a few of Some of the All of the questions Answer to questions from the questions questions from from the lab write-up Questions the lab-write up from the lab the lab write- are addressed are addressed. write-up are up are addressed addressed 0 1 2 3 Conclusion is Conclusion Conclusion Conclusion includes poorly written includes a accurately an accurate summary, and/or illogical, summary of the summarizes a complete answer to and includes experiment, an the the question which only an inaccurate experiment, refers to whether the incomplete answer to the answers the hypothesis was summary or question, question and supported, and a clear Conclusion whether the whether the refers back to description of the hypothesis was hypothesis was the hypothesis, learning, possible supported or an supported, and and describes sources of error, and inaccurate either a what was applications. description of possible source learned, a the learning. of error and possible source application. of error and an application of the results. 0.5 1 1.5 2 Grammar is Grammar is Grammar is Grammar is direct, garbles or unclear or imprecise or concise, unambiguous copied from lab written as awkward. and original. Style is instructions. instructions. Style is overly engaging but not There are many There are dry or overly conversational. errors in numerous conversational. Spelling, punctuation Presentation spelling, errors in There are and grammar are punctuation and spelling, occasional correct. grammar punctuations errors in and/or spelling, grammar punctuation and/or grammar 11  Guidelines Before and After the Laboratory Experiment 1. Index card must be passed before the laboratory time. Index card must comprise of schematic diagram of the procedure of the laboratory experiment. No index card, no entry. 2. Garments are required during laboratory experiment. No garments, no lab experiment. 3. Borrow materials to the Laboratory Technician three days before scheduled laboratory. Pass your borrower slip with your group members’ name and signature, duly signed with your instructor. No additional materials will be borrowed during laboratory class, except if there are additional materials instructed by the professor/instructor. 4. There will be announced and/or surprised pre-lab and post-lab quizzes. 5. Results will be checked by the instructor after the experiment. 6. Clean Up. Clean your respective working area and throw garbage before leaving the laboratory room. 7. Lab reports will be submitted a week after the laboratory experiment has been performed. Note: Do not place lab reports in the teacher’s table unless any Food Technology instructor will receive it indicating date and time of submission on instructor’s behalf Agreed and Signed by: _________________________________ (Student’s signature over printed name) ________________________________ Date 12  Water and Water Activity Experiment No. 1 Introduction: Water is an essential component of living things. It represents a major function of the tissues of plants and animals ranging from 65 to 95%. It performs number of functions like serving as a medium and carrier of nutrients and as a reactant in biochemical reactions. It also helps in the maintenance of the conformation of polymers as well as the structural integrity of the tissue. Water is so essential that organisms die within a short time withdrawal of water. Water is an important ingredient in a number of fabricated foods like butter, margarine, mayonnaise and salad dressing. Its presence determines the texture/crispness of the food system. Water is also necessary for microbial growth and some chemical reactions in food. Thus, it affects the stability of the food. Two important terms that are important in formulating safety and stability of food products are moisture content and water activity. According to Mermelstein (2009), moisture content is, simply, how much water is in a product. It influences the physical properties of a substance, including weight, density, viscosity, conductivity, and others. It is generally determined by weight loss upon drying. Water activity, aW, on the other hand, is a measure of how much of that water is free, i.e., unbound, and thus available to microorganisms to use for growth. Both moisture content and water activity—the ratio of the water vapor pressure of a substance such as food to the water vapor pressure of pure water under the same conditions. Objectives: At the end of the experiment, the students should be able to: 1. Determine the interrelationship of water content and water activity. 2. Discuss the influence of water on food texture. 3. Assess the effect of water to crispness of food. 4. Assess the influence of water on certain biochemical reactions. 5. Explain the relationship of water content and food stability. 6. Determine the water activity of food. A. MOISTURE AND TEXTURE A.1. Effect of Moisture on Texture of Pechay Materials: pechay or lettuce knife spatula Procedure: 1. Determine the percentage moisture content of two samples of pechay (refrigerated and not refrigerated stored for 24 hours) by getting the mass of the two samples before and after 24 hours. 2. Tabulate and describe the appearance and texture of both samples. Discuss the significance of your results. 13 A.2. Effect of Moisture on Crispness of Foods Materials: Two crisp food products larger container Two small beakers zip-lock plastics bags Procedure: 1. Choose two products, like a rice cracker, crisp bread, potato crisp that consumers expect to be crisp. 2. All containers and surfaces must be clean and the experiment should be carried out in a hygienic environment. Use clean hands or gloves. 3. Place some water in a small beaker inside a larger container (e.g. a casserole/mixing bowl). 4. Mark positions in the container so that samples can be identified. 5. Open up the product packaging but then keep it in a sealed bag. 6. Take one sample, weigh it and place it in the large container and note the time and mass. 7. After 20 minutes, repeat step 6 with another sample. Continue this until you have enough samples each of which will be exposed to a humid environment for a different length of time. 8. Remove each sample and place them in individual bags to avoid any more moisture gain or loss. 9. Measure the mass of each. You will need to remove each sample from its bag but replace it as soon as possible. 10. Break off about half of each sample, noting the manner in which in breaks and bite it. Describe your perception of the bite in terms of crispness on a scale of 1-4. B. FREEZING OF WATER1 Materials: ice cream cups spoons Timer freezer Procedure: 1. Remove a cup of ice cream from the freezer and leave it on top of the table for 20 minutes. 2. Place it back into the freezer until it freezes (at least 24 hours). 3. Evaluate the texture of the sample. Note the presence of large ice crystals. 4. Compare it with the sample that remained in the freezer. 5. Tabulate data in Table 1.1 and discuss your result. C. MOISTURE CONTENT AND ENZYME ACTIVITY Objective: To determine the influence of moisture on enzyme activity. Materials: soybeans or mungo mortar and pestle 14  Distilled water timer Procedure: 1. Pulverize the dry soybeans using aluminum mortar and pestle. 2. Discard seed coat. 3. Divide into two portions and place in separate petri dishes. 4. Add enough water to moisten one of the samples and compare the aroma and taste developed after 10 minutes. 5. Tabulate data in table 1.2 and discuss the significance of your observations. D. DETERMINATION OF WATER ACTIVITY Water activity is determined in the lab using a water activity meter. This machine measures the vapor pressure of the water surrounding the food and divides it by the vapor pressure of pure water to give a value between 0.0 – 1.0. Materials and Equipment 1. Food samples – flour, ketchup, biscuit, orange juice and cooking oil 2. Water activity cups 3. Water activity meter Method 1. Transfer food sample to water activity cup, filling it to about half full. Note: Biscuit should be ground uniformly before measurement 2. Place in water activity meter, close and measure 3. Record the water activity and the temperature 4. Repeat measurement, calculate and report the average. Results: Table 1.1 Crispness Evaluation of Foods Samples Crispness 1. 2. Not crisp – 1; Slightly crisp – 2; Moderately crisp – 3; Very crisp - 4 Table 1.2 Sensory Evaluation of Ice Cream Samples Mouthfeel Appearance 1. Frozen, fresh 2. Thawed and refrozen Mouthfeel: Smooth – 1; Neither – 2; Creamy – 3 Appearance: Uniform – 1; Neither – 2; Not uniform – 3 Table 1.3 Sensory Evaluation of Beans Samples Aroma Taste 1. Dry beans 15  2. Moisten beans Aroma: Use one or more of ff descriptors: acidic, aromatic, foul, fragrant, fresh, musty, nasty, noxious, piney, pungent, sharp, smelly, stinky, stuffy Taste: sweet, acidic, biting, bitter, briny, dry, flavorful, sharp, sour, tangy, tart, zingy Table 1.4 Water activity of Foods Samples Water activity 1. 2. 3. 4. Questions: 1. What is the relationship between moisture and texture? 2. Which of the two ice cream samples in Part B has better texture? Why? 3. Discuss the relationship between moisture content and enzymatic activity. 4. How is water activity measured in food? How does it differ to moisture content? What is the important in the food system? References: 1Flores, Dulce M. Laboratory and Lecture Notes in Food Chemistry. University of the Philippines in Mindanao. 2 New Zealand Institute of Food Science and Technology Organization 3 Simons, C. 2018. How to Measure Water Activity. Food Science. 16  CARBOHYDRATES4 Experiment No. 2 Introduction: Carbohydrates make up a group of chemical compounds found in plant and animal cells. They have the empirical formula CnH2nOn, or (CH2O)n. An empirical formula tells the atomic composition of the compound, but nothing about structure, size, or what chemical bonds are present. Since this formula is essentially a combination of carbon and water, these materials are called “hydrates of carbon”, or carbohydrates for short. Carbohydrates are the primary products of plant photosynthesis. The simplified light- driven reaction of photosynthesis results in the formation of a carbohydrate: nH2O + nCO2 → -(CH2O)n- + nO2. This type of carbohydrate is found in the structures of plants and is used in the reverse reaction of photosynthesis (respiration) or is consumed as fuel by plants and animals. Carbohydrates are widely available and inexpensive, and are used as an energy source for our bodies and for cell structures. Food carbohydrates include the simple carbohydrates (sugars) and complex carbohydrates (starches and fiber). Before a big race, distance runners and cyclists eat foods containing complex carbohydrates (pasta, pizza, rice and bread) to give them sustained energy. Carbohydrates are divided into monosaccharides, disaccharides, and polysaccharides. As shown in the following molecular model structures, carbohydrates may be found as hexagon (6-sided, see Figure 1A) and pentagon (5-sided, see Figure 1B) shaped rings. Monosaccharides Monosaccharides are single-molecule sugars (the prefix “mono” means one) that form the basic units of carbohydrates. They usually consist of three to seven carbon atoms with attached hydroxyl (OH) groups in specific stereochemical configurations. The carbons of carbohydrates are traditionally numbered starting with the carbon of the carbonyl end of the chain (the carbonyl group is the carbon double-bonded to oxygen). The number of carbons in the molecule generally categorizes monosaccharides. For example, three-carbon carbohydrate molecules are called trioses, five-carbon molecules are called pentoses, and six-carbon molecules are called hexoses. Ribose and 2-deoxyribose are pentoses, and both have a crucial role in reproduction as polymers known as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). One of the most important monosaccharides is glucose (dextrose). This molecule is the primary source of chemical energy for living systems. Plants and animals alike use this molecule for energy to carry out cellular processes. Mammals produce peptide hormones (insulin and glucagon) that regulate blood glucose levels, and a disease of high blood glucose is called diabetes. Other hexoses include fructose (found in fruit juices) and galactose. Different structures are possible for the same monosaccharide. Although glucose and fructose are identical in chemical composition (C6H12O6), they are very different in structure (see molecular models). Such materials are called isomers. Isomers in general have very different physical properties based on their structure. 17 Figure 1 A. Glucose, a six-membered ring monosaccharide. B. Fructose, a five-membered ring monosaccharide. C. Sucrose, a disaccharide containing glucose and fructose. D. Molecular representation of starch illustrating the alpha-glycosidic linkages joining monosaccharides to form the polysaccharide structure. Disaccharides Disaccharides are two monosaccharide sugar molecules that are chemically joined by a glycosidic linkage (- O -) to form a “double sugar” (the prefix “di” means two). When two monosaccharide molecules react to form a glycosidic bond (linkage), a water molecule is generated in the process through a chemical reaction known as condensation. Therefore, condensation is a reaction where water is removed and a polymer is formed. The most well- known disaccharide found in nature is sucrose, which is also called cane sugar, beet sugar, or table sugar (see Figure 1C). Sucrose is a disaccharide of glucose and fructose. Lactose or milk sugar is a disaccharide of glucose and galactose and is found in milk. Maltose is a disaccharide composed of two glucose units. Disaccharides can easily be hydrolyzed (the reverse of condensation) to become monosaccharides, especially in the presence of enzymes (such as the digestive enzymes in our intestines) or alkaline catalysts. Invert sugar is created from the hydrolysis of sucrose into glucose and fructose. Bees use enzymes to create invert sugar to make honey. Taffy and other invert sugar type candies are made from sucrose using heat and alkaline baking soda. Disaccharides are classified as oligosaccharides (the prefix “oligo” means few or little). This group includes carbohydrates with 2 to 20 saccharide units joined together. Carbohydrates containing more than 20 units are classified as polysaccharides. Polysaccharides 18  Polysaccharides (the prefix “poly” means many) are formed when many single sugars are joined together chemically. Carbohydrates were one of the original molecules that led to the discovery of what we call polymers. Polysaccharides include starch, glycogen (storage starch in animals), cellulose (found in the cell walls of plants), and DNA. Starch is the predominant storage molecule in plants and provides the majority of the food calories consumed by people worldwide. Most starch granules are composed of a mixture of two polymers: a linear polysaccharide called amylose and a branched-chain polysaccharide called amylopectin. Amylopectin chains branch approximately every 20- 25 saccharide units. Amylopectin is the more common form of starch found in plants. Animals store energy in the muscles and liver as glycogen. This molecule is more highly branched than amylopectin. For longer-term storage, animals convert the food calories from carbohydrates to fat. In the human and animals, fats are stored in specific parts of the body called adipose tissue. Cellulose is the main structural component of plant cell walls and is the most abundant carbohydrate on earth. Cellulose serves as a source of dietary fiber since, as explained below, humans do not have the intestinal enzymes necessary to digest it. Starch and cellulose are both homopolymers (“homo” means same) of glucose. The glucose molecules in the polymer are linked through glycosidic covalent bonds. There are two different stereochemical configurations of glycosidic bonds—an alpha linkage and a beta linkage. The only difference between the alpha and beta linkages is the orientation of the linked carbon atoms. Therefore, glucose polymers can exist in two different structures, with either alpha or beta linkages between the glucose residues. Starch contains alpha linkages (see Figure 1D) and cellulose contains beta linkages. Because of this difference, cornstarch has very different physical properties compared to those for cotton and wood. Salivary amylase only recognizes and catalyzes the breakdown of alpha glycosidic bonds and not beta bonds. This is why most mammals can digest starch but not cellulose (grasses, plant stems, and leaves). Food Uses of Carbohydrates Carbohydrates are widely used in the food industry because of their physical and chemical properties. The sweet taste of sucrose, glucose, and fructose is used to improve the palatability of many foods. Lactose is used in the manufacture of cheese food, is a milk solids replacer in the manufacture of frozen desserts, and is used as a binder in the making of pills/tablets. Another useful aspect of some carbohydrates is their chemical reducing capability. Sugars with a free hemiacetal group can readily donate an electron to another molecule. Glucose, fructose, maltose, and lactose are all reducing sugars. Sucrose or table sugar is not a reducing sugar because its component monosaccharides are bonded to each other through their hemiacetal group. Reducing sugars react with the amino acid lysine in a reaction called the Maillard reaction. This common browning reaction produced by heating the food (baking, roasting, or frying) is necessary for the production of the aromas, colors, and flavors in caramels, chocolate, coffee, and tea. This non-enzymatic browning reaction differs from the enzymatic browning that occurs with fresh-cut fruit and vegetables, such as apples and potatoes. Carbohydrates can protect frozen foods from undesirable textural and structural changes by retarding ice crystal formation. Polysaccharides can bind water and are used to thicken liquids and to form gels in sauces, gravies, soups, gelatin desserts (Jell-O®), and candies 19 like jelly beans and orange slices. They are also used to stabilize dispersions, suspensions, and emulsions in foods like ice cream, infant formulas, dairy desserts, creamy salad dressings, jellies and jams, and candy. Starches are used as binders, adhesives, moisture retainers, texturizers, and thickeners in foods. In the following experiment we will be investigating pectin. Pectin is a polysaccharide that is found in green apples and in the peel of limes and lemons. Pectin forms a gel when heated with an acid and sugar, and is used to make high-sugar jellies, jams, and marmalade. Pectin solutions form gels when an acid and sugar are added. The acid will reduce the pH of the solution and cause the carbohydrate molecules to form junctions. From these junctions a network of polymer chains can entrap an aqueous solution. The sugar increases junction formation. The pectin makes the gel, and the low pH and the amount of soluble solids adjusts the rigidity. The optimum conditions for jelly strength are 1% pectin, a pH of 3.2, and a sugar concentration of 55% (by weight). Activity Objective To observe how pectin can be used to form a gel and the effects of too little and too much sugar on gelling. Materials Required Sure-Jell ® Heatproof gloves Concentrated fruit juice (apple, grape), if frozen, thawed Balance or scale Granulated sugar Graduated cylinder Water Heatproof pad 600-milliliter beakers Stirring rod/spoon/wooden Popsicle Bunsen burner with stand or hot plate Experimental Procedure Part 1 1. Measure out 53 grams (1/4 cup) of sugar. 2. Put 18 milliliters (0.75 fluid ounce) of fruit juice concentrate, 60 milliliters (1/4 cup) of water, and 7 grams (3 teaspoons) of Sure-Jell into a 600-milliliter beaker. 3. Place the beaker on a hot plate or Bunsen burner and stir constantly over a high heat until bubbles form all around the edge. 4. Add the sugar. Bring the mixture to a boil and boil hard, while stirring, for one minute. Be sure to adjust the heat source so that the liquid does not boil up the sides of the beaker. Caution! This can boil over very quickly if it’s not carefully watched. 20  5. Using gloves, remove the beaker from the heat source. Place the beaker on a heatproof pad to cool. Allow the jelly to cool. Use a spoon to skim off the foam on the top. 6. Record your results. Part 2 1. Measure out 26 grams (1/8 cup) of sugar. 2. Repeat steps 2, 3, 4, and 5 in Part 1. 3. Record your results. Part 3 1. Measure out 106 grams (1/2 cup) of sugar. 2. Repeat steps 2, 3, 4, and 5 in Part 1. 3. Record your results. Results DATA TABLE - JELLY CONSISTENCY EXPERIMENT JELLY CONSISTENCY Part 1 Normal Part 2 Half sugar Part 3 Twice sugar Questions 1. How did the consistency of the jelly change when you changed the ratio of sugar to pectin? 2. Why did the consistency change when you changed the ratio of sugar to pectin? Source: 4Institute of Food Technologists, IFT Experiments in Food Science Series Copyright Purdue Research Foundation. All rights reserved. 2000 21  Carbohydrates: Sugars Experiment No. 3 Introduction: Carbohydrates are a class of natural compounds that contain either an aldehyde or a ketone group and many hydroxyl groups – they are often called polyhydroxy aldehydes or ketones. A monosaccharide consists of a single carbohydrate molecule, containing between 3 and 7 carbons. Examples of monosaccharides are glucose and fructose. A disaccharide consists of two monosaccharides that are linked together. Sucrose and lactose are disaccharides. A polysaccharide consists of many monosaccharides linked together. Starch, pectin, glycogen, and cellulose are examples of polysaccharides. Carbohydrates are used for energy. The carbohydrates that we eat are broken down in our bodies and eventually form water and carbon dioxide. The energy obtained in this process is used for other reactions that must occur in the body. Excess carbohydrates that we eat can be stored in the liver as glycogen or can be converted to fats. Plants create carbohydrates in the process of photosynthesis, where energy from the sun is used to build carbohydrates from water and carbon dioxide. Objectives: At the end of the experiment, the students should be able to: 1. Describe the role of sugar in fermentation and caramelization process. 2. Discuss sugar as humectant and how it preserves food. 3. Explain caramelization process and the importance of this reaction in food processing. Procedure: A. Fermentation Test Materials: sucrose, water, yeast, cotton, Erlenmeyer flask Procedures: 1. Prepare an 8% sugar solution by dissolving 8 g of sucrose in 100 mL water in an Erlenmeyer flask. 2. Inoculate with 2-3 grams yeast. 3. Cover the flask with cotton plug. 4. Smell the aroma of flask content after 3 days. 5. Record your observations. B. Sugar as Humectant Materials: pineapple or mango, sucrose, oven drier, refractometer 22 Procedures: 1. Pare mango or pineapple 2. Slice and cut into 1 cm cubes. 3. Soak one half in a 50 Brix (percent by weight of sugar in solution) sugar solution overnight. 4. Place the other half in an oven at 60oC overnight to dry. 5. Remove the fruit in the sugar solution after one day of soaking, and dry in an oven overnight. 6. Compare the texture of the two samples. 7. Determine the moisture content of the samples. C. Caramelization Materials: sucrose, test tube, balance, hot plate, water bath, distilled water Procedures: 1. Place a pinch of sucrose in a test tube and heat. 2. Describe the changes that occur. 3. Stop heating when sucrose completely turns brown. 4. Cool slightly and add water to dissolve. 5. Note the color, flavor and taste. 6. Dissolve a similar amount of original sample in water. 7. Compare with the heated dissolved sample. 8. Describe the chemistry involved. Results: Data Sheets: A. Fermentation Table 5.1.Change in carbohydrate induced by yeast Observation Aroma Color Reaction After 3 days of fermentation 23  B. Sugar as Humectant Table 5.2. Influence of sugar on dehydrated fruit Sample Texture Moisture 1. Soaked in sugar solution and dried 2. Just oven-dried C. Caramelization Table 5.3. Effect of heating on sugars Original Sample Caramelized Sample Color Flavor Taste Questions: 1. What is humectant? How does sugar preserve food materials like jams and jellies? 2. What is caramelization? What is the importance of the reaction in food processing? 24  Benedict’s test5 – Determination of Reducing Sugar Experiment No. 4 Introduction: Benedict’s test is used to test for simple carbohydrates. The Benedict’s test identifies reducing sugars (monosaccharide’s and some disaccharides), which have free ketone or aldehyde functional groups. Some sugars such as glucose are called reducing sugars because they are capable of transferring hydrogens (electrons) to other compounds, a process called reduction. When reducing sugars are mixed with Benedict’s reagent and heated, a reduction reaction causes the Benedicts reagent to change color. The color varies from green to dark red (brick) or rusty- brown, depending on the amount of and type of sugar. Benedict’s quantitative reagent contains potassium thiocyanate and is used to determine how much reducing sugar is present. This solution forms a copper thiocyanate precipitate which is white and can be used in a titration. The titration should be repeated with 1% glucose solution instead of the sample for calibration. Objectives: At the end of the experiment, the students should be able to: 1. Detect the presence of reducing sugar in the sample solution 2. Estimate the concentration of reducing sugar in the sample solution Procedure: Materials: test tubes, test tube rack, five samples (choose your food samples), Benedict’s reagent, water bath 1. Approximately 1 ml of sample is placed into a clean test tube. 2. 2 ml (10 drops) of Benedict’s reagent (CuSO4) is placed in the test tube. 3. The solution is then heated in a boiling water bath for 3-5 minutes. 4. Observe for color change in the solution of test tubes or precipitate formation. Result Interpretation: If the color upon boiling is changed into green, then there would be 0.1 to 0.5 percent sugar in solution. If it changes color to yellow, then 0.5 to 1 percent sugar is present. If it changes to orange, then it means that 1 to 1.5 percent sugar is present. If color changes to red, then 1.5 to 2.0 percent sugar is present. And if color changes to brick red, it means that more than 2 percent sugar is present in solution. 25 Positive Benedict’s test: Formation of a reddish precipitate within three minutes. Reducing sugars present. Example: Glucose Negative Benedict’s test: No color change (Remains Blue). Reducing sugars absent. Example: Sucrose. 5Aryal, S. 2022. Benedict’s Test- Principle, Composition, Preparation, Procedure and Result Interpretation. Retrieved from https://microbiologyinfo.com/benedicts-test-principle-composition-preparation-procedure-and-result- interpretation/ Data Table. Reducing sugar of foods Food Sample Estimated percent Presence/Absence if sugar reducing sugar 1. 2. 3. 4. 5. 26  Testing Foods for Starch6 Experiment No. 5 Introduction Foods can be starchy or non-starchy. Starchy foods contain the carbohydrate starch, which is converted to sugar (glucose) inside our body for energy production. There is a simple chemical test that you can do to detect starch, which involves an iodine solution. The iodine solution turns any food that contains starch dark blue. In this experiment, students will differentiate starchy and non-starchy foods through iodine test. This will enable the students to identify food with starch. Materials Iodine tincture or solution (2%), such as the type used in a first aid kit as an antiseptic to treat minor wounds Corn starch Water Cups (2) Knife Cutting board 1/4 teaspoon Sheet of aluminum foil Pipette or medicine dropper A variety of foods, such as: o Potatoes o Pasta o Vegetables o Fruits o Crackers o Candy Optional: Microwave Optional: Refrigerator Optional: Liquid foods or drinks such as yogurt, juices, or milk Procedure 1. Fill both cups about half full of room-temperature or cold water. Label one cup "+" and one cup "-". 2. Add 1/4 teaspoon of corn starch into the "+" cup and mix the solution. 3. Put on safety glasses and carefully open the iodine solution. Note, that the iodine will stain your countertop or clothes, so be careful when you handle it and try to avoid any spills. Make sure to wear lab gown to protect your clothes from potential spills. 4. Using the pipette, suck up some of the iodine solution. 5. Carefully add a couple of drops of the iodine solution to the cup with just water. 6. Next, add a couple of drops of the iodine solution to the cup with water and corn starch. 27  7. Now start testing food samples. With the knife, cut off a small piece of every food that you want to test. 8. Place the pieces of food next to each other on a sheet of aluminum foil. 9. Suck up more of the iodine solution with the pipette. 10. Place one drop of the iodine solution on the first food that you want to test. Wait about 1 minute and observe what happens. 11. Continue to test the other foods by adding one drop of iodine solution to them. 12. Record your observations. NOTE. Any remaining iodine solution in your pipette can be flushed down the sink. Dispose of the used foods in the trash. DO NOT EAT any food that has come in contact with the iodine solution! Data Table Food Sample Positive/Negative Qualitative Observation Potatoes Pasta Vegetables Fruits Crackers Candy Questions to Answer: 1. What foods contain starch, and which food aren’t? 2. Explain the mechanism of action of iodine solution in identifying starch in food. 3. Evaluate the importance of testing starch in food. 6 Lohner, S. (2002). Science Buddies. Retrieved from https://www.sciencebuddies.org/stem- activities/starch-food-test. 28  Lipids7 Experiment No. 6 Lipids include fats, oils, waxes, cholesterol, other sterols, and most steroids. In the body, fat serves as a source of energy, a thermal insulator and cushion around organs, and an important cellular component. The fat-soluble vitamins are A, D, E, and K. Since fats have 2.25 times the energy content of carbohydrates and proteins, most people try to limit their intake of dietary fat to avoid becoming overweight. The food industry has a big market for low-fat and non-fat foods. Lipids are classified as organic compounds that are soluble (dissolvable) in organic solvents, but only sparingly soluble in water. Lipids are biologically important for making barriers (membranes of animal cells), which control the flow of water and other materials into a cell. Fats and oils make up 95% of food lipids and phospholipids, and sterols make up the other 5%. Traditionally, fats were considered to be solid at room temperature, and oils were considered to be liquid. However, this designation is often used to distinguish between fats and oils from animals and plants, respectively. Animal fats are found in meats (beef, chicken, lamb, pork, and veal), milk products, eggs, and seafood (fish oil). Plant (vegetable) oils come from nuts (peanuts), olives, and seeds (soybean, canola, safflower, and corn). We use lipids for flavor (butter and olive oil), to cook foods (oils and shortening), to increase the palatability of foods by improving the texture or “mouthfeel” (cakes, creamy ice cream), and in food processing (emulsifiers). Fatty acids are generally long, straight chains of carbon atoms with hydrogen atoms attached (hydrocarbons) with a carboxylic acid group (COOH) at one end and a methyl group (CH3) at the other end. These long, straight chains combine with the glycerol molecule (see Figure 1A) to form lipids (glycerol lipids). Figure 1 A. Glycerol molecule is the backbone of a glycerol lipid. The triacylglycerol contains three fatty acids attached at the oxygen atoms of glycerol. B. Configuration of a cis double bond. C. Configuration of a trans double bond. 29  D. Linoleic acid is an essential fatty acid containing two double bonds. It is needed for growth and health. E. Stearic acid is a saturated fatty acid found in foods from animal and plant sources. F. Milk fat triacylglycerol molecule illustrating the ester bonds between fatty acids and glycerol. Most naturally occurring fatty acids contain an even number of carbon atoms. The 18- carbon fatty acids are the most abundant in our food supply; examples are linoleic acid (an omega-6 fatty acid) found in corn oil and linolenic acid (an omega-3 fatty acid) found in flaxseed oil. Linoleic and linolenic acids are considered essential fatty acids because they are needed for normal physiological functions and our body cannot make them. We need to get these fatty acids from food sources. These fatty acids are found in the vegetable oils used in several different food products. The fats that you see in raw beef, chicken, and pork are known as visible fats. These fats are in plain view and are solid at room temperature. Vegetable oils are also visible fats. The fats that are in snack foods, cookies, desserts, and candy are known as invisible fats. Although you cannot see them, they can add extra calories to your diet. Activity Objective In this experiment, we will be extracting and examining the fat in chocolate, potato chips, and sunflower seeds. In chocolate, sugar and cocoa are dispersed in a crystallized fat matrix. To keep the fat from separating out of the chocolate, an emulsifier called lecithin is used. The fat in the potato chip is mostly on the surface of the chip from the frying process. The fat in the sunflower seed is in the seed itself. The cooking oils that we use come primarily from nuts and seeds. Examples of these fat sources are corn, soybean, and peanut oils. Materials Required Chocolate chips (semi-sweet) Balance or scale Sunflower seeds Microwave Potato chips Paper towels Acetone Foil 100-mm Petri dishes Hammer 100-and 600-milliliter beakers Safety goggles Graduated cylinder Latex or rubber gloves Experimental Procedure Part A. Visual evidence of invisible fats from foods Part 1. Chocolate Chips 1. Measure out 2 grams of chocolate chips and place on a paper towel. 2. Microwave for 40 seconds on high. 3. Fold the paper towel over the chocolate chips and gently press the chocolate chips flat with your fingers. 4. Allow it to sit for 5 minutes. Open up the paper towel. Record your results. 30 Part 2. Potato Chips 1. Measure out 2 grams of potato chips and place on a paper towel. 2. Microwave for 25 seconds on high. 3. Fold the paper towel over the potato chips and crush the chips with a hammer. 4. Allow it to sit for 5 minutes. Open up the paper towel. Record your results. Part 3. Sunflower Seeds 1. Measure out 2 grams of sunflower seeds and place on a paper towel. 2. Microwave for 25 seconds on high. 3. Fold the paper towel over the sunflower seeds and crush the seeds with a hammer. 4. Allow it to sit for 5 minutes. Open up the paper towel. Record your results. Part B. Quantitative measurement of invisible fats from foods Part 1. Extraction of Fat from Chocolate Chips 1. Weigh out 5 grams (9 chips) of chocolate chips. Crush the chocolate between two sheets of foil with a hammer. 2. Label the beakers that you are using to put the food in, one each for chocolate chips, potato chips, and sunflower seeds. Record the weights of the labeled beakers. 3. Using the beaker that is labeled for chocolate chips and place the crushed chocolate chips in the beaker. Record the weight with the crushed chocolate chips. 4. Add 10 milliliters of acetone to the crushed chocolate chips in the beaker. 5. Swirl for 1 minute in a hood, or stir with a glass rod (in a well ventilated area). 6. Carefully decant the acetone into the Petri dish, making sure the chocolate remains in the beaker. 7. Add 10 milliliters of acetone to the chocolate and repeat steps 5 and 6. 8. Allow the acetone in the Petri dish to dry overnight in a hood (or a well ventilated area) to visualize the lipid that was extracted. 9. Allow the beaker with the chocolate to dry overnight. Weigh the beaker with the chocolate. 2. Extraction of Fat from Potato Chips 1. Weigh out 5 grams of potato chips. Break into dime-size pieces with your fingers. 2. Repeat steps 2-9 in Part 1. Part 3. Extraction of Fat from Sunflower Seeds 1. Weigh out 5 grams of sunflower seeds. Crush the seeds between two pieces of foil with a hammer. 2. Repeat steps 2-9 in Part 1. 31  Data Table – Extraction of Lipids Food Weight of Weight of Weight of Weight of Weight lost % Lipid beaker beaker raw food beaker from food extraction with raw with dried food food Chocolate chips Potato chips Sunflower seeds Data Table – Description of Fats Food Color Texture Odor Viscosity Chocolate chips Potato chips Sunflower seeds Questions 1. How can you tell that the dark wet spot on the paper towel is fat and not water? 2. Rank from most to least the percentage of lipid extracted from all three foods. 3. Look at the Nutrition Facts label on the packages of all three foods and rank them. 4. Did your ranking agree with the ranking of the product labels? 5. Determine which lipids contained saturated and unsaturated fatty acids in this experiment, based on your descriptions of the fats in the Petri dishes. Source: 7Institute of Food Technologists, IFT Experiments in Food Science Series Copyright Purdue Research Foundation. All rights reserved. 2000 32  Have Your Chips Lost Their Chomp? Understanding How Food Becomes Rancid8 Experiment No. 7 Introduction Fat rancidity is a process in which fats and oils undergo deterioration to finally produce unpleasant odors and flavors. This occurs by two major mechanisms: (a) Oxidative Rancidity: This type of rancidity takes place whenever fats react with oxygen. Usually, it undergoes the breakdown of unsaturated fats into small, volatile compounds that produce off-flavors and odors. It is accelerated by heat, light, and metals. (b) Hydrolytic Rancidity: It is the reaction of fats with water to produce free fatty acids and glycerol. Further, the free fatty acids can again form foul smells. This type of rancidity most commonly exists in high-moisture-content fats or in environments with excessive humidity. This can be done by storing fats and oils in well- sealed containers, which exclude light and heat. Other techniques include treating with antioxidants or preservatives to extend shelf life. The objective of this experiment is to determine what factors cause potato chips to spoil and go rancid. Materials and Equipment Canning jars, 1-quart (qt.) size, clean and with the rings and lids (8) Aluminum foil (1 roll) Scotch® tape Potato chips with fat (3 large or family-size bags) Measuring cup, ¼-cup Raisins, (3 15-ounce [oz.] boxes) Permanent marker Masking tape Lab notebook Optional: Graph paper Experimental Procedure Note: Oxidative rancidity makes food taste bad, but it will not make you sick. 1. Cover the sides and the bottom of two of the canning jars with aluminum foil so that when the lid is screwed on, no light will enter the jars. You can use Scotch tape to securely attach the foil to the jars. 2. Open the bags of potato chips and the boxes of raisins. Fill one of the foil-covered jars almost full with potato chips. Place ¼ cup of raisins in the other foil-covered jar. Label the jars with masking tape and a permanent marker, with the type of food and trial #, such as Potato Chips: Trial 1. Screw the lids tightly onto the jars so that no air can enter the jars. 33 3. Now fill one of the uncovered jars almost full with potato chips and another uncovered jar with ¼ cup of raisins. Label these jars the same was as you did in step 2. Screw lids tightly onto both jars. 4. Repeat steps 2–3 two additional times, labeling four jars for trial 2. You should now have 8 jars. 5. Place the jars labeled for trial 1 on a windowsill or other well-lit spot. Make sure that the jars will not be disturbed wherever they are located. Note down the location of these four jars in your lab notebook, as well as the time and date when you placed the jars on the windowsill. Find other windowsills or well-lit spots in your house. Put the four jars from trial 2. Note down all locations, dates, and times in your lab notebook. 6. Keep the jars on the windowsills or well-lit spots for 2 weeks, but on the first day and every two days after that, open each jar so you and your groupmates can sample the potato chips and the raisins. Each volunteer should only sample one piece of each. When you are finished, remember to tightly screw on the correct lid again. Try to pick the same time of day so roughly the same amount of time has passed between observations. In your lab notebook, describe the taste and whether or not the taste has changed, using the following rating system (try not to focus on the texture—just the taste): o 5 - The potato chip/raisin tasted great, I really liked it. o 4 - The potato chip/raisin tasted good. o 3 - The potato chip/raisin tasted okay. o 2 - The potato chip/raisin didn't taste good. o 1 - The potato chip/raisin tasted awful, I wish I had never eaten it. 8. Record your data in a table. To analyze the data, make a plot for each volunteer for each location. If you need help making plots, or would like to do your plots online, try using the following website: https://nces.ed.gov/nceskids/CreateAGraph/default.aspx. You can also make your plots by hand. You will have three sets of plots for each volunteer. One plot for each location. Label the y-axis Rating and label the x-axis Time after placing in light. You will plot all four jar and food data sets on the same plot. 9. What do your results show? Did both raisins and potato chips become rancid? What did you discover as one of the key differences between raisins and potato chips? What is the difference in the amount of fat, protein, and carbohydrates (Hint: You can look on the boxes of each to find this information)? 34 Data Table Questions to Answer What are fats? Are fats good for you? How does the process of oxidative rancidity occur? How do food manufacturers prevent foods from going rancid? 8Clemson University, Department of Food Science and Human Nutrition. (n.d.). Oxidative Rancidity. Retrieved August 2024 from https://www.sciencebuddies.org/science-fair- projects/project-ideas/FoodSci_p052/cooking-food-science/how-food-becomes-rancid 35  Proteins9 Experiment No. 8 Introduction: Proteins are the most complex and important group of molecules because they possess diverse functionality to support life. Every cell that makes up plants and animals requires proteins for structure and function. Your body and plants also have enzymes. These specialized proteins catalyze chemical reactions that are necessary for metabolism and cell reproduction. Your muscles are made from a variety of proteins, and these proteins allow your muscles to contract, facilitating movement. Other types of proteins in your body are the peptide hormones; insulin and glucagon are two common examples. Proteins are complex polymers composed of amino acids. Amino acids contain carbon, hydrogen, nitrogen, and sometimes sulfur and serve as the monomers for making peptides and proteins. Amino acids have a basic structure that includes an amino group (NH2) and a carboxyl group (COOH) attached to a carbon atom (see Figure 1A). This carbon atom also has a side chain (an “R” group). This side chain can be as simple as an -H or a -CH3, or even a benzene group. The R groups on an amino acid are analogous to an athlete's clothing and sports equipment. By changing clothing or equipment, an athlete can become more effective as a soccer, football, or baseball player. Although this person is still an athlete, the change can make the athlete more effective in a particular activity or function. The same is true with amino acids. They are still amino acids regardless of the attached R group, but different R groups produce different functions and different properties. Objectives: At the end of the experiment, the students should be able to: 1. Describe protein. 2. Identify food proteins. 3. Demonstrate biuret test for presence of protein in food. Materials: Distilled white vinegar (acetic acid), 5% acidity Hot plate/Bunsen burner Pasteurized whole milk Beakers Graduated cylinder Thermometer Balance Cheesecloth Epsom salt (magnesium sulfate) Foil Rubber bands Raw potato Stirring rod/wood Popsicle sticks Eyedroppers Heatproof gloves Heatproof pad Bread Potato chips Experimental Procedure 36 Part 1. Precipitation of casein from milk with an acid (vinegar) 1. Weigh the empty beaker and record the weight. Weigh and record the weight of 120 milliliters (1/2 cup) of milk in the beaker. Record the weight of the milk in the data table (weight of beaker with milk −weight of beaker = weight of milk). 2. Place the beaker with the milk on a hot plate. Heat the milk to 21oC (70oF). Turn off the hot plate and remove the beaker. 3. Add 11 milliliters (2 teaspoons) of vinegar to the warm milk and stir for 2 minutes, then allow the milk to sit for 5 minutes. The casein will precipitate into heavy white curds. 4. Cut out a piece (2−3 layers) of cheesecloth large enough to cover the top and 2 inches down the sides of a beaker. Using the rubber band, fasten the cheesecloth over the top of the beaker. Pour the curdled milk into the beaker, collecting the curds (casein) in the cheesecloth and allowing the vinegar and whey to drain off into the bottom of the beaker. 5. Gather up the cheesecloth with the casein and rinse in cool water by dipping into another beaker containing water. 6. Squeeze the casein until almost dry, then spread out the cheesecloth to let the casein dry for 5 minutes. 7. Weigh the precipitate. (Do not weigh the cheesecloth with the precipitate). Record your results. Test the precipitate using biuret test. Variations: Test the effect of low temperature on the activity of acid. Repeat the experiment with cold milk at 4oC (40oF). Record your results. Test the effect of high temperatures on the activity of acid. Repeat the experiment with hot milk heated to 70oC (160oF). Record your results. Part 2. Coagulation of protein from milk using a salt (magnesium sulfate) 1. Weigh the empty beaker and record the weight. Weigh and record the weight of 120 milliliters (1/2 cup) of milk in the beaker. Record the weight of the milk in the data table (weight of beaker with milk − weight of beaker = weight of milk). 2. Place the beaker with the milk on a hot plate. 3. Bring the milk to a boil and turn off the heat. Monitor this step closely; do not allow the milk to boil over the top of the beaker. 4. Add 1.6 grams (1/4 teaspoon) of Epsom salt (magnesium sulfate, a mineral salt) to the hot milk and stir. 5. Wait until the curds are floating in an almost clear liquid. 6. Fasten a piece (2−3 layers) of cheesecloth over the top of a beaker with a rubber band. Pour the soy curds and liquid into the beaker, collecting the curds in the cheesecloth and allowing the liquid to drain into the bottom of the beaker. 7. Gather up the cheesecloth and squeeze out as much water as possible. Spread out the cheesecloth to allow the curds to dry for 5 minutes. 8. Weigh the curds. (Do not weigh the cheesecloth with the curd.) Record your results. Test the curds using biuret test. 37 Variations: Test the effect of low temperature on the activity of salt. Repeat the experiment with cold milk at 4oC (40oF). Add 1.6 grams (1/4 teaspoon) of Epsom salt to 120 milliliters (1/2 cup) of cooled milk. Record your results. Test the effect of high temperatures on the activity of acid. Repeat the experiment with hot milk heated to 70oC (160oF). Add 1.6 grams (1/4 teaspoon) of Epsom salt to 120 milliliters (1/2 cup) of boiled milk. Record your results. Source: 9Institute of Food Technologists, IFT Experiments in Food Science Series Copyright Purdue Research Foundation. All rights reserved. 2000 Part 3. Biuret Test (Dahal, 2024) Biuret Test is the test used to detect the presence of peptide bonds in the sample and to test for the presence of proteins or peptides. Procedure 1. Label three test tubes as ‘test’, ‘positive’, and ‘negative’. 2. In the test tube labeled as ‘test’, dispense 1-2 mL of sample, in the test tube labeled as ‘positive’, dispense 1-2 mL of albumin solution, and in the test tube labeled as ‘negative’, dispense 1-2 mL of distilled water. 3. In each tube, add an equal volume of (1-2 mL) of Biuret reagent. 4. Shake well and let it stand at room temperature for 5 minutes. 5. Observe the tubes for the development of violet color in the suspension. Result and Interpretation of Biuret Test Positive Biuret Test: Formation of purple color after the addition of Biuret reagent. (Tube with albumin solution will turn purple.) Negative Biuret Test: No formation of violet/purple color (or formation of blue color) solution after the addition of Biuret reagent. (Water will turn to blue color.) 38 Data Sheets: A. MILK AND MILK CURDS Weight of Weight of curd Describe the curd milk (color, texture) Milk + acid Milk + MgSO4 B. MILK CURDS at Different Temperature Weight of milk Weight of Describe the curd curd (color, texture) Using Acid Low Temperature High Temperature Using salt Low Temperature High Temperature C. BIURET TEST ON FOODS Sample Color Positive/Negative Milk + acid precipitate Milk + Epsom salt coagulum Potato chip Raw potato Bread 39 Questions: 1. Compare the weights of the curds from the milk using acid with that from the Milk using salt. 2. Why did the casein that was coagulated with the acid weigh more than the casein that was precipitated with the salt? 3. How did the biuret test indicate the presence of proteins? 40  Functional Properties of Proteins10 Experiment No. 9 Introduction: Proteins are important in foods both for its nutritional contribution as well as for its functionality. Proteins are essential in the food. It act as important component of the cells and tissues as well as perform important functions in biochemical reactions. As a biologically active component, it catalyzes biochemical reactions. As a structural component, it is responsible for the form and organization of the cells and tissues. This structural function is also important in food processing. Proteins are responsible for the many characteristic changes in foods. Development of color and flavour in many processed foods are determined by the presence of protein. Objectives: At the end of the experiment, the students should be able to: 1. Identify the functional properties of proteins and their role in food. 2. Discuss the functional properties of proteins. Materials: Flour Cake flour - 200g mixing bowl Bread flour - 200g oven Dry yeast - 3g cheese cloth Mineral yeast food - 1.5 balance Sugar - 12 test tube Salt - 4 thermometer Shortening - 12 stove Water - 116 refrigerator Egg beater Starch solution, 2% water bath Egg albumin (egg white) timer Papain (from unripe papaya) ruler beaker Experimental Procedure Part 1. Role of gluten in Breadmaking 1. Weigh all ingredients thoroughly. 2. Blend the flour and mineral yeast food and set aside. 3. Dissolve dry yeast in the solution obtained after mixing the sugar, water and salt thoroughly. 4. Pour the solution into the blended flour. Mix well. 41  5. When all the ingredients are well blended, knead the dough using the heels of the hands against the table top. 6. Use shortening instead of dusting flour to prevent the dough from getting sticky. 7. After thorough kneading, allow the dough to rest for about 10 minutes, and then proceed to the development of the gluten (slap the dough against a hard surface such as a table). 8. Ferment for 1-3 hours. Half-way before the time of fermentation is through, punch it down to expel the gas generated during the period. 9. Cut down several pieces and form a baston. 10. Roll baston over the bread crumbs and rest for 10-15 min. 11. Cut baston to approximately 25 g per piece and place in a slightly greased baking sheet. 12. Proof for 40-60 min. 13. Bake at 380oF for 12 min or until done. 14. Repeat above experiment using cake flour. Part 2. Foaming Property of Protein 1. Place 50 mL of egg white in a 400 mL beaker. 2. Beat vigorously for 10, 20, 40, and 60 seconds, respectively. 3. Note the volume after each period of beating. 4. Repeat the experiment with another 50 mL of egg white previously heated in a water bath to 75oC and cooled. 5. Repeat the experiment with 2% starch solution. 6. Note the change in volume. Part 3. Enzymatic Activity 1. Place 1 mL egg white in a test tube. 2. Determine the viscosity by laying the test tube on its side and measuring the distance travelled by the albumin after 30 seconds. 3. Add 0.5 g papain. 4. Incubate the mixture at 30oC to 35oC and observe the change in viscosity after 30, 60, 90, and 120 min interval. 5. Slowly turn the test tube to each side and measure the distance the liquid will travel after 30 seconds. (Note: do not spill the contents). 6. Describe the reaction. Source: 5 Ricardo R. Del Rosario. 1991. Laboratory Manual in Food Chemistry. UPLB. 42 Data Sheets: A. Sensory Qualities of Bread Type of Flour Appearance Texture Volume Bread flour Cake flour B. Effect of heat and time of beating on the foaming characteristics of untreated and heat treated egg white Volume Sample 10 sec 20 sec 40 sec 60 sec Unheated egg white Heated egg white Starch solution C. Enzyme activity and its effect on protein properties Time (min) Distance Travelled (cm) 0 30 60 90 120 Questions: 1. What is the role of gluten in breadmaking? 2. Can we use cake flour in breadmaking? Why? 3. What are the components of gluten? 4. What is a foam? 5. How does foam differ from an emulsion? 43 6. What is the role of protein in foam formation? What could take the place of protein in foams? 7. What is an enzyme? A proteolytic enzyme? 8. What does the reduction of viscosity or increase in fluidity indicate? 9. What other food system can make use of this reaction? 44  Protein Coagulation or Denaturation11 Experiment No. 10 Introduction Proteins are large molecules made up of small amino acids. Proteins are held in a natural shape due to the interaction of side groups on the amino acids from one part of the molecule to another area of the molecule. These interactions may be hydrogen bonds or disulfide bonds. We can denature the proteins by disrupting the H-bonds that are within the structure. When this happens, the overall shape of the protein changes and new properties can be observed. The shape of a protein is associated with food processing properties, such as solubility, gel formation, and enzyme activity. When proteins are coagulated they clump into a semi-soft, solid-like substance. A chemical change has taken place because a new substance is produced. The first step in protein digestion is coagulation. In the egg whites, the albumin will change from clear to white. Students will explore how the following denature egg albumin. Heat – done by cooking Acids & bases – can form ions on some side groups of amino acids Organic compounds – form their own hydrogen bonds with the amino acids Heavy metals – react with disulfide bonds In this experiment, students will learn several ways in which proteins are coagulated. Objective: To experiment with different methods of denaturing the protein found in egg white (albumin) and milk Materials: Raw eggs wire gauze forceps test tubes milk 250-ml beaker medicine dropper dilute hydrochloric acid watch glass Hot plate NaCl NaHCO3 Lemon juice Stirring rod 1% Ag NO3 (Heavy metals are not allowed in food supply) Procedures: Part A. Coagulation of Egg White 1. Half fill a 250-mL beaker with water. Place it on a tripod and boil the water gently. 2. Turn off the Bunsen burner. Drop some egg white into the hot water. Wait two or three minutes and record your observations. 3. Remove about half of the coagulated egg white with forceps, and place it on your watch glass. Resume boiling the remaining egg white for five more minutes. Compare the raw egg white, the two-to-three-minute egg white, and the eight- minute egg white. Record your observations. 45 Part B. Factors that Affects Coagulation of Egg White 1. Place 300 mL of water in a 400 mL beaker, heat to boiling. 2. Label 6 test tubes #1-6 3. Separate 3 eggs, placing the egg white in a test tube until half filled. Discard the egg yolk. 4. Place test tube 1 in the boiling water and allow to “cook” till egg turns white. 5. Add NaCl to test tube #2 and stir. 6. Add NaHCO3 to test tube #3 and stir. 7. Add lemon juice to test tube #4 and stir. 8. Add rubbing alcohol to test tube #5 and stir. 9. Add 1% AgNO3 to test tube #6. 10. Record observations on the data table. Part C. The Coagulation of Milk Protein 1. Add one inch of milk to a test tube. Add hydrochloric acid to the milk, with a medicine dropper, until a change is seen. Record your observations. 2. Allow the test tube to stand undisturbed for five minutes. Decant the liquid. Describe the residue in the test tube; which food does it resemble? Data Table Test Tube Added Observations 1 Heat 2 NaCl – Ionic Compound 3 NaHCO – Base 4 Lemon juice – Acid 5 Rubbing alcohol - organic liquid 6 AgNO3 – heavy metal Questions: 1. Which is easier to digest, a hard-boiled egg or a raw egg; sour milk or sweet milk? Explain. 2. How is milk coagulated in the stomach? 3. Why does boiled milk develop a “skin”? 4. List two ways in which proteins are coagulated? 5. Why is baked bread easier to digest than unbaked dough? 6. Which method appeared to have the most dramatic denaturing affect on egg albumin? Why do you think this method had a greater affect? 7. Of the methods you tested, which would be more likely to be used in the food industry? Source: 11Rita Snyder, Deb Dommel 46  Enzymes12,13 Experiment No. 11 Introduction: Enzymes are complex proteins that cause a specific chemical change in all parts of the body. For example, they can help break down the foods we eat so the body can use them. Blood clotting is another example of enzymes at work. They accelerate biochemical reactions and are responsible for many reactions like ripening, deterioration or other changes in plant tissues. Enzymes are active at low temperatures compared to inorganic catalysts. They are specific in the reactions it catalyzes and has replaced many inorganic catalysts which require higher temperature. Objectives: At the end of the experiment, the student should be able to: 1. Identify the properties of enzymes. 2. Discuss the properties of enzymes and its reaction. 3. Assess the effect of several factors in the activity of enzymes. 4. Explain the effect of PME of softening enzyme of fruits on processing. Materials: Ripe banana knife Red ripe tomato glass jar Blender strainer frying pan watch glass beaker Buffer solution timer Experimental Procedure Part 1. Properties of Enzyme A. Effect of pH 1. Place 5-10 mL of each buffer (pH 3,7,10) in test tubes and label properly. 2. Prepare slices of banana, saba or lakatan (must be cut under water). 3. Drop one slice of each fruit into the different test tubes. 4. Set aside some slices to serve as control and place in watch glass. 47  5. After one minute, remove the slices from the test tube. 6. Observe the development of brown color after 30 minutes. 7. Compare with the untreated samples. 8. Use 9-point scale for color evaluation (1-least colored; 9-hihgly colored) B. Effect of Temperature 1. Heat distilled water to 45, 65, 85, and 100 oC, respectively. 2. Cut pieces of banana into ½ cm x ½ cm x ½ cm pieces. 3. Add several pieces into heated water and remove samples after 0, 10, 30, and 45 seconds, respectively. 4. Cool the samples with water. 5. Compare the color development of the fruit slices. 6. Use the 9-point scale for grading. Part 2. Pectin Methyl Esterase (PME) 1. Weigh 250 g tomatoes (per group) 2. One will employ heat treatment (blanching) before the fruits are comminuted while the other group will process the tomato without heating. 3. For the heated trial, place the tomatoes in boiling water for 2-3 minutes. 4. Remove the tomatoes when the skin loosens. 5. Place in tap water to cool. 6. For the untreated trial, proceed directly to cutting and homogenization. 7. Cut the tomatoes in halves and homogenize in a waring blender. 8. Filter out the seeds using a coarse filter. 9. Add 0.5 g salt. 10. Heat the juice from 75 to 85°C and fill in 8 oz. Bottle. 11. Put on the lid or cover, seal and process for 30 minutes in boiling water. 12. Remove from the boiling water bath, cool and observe. 13. Examine the process again after 3 days. 14. Compare the products obtained as to their appearance, texture, flavour and aroma. Part 3. Pectin Lyase Effect on Fruit Juice 1. Cut fruit (use pineapple/dragonfruit/apple) and remove peels (if any). 2. Homogenize the pulp in a blender and add pectin lyase enzymes to two samples at different concentrations (1% and 5%). Have a control or test sample. Place samples in Erlenmeyer flask. 3. Using a water bath, heat the samples with enzymes at 50C for 30 minutes. 4. Manually extract the control sample. 5. Prior to juice extraction of heat and enzyme treated samples, chill the mixture and press using cheesecloth. The juice yield will be quantified using the formula below. 𝑄𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑐𝑙𝑒𝑎𝑟 𝑗𝑢𝑖𝑐𝑒 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑌𝑖𝑒𝑙𝑑 (%) = 𝑥 100 𝑄𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑝𝑢𝑙𝑝 𝑢𝑠𝑒𝑑 where Quantity of pulp used = Weight of fruit + Volume of water added 48 Data Sheets: 1.A. Effect of pH on browning reactions in fruits pH Banana Control 3 7 10 1.B. Effect of temperature on browning reactions in fruits Heating time (sec) Banana Temperature (oC) Control 0 45 15 30 45 65 15 30 45 85 15 30 45 100 15 30 45 49  2. Influence of heat treatment on the quality of tomato sauce Characteristic Unheated Heat treated After processing Appearance Texture Flavor Aroma After 3 days Appearance Texture Flavor Aroma Texture – Viscous or fluid Flavor/Aroma – typical tomato or not typical Appearance – homogenous or heterogeneous Questions: 1. What is the reaction involved in enzymatic browning? 2. How does pH affect the rate of enzymatic browning? 3. How does heat treatment affect the rate of enzymatic browning? 4. Why did the two products differ in sensory qualities? 5. What are pectin esterases? PMS? Pectin Lyase? What is their mode of action? 6. Give the importance of these enzymes in food processing. References: 12Flores, Dulce M. Laboratory and Lecture Notes in Food Chemistry. University of the Philippines in Mindanao. 13Ricardo R. Del Rosario. 1991. Laboratory Manual in Food Chemistry. UPLB. 50