Food Preservation Techniques

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Questions and Answers

What is the main principle behind food preservation through drying?

Drying reduces the water activity in food systems, which inhibits the growth of microorganisms and slows down spoilage processes, thus extending shelf life.

Describe the process of drying food using a spray dryer.

In spray drying, liquid food is atomized into tiny droplets and exposed to hot air in a drying chamber. This rapid evaporation of moisture creates a dried powder, which is separated from the air by a cyclone.

What is the main difference between oven drying and freeze drying in terms of the phase change involved?

Oven drying involves water changing from liquid to gas, while freeze drying involves water directly changing from solid (ice) to gas (water vapor) through sublimation.

What are two advantages of freeze drying compared to oven drying?

<p>Freeze drying preserves the original flavor and texture of the food better than oven drying, and it also leads to less nutrient loss.</p> Signup and view all the answers

Why is using freeze drying beneficial for preserving the aroma of food products compared to oven drying?

<p>Freeze drying uses low temperatures, which helps to minimize the loss of volatile aroma compounds that would evaporate at higher temperatures used in oven drying.</p> Signup and view all the answers

What is the role of the atomizer in a spray drier?

<p>The atomizer converts the liquid food into a fine mist of droplets, maximizing the surface area for rapid evaporation.</p> Signup and view all the answers

Explain the significance of the sublimation process in freeze drying.

<p>Sublimation is the key process in freeze drying where ice directly changes to water vapor, removing moisture without damaging the food structure by high temperatures like in oven drying.</p> Signup and view all the answers

How do drying parameters like pump speed, inlet temperature, air flow rate and compressor pressure affect the drying process?

<p>These parameters influence the evaporation rate, droplet size, and drying time, ultimately affecting the properties of the final dried product.</p> Signup and view all the answers

Based on the provided information, describe two advantages of freeze drying over oven drying.

<p>Advantages of freeze drying over oven drying include preservation of food quality by avoiding high temperatures and minimizing the loss of volatile compounds like aroma.</p> Signup and view all the answers

What is the purpose of dividing the banana slices into two groups and drying them at different temperatures in the oven drying experiment?

<p>To observe and compare the effects of different drying temperatures on the color, hardness, appearance, and aroma of the dried banana slices.</p> Signup and view all the answers

What is the expected outcome of drying banana slices at a lower temperature compared to a higher temperature in terms of color, hardness, and aroma?

<p>Drying at a lower temperature would likely result in a lighter color, softer texture, and a more intense aroma compared to drying at a higher temperature.</p> Signup and view all the answers

Why is spray drying commonly used for producing high-value products in powder form?

<p>Spray drying can produce high-quality, consistent powder products that are well-suited for long-term storage and distribution, making it suitable for high-value applications.</p> Signup and view all the answers

Explain the role of heat in the drying process, as described in the experiment.

<p>Heat is essential for providing energy to evaporate water from the banana slices, thus removing moisture and leading to drying.</p> Signup and view all the answers

How does drying help to preserve food? Briefly explain the mechanism.

<p>Drying reduces water content in food, hindering the growth of microorganisms and slowing down enzymatic activity, which are responsible for spoilage.</p> Signup and view all the answers

Explain the function of the cyclone in a spray dryer.

<p>The cyclone uses centrifugal force to separate the dried food particles from the hot air stream, collecting the powder in a collection bottle.</p> Signup and view all the answers

What is the main function of the atomizer in a spray dryer?

<p>The atomizer sprays the liquid feed into fine droplets to increase the surface area for drying.</p> Signup and view all the answers

Why is a peristaltic pump used in the spray drying process?

<p>A peristaltic pump is used to transport the liquid feed consistently to the atomizer.</p> Signup and view all the answers

How does the cooling effect of freezing improve the quality of preserved foods?

<p>Freezing slows down enzyme activity and microbial growth, preserving the food's texture, flavor, and nutritional value.</p> Signup and view all the answers

What causes the difference in moisture content of milk powder from the cyclone and collection bottle?

<p>The cyclone captures larger droplets, leading to lower moisture content, while the collection bottle holds finer droplets with higher moisture content.</p> Signup and view all the answers

Explain the role of blanching in the freezing process of snap beans.

<p>Blanching halts enzyme activity that can cause loss of flavor, color, and texture during freezing.</p> Signup and view all the answers

What is freezer burn and how does it affect frozen foods?

<p>Freezer burn is the drying of a food's surface due to moisture loss, leading to texture and flavor changes.</p> Signup and view all the answers

How can the packaging of frozen food impact its quality?

<p>Proper packaging minimizes air exposure and moisture loss, reducing the risk of freezer burn.</p> Signup and view all the answers

Calculate the production percentage of milk powder if 800g was obtained from a 1000g feed.

<p>The production percentage is 80%.</p> Signup and view all the answers

What are the two physical characteristics analyzed in the snap beans after thawing?

<p>Appearance and odor.</p> Signup and view all the answers

Explain the purpose of blanching before freezing food.

<p>Blanching deactivates enzymes that can cause flavor and color degradation during storage.</p> Signup and view all the answers

What immediate action is taken after cutting the snap beans into 2 cm pieces?

<p>The cut snap beans are divided into two portions.</p> Signup and view all the answers

What is the storage temperature required for the snap beans in the freezer?

<p>-18°C.</p> Signup and view all the answers

What temperature range is generally adequate for canning low-risk foods?

<p>The temperature range for canning low-risk foods is between 85°C to 100°C.</p> Signup and view all the answers

How long are the snap beans stored in the freezer before being analyzed?

<p>1 week.</p> Signup and view all the answers

What happens to the snap beans after they are removed from the freezer?

<p>They are allowed to thaw at room temperature.</p> Signup and view all the answers

Why is packaging crucial in the freezing of foods?

<p>Packaging prevents freezer burn and preserves the quality of the food during storage.</p> Signup and view all the answers

What is the main difference between high acid and low acid foods in terms of pH?

<p>High acid foods have a pH of less than 4.6, while low acid foods have a pH of more than 4.6.</p> Signup and view all the answers

What is the main difference in treatment between the two groups of snap beans in Part II?

<p>One group is packed into a plastic bag while the other is left unpackaged on a tray.</p> Signup and view all the answers

What specific adjustment is made to the sucrose solution before using it in canning?

<p>The sucrose solution is adjusted to a pH of 3.5 using citric acid.</p> Signup and view all the answers

Why are foods with a water activity higher than 0.85 and a pH greater than 4.6 categorized as high-risk?

<p>They are categorized as high-risk because pathogenic microorganisms can grow and multiply in them.</p> Signup and view all the answers

What process is performed on the papaya slices before placing them in sterilized cans?

<p>The papaya slices are blanched by immersing them in boiling water for 2 minutes.</p> Signup and view all the answers

What substance is added to the sucrose solution before canning it with papaya?

<p>A 5% calcium chloride solution is added to the sucrose solution with calcium.</p> Signup and view all the answers

What is the first step in the preparation of papaya for canning?

<p>The first step is to remove the outer skin and core of the fruits.</p> Signup and view all the answers

What must be done with the water after blanching the papaya slices?

<p>The excessive water must be drained after blanching.</p> Signup and view all the answers

How does BHA function to prevent rancidity in fried banana slices?

<p>BHA acts as an antioxidant, inhibiting the oxidation of fats which leads to rancidity.</p> Signup and view all the answers

What visual differences were observed between banana slices fried without BHA and those with BHA?

<p>The banana slices fried with BHA typically retained a brighter color compared to those fried without BHA.</p> Signup and view all the answers

Explain the role of the oil temperature in frying banana slices with and without BHA.

<p>The oil temperature at 170°C is crucial for achieving the right texture and proper cooking of the banana slices regardless of BHA addition.</p> Signup and view all the answers

What are the four types of browning reactions mentioned, and which one is enzymatic?

<p>The four types are caramelization, Maillard reaction, oxidation of ascorbic acid, and enzymatic browning; the only enzymatic reaction is the enzymatic browning.</p> Signup and view all the answers

Discuss how the storage method of the fried banana slices might influence their shelf-life.

<p>Storing fried banana slices at room temperature can expose them to air, leading to oxidation and potential rancidity.</p> Signup and view all the answers

What consequences does non-enzymatic browning have on food quality?

<p>Non-enzymatic browning can lead to undesirable colors and flavors, affecting the overall appeal and taste of the food.</p> Signup and view all the answers

What is the primary enzymatic agent responsible for browning in fruits like bananas?

<p>The primary enzymatic agent responsible for browning is polyphenol oxidase (PPO).</p> Signup and view all the answers

How might the results of frying banana slices with BHA affect consumer preferences?

<p>Fried banana slices with BHA may be preferred due to their better appearance, aroma, and extended shelf-life.</p> Signup and view all the answers

What is the covalent bond formed specifically between two monosaccharides called?

<p>Glycosidic bond (A)</p> Signup and view all the answers

Which of the following monosaccharides is a constituent of lactose?

<p>Galactose (B)</p> Signup and view all the answers

What makes sucrose unable to act as a reducing sugar?

<p>The glycosidic linkage between glucose and fructose involves aldehyde and ketone groups (D)</p> Signup and view all the answers

What is the main difference between α and β glycosidic linkages in disaccharides?

<p>α linkages are hydrolyzed by human gut enzymes, while β linkages are not (B)</p> Signup and view all the answers

Which of the following statements accurately describes the transformation of galactose in human metabolism?

<p>Galactose is transformed into glucose for energy. (B)</p> Signup and view all the answers

What is the primary source of energy for the heart muscle in emergency situations?

<p>Glycogen stored in the heart muscle (D)</p> Signup and view all the answers

What is the primary difference between amylose and amylopectin?

<p>Amylose is a straight chain polymer of glucose while amylopectin is branched. (C)</p> Signup and view all the answers

Which of the following monosaccharides is known as "fruit sugar"?

<p>Fructose (C)</p> Signup and view all the answers

Which of the following is a non-reducing sugar?

<p>Sucrose (D)</p> Signup and view all the answers

What is the key characteristic that distinguishes polysaccharides from other carbohydrates?

<p>They are composed of three or more monosaccharide units. (B)</p> Signup and view all the answers

What is the primary function of oligosaccharides in the large intestine?

<p>They are broken down by bacteria to produce short-chain fatty acids. (B)</p> Signup and view all the answers

Why is an increase in ketone production problematic in conditions like starvation or diabetes?

<p>Cells cannot utilize ketones for energy as efficiently as carbohydrates. (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of dextrins?

<p>They are composed exclusively of glucose units. (B)</p> Signup and view all the answers

What causes ketoacidosis?

<p>Breakdown of fatty acids in the absence of sufficient carbohydrates. (A)</p> Signup and view all the answers

Which of the following foods is NOT a significant source of oligosaccharides?

<p>Potatoes (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of glucose?

<p>It is primarily found in dairy products. (C)</p> Signup and view all the answers

What is the approximate relative sweetness of lactose compared to sucrose?

<p>1/6 (D)</p> Signup and view all the answers

What is the most crucial reason why the Central Nervous System (CNS) relies on glucose from blood circulation?

<p>The CNS cannot store glucose effectively. (D)</p> Signup and view all the answers

What is the main distinction between pentoses and hexoses?

<p>Pentoses contain five carbon atoms, while hexoses contain six carbon atoms. (A)</p> Signup and view all the answers

Which of the following polysaccharides is primarily responsible for the branched structure of starch?

<p>Amylopectin (B)</p> Signup and view all the answers

What is the main difference between lactose intolerance and milk allergy?

<p>Lactose intolerance is an inability to digest lactose, while milk allergy is an immune response to milk protein. (B)</p> Signup and view all the answers

What is the primary function of carbohydrates in the body?

<p>To provide energy (D)</p> Signup and view all the answers

What is the recommended percentage of total calorie intake that should come from carbohydrates?

<p>50-60% (B)</p> Signup and view all the answers

Which of these is NOT a function of carbohydrates in food?

<p>Serving as a primary source of vitamins (C)</p> Signup and view all the answers

What is the role of glycogen in the body?

<p>Storing energy (D)</p> Signup and view all the answers

What is the protein-sparing action of carbohydrates?

<p>Preventing the breakdown of protein for energy (B)</p> Signup and view all the answers

What is the antiketogenic effect of carbohydrates?

<p>Preventing the formation of ketone bodies (D)</p> Signup and view all the answers

Which of the following is NOT a type of carbohydrate?

<p>Fat (C)</p> Signup and view all the answers

What is the main difference between complex carbohydrates and simple carbohydrates?

<p>The number of sugar molecules they contain (D)</p> Signup and view all the answers

What is the main structural difference between cellulose and hemicellulose?

<p>Cellulose is a linear polymer, while hemicellulose is branched. (B), Cellulose is more rigid than hemicellulose. (D)</p> Signup and view all the answers

Which of the following is NOT a component of dietary fibre?

<p>Lactose (B)</p> Signup and view all the answers

Why is cellulose considered indigestible in humans?

<p>Humans lack the necessary enzyme to break down cellulose. (C)</p> Signup and view all the answers

Which of the following is NOT a typical source of hemicellulose?

<p>Meat (B)</p> Signup and view all the answers

What is the primary function of lignin in plants?

<p>Provides structural support to the plant. (C)</p> Signup and view all the answers

Which of these statements BEST describes the relationship between dietary fibre and stool bulking?

<p>Dietary fibre absorbs water, leading to softer, larger stools. (D)</p> Signup and view all the answers

Which of the following is the most soluble component of the plant cell wall?

<p>Pectic substances (C)</p> Signup and view all the answers

What is the primary function of dietary fibre in the human body?

<p>Promotes digestive health and regularity. (D)</p> Signup and view all the answers

What is the main source of energy during an emergency situation for the heart?

<p>Stored glycogen in the cardiac muscles (A)</p> Signup and view all the answers

What is the primary role of glucose in the Central Nervous System (CNS)?

<p>It provides energy for nerve cells. (A)</p> Signup and view all the answers

Which of the following is NOT a monosaccharide?

<p>Sucrose (B)</p> Signup and view all the answers

Which monosaccharide is known as "fruit sugar"?

<p>Fructose (A)</p> Signup and view all the answers

What is the term for the accumulation of ketones in the blood, often seen in conditions like starvation and diabetes?

<p>Ketosis (A)</p> Signup and view all the answers

Which of the following statements accurately describes the structure of carbohydrates?

<p>Carbohydrates are composed of carbon, hydrogen, and oxygen in the ratio CnH2nOn. (D)</p> Signup and view all the answers

Which of the following is NOT a type of polysaccharide?

<p>Maltose (A)</p> Signup and view all the answers

Which of the following is the sweetest monosaccharide?

<p>Fructose (B)</p> Signup and view all the answers

Which of the following is NOT a function of carbohydrates in food?

<p>Serve as a primary source of energy. (D)</p> Signup and view all the answers

What is the main storage form of glucose in the body?

<p>Glycogen (B)</p> Signup and view all the answers

What is the role of carbohydrates in preventing ketogenesis?

<p>Carbohydrates inhibit the breakdown of fatty acids and amino acids into ketone bodies. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the role of carbohydrates in the body's metabolic functions?

<p>Carbohydrates primarily provide energy for the brain and nervous system. (B)</p> Signup and view all the answers

Which of the following examples BEST illustrates the effect of carbohydrates on food texture?

<p>The chewy texture of a bread roll. (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of oligossacharides?

<p>They are found in significant amounts in many foods. (B)</p> Signup and view all the answers

Which of the following food sources is most likely to contain a high amount of raffinose?

<p>Soybeans (A)</p> Signup and view all the answers

Which of the following statements BEST describes dextrin?

<p>Dextrin is a type of polysaccharide produced by heating starch with moisture and an acid. (B)</p> Signup and view all the answers

What is the primary function of oligoenzymes in the large intestine?

<p>Breakdown of complex carbohydrates (A)</p> Signup and view all the answers

Which of the following statements accurately describes lactose?

<p>Lactose is a disaccharide found in mammalian milk, composed of glucose and galactose. (D)</p> Signup and view all the answers

What type of bond is formed between two monosaccharides to create a disaccharide?

<p>Glycosidic bond (B)</p> Signup and view all the answers

Which of the following statements is TRUE regarding cellulose?

<p>It is the primary component of plant cell walls, making up 20-25%. (B)</p> Signup and view all the answers

What is the key distinguishing feature of hemicellulose compared to cellulose?

<p>Hemicellulose has a branched structure due to the presence of both hexose and pentose sugars. (B)</p> Signup and view all the answers

Which of the following is NOT a type of hemicellulose?

<p>Pectin (A)</p> Signup and view all the answers

What is the primary constituent of pectic substances?

<p>D-galacturonic acid (A)</p> Signup and view all the answers

Which of the following statements BEST describes the role of lignin in plant tissues?

<p>It contributes to the rigidity and strength of mature plant tissues. (B)</p> Signup and view all the answers

What is the PRIMARY function of dietary fibre in relation to digestion?

<p>Adding bulk to faecal matter and aiding in its passage (A)</p> Signup and view all the answers

Which of the following is a correct example of a sugar commonly found as an intermediate product of starch degradation?

<p>Maltose (C)</p> Signup and view all the answers

Which disaccharide is composed of glucose and fructose?

<p>Sucrose (B)</p> Signup and view all the answers

Which of the following is a characteristic of non-reducing sugars?

<p>They cannot donate electrons to other molecules. (A)</p> Signup and view all the answers

What is the primary role of galactose in human metabolism?

<p>Being converted to glucose for energy. (C)</p> Signup and view all the answers

Which of the following is a source of galactose in the human diet?

<p>Lactose (C)</p> Signup and view all the answers

Flashcards

Freeze-drying

A method of removing moisture from food by freezing and sublimating the ice.

Advantages of freeze-drying

Two benefits include better preservation of nutrients and lower weight post-processing.

Disadvantages of freeze-drying

High costs and longer processing time compared to oven drying.

Spray drying

A drying process where liquid is sprayed into droplets and dried instantly with hot air.

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Function of spray dryer components

The main parts regulate drying conditions like temperature and flow rate.

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Cyclone in spray drying

A device that separates dried particles from hot air using centrifugal force.

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Pulse of spray-dying

An initial step to dry food quickly, often through high-temperature exposure.

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Drying parameters

Key settings including pump speed, inlet temperature, and airflow in spray drying.

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Oven Drying

A method that heats food to remove moisture, affecting its properties.

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Physico-Chemical Properties

Characteristics of food that involve physical and chemical changes during drying.

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Sensorial Properties

Attributes related to the senses, like taste and smell, after drying.

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Drying Process Objective

To dry banana slices and observe temperature effects on their properties.

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Temperature Effects

Different drying temperatures influence the final attributes of dried food.

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Sublimation

The process where ice changes directly from solid to gas.

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Volatile Compounds

Compounds that can easily evaporate, often influencing aroma and flavor.

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Canning

A method for preserving food by sealing it in containers under heat.

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High Acid Foods

Foods with a pH value less than 4.6, preserving well through canning.

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Low Acid Foods

Foods with a pH value higher than 4.6, need more careful preservation.

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Water Activity (aw)

The measure of water available for microbial growth in foods.

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Low-Risk Foods

Foods with higher aw and lower pH, which are less likely to spoil.

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High-Risk Foods

Foods with higher aw and higher pH, requiring strict safety measures.

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Syrup Preparation

Combining sucrose with citric acid to create preserving syrup for canning.

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Blanching

A process of briefly boiling food to prepare it for canning.

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Spray Dryer Components

Parts include atomizer, pump, blower, cyclone, and chamber, each with a specific function.

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Moisture Content (M.C.)

The percentage of moisture in milk powder measured from different components.

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Freezing Method

A preservation method that involves lowering temperature below water's freezing point.

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Freezer Burn

Surface drying of food due to loss of moisture to the environment.

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Quality Control in Freezing

Managing freezing conditions to optimize the quality of frozen food.

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Effect of Packaging

How the method of packaging impacts the quality of frozen food.

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Supermarkets and Freezing

The rise of supermarkets has increased the use of freezing for food preservation in Malaysia.

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Preparing Snap Beans

Cleaning and cutting snap beans into 2 cm pieces before storage.

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Manual Electric Sealer

A device used to seal bags for food preservation.

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Freezing Temperature

Storing food at -18°C to maintain quality.

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Thawing

The process of letting frozen food return to room temperature.

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Evaluating Food Quality

Analyzing snap beans based on appearance, color, odor, and firmness.

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Importance of Packaging

Packaging helps prevent freezer burn and maintains food quality.

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Effect of Blanching

Blanching helps retain color, taste, and nutrients when freezing vegetables.

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BHA (Butylated Hydroxyanisole)

A preservative added to oil to prevent rancidity in fried foods.

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Frying process duration

Banana slices are fried for 5 minutes in both treatments.

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Temperature for frying

Both fryers must be heated to 170°C before use.

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Effects of BHA on rancidity

BHA reduces rancidity, improving shelf-life of fried products.

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Enzymatic browning

A reaction causing browning in foods due to polyphenol oxidase.

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Non-enzymatic browning

Browning that occurs without enzymes, including caramelization and Maillard reaction.

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Evaluation of fried products

Assessment of color, rancidity, and aroma between BHA-treated and untreated food.

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Storage of fried banana slices

Fried slices are stored at room temperature for evaluation after 3 weeks.

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Carbohydrate

A nutrient that provides energy, containing elements C, H, and O.

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Energy from Carbohydrates

Carbohydrates provide 17 kJ or 4 kcal of energy per gram.

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Complex Carbohydrates

Preferred form of carbohydrates, include starch and natural sugars.

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Functions of Carbohydrates

Carbs serve multiple roles: energy storage, taste enhancement, and texture.

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Protein-Sparing Action

Adequate carbohydrates prevent protein from being used for energy.

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Glycogen

The stored form of glucose in the body, mainly in liver and muscles.

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Antiketogenic Effect

Prevents the formation of ketone bodies during fat breakdown.

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Recommended Carbohydrate Intake

50 to 60% of total calories should come from carbohydrates.

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Galactose

A monosaccharide produced from lactose digestion that can be converted to glucose for energy.

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Disaccharides

Carbohydrates formed by two monosaccharides joining through dehydration synthesis, releasing water.

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Glycosidic Bond

A covalent bond formed between monosaccharides during disaccharide formation, can be alpha or beta type.

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Sucrose

A common disaccharide composed of glucose and fructose, used as table sugar, sweetness standard is 100.

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Reducing Sugar

Sugars that can donate electrons in a chemical reaction; sucrose is not a reducing sugar due to its structure.

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Ketoacidosis

A condition caused by the accumulation of ketones in the blood due to fat breakdown.

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Cardiac Muscle Energy

Cardiac muscles rely on glycogen as a primary energy source, especially in emergencies.

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CNS Glucose Dependence

The Central Nervous System requires glucose from blood and has no storage for it.

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Carbohydrate Classification

Carbohydrates are classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides based on molecule size.

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Monosaccharides

The simplest forms of sugar, consisting of single sugar units like glucose and fructose.

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Glucose

The most common monosaccharide, moderately sweet and found in many fruits.

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Fructose

The sweetest monosaccharide, naturally occurring in many fruits, known as fruit sugar.

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Types of Carbohydrates

Carbohydrates are divided into simple (mono, di) and complex (oligo, poly) based on structure.

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Lactose intolerance

A condition where the body cannot digest lactose, causing diarrhea.

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Maltose

A sugar formed from two glucose units, present in malted cereals.

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Oligosaccharides

Carbohydrates with 3 to 10 monosaccharides, not digested fully in the stomach.

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Polysaccharides

Large carbohydrates made of more than 10 monosaccharides, like starch and fiber.

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Starch

A major polysaccharide found in many staple foods, serving as energy storage.

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Amylose

A type of starch with a straight chain of glucose units, linked by α 1-4 bonds.

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Amylopectin

A branched form of starch with glucose units linked by α 1-4 and α 1-6 bonds.

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Maltodextrin

Intermediate product of starch degradation, between sugar and starch.

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Cellulose

Main component of plant cell walls, indigestible in humans, affects stool bulk.

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Hemicellulose

Heterogeneous polysaccharides, less rigid and soluble than cellulose, with branched structures.

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Pectin

Polymers of D-galacturonic acid, forms gels, mainly from fruits like apples.

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Lignin

A polymer of modified phenylpropane, found in woody plants, offers rigidity.

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Dietary Fiber

Indigestible portion of the diet, resistant to human enzymes, includes cellulose & lignin.

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Function of Dietary Fiber

Helps in stool bulking, retains water and increases solid excretion.

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Sources of Dietary Fiber

Found in plants like veggies, cereals, and bran, includes cellulose and hemicellulose.

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Study Notes

Fruit Jam Production

  • Fruit jams are a popular food item made from pineapple, strawberries, papaya, and other fruits.
  • Fruit jams are consumed with bread during breakfast, lunch, and snacks.
  • Jam production is a preservation method for fruits. Other methods include pickling and canning.
  • Jams are categorized as intermediate moisture foods (IMFs) containing 15-30% moisture.
  • Stability of IMFs is high without refrigeration.
  • Preservation of IMFs is achieved through a reduction in water activity (aw).
  • Gel formation in jams is enabled by pectin, a naturally occurring substance in fruit.
  • Sugar and acid content in fruit also impact gel formation.

Jam Preparation Methodology

  • Pineapple is used as the fruit for jam preparation.
  • Outer skin and core are removed from the pineapple.
  • The washed pineapple is chopped into 1 cm pieces.
  • Pineapple pulp is created using a blender, aided by distilled water.
  • Pineapple pulp is divided into 4 portions for various treatments.
  • Table 1.1 details the different treatments and their ingredient quantities (pineapple pulp, water, sugar, pectin, citric acid).
  • Fruit pulp is boiled in the pot until the fruit tissues soften.
  • Pectin and sugar, in quantities as shown in Table 1.1, are added to the boiling fruit pulp mix while stirring.
  • The mixture is heated until it reaches a total soluble solid content of 60° Brix.
  • Citric acid, per Table 1.1, is added to the mixture, mixed well, and the pH is checked.
  • The mixture is poured into cans, sealed, and stored at room temperature.
  • Color, texture, and aroma are analyzed after one week.

Oven Drying Methodology

  • Bananas are peeled and sliced into 3 mm thick pieces.
  • A total of 16 slices are prepared and split into two groups of 8.
  • Banana slices are placed on separate trays.
  • The first group is placed in an oven and dried overnight at 60°C.
  • The second group is dried overnight at 100°C in a separate oven.
  • In the morning, properties (color, hardness, appearance, and aroma) of the dried slices are assessed.

Freeze Drying Methodology

  • Three groups (A, B, and C) of potatoes are prepared for the study.
  • Two groups (A and B) are frozen and freeze-dried while group C is oven-dried for comparison.
  • The freeze-dried samples (group A) have been prepped and frozen.
  • Further prep of samples for Group B and C is described in detail below.
    • Potatoes are peeled, washed, and cleaned.
    • Potatoes are cut into 0.5cm x 2cm x 3 cm pieces.
    • Potatoes are placed on trays into the drying chamber.
    • Group A and B are freeze-dried for 24 hours.
    • Group C is oven-dried at 60°C for 24 hours.
  • Group A, B, and C samples are assessed for moisture content, appearance, color, (and possibly texture, and aroma, if relevant information is available).

Spray Drying Methodology

  • Milk is the substance used in the spray drying process.
  • The spray dryer's components (atomizer, peristaltic pump, blower, cyclone, drying chamber) are described and shown.
  • Spray drying parameters (pump speed, inlet temperature, air flow rate, compressor pressure) can be controlled using different components.
  • Detailed procedures on how to operate a spray dryer are provided, including setting temperatures (180°C is a key parameter), adjusting air flow rate, controlling pump speed, initiating compressor, and observing water droplet evaporation inside the drying chamber.
  • Milk powder is a product obtained through the spray drying of milk.
  • The milk powder is collected in a collection bottle and a cyclone.
  • The production percentage of milk powder is calculated based on the weight of milk powder collected from both the bottle and cyclone divided by the weight of the initial liquid milk.
  • The moisture content of the milk powder is determined from both the cyclone and the collection bottle separately.

High Acid Food Canning Methodology

  • Papaya is selected as the food item.
  • The outer skin and core of the papaya are removed.
  • Papaya is cut into 1 cm slices.
  • Two groups of 350g papaya slices each are prepared.
  • Two sterilized containers are used.
  • Papaya slices are blanched in hot water for 2 minutes before draining the excessive water.
  • Syrup solutions (30% sucrose, pH 3.5, and 5% calcium chloride at 50°C) are poured into each sterilized container, with a 1 cm headspace left on top.
  • The containers are exhausted in boiling water (85°C) for 10 minutes and then heated in a retort at 100°C for 15 minutes, with a 10-15 minute cooling process using running water.
  • The contents' color, firmness, and aroma are evaluated for quality after opening.
  • A visual diagram (Figure 6.1) of the retort heating system is included.

Anti-oxidants for Food Preservation

  • To observe the effect of using antioxidants on the occurrence of rancidity, sliced bananas are used.
  • The bananas are divided into 2 groups.
  • One group is fried without BHA, and the other is fried with BHA.
  • The fried bananas from both groups are stored at room temperature for three weeks.
  • The fried bananas are assessed for attributes (color, rancidity, aroma).
  • The effect of BHA on the product's shelf life is considered.

Anti-Browning

  • Apples are prepared by peeling and slicing them into small pieces.
  • Two groups are created (1 and 2).
  • The first group is blanched in boiling water for 3 minutes.
  • The second group is not blanched.
  • Apples from both groups are then blended.
  • Color and aroma are assessed for both groups after 30 minutes at room temperature.

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Related Documents

Food Preservation Laboratory 1 - Fruit Jam PDF
Basic Food Science and Nutrition PDF
Basic Food Science And Nutrition: Carbohydrate PDF

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