Food Preservation Laboratory 1 - Fruit Jam PDF

LABORATORY 1 FRUIT JAM Introduction : Fruit jams are a popular food product among consumers. It is commonly produced from pineapple, strawberry, papaya and other fruits. Fruit jams are usually consumed with bread during breakfast, morning and evening...

LABORATORY 1 FRUIT JAM Introduction : Fruit jams are a popular food product among consumers. It is commonly produced from pineapple, strawberry, papaya and other fruits. Fruit jams are usually consumed with bread during breakfast, morning and evening tea breaks. In addition, fruit jams are also used in other products such as pastry products. Production of jam gives another alternative for the preservation of fruits apart from methods such as pickling, canning and others. Fruit jam is categorized as an intermediate moisture food (IMF). IMFs contain a significant amount of moisture (15 - 30%). However, IMFs are stable without refrigeration for a moderately long period of time. The preservation approach in IMFs is through the reduction of water activity (aw). Producing jams depends on the existence of pectin that enables gel formation. Pectin exists naturally in fruits but at varying quantities. Gel formation in jams also depends on the presence of sugar and acid. Objective : i. To conduct the steps in preparing fruit jams. ii. To observe the function of each ingredient used in preparing fruit jams. Methodology : 1. Pineapple will be used in making fruit jam. Remove the outer skin and core of the fruits. Wash the fruits using chlorinated tap water. 2. Cut the washed pineapple into small pieces approximately 1 cm in dimension. 3. Pulp the pineapple pieces using a blender while adding some distilled water to ease the process. 4. Divide the pineapple pulp into 4 portions to be used for the following treatments (Table 1.1) : Table 1.1: Pineapple jam formulation for different treatments. 1  Content Pineapple Water Sugar (g) Pectin (g) 50% citric acid pulp (g) (ml) (ml) Treatment 1. Control 250 80 375 3.125 4.4 2. Without sugar 250 80 0 3.125 4.4 3. Without acid 250 80 375 3.125 0 4. Without pectin 250 80 375 0 4.4 4. For each of the 4 treatments, place the fruit pulp in a pot, add 80 ml of distilled water and heat until it boils to soften the fruit tissues. 5. Mix pectin (grade 150) and sugar in the amounts as described in Table 1.1 for each treatment. Pour the pectin-sugar mix gradually into the boiling fruit pulp mixture while continuously stirring. 6. Heat the mixture until a total soluble solid content of 60 o Brix is achieved. Immediately, add citric acid in amounts as described in Table 1.1 for each treatment and mix thoroughly. 7. Take a small amount of the mixture and determine the pH. 8. Pour the mixture into a can, put on the lid, and seam it. After seaming, store all canned jams at room temperature in the laboratory. 9. In the following week, open each canned jam and analyze the color, texture and aroma. 2  REPORT SHEET LABORATORY 1 FRUIT JAM Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the jams from different treatments in the table below: Attribute Color Firmness Viscousness Aroma Treatment 1. Control 2. Without sugar 3. Without acid 4. Without pectin Discussion : 1. Why is it necessary to add sugar during jam making? 3 2. Why is it necessary to add acid during jam making? 3. Why is it necessary to add pectin during jam making? Conclusion : 4  LABORATORY 2 OVEN DRYING Introduction : Drying is one of the oldest methods of preservation. Drying involves the reduction of moisture from the food system. There are several types of drying methodology used for food products such as oven drying, freeze drying and spray drying. Each of the drying process is based on a different principle. Oven drying involves the supply of heat to the product using air as the heating medium. Elevated temperature induces water to evaporate, leaving the food system. Reduction of moisture from the food will result in decreased moisture availability for the growth of microorganisms, enzyme activity and chemical reactions. Drying temperature directly will affect the transfer of heat to the product and thus will affect the rate of evaporation. Many food components are affected by high temperature. Using oven drying will expose the food components to high temperature thus causing changes in its physico-chemical and sensorial properties. Objective : i. To conduct a drying process for the drying of banana slices. ii. To observe the effects of drying temperature on the properties of dried banana slices. Methodology : 1. Peel and slice the bananas 3 mm in thickness. Prepare 16 slices. 2. Divide the 16 banana slices into two groups of 8 slices each. 3. Place each group of banana slices on two separate trays. 4.. Place the 1st group of banana slices in an oven and dry it overnight at 60oC. 5. Place the 2nd group of banana slices in another oven and dry it overnight at 100oC. 6. In the following morning, take out the banana slices and evaluate its properties. 5  REPORT SHEET LABORATORY 2 OVEN DRYING Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the banana slices from different treatments in the table below: Attribute Color Hardness Appearance Aroma Treatment 1. Oven temperature : 60 oC 2. Oven temperature : 100oC Discussion : 1. How does drying preserves foods? 6 2. What is the function of supplying heat during drying? 3. What are the effects of using different temperature during drying? Conclusion : 7  LABORATORY 3 FREEZE DRYING Introduction : Apart from oven and spray drying, another widely used drying method in the food industry is freeze drying. Freeze drying involves the expulsion of moisture from the food system through sublimation, where water in a solid phase (ice) directly changes to a gaseous phase (water vapor) without going through the liquid phase. Food products that are dried using freeze drying are not exposed to high heat as experienced in oven and spray drying. The low temperature drying of freeze drying will reduce the loss of volatile compounds such as aromatic compounds from the food system. In order to enable the sublimation process to occur, food products to be freeze dried have to be frozen and subsequently exposed to very low pressure. The low pressure applied has to be below the triple point pressure for the sublimation to occur. Heat has to be applied to evaporate the moisture. The efficiency of the drying process depends on the rate of heat supplied to the product. Objective : i. To observe the components and conduct operation of a freeze-drier. ii. To observe the properties of a freeze dried product. Methodology : 1. In this laboratory, we will dry 3 groups of sample (A, B and C) from potatoes. Group A and B will be freeze dried, while group C will be oven dried for the purpose of comparison. 2. Group A is frozen potatoes while group B and C is unfrozen potatoes. 3. Group A has been prepared and frozen for 24 hrs by the laboratory assistants. You need to prepare samples for group B and C. 8 4. Peel, wash and clean the potatoes. Cut the potatoes into 6 pieces with dimensions of 0.5 cm x 2 cm x 3 cm. Divide the 6 pieces into 2 groups, each consisting of 3 pieces. Designate the 2 groups as B and C. 5. Place group A and B on pans and into the drying chamber of the freeze dryer. 6. You will be given an explanation on the components and functions of the freeze drier. 7. Start the freeze drier and freeze dry groups A and B for 24 hrs. 8. Place samples from group C on pans and dry in an oven at 60oC for 24 hrs. 9. After drying for 24 hrs, take out all samples from groups A, B and C. 10. Compare the samples from all the groups. Determine the moisture content, appearance and color of samples from each group. 9  REPORT SHEET LABORATORY 3 FREEZE DRYING Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the dried potatoes from different treatments in the table below: Attribute Moisture Appearance Color content (%) Treatment A. Frozen and freeze-dried B. Unfrozen and freeze-dried C. Oven dried Discussion : 1. How is drying by freeze-drying possible at room temperature? 10 2. Give two advantages of freeze drying compared to oven drying? 3. Give two disadvantages of freeze drying compared to oven drying? Conclusion : 11  LABORATORY 4 SPRAY DRYING Introduction : Drying is a process commonly used in food preservation. In general, food systems which contain a lower level of water activity have a longer shelf life. The preservation effect of drying is due to the reduction of moisture in the food system. Drying of food can be done using several methods which include oven drying, osmotic drying, freeze drying and spray drying. Spray drying involves the spraying of the food to be dried in the form of tiny droplets by the atomizer and subsequently exposing the droplets to hot air in the drying chamber. Exposure of the tiny droplets to hot air will result in flash evaporation of moisture due to the high temperature used, thus producing a dried product in small particles. The dried small particles will be carried by the hot air from the drying chamber into the cyclone. In the cyclone, dried particles will be separated from the hot air by the centrifugal force produced by the swirling action and collected in the collection bottle. As spray drying requires a large initial capital, it is commonly used to produce high value products in powder form. Objective : i. To observe the functions of a spray dryer’s components. ii. To conduct a drying process using a spray dryer. Methodology : I. Components of a spray dryer. 1. You will be shown the basic components of a spray drier (Figure 4.1). 2. You will also be shown how drying parameters can be controlled during the drying process using the different components. 12  Figure 4.1: Lab scale spray dryer 3. Drying parameters that will be shown are pump speed, inlet temperature, air flow rate and compressor pressure. II. Drying operations of a spray dryer. 1. You will be shown how to operate a spray dryer (Model SD-05, Labplant Inc., UK). You will spray dry milk in liquid form to produce milk powder. 2. Place the feeding tube in a container of water and start the operations of the spray dryer. 3. A general operating procedure is as follows: i. Set the inlet temperature to 180OC. ii. Turn on the blower and heater to achieve the set temperature. iii. Set the air flow rate to a scale of 31 (approximately 53.7 m3/hr). iv. When the heater temperature has reached approximately 150oC, turn on the pump. v. Set the pump speed to a scale of 6 (approximately 335 ml/hr). vi. When the sample nears the atomizer, turn on the compressor. Set the compressor to maximum pressure. 13 4. Observe the spraying of water in the drying chamber. Water droplets should be evaporated in the drying chamber. Inadequate drying may be seen as water droplets at the walls of the drying chamber or the cyclone. 5. If the operation of the spray dryer is satisfactory, remove the feeding tube from the container of water and place it into the container containing milk. 6. Observe the drying process of the milk in the drying chamber and the separation of the dried particles in the cyclone. 7. Record the parameters used during the spray drying including outlet temperature. 8. After completion of the spray drying, remove the feeding tube from the container of milk into the container containing water and shut down the spray dryer. 9. Shutting down operation of the spray dryer is as follows: i. Turn off the heater ii. When the heater reached 100OC, turn off the blower and the compressor. iii. Lastly, turn off the pump. 10. After spray drying, collect the milk powder from the collection bottle and cyclone separately. 11. Weigh the milk powder and calculate the production percentage as follows: Production, % (w/w) = (Weight of milk powder from collection bottle + collected milk powder from cyclone/Weight of liquid milk) x 100% 12. Determine the moisture content of the milk powder from the cyclone and collection bottle separately. % Production = (Weight of powder from collection bottle + weight of powder from cyclone)(100) (Weight of liquid milk) 14  REPORT SHEET LABORATORY 4 SPRAY DRYING Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Draw a schematic diagram of a spray dryer. Label the basic components of the spray dryer. 15 2. Weigh and record the weight of milk powder from the collection bottle and cyclone in the table below: Spray Dryer Part Weight (g) Cyclone Collection bottle 3. Calculate the production (%) of milk powder. 4. Determine and record the moisture content (M.C: %) of milk powder from the cyclone and collection bottle in the table below: Spray Dryer Part Moisture content (%) Cyclone Collection bottle 16 Discussion : 1. What is the function of each of the spray dryer components in the table below? Spray Dryer Part Function Atomizer Peristaltic pump Blower Cyclone Drying chamber 2. Why is the moisture content of the milk powder from the cyclone and collection bottle different? Conclusion : 17  LABORATORY 5 FREEZING OF FOODS Introduction : Freezing is a method of food preservation based on low temperature. It involves lowering of the temperature to below the freezing point of water in the food system. Thus, it results in the formation of ice crystals in the microstructure of the frozen food. Freezing has been widely used in preserving raw and processed foods. In Malaysia, the use of freezing as a method of food preservation has gained popularity with the increased number of supermarkets and hypermarkets. This is compounded by the changing food habits of Malaysians. The freezing process involves several phenomena which, if not controlled, will result in a negative effect on the quality of the frozen food. One of the phenomena is freezer burn. Freezerburn is the drying of the product’s surface due to the loss of surface moisture to its surrounding. Blanching is a common pre-treatment before freezing to deactivate enzymes that will produce undesirable taste and aroma during freezing. Thus, freezing of foods need to be controlled to optimize the quality of the product. Objective : i. To observe the effect of blanching on frozen food. ii. To observe the effect of packaging on frozen food. Methodology : I. Effect of blanching on the quality of frozen food. 1. Clean and wash the snap beans provided. 2. Cut the snap beans into pieces of 2 cm in length. 3. Divide the cut snap beans into 2 portions. 18 4. Place the 1st portion of the snap beans into a plastic bag and seal the bag using a manual electric sealer. 5. Blanch the 2nd portion of the snap beans by immersing the beans in boiling water for 2 minutes followed by another 2 minutes of draining. 6. Place the blanched snap beans into a plastic bag and seal the bag using a manual electric sealer. 7. Store both bags of snap beans in a freezer at -18OC for 1 week. 8. The following week, remove the snap beans from the freezer and let it thaw at room temperature. 9. Analyze the snap beans from the aspects of appearance, color, odor and firmness. II. Effect of packaging on the quality of frozen food. 1. Prepare two groups of snap beans as in Part 1 above. 2. Blanch both groups of snap beans. 3. Place the 1st group of snap beans into a plastic bag and seal the bag using a manual electric sealer. 4. Place the 2nd group of snap beans on a tray without any covering or packaging. 5. Store both group of snap beans in a freezer at -18OC for 1 week. 6. The following week, remove the snap beans from the freezer and let it thaw at room temperature. 7. Analyze the snap beans from the aspects of appearance, color, odor and firmness. 19  REPORT SHEET LABORATORY 5 FREEZING OF FOODS Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the snap beans from different treatments in the table below: Attribute Color Firmness Appearance Odor Treatment Part I 1. Unblanched snap beans. 2. Blanched snap beans. Part II 3. Unpackaged snap beans. 4. Packaged snap Beans. Discussion : 1. Why is blanching an important step in the freezing of vegetables? 20 2. Why is packaging important for the freezing of foods? Conclusion : 21  LABORATORY 6 CANNING OF HIGH ACID FOODS Introduction : Canning is one of the most widely used food preservation method. Canning is considered to be a practical and convenient method of preserving foods. Procedures involved during canning depend on the acidity of the food. In general, foods can be categorized into high and low acid foods. High acid foods are foods that have a pH value of less than 4.6, while, low acid foods are foods that have a pH of more than 4.6. Food systems with a water activity (aw) higher than 0.85 and pH less than 4.6 is not suitable for the growth of pathogenic micro-organisms that can ill-affect the health of consumers. However, pathogenic micro-organisms can grow and multiply in food systems with a water activity higher than 0.85 and a pH higher than 4.6. Thus, foods with water activity (aw) higher than 0.85 and pH less than 4.6 are categorized as low-risk foods. Foods with water activity (aw) higher than 0.85 and pH higher than 4.6 are categorized as high-risk foods. Canning of low-risk foods does not involve an extreme heat treatment step. Usually, a temperature of between 85OC to 100OC is adequate. Objective : i. To conduct the general steps in canning of high acid foods. ii. To observe the function of the steps involved in canning of high acid foods. Methodology : I. Preparation of syrup: 1. Two solutions of syrup need to be prepared as follows: a. Sucrose solution at 30% (w/v) - After the sucrose solution has been prepared, adjust the pH to 3.5 using citric acid. 22  b. Sucrose solution at 30% (w/v) with calcium - After the sucrose solution has been prepared, adjust the pH to 3.5 using citric acid and add 5% calcium chloride at 50OC. II. Canning of papaya: 1. Papaya will be used as samples for canning. Remove the outer skin and core of the fruits. Wash the fruits using chlorinated water. 2. Cut the papaya into 1 cm slices. Weigh 350 g of the papaya slices and divide into 2 groups. 3. Prepare 2 sterilized cans. 4. Blanch both groups of papaya slices by immersing them in boiling water for 2 minutes and afterwards drain the excessive water. 5. Place both groups of blanched papaya slices separately into the sterilized cans. 6. Pour the syrup solution into the cans, each can with a different syrup solution. Leave a headspace of 1 cm. 7. Exhaust the filled cans by placing them in boiling water for 10 minutes to achieve approximately 85OC in the can. Stir slowly the contents of the cans during exhausting. 8. Seal the cans and place them in the retort (Figure 6.1) to be heated for 15 minutes at 100OC. Then, cool the cans by placing them under running water. 9. Open each can and analyze the color, firmness and odor of the contents. Figure 6.1: Retort heating system 23  REPORT SHEET LABORATORY 6 CANNING OF HIGH ACID FOODS Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the canned papaya from different treatments in the table below: Attribute Color Firmness Odor Treatment 1. Without Ca2+ 2. With Ca2+ Discussion : 1. Why is it necessary to add Ca2+ into the syrup used for canning? 24 2. What is it necessary to exhaust the cans before seaming? 3. Why is it necessary to leave a headspace of 1 cm in the can? Conclusion : 25  LABORATORY 7 FOOD PACKAGING Introduction : Food packaging is an important step in the production of food. Packaging of foods is meant to protect foods from factors that may affect its safety or quality. Factors affecting the safety or quality of foods that may be protected by packaging include relative humidity, ultra-violet rays, oxygen and contaminants from the environment. Apart from protecting and preserving foods, packaging also plays an important role in several other aspects such as consumer education, providing convenience to the consumer and during handling, marketing and branding. With the numerous functions of food packages, compounded by the uniqueness of each food system, there is no one packaging machine that will suit all type of food products. Currently, there are numerous packaging materials and machines that may be utilized to suit the needs and demands of each food system and producer. Among the most commonly used packaging machines in the food industry is the form- fill-seal machine, the container sealing machine and the cup sealing machine. The form-fill-seal packaging machine is most suitable for dry, flowable products such as spices, flour, rice, extruded products and tapioca chips. Container and cup sealing machines are used to seal food products placed in a container or cup package. These types of packages are suitable to most types of food products whether dry or containing high moisture. Examples of products commonly packaged in container or cup packages are snacks, jellies, drinks and yogurts. Objective : i. To observe the operations of a form-fill-seal packaging machine. ii. To observe the operations of a container and cup sealing machine. 26 Methodology : I. Form-fill-seal packaging machine. 1. Place the packaging film in the appropriate manner into the machine as stated in the machine’s manual. 2. Turn ON the power and choose auto. The power indicator light will lit up. 3. Set the sealing temperatures for the horizontal and vertical sealer first at 80, then 140 and lastly 180oC. 4. Turn on the main motor and the machine will start to operate. Compare the strength and quality of the seals on the package between the 3 sealing temperatures. 5. Rate the strength and quality of the seals according to the category (refer to the report sheet). (A) Figure 7.1: Form-fill-seal packaging machine. II. Container and cup sealing machine. 1. Place the packaging film in the appropriate manner into the machine as stated in the machine’s manual. 2. Turn ON the power and choose auto. The power indicator light will lit up. 27 3. Set the temperature of the sealer at 160-170OC. Wait until the indicator light turns off indicating that the set temperature has been attained. 4. Pour juice into the cup until ¾ has been filled. 5. Turn on the main motor and observe the operations of the machine. (A) (B) Figure 7.2: Types of food packaging machines: (A) Container sealing machine and (B) cup sealing machine. 28  REPORT SHEET LABORATORY 7 FOOD PACKAGING Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Record your observation of the packaging seal from the form-fill-seal machine in the table below: 1- Weak 2- Moderate 3- Strong Sealing Temperature 80OC 140OC 180OC Attribute Strength of vertical sealing Strength of horizontal sealing Seal wrinkles Overall acceptance 29 Discussion : 1. Why is it necessary to have the right temperature for sealing? 2. What are the factors that affect the sealing temperature? 3. Describe the process sequence during packaging using the form-fill-seal machine. 30 Conclusion : 31  LABORATORY 8 ANTIOXIDANTS Introduction : Oxidation is one of the most common chemical reactions that occurred in food products that will lower its quality. Oxidation will cause rancidity resulting in the formation of an undesirable aroma and taste. Even though rancidity is not a health hazard, it causes an undesirable eating experience. Oxidation most commonly occur in food systems that contain oil or food products such as ‘kerepek’ and biscuits. Antioxidants are a group of compounds that, when added to foods, is capable of reducing oxidation and the onset of rancidity. There are natural and synthetic antioxidants. Natural antioxidants can be found in fruits and vegetables such as ascorbic acid and phenolic compounds. Examples of common synthetic antioxidants are butylated hydroxytoluene (BHA) and butylated hydroxy toluene (BHT). Commonly, synthetic antioxidants were used during food processes as natural antioxidants are expensive to use and may not be economically viable in the long run. Objective : i. To observe the effect of using antioxidants on the occurred of rancidity. Methodology : 1. Peel and slice bananas 3 mm in thickness. Prepare 16 slices. 2. Divide the 16 banana slices into two groups of eight slices each. 3. Prepare two fryers for frying by putting in 1 liter of cooking oil into the fryers. 4. Add 200 mg/kg of BHA into the oil of one of the fryer and mix thoroughly. 5. Heat the oil of both fryers to a temperature of 170oC. 6. When the oil temperature has reached 170oC, fry the banana slices from the 1st group in the oil without BHA for 5 mins. 32 7. Fry the banana slices from the 2nd group in the oil mixed with BHA for 5mins. 8. Place the fried banana slices in two separate microwave plastic containers and store at room temperature. 9. After 3 weeks, evaluate the fried banana slices. 33  REPORT SHEET LABORATORY 8 ANTIOXIDANTS Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the fried banana slices from different treatments in the table below: Attribute Color Rancidity Aroma Treatment 1. Fried without BHA 2. Fried with BHA Discussion : 1. What is the mechanism of action of BHA? 34 2. What is the effect of using BHA with regards to rancidity? 3. Based on your results, what is the benefit of using BHA with regards to product shelf-life? Conclusion : 35  LABORATORY 9 ANTI-BROWNING Introduction : Browning is a common phenomenon in food systems. Certain browning reactions are desirable. Through browning reactions, flavor and color can be produced. However, there are browning reactions that are undesirable where undesirable color and tastes are produced. There are 4 types of browning reaction but only one is enzymatic. The non-enzymatic browning reactions are carameliztion, Maillard reaction and oxidation of ascorbic acid. Enzymatic browning occurred when the polyphenol oxidase enzyme (PPO) oxidizes phenolic compounds to produce a brown pigment. Examples of the enzymatic browning are the change in color of cut banana or apples from white or light to brown. Even though the brown pigment produced during browning is not hazardous, it negatively affects consumer acceptance. As PPO is responsible for the browning reaction, deactivation of PPO is the most common approach taken to reduce enzymatic browning. Currently, there are several anti-browning agents commercially available such as citric acid and sulphite. As PPO is heat labile, it can also be inactivated by using heat. Objective : i. To observe the effect of using heat to reduce browning reaction. Methodology : 1. Peel the skin of an apple, wash and cut into 8 pieces. 2. Divide the 8 pieces of apple into 2 groups consisting of 4 pieces each. 3. For the 1st group, blanch in 1liter of boiling water for 3 mins. 4. Blend both the 1st and 2nd group of apples separately. 5. Observe the color of the apple blend at room temperature for 30 mins. 36  REPORT SHEET LABORATORY 9 ANTI-BROWNING Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write your evaluation of the apple blend from different treatments in the table below: Attribute Color Aroma Treatment 1. Blend after blanching 2. Blend without blanching Discussion : 1. Name the two categories of browning reaction in food? 37 2. Why does enzymatic browning occurs only when an apple is cut? 3. How does blanching affects browning reaction? Conclusion : 38  LABORATORY 10 ANTI-MICROBIAL Introduction : Microbes are the number one threat to food safety and quality. Thus, in food preservation, extra attention is given in ensuring that the microorganism is not a threat to food safety. Using anti- microbial agents is one way of eliminating or reducing the microbial threat. There are many anti- microbial agents being used in the food industry. Among them are propionic acid, benzoic acid, sulphuric acid and citric acid. The use of anti-microbial agents as food additives is controlled under the Food Act and Regulation 1983. The act dictates the type and maximum allowable level of anti- microbial agents that can be used in different food products. Under the Food Act and Regulation 1983, anti-microbial agents may fall under the definition of food preservatives which is defined as any substance that, when added to food, is capable of inhibiting, retarding or arresting the process of decomposition, fermentation or acidification of such food but shall not include herb, spice, vinegar or wood smoke. Objective : i. To observe the effect of using anti-microbial agent on the growth of mold in bread. 39 Methodology : 1. Prepare ingredients to bake two loaves of bread as in the table below: Amount Ingredient Bread 1 Bread 2 1. Wheat flour (g) 400 400 2. Propionic acid (g) Nil 1 3. Yeast (g) 6 6 4. Sugar (g) 24 24 5. Salt (g) 6 6 6. Water (g) 252 252 2. Place all ingredients in the bread maker and the start the bread making process. 3. After the loaves of bread are baked, let them cool to room temperature in the bread maker. 4. Subsequently, place the bread loaves in separate plastic packages and close it using adhesive tape. 5. Store the bread loaves at room temperature. Check the bread loaves closely and determine the number of days before each bread loaf starts to mold. 40  REPORT SHEET LABORATORY 10 ANTI-MICROBIAL Name : _____________________________________ Matric No.: _______________ Date : _____________________________________ Group : _______________ Demonstrator : _____________________________________ Results : 1. Write the number of days before each bread loaf starts to mold in the table below: Loaf Number of days Bread 1 (without propionic acid) Bread 2 (with propionic acid) Discussion : 1. What is the purpose of adding propionic acid to the bread that you have baked? 41 2. What is the maximum allowable level of propionic acid in the bread as stated in the Food Act and Regulation 1983? 3. What is the maximum allowable level of benzoic acid in chilli slurry and curry paste as stated in the Food Act and Regulation 1983? Conclusion : 42  REFERENCES 1. Brennan, J.G., J.R. Butters, N.D. Cowell & A.W. 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Food Preservation Techniques. CRC Press, New York. 43