Clinical Nutrition: Yoghurt Preparation - Research Proposal Example

Yoghurt Preparation Introduction Fermentation is an important reaction that makes fermented dairy products such as yoghurt, kefir, sour cream and cheese healthy products in our diets. Such products have been considered to have good impact on the digestive system. Use of such products has greatly been influenced by cultures around the world. Such products have been availed to people in retail stores and supermarkets in almost all the regions of the world. As Ramesh (2006) postulates, the production of fermented products has become an extremely new industrial technique. This technique has taken a substantial position in market share and consumer acceptance across the world. Yoghurt is one of the most common of fermented dairy products that has continuously been used in so many generations. This paper has comprehensively looked into the process of yoghurt production. Such experimental yoghurt however must not be expected to be similar to commercially produced yoghurt and will differ in terms of pH, taste and even color. The paper has as well looked into determining pH of the yoghurt. Yoghurt Experimental Yoghurt is a fermented milk product. Its production has a very long history that dates back to many years ago. History of this milk product has it that, the product is healthy and has extra nutritional benefits that has widely enhanced it usage. Fermented products have been associated with changes in the metabolism and equilibrium of gut flora a phenomenon which may result to desirable changes in the host (Ramesh, 2006). In addition to this, yoghurt has been found to be a source of vitamins and mineral salts. In the Persian legend, Abraham is seen to owe his longevity to continued usage of yoghurt. As Robinson (2007) observes, consumption of yoghurt played a fundamental role in healing of Emperor Fransis of France from his debilitating illness. Fermentation has been associated with improved digestibility of milk proteins. Lactose milk sugar is broken down by fermentative bacteria partially into lactic acid, this means that even lactose intolerant individuals can find yoghurt a better milk product than milk products. Milk proteins also undergo some structural changes during fermentation which enhances their digestibility. During the process of fermentation, the culture bacteria have antimicrobial activities which help in elimination of the putrefactive bacterial colonies which may be longed in the gut. In yoghurt production, a cow’s milk is preferred but goat’s milk is sometimes used. Thickening sometimes is required and is done by adding an amount of powdered milk. Bacterial culture used contains strains of Lactobacillus bulgaris (BGPKM1) and Streptococcus thermophilus (BGTMS2). The process involves first pasteurization at a temperature of 850C for 20 minutes. Normal pasteurization involves heating the milk upto a temperature of 750C for 15 seconds. Such treatment ensures that potential pathogenic microorganisms including fungal spores are killed. Such treatment also helps in coagulating the whey to help in curdling. From the pasteurization chamber, the milk is cooled to about 440C which is the fermentation temperature favourable for the fermentation cultures. The culture is introduced and may sometimes include probiotic bacteria such as Bifidobacteria spp or Lactobacillus acidophilus. Lactose in the milk is fermented into lactic acid which lowers the PH to around 4.5. This acidic pH leads to coagulation of casein into a thick gel. Bacterial action also leads to formation of by-products through fat hydrolysis which improves on the flavor of the yoghurt. The presence of polysaccharides in the yoghurt improves on its viscosity. Commercial yoghurts are available in different forms e.g. Set yoghurt contains added milk solids and is fermented top form a firm mixture called natural yoghurt. Such is availed as a low fat, full fat and green fat. Full fat contains 3.5% milk fat while green fat has 10% milk fat. Drinking yoghurt contains fewer solids and has fruit flavor additives. Stirred yoghurt is produced in large vats and has milk solids, fruit flavors and thickeners added to it. It is also available in low fat, wide fat and in variety of flavors. Experimental Objectives This experiment majorly aimed at looking into the process of yoghurt production. Students were also required to determine pH and of the produced yoghurt and the titratable acidity that is present in milk and that in fermented milk. Methodology Students were required to work in groups of 2 and together they were required to: 1. Ferment milk a) Place 150ml of UHT skimmed milk into a beaker at 450C b) Add 0.5g of yoghurt culture which has been freeze dried to the skimmed milk and stir with a spoon. The yoghurt culture contained Lactobacillus bulgaricus & Streptococcus thermophilus (delvo yog ty-17A). c) The set up was to be covered with an aluminium foil and incubated in a water bath at 440C and left for about 1hour. 2. The students were required to measure the pH and titratable acidity of the UHK milk, fermented milk and commercial yoghurt. 3. Students were also to observe consistency of milk, aroma before and after fermentation. Titratable Acidity Titratable acidity is determined by measuring the amount of alkali needed to neutralize acidity in a given food sample as will be indicated by colour change in indicator used. Phenolphthalein was used in this case. Procedure 1. The burette was filled with 0.1M NaOH. 2. 10g milk or yoghurt sample was weighed in a conical flask and onto it was added 25ml of distilled water. 3. A few drops of phenolphthalein were added into the conical flask to help in detecting the end point. 4. Titrate the NaOH in the burette against the food sample until a pink color is observed in the conical flask. 5. Calculate the volume of titre by subtracting the final burette reading from the initial reading. 6. Repeat this procedure three times to increase the accuracy of the average titre. Calculating Titratable acidity Titratable acidity % = mls NaOH x Mwt of the acid x Molarity NaOH x 100 1000 x Sample g Weight (or ml volume) x Valency Organic acids and their corresponding molecular weights and valency M.Wt Valency Acetic acid - sauces and pickles 60.05 1 Citric acid - fruit and juices 192.12 3 (Anhydrous) Lactic acid - yoghurt, sauerkraut 90.08 1 Malic acid - apples 134.09 2 Tartaric acid - grapes 150.09 2 Results Table 1. Titratable acidity Sample Sample weight (g) First burette reading (ml) Second burette reading (ml) NaOH volume (ml) Original milk Replicate 1 10 0.00 1.65 1.65 Replicate 2 10 162 3.25 1.65 Replicate 3 10 3.25 4.25 1.65 Fermented milk Replicate 1 10 23.5 30.9 7.4 Replicate 2 10 30.9 38.4 7.5 Replicate 3 10 38.4 45.45 7.1 Commercial yoghurt Replicate 1 4 4.8 11.4 6.6 Replicate 2 4 11.4 17.2 5.8 Replicate 3 4 17.2 23.1 5.9 Table 2. Titratable acidity and pH measurement Sample pH Titratable acidity TA % 1 2 3 Average UHT skim milk 6.7 0.149 0.149 0.149 0.149 Fermented milk 4.59 0.667 0.676 0.6396 0.627 Commercial yoghurt 4.32 1.49 1.31 1.33 1.38 Table 3. Consistency and Aroma assessment Sample Protein g/100g Consistency Aroma UHT skim milk 305 Fermented milk 3.5 Commercial yoghurt 5.2 Sour strong Equipment and Consumable list for Laboratory set up 1. UHT skim milk (No Name Brand) 2. 150ml x 12 x 2 (control & test) = 4 L 3. Yoghurt culture freeze dried – delvo yog ty-17A from DSM, Moorebank (DSM Lactobacillus bulgaricus and Streptococcus thermophilus) 4. Commercial “traditional” skim yoghurt – direct set e.g. (Paul’s 500 g Natural) 50g per grp x 12 = 1 kg 5. Distilled water wash bottles 1 per bench, plus at each pH meter. 6. Standardised 0.1M NaOH (50ml x 12 = 0.6 L minimum; Plus at least 1L spare. ) 7. Phenolphthalein indicator, 1 per titration set-up. (12) 8. Aluminum Foil 9. Warm water baths at 44oC – enough to fit 12 x 200 ml beakers 10. pH meters (and calibration buffers) – 4 or more 11. Balances – 4 or more 12. Titration Burettes – 12 set-ups - checked for operation 13. 200 ml Beakers – 3 per set-up (36) 14. 100 ml Beakers – 1 per set-up (12) 15. small funnels – 1 per set-up (12) 16. Conical flasks 100ml or 200ml – 3 per set-up (36) 17. Disposable Plastic pipettes for sub culturing or measuring milk 18. 10ml pipettes (TA%) – 1 box available 19. 25ml measuring cylinders – 1 per set-up (12) 20. Spoons for measuring yoghurt 21. Micro-wipes, paper towels, 22. Plastic wrap to cover beakers during fermentation. Discussion The experimental procedure has elucidated the characteristic differences between fresh milk and fermented milk. Bacterial cultures are fundamental in m ilk fermentation including yoghurt production. The results indicated difference in pH and titratable acid amounts in fresh milk, yoghurt and fermented milk. The results have shown that fermented milk contains lactic acid but commercial yoghurt has the highest amount of lactic acid. In industrial production of yoghurt, the growth of bacteria is controlled so as to avoid excessive acid which could render the milk unpalatable. The aroma of commercially produced yoghurt is strong and nice and is achieved by addition of flavors which could either be natural or artificial. Such chemical additives do not however alter the nutritional value of the milk but only enhance their characteristic value. Food colors and different flavors increased a wide variety from which consumers can choose from according to their taste and preferences. Conclusion It should be noted that there are significant differences between commercially produced yoghurt and that which is prepared in a lab. This is because commercial yoghurt is produced under highly controlled environment which is paramount in the quality of the product. It is however important to regulate the chemicals that are sometimes applied in commercial yoghurts to ensure that such do no harm the consumer. References Guerin-Danan, C, Chabanet, C, Pedone, Ch, Popot, F, Vaissade, P, Bouley, C, Szylit, O, & Andrieux, C 1998;"Milk fermented with yogurt cultures and Lactobacillus casei compared with yogurt and gelled milk: influence on intestinal microflora in healthy infants", The American Journal of Clinical Nutrition. no. 67, pp. 111–7. Ramesh, C 2006, Manufacturing yogurt and fermented milks, John Wiley & Sons, New York. Robinson, R. K 2007, "Fermented Milks: Yoghurt Types and Manufacture", Encyclopedia of Dairy Sciences, pp. 1055-1058. Robinson R. K 2007, "Fermented Milks: Yoghurt, Role of Starter Cultures", Encyclopedia of Dairy Sciences, pp. 1059-1063. Available from: ScienceDirect. Read More