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Kerala Veterinary and Animal Sciences University, Wayanad
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ThesisItem Open Access EFFECT OF NISIN ON THE KEEPING QUALITY OF Dahi(COLLEGE OF VETERINARY AND ANIMAL SCIENCES Mannuthy - Thrissur, 1992-09-28) SREEJA RAMACHANDRAN; Prasad, V.An experiment was conducted to find out the effect of preservatives such as nisin and potassium sorbate on the keeping quality of dahi. An attempt was also made to study the quality of dahi produced under household conditions with a special emphasis on the maintenance of starter. An exhaustive review of literature has been presented on the use of various preservatives in dahi, keeping quality and other related aspects. The methods of analysis of some important components of dahi has been detailed. Dahi was prepared under laboratory conditions (Method I) and under household conditions (Method II). Both were divided into four parts and applied four treatments namely (1) Treatment A - with 1000 lU nisin/i^ g curd (2) Treatment B - with 10 ml of nisin producing organism capable of producing 1000 lU of nisin/100 g curd (3) Treatment C with 0.2 per cent potassium sorbate (4) Treatment D - Dahi stored as such without any treatments. All treatments were compared with dahi at 0 hour (control). The dahi after treatments A, B, C and D from methods I and II were mixed well and transferred to 100 ml cups and stored at room temperature. Samples from each treatment were subjected to chemical, microbiological and organoleptic evaluation on the 2nd, 3rd, 4th, 7th, 10th and 21st day of storage for acidity, pH, lipolysis, proteolysis, diacetyl, total lactic count, coliform count and yeast and mould count. There was a decrease in acidity for all treatments from the initial level under method I. Whereas acidity was maintained to the initial level under method II. There was only a slight change in pH during different periods of storage for all the treatments under both methods. Proteolysis of dahi remained to the initial level upto 24 hours then increased gradually under both methods. Tyrosine value was higher under household conditions which could be due to the presence of proteolytic bacteria other than starter organisms that have gained entry into dahi through starter culture. An abrupt reduction in diacetyl contents was noticed in dahi during storage. This could be due to the reduction of diacetyl by the enzyme diacetyl reductase produced by certain streptococci. With regard to the free fatty acid content treatments A, B and C were effective in controlling the breakdown of fat during storage. Addition of nisin did not alter the total lactic count and it was maintained to initial level even after storage for 4 days. Nisin producing organisms multiplied during storage. In potassium sorbate added dahi a reduction in lactic count was noticed probably due to depletion of nutrients rather than the direct effect. Growth and multiplication of yeast, mould and coliforms were controlled in both methods by nisin or nisin producing organisms in dahi. Potassium sorbate completely eliminated yeast and mould and coliform growth in dahi but it reduced flavour score during sensory evaluation. Sli., From the above findings it was concluded that the lowacidity produced on storage might be due to the fact that the lactic acid bacteria added were low acid producers. There was a reduction in flavour score for potassium sorbate added dahi but at the same time it was found to suppress the yeast and mould growth completely. Hence it is recommended that potassium sorbate preferably at a reduced level of 0.1 per cent along with nisin producing organisms can keep up the quality of dahi under room temperature. Also it is advisable to change the culture at least once a week to get good quality dahi with characteristic diacetyl flavour under household conditions.ThesisItem Open Access EFFECT OF FEEDING ADDITIVES ON TOTAL SOLIDS OF COWS' MILK(COLLEGE OF VETERINARY AND ANIMAL SCIENCES Mannuthy - Thrissur, 1992-08-31) SATHIAN, C. T; FRANCIS, U.TThesisItem Open Access UTILISATION OF SKIM MILK FILLED WITH COCONUT MILK FOR PREPARATION OF INDIGENOUS DAIRY PRODUCTS(COLLEGE OF VETERINARY AND ANIMAL SCIENCES Mannuthy - Trichur, 1992-08-14) MINI JOSE; Mukundan, MA detailed study was carried out to determine the quality of coconut fat filled milk for the preparation of indigenous milk products such as paneer, rasogolla and whey drinks. A modified version of Precision Penetrometer to measure the springiness of rasegolla was designed, fabricated and used in the present study. An exhaustive review of literature has been presented on the use of vegetable fat for substitution of milk fat for preparation of various dairy products apart from preparation ana other related aspects of paneer, rasogolla and whey drinks. The methods of chemical analysis and sensory evaluation of these products have been detailed. The control samples of paneer, rasogolla and whey drinks were prepared using cows' milk while experimental sanples were prepared using skim milk filled with coconut fat. The milks were standardized to four per cent fat. The moisture, fat and acidity were found to be similar in control paneer and experimental paneer. The control oareer was found to have higher yield but low protein content when compareci to experimental paneer. On sensoryevaluation, control paneer was graded as of 'excellent quality' while experimental paneer was graded as of 'good quality'. The control and experimental samples of rasogolla were found to have same springiness. Control samples of rasogolla obtained 'excellent' grade on sensory evaluation but the experimental rasogolla was graded as of 'good' quality. The difference in the quality of paneer and rasogolla was due to the natural flavour of coconut milk carried over to the products. Both control and experimental samples of rasogolla were found to have good shelf life of three days, at room temperature. Pineapple and lemon flavoured control and experimental whey drinks were found to be equally acceptable with no difference in appearance, odour, flavour and body characteristics. The chemical and sensory evaluation of paneer, rasogolla and whey drinks prepared from cows' milk and coconut fat filled milk revealed no significant difference between them .