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ThesisItem Open Access Immobilization of Beta Galactosidase for production of fermented milk products with low lactose(Department of Dairy Science, College of Veterinary and Animal Sciences, Mannuthy, 1996) Geetha, R; KAU; Prasad, VAn immobilized β – galactosidase enzyme system was developed using permeabilized cells of K. fragilis as an enzyme source and food grade agar as the immobilizing agent. This was utilised for hydrolysing lactose content present in milk, which in turn was used for preparing selected fermented products with low lactose content. An attempt was also made to assess the possibility of utilisation of whey as a medium for culture maintenance with a view to utilise the by – product. A detailed review of literature has been presented about β – galactosidase specific activity of different organisms, various immobilization techniques,influence of lactose hydrolysis on physico chemical properties of the product and also about the utilisation of whey as a media for culture maintenance. The experiment comprised of determination of β – galactosidase specific activity of permeabilized cells of three selected organisms and assessing the suitability of agar and sodium alginate as immobilizing agents. Since β – galactosidase specific activity was found to be the highest for K. fragilis, it was selected as the best enzyme source. Agar was selected as the suitable immobilizing agent because it was found to be safe, economical and comparatively more efficient. Using these two raw materials an efficient immobilized enzyme system was developed and its efficiency was assessed by estimating the rate of lactose hydrolysis at fixed time intervals. Selected strains of starter bacteria were screened for their performance in four different media viz. Skim milk, 50 per cent lactose hydrolysed skim milk, condensed whey, and 50 per cent lactose hydrolysed condensed whey. Two media were selected from among the four, which stimulated the starter activity and used for further studies. Three different products viz., yogurt, bifidus yogurt and acidophilus milk were prepared using 50 per cent lactose hydrolysed milk obtained by passing through the immobilized enzyme system and cultures maintained separately in lactose hydrolysed milk and lactose hydrolysed whey. Two control products were prepared with ordinary milk and above described cultures. All the three products under different treatments were analysed for acidity, pH, tyrosine value, total lactic count and sensory evaluation. The results obtained in the study were compared with similar reported findings and the following conclusions were made. 1. Permeabilized cells of K. fraglis possessed better B – galactosidase specific activity than the cells of S. thermophiles and L. delbrueckii sub sp. bulgaricus. 2. Food grade agar was found to be an efficient immobilizing agent than sodium alginate. 3. The immobilized enzyme prepared with 10 g of K. fragilis could hydrolyse 50 per cent of lactose content present in 250 ml of milk, after holding in the column for four hours at room temperature (300 C). 4. The rate of lactose hydrolysis was found to be the maximum within first half an hour, thereafter a decline in the rate of hydrolysis was observed. 5. This system was repeatedly used in five batches without any change in its efficiency or mechanical stability of the beads but after which a reduction in activity was noticed. 6. A slight brownish discolouration was observed on the beads when the column was stored for a long period. 7. Repalcement of skim milk with whey was a starter media slightly enhanced the activity of cultures, especially, S. thermophilus, L. lactis and B. bifidum whereas L. acidophilus and L. delbrueckii sub sp. bulgaricus performed better in skim milk, especially when the media was subjected to lactose hydrolysis. 8. The utilisation of lactose hydrolysed milk for preparation of products slightly enhanced the acidity, proteolytic activity and viable cell count of yogurt, bifidus yogurt and acidophilus milk. 9. In the case of treatment yogurts (Y1 and Y2) prepared with lactose hydrolysed milk, a significantly higher protolytic activity was observed. 10. Organoleptic evaluation indicated that the utilisation of lactose hydrolysed milk and cultures maintained in lactose hydrolysed skim milk and whey did not affect the flavour and textural characteristics of yogurt. On the contrary the flavour as well as body and texture scores of bifidus yogurt and acidophilus milk were slightly improved by this technique.ThesisItem Open Access Effect of different freezing rates on canine spermatozoa(Department of Animal Reproduction, College of Veterinary and Animal Sciences, Mannuthy, 2000) Geetha, R; KAU; Sreekumaran, TThe objective of the study was to find out the effect of different freezing rates on post thaw motility, livability and acrosomal damage of dog spermatozoa. A total of 36 ejaculates of good quality collected from SIX Dachshund dogs by digital manipulation were processed for freezing in Tris citric acid fructose egg yolk diluent containing four per cent glycerol. The processed semen samples were subjected to three different freezing protocols such as 4cm height above the liquid nitrogen level for 10 minutes (Fast freezing), Scm for 15 minutes (Moderate freezing) and 12cm for 20 minutes (Slow freezing). The mean volume of sperm rich fractions was 0.6S±0.03ml. The colour and consistency of sperm rich fractions were thin milky. The mean density of sperm rich fraction was DD(D) and mean pH was 6.63±O.02. The mean concentration of sperm rich fraction was 221±7.36 millions per ml and the average initial motility was found to be 75±O.93 per cent. The mean percentage of live sperm count, sperm abnormalities and acrosomal damage of spermatozoa was Sl.17±O.73, 5.23±O.29 and 2.32±O.25 respectively. Significant (Pabnormalities and acrosomal damage of spermatozoa was found between dogs. The average percentage of motility, live sperm count, sperm abnormalities and acrosomal damage of spermatozoa was 70.41± 1.22, 75.63±O.65, 7.28±0.43 and 5.34±O.31 after dilution, 58.75±1.34, 63.60±O.89, 10.04±O.32 and 10.13±0.41 after chilling and 47.78±1.59, 50.65±1.31, 11.79±O.36 and 16.20±O.57 after equilibration period respectively. There was significant (Preduction in sperm motility and livability and increase in sperm abnormalities and acrosomal damage of spermatozoa after dilution, chilling and equilibration period. Significant (Pwas found between dogs for the above parameters. The percentage of post thaw motility of spermatozoa was significantly (Pwhen compared to moderate (25.83±1.66) and slow (24.44±1.27) freezing rates. There was significantly (Pof live sperms and lower percentage of sperm abnormalities in fast freezing rate than in moderate and slow freezing rates. Eventhough the percentage of acrosomal damage was not statistically ( significant among fast, moderate and slow freezing rates, lower percentage of acrosomal damage was recorded in fast freezing rate. From this study it could be inferred that fast freezing in which the straws were frozen at to 4cm height above the liquid nitrogen level for 10 minutes was superior to moderate (8cm for 15 minutes) and slow (12 cm for 20 minutes) freezing rates.