Loading...
Theses
Browse
Search Results
ThesisItem Open Access Qualitative changes of yoghurt prepared from milk preserved by different methods(Department of Dairy Science, College of Veterinary and Animal Sciences,Mannuthy, 1990) Prasad, V; KAU; Sukumaran, M VAn experiment was conducted to study the qualitative changes of yoghurt prepared from milk preserved by different methods. An attempt was also made to study the efficiency of LP system in controlling psychrotrops in refrigerated milk thereby extending the keeping quality of such stored milk. The efficacy of the system was compared with pasteurized milk and raw milk stored under similar conditions. An exhaustive review of literature has been presented on the use of various preservation methods employed in milk, quality of yoghurt and other related aspects. The methods of analyses of some important components of milk and yoghurt has been detailed. The milk after collection were divided into three portions and used for various treatments A (raw milk as such), B (laboratory pasteurized) and C )LP activated). Samples in each treatment were again divided into four parts and stored under refrigeration for 0, 24, 48 and 72 hours for further analysis and yoghurt preparation. When raw milk was stored under refrigeration, acidity developed to a significantly high level (P < 0.05) at the end of 72 hours of storage whereas no significant increase in activity was noticed in treatments B and C. This result was corroborated by a decrease in both psychrotrophic and total bacterial counts in milk under treatments B and C. So it was concluded that the development of acidity in treatment A could be due to bultiplication of microbes particularly psychrotrophs. In B and C its growth was arrested by the treatments. Hydrogen peroxide and thiocyanate were detected in all raw milk samples at a level of 3.78 and 7.33 ppm respectively. The level of H2 O2 and SCN – used for the activation of LP system for the study were found to be adequate, since the psychrotrophic count in milk at the end of 72 hours in treatment C was less than that found in treatment B. The residual H2 O2 and SCN – contents at the end of 72 hours were found to be within the normal level found in milk thus having no health hazards, by this method of preservation. When yoghurt samples were prepared from stored milk no significant differences between treatments were noticed in the values of fermentation period, acidity, pH, total proteins and total solids. A significant increase in NPN and tyrosine values were noticed in yoghurt prepared from milk under treatment A indicating extensive proteolysis in milk during storage under this treatment. However, no difference was noticed between treatments B and C. Diacetyl and acetaldehyde were produced at a desirable level in yoghurt samples under all the three treatments. A proper ratio of Str. Thermophiles – 6 and L. bulgaricus – 4 was found to be maintained in all yoghurt samples. On organoleptic evaluation the yoghurt prepared from milk under treatment C could not be distinguished from other two treatments. In fact, yoghurt under C got a higher total score on organoleptic evaluation than A and B. Low score for body and texture, and falvour was observed under treatment A. This may be attributed to the effect of growth of psychrotrophs in raw milk during refrigeration. From the results, it was concluded that good quality yoghurt can be prepared from milk stored under refrigeration following pasteurization or LP activation. Yoghurt samples prepared from milk stored under treatment A was found to be of inferior quality when compared to B and C. The result also confirmed that LP system can be recommended as a safe preservative for extending storage life of refrigerated milk. When such stored milk was used for yoghurt production, no significant difference in the quality was noticed when compared to yoghurt under treatment B. Suggesting that LP activated milk can be conveniently and economically used for the production of fermented milk products like yoghurt without any apparent harmful effect.ThesisItem Open Access Studies on the influence of tannins on nucleic acid and protein syntheses in ruminants(Faculty of Dairy and Animal Husbandry, Haryana, 1976) Sadanandan, K P; KAU; Arora, S PA study was conducted to elucidate the influence of tannins on synthesis of nucleic acids and protein in liver of rats. In vitro and in vivo studies in buffaloes were also conducted to ascertain the effect of tannins on rumen metabolism. In experiment 1, 30 weanling rats were distributed into three groups of 10 each in a randomized block design. The influence of addition of 0% (group A), 2.5% (group B) and 5% (group C) tennins in the feed on feed consumption, growth rate, nitrogen and dry matter digestibility was investigated. Further RNA, DNA and protein in liver were estimated to asses liver function. The feed consumed daily on DM basis (g); weight gain per three day interval (g); and gram feed per gram weight gain, respectively for groups A, B and C were : 20.05 + 7.6, 7.87 + 0.41, 2.73 +0.05; 16.66 + 6.0, 5.69 + 0.35, 3.14 + 0.07 and 16.11 + 5.4, 4.53 + 0.21, 3.80 + 0.11. The DM and N digestibility (%), respectively for groups A, B and C were: 78.56 + 0.44, 78.28 + 0.56; 78.62 + 0.64, 73.50 + 0.86 and 78.82 + 0.52, 69.97 +0.75. Feed consumption in group A was significantly (P <0.01) higher than in group B and C. The difference in feed consumption between groups B and C was not significant. Significant differences were found amongst all treatment groups in weight gain (P< 0.05) and food : gain ratios (P < 0.01). DH digestibility did not reveal any significant difference between groups whereas the differences in N-digestibility were significant (P<0.01). The addition of tennis in the diet significantly depressed feed consumption, weight gain, and N – digestibility which resulted in widened feed : gain ratios. The average liver weights (g): total protein (mg) ; RNA (mg) and DNA (mg), respectively for groups A, B and C were : 3.61 + 0.21, 717.3 + 4.76, 21.42 + 1.41, 5.36 + 0.41, 2.85 + 0.23, 569.0 + 4.31, 16.40 + 1.60, 4.29 + 0.45 and 2.44 + 0.01, 507.9 + 2.55, 13.79 + 0.58, 3.34 + 0.16. The liver weight in group A was significatly (P<0.05) higher than in group C. The total protein content in group A was significatly (P<0.01) higher than in group B and C. But the difference between groups B and C was not significant. RNA and DNA contents differed significantly (P<0.01) amongst the three groups. The average protein (mg), RNA (mg) and DNA (mg), respectively for the groups A, B and C were : 198.69 + 3.31, 5.93 + 0.18, 1.48 + 0.05, 199.89 + 5.14, 5.68 + 0.16, 1.49 + 0.06 and 208.16 + 2.32, 5.66 + 0.03, 1.38 + 0.04 per gram of tissue. There were no significant differences in the parameters studied amongst the three groups. The body weight : liver weight ratios, protein : RNA ratios and protein : DNA ratios, respectively for groups A, B and C were : 29.0 + 2.23, 33.2 + 1.01, 134.9 + 5.04, 30.3 + 2.45, 35.4 + 1.22, 136.7 + 5.75 and 31.0 + 2.66, 36.9 + 1.01, 153.7 + 4.17. There were no significant differences amongst the ratios except that protein : DNA ratio in group C was significantly (P<0.05) wider than in group A and B indicating probable hypertrophy of liver cells in that group. It was apparent that tannins exerted their harmful effects by affecting protein digestibility in the gastro-intestinal tract and thereby adversely affected liver size and growth rate. In experiment 2, in vitro trials were conducted by taking buffalo rumen liquor through a rumen fistula on a control ration without tannic acid. For N solubility and DH digestibility studies, the substrate used was : Maize, 50 parts ; grount nut cake, 21 parts and wheat bran 26 parts, ground into 40 mesh size. To study the influence of tannins on protein synthesis, nucleic acid synthesis and production of VFA, the substrates used were : cellulose 0.75 g. starch 0.25 g and ammonium sulphate 151 mg. McDougall’s artificial saliva was used as buffer (PH 6.8) for 32 P uptake by rumen microbes, the substrate was prepared from glucose 600 mg and ammonium sulphate 85mg. A mineral solution containing cysterine – HCL described by Bucholts and Bergan (1973) was used as a buffer. The levels of tannic acid, respectively in groups 1,2,3,4 and 5 were : 0, 1.25, 2.5, 5.0 and 7.5% in all the experiments. The E solubility and DM digestibility (%) respectively, for treatments 1,2,3,4 and 5 were : 36.72 + 0.425, 43.80 + 2.63 : 24.48 + 0.311, 37.60 + 2.14, 20.81 + 0.589, 30.27 + 1.85 : 17.55 + 0.312, 21.89 + 1.93 and 15.30 + 0.473, 13.20 + 1.15. Addition of tannins depressed N solubility and DM digestibility. The protein – N (mg) ; RNA – N (mg): DNA-N (mg) and TVFA (meq) (all per 100 ml) respectively for treatments 1,2,3,4 and 5 were : 30.19 + 1.274, 2.156 +0.107, 0.795 + 0.054, 15.46 + 0.315, 23.84 + 1.021, 1.565 + 0.101, 0.561 + 0.025, 12.34 + 0.194, 18.59 + 0.582, 1.185 + 0.046, 0.426 +0.021, 9.38 + 0.425, 16.27 + 1.318, 1.00 + 0.042; 0.337 + 0.013, 7.29 + 0.359 and 14.61 + 0.271, 0.865 + 0.034, 0.290 + 0.006, 5.49 + 0.235. Addition of tannins significantly (p<0.01) depressed all the parameters studied and in treatment 5, the levels were more or less the same as in 0 hour control indicating complete inhibition of microbial multiplication at 7.5% tannic acid level. The RNA –N : protein – N, DNA – N: protein – N and total nucleic acid – N: protein – N ratios respectively for treatments 1,2,3,4 and 5 were : 0.072 + 0.0018, 0.026+ 0.0013, 0.098 + 0.0015, 0.066 + 0.0018, 0.023 + 0.0045, 0.089 + 0.0022; 0.064 + 0.0018, 0.023 +0.00084, 0.087 + 0.0024, 0.062 + 0.0016, 0.021 + 0.00077, 0.082 +0.0020 and 0.058 + 0.0013, 0.020 + 0.00055, 0.078 + 0.0016. The ratios were narrower in control group when compared to tannic acid groups. With regards to 32P uptake by rumen microbes, a progressive decrease was observed with increase in tannin concentration. 32p uptake (mg) per 100 ml respectively for groups 1,2,3 and 4 were : 2.640, 1.835, 1.202 and 0.52. In group 5 there was no 32P uptake. Tannins depressed microbial multiplication indirectly by making the protein source not available due to its precipitation. Direct harmful effect was also possible on microbes, especially, at higher concentrations of tannins in the media without any protein source. In experiment 3, four adult fistulated female buffaloes were randomly distributed in a Latin square design. The treatments I, II, III and IV respectively contained 0, 1.25, 2.5 and 5% tannins made available from 0, 14, 28 and 40% salseed meal in the ration. In treatment IV, 1.436% pure tannic acid was also added to get 5% total tannins. The DCP and TDN contents were approximately 14 and 72% in all the rations. The effect of tannins in feeds was determined through the levels of protein –N, RNA – N, DNA –N and TVFA. The protein –N, RNA – N and DNA-N levels ( all in mg per 100 ml of SRL) and TVFA levels ( meq/100 ml of SRL), respectively for treatments I,II,III and IV were : 43.73 + 1.813, 3.86 + 0.134, 1.63 + 0.053, 9.59 + 0.205; 49.087 + 1.912, 3.75 +0.115, 1.59 + 0.057, 0.43 + 0.215, 54.86 + 1.850, 3.62 + 0.089, 1.50 +0.041, 9.20 +0.188 and 61.89 + 2.050, 3.26 + 0.097, 1.37 + 0.046, 8.48 + 0.283. Protein - N level in treatment L was significantly (P< 0.05) lessthan in ratios II, III and IV and there was a progressive and significant (P< 0.05) increase in order of treatments. RNA – N and TVFA levels in treatment I were significantly higher (P< 0.01) than in treatment IV. DNA levels were significantly lesser (P<0.05) in treatment III than in treatment I and again lower in treatment IV than in treatment III. Nucleic acid - N : protein – N ratios is SRL respectively for treatments I, II, III and IV were : 0.125 + 0.0012, 0.108 + 0.0020, 0.093 + 0.0026 and 0.072 + 0.0011. The ratio in treatment L was significantly higher than in treatments II, III and IV. The differences amongst the four treatments were significant (P<0.01). Addition of tannins in the rations resulted in an increase in protein - N, but progressively depressed the RNA – N and DNA – N levels with less production of TVFA. Further in experiment 3, the protein - N, RNA – N and DNA – N contents of bacteria separated from SRL were also determined to ascertain the effect of tannins on RNA – N: protein – N; DNA – N : protein – N and total nucleic acid : protein - N ratios. Protein – N (mg), RNA – N (mg); and DNA –N (mg) in bacteria separated from 100 ml SRL respectively for treatments I, II,III and IV were : 23.93 + 0.571, 2.385 + 0.87, 1.204 + 0.036, 23.71 + 0.627, 2.296 +0.062, 1.180 + 0.019, 22.79 +0.590, 2.230 +0.044, 1.111 + 0.059 and 20.91 + 0.544, 205 + 0.046, 1.010 + 0.053. Protein -N, RNA –N and DNA – N levels decreased as levels of tannins in rations increased. But the differences were significant (P<0.01) only between treatment I and IV. RNA – N : protein - N, and total nucleic acid – N : protein – N ratios respectively for treatments I, II, III and IV were : 0.099 + 0.0030, 0.150 +0.0027; 0.097 + 0.0023, 0.147 + 0.0029; 0.098 + 0.0024, 0.147 + 0.0017 and 0.098 + 0.0020, 0.146 +0.0025. The differences in the ratios amongst the different treatments were not statistically significant. The addition of tannins at the levels tried had no significant influence on the nucleic acid – N : protein – N ratios in the bacteria. From the value obtained for nucleic acid – N and nucleic acid – N : protein – N ratios in separated bacteria, the microbial contribution of protein - N to the tungestic acid precipitate of SRL was calculated. The values obtained were : 83.67, 74.01, 63.58 and 51.14 % for treatments I,II,III and IV respectively. The tannins present is the feed partially protected the proteins from microbial attack and hence the contribution of dietary protein - N in the SRL increased. Simultaneously the quantity of microbial protein synthesis decreased due to the limitations imposed by tannins on microbial multiplication.ThesisItem Open Access Somatic cell count and its influence on the quality of milk in cross-bred cows(Kerala Agricultural University;Thrissur, 2001) Sathian, C.T.; KAU; Mukundan, M
