Tyagi, S.M.Malhotra, Ruchika2019-12-122019-12-122006-07http://krishikosh.egranth.ac.in/handle/1/5810137549Studies were conducted to investigate the effect of incorporation of aloe vera gel juice in milk on the quality characteristics of yoghurt. The level of aloe vera gel juice was optimized on the basis of growth and acivity in terms of pH and acidity. Yoghurt cultures L.bulgaricus and S. thermophilus and probiotic culture L.acidophilus were used singly or in combination to study the effect of varying levels of aloe vera gel juice added to cow milk containing 3.0% and 0.5% fat. A 10% aloe vera gel juice level gave desirable results, i.e. lowest pH and highest titratable acidity and total viable counts. Medium and low fat yoghurt samples were prepared from standardized milks containing 3.0% or 0.5% fat after adding 4 per cent Skim milk powder, 7 per cent sugar and 0.2-0.3% sodium alginate using C1 culture (L.bulgaricus and S.thermophilus,1:1,Control/Regular yoghurt), C2 culture (S.thermophilus and L.acidophilus ,1:1, Acidophilus yoghurt) and C3 culture (L.bulgaricus, S. thermophilus and L.acidophilus, 1:1:1, Bioyoghurt), with or without addition of optimized level of aloe vera gel juice. The moisture content of yoghurts ranged between 81.50 to 85.0% depending on the composition of milk and incorporation of aloe vera gel juice. The aloe vera added yoghurt had slightly lower fat, protein, carbohydrate and ash contents. Addition of aloe vera gel juice to yoghurt had a significant (P<0.01) effect on acid production. Lowest pH (4.30) and highest titratable acidity (1.0%) were obtained in medium fat yoghurt aloe vera added yoghurt with C3 culture followed by C1 and C2 cultures. The acetaldehyde, soluble nitrogen and free fatty acid contents significantly (P<0.01) increased on incorporation of aloe vera gel juice. The highest acetaldehyde (33.0 ppm) was produced in medium fat aloe vera added yoghurt prepared by C2 culture whereas maximum soluble nitrogen (0.078%) and free fatty acid (8.0 meq/ml) were given by C3 culture. The incorporation of aloe vera significantly (P<0.01) increased syneresis whereas decreased curd tension and viscosity. Maximum syneresis (22.3 ml) was observed in low fat aloe vera added yoghurt prepared using C1 culture while highest curd tension (45.5 g) and maximum viscosity (6200 cP) was obtained in medium fat yoghurt without aloe vera prepared by using C1 and C3 cultures, respectively. Total viable counts significantly (P<0.01) increased on adding aloe vera gel juice to yoghurt mix. The maximum total viable count (4.2 X108) was noted in aloe vera added medium fat yoghurt prepared by C3 culture. No yeast and mold counts were detected in fresh samples. During storage of yoghurt for 28 days at 5+10C, the lowest pH (3.10) and highest acidity (1.80%) was obtained in medium fat yoghurt without aloe vera prepared using C1 culture. The titratable acidity, soluble nitrogen, free fatty acid content, curd tension, syneresis and yeast and mold counts significantly (P<0.05) increased during storage whereas pH, acetaldehyde content, viscosity, total viable counts and sensory scores significantly (P<0.05) decreased during storage for all yoghurt samples. Yoghurts prepared from C1 and C3 cultures retained significantly (P<0.05) superior quality as compared to yoghurt prepared by using C2 culture. Keeping quality of aloe vera added yoghurts was better in all parametric terms than the ones without aloe vera. Satisfactorily good quality aloe vera gel juice added yoghurt with therapeutic value could be prepared by incorporation of 10 per cent aloe vera to medium fat as well as low fat milks with a shelf life of 24 days.ennullThesis