Porosity, Specific Gravity and Fat Dispersion in Blue Cheeses

Porosity was measured in Blue cheeses made from (i) homogenized butter oil - reconstituted nonfat dry milk (4% fat). (ii) homogenized butter oil reconstituted nonfat dry milk (14% fat) standardized to 4% fat with reconstituted nonfat dry milk , (iii} homogenized raw c ream (14% fat) standardized to 4% fat with raw skim milk , and (iv) homogenized pasteurized cream (14% fat) standardized to 4% fat with pasteurized skim milk. Cheeses made from (i) were the most porous and were significantly different from the other cheeses . In cheeses made from (i) and (ii) , about 40% of the holes were less than 2 um2 in area, while in cheeses made from {iii) and (iv), 50% of the holes were less than 2 um2. Cheeses made from (iii) did not contain holes larger than 22 1.1 um2, whereas cheeses mode from (iv), (ii) and (i) contained 0.76 , 1. 29, and 5.27 %, respectively, of holes larger than 22 11m2. Cheeses made from (i) had the lowest specific gravity and we re significantly different from the others . Fat was well dispersed in cheese made from (i) with few small clusters. The other cheeses contained many large clusters of fat globules, and the fat distribution was less uniform than in cheeses made from (i)

Improving viability of bifidobacteria by microentrapment and their effect on some pathogenic bacteria in stirred yoghurt

Fifteen batches of stirred youghurt were made to study the effect of microentrapment on the viability of bifidobacteria and their ability to inhibit the growth ofE. coliandStaph. aureus. Entrapped cells ofBifidobacterium bifidumandBifidobacterium infantiswere able to produce antimicrobial agents which inhibitedE. coliandStaph. aureusused as test organisms. Viable counts of unentrapped bifidobacteria decreased sharply, while entrapped cells of bifidobacteria were quite stable during refrigerated storage of stirred yoghurt.Bif. infantiswas more tolerant to storage conditions thanBif. bifidum. Microentrapment of bifidobacteria improved their survival during storage of stirred yoghurt, especiallyBif. bifidum, whose viability was not significantly (P≯0.05) different from entrappedBif. infantis. Viable counts ofE. colidecreased during storage of stirred yoghurt. Addition to bifidobacteria caused a sharp decrease in the viability ofE. coli.E.coligrowth was not detected at the 5th day, when entrapped cells of bifidobacteria were added to stirred yoghurt, whileE. coligrowth was not detected at the 7th day of storage in yoghurt containing unentrapped bifidobacteria. Addition ofBif. bifiduminhibited the growth ofE. colimore effectively thanBif. infantis. Staph. aureusshowed similar patterns toE. coli, except theStaph. aureuswas more tolerant to storage conditions. The counts of total bacteria, lactobacilli andStreptococcus salivariussubsp.thermophilusincreased up to the third day then declined till the end of storage. Titratable acidity increased gradually during the first 3 days of storage then increased slightly up to the end of storage, while pH values dropped during storage. Adding bifidobacteria,E. coliandStaph. aureusdid not affect significantly (P≯0.05) the counts of lactobacilli andStr. salivariussubsp.thermophilus, acidity and pH value

Porosity, Specific Gravity and Air Content in Blue Cheeses

Porosity and specific gravity were determined in Blue cheeses made from (A) homogenized 14% fat pasteurized cream standardized to 3.9% fat with pasteurized skim milk, (B) homogenized 14% fat raw cream standardized to 3.9% fat with raw skim milk, and (C) pasteurized milk (3.9% fat). There were no significant differences between cheeses made from (A) a nd (B) in porosity and specific gravity. Cheeses made from (A) and (8) had greater porosity, lower specific gravity and more, but smaller holes than cheese made from (C). The negative linear relation ship between porosity and specific gravity, and the insignificant differences in fat and moisture content in cheese made from (A), (B) and (C) suggest that many of the holes contained air and not whey

Acid, bile, and heat tolerance of free and microencapsulated probiotic bacteria

Eight strains of probiotic bacteria, including Lactobacillus rhamnosus, Bifidobacterium longum, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, B. lactis type Bl-O4, and B. lactis type Bi-07, were studied for their acid, bile, and heat tolerance. Microencapsulation in alginate matrix was used to enhance survival of the bacteria in acid and bile as well as a brief exposure to heat. Free probiotic organisms were used as a control. The acid tolerance of probiotic organisms was tested using HCl in MRS broth over a 2-h incubation period. Bile tolerance was tested using 2 types of bile salts, oxgall and taurocholic acid, over an 8-h incubation period. Heat tolerance was tested by exposing the probiotic organisms to 65°C for up to 1 h. Results indicated microencapsulated probiotic bacteria survived better (P < 0.05) than free probiotic bacteria in MRS containing HCl. When free probiotic bacteria were exposed to oxgall, viability was reduced by 6.51-log CFU/mL, whereas only 3.36-log CFU/mL was lost in microencapsulated strains. At 30 min of heat treatment, microencapsulated probiotic bacteria survived with an average loss of only 4.17-log CFU/mL, compared to 6.74-log CFU/mL loss with free probiotic bacteria. However, after 1 h of heating both free and microencapsulated probiotic strains showed similar losses in viability. Overall microencapsulation improved the survival of probiotic bacteria when exposed to acidic conditions, bile salts, and mild heat treatment. © 2007 Institute of Food Technologists.link_to_subscribed_fulltex