Preliminary studies on the gelation processes of fermented and GDL-acidified bovine and caprine milk systems

Bovine and caprine milk gels were made by GDL-acidification and yogurt fermentation (using 'ropy' and 'non-ropy' starter cultures). The respective gelation processes were monitored rheologically using dynamic oscillatory testing. The bovine fermented systems produced gel structures with about half the strength of the equivalent chemically acidified gels. The fermented caprine milk systems produced gel structures some eight to 10 times weaker than the equivalent acidified systems. In all cases the caprine systems were weaker than the bovine gels despite having higher protein contents. In all cases the 'ropy' milk systems followed somewhat different gelation patterns and formed weaker gels than the equivalent 'non-ropy' and GDL-acidified systems. These data suggested that the starter culture material (biomass and extracellular polysaccharides) may have interfered with the protein–protein interactions during yogurt fermentation. This produced weaker gel structures, possibly by a modified gelation mechanism .     

Effect of calcium, fat and total solids on the rheology of a model soft cheese system

The aim of this work was to assess the effects of calcium, fat and total solids on the rheology of a model soft cheese. Several batches of reconstituted skim milk with 9, 12 and 15% w/v total solids and reconstituted whole milk with 12, 15 and 18% w/v total solids were used to make a soft stranded cheese whose rheological characteristics, G" (storage modulus or elastic component) and G' (loss modulus or viscous component), were measured using an RTI Stress Controlled Rheometer (RTI). All factors investigated had a significant effect on the rheology of the soft cheese; however, they affected the rheological parameters differently, suggesting that the structural changes are not a result simply of the concentration of material in solution .     

Continued inhibitory effect of carbon dioxide packaging on Listeria monocytogenes and other microorganisms on normal pH beef during abusive retail display

Beef steaks of normal pH (5.3–5.5) were inoculated with Listeria monocytogenes , individually packaged in saturated carbon dioxide atmosphere packaging (SCAP) for <3 h or 5 or 8 weeks or in vacuum packaging (VP) for <3 h, and stored at −1.5°C. After each storage period, 27 individually packaged steaks were removed from their storage packs, overwrapped and placed on retail display under conditions simulating gross temperature abuse (12.25°C). Other steaks were removed from their storage packs and rinsed to remove L. monocytogenes cells, which were re-inoculated onto freshly cut beef steaks to simulate cross-contamination. These crosscontaminated steaks were overwrapped and also subjected to abusive display. Meat pH did not change significantly during storage or retail display. During the retail display of steaks previously stored in SCAP, the lag phase of aerobic bacteria and lactic acid bacteria was longer after prolonged storage compared to short (<3 h) exposure to carbon dioxide. For the same samples, L. monocytogenes failed to grow during retail display or grew only slightly after a prolonged lag phase (>75 h), even after only brief exposure time (<3 h) to carbon dioxide. In contrast, with cross-contaminated steaks, when the inocula had been exposed to SCAP or VP for a short time (<3 h) the L. monocytogenes lag phase was shorter (<20 h). Inocula from steaks stored in SCAP for 5 or 8 weeks did not grow on the cross-contaminated steaks. It is concluded that exposure of both the beef substrate and the L. monocytogenes inoculum to carbon dioxide during prolonged chilled storage does not increase the risk of growth of L. monocytogenes when that meat is subsequently placed on retail display, nor is there a large risk of growth of L. monocytogenes where cross-contamination from SCAP stored raw beef to fresh raw beef occurs prior to retail display.     

Growth of the psychrotrophic pathogens Aeromonas hydrophila, Listeria monocytogenes and Yersinia enterocolitica on smoked blue cod (Parapercis colias) packed under vacuum or carbon dioxide

Commercially prepared smoked blue cod ( Parapercis colias ) was divided into 25-g subsamples which either served as uninoculated controls or were inoculated with a two-strain cocktail of one of the psychrotrophic pathogens Aeromonas hydrophila, Listeria monocytogenes or Yersinia enterocolitica. The inoculated and control subsamples were then either vacuum or carbon dioxide packed prior to storage at 3°C or −1.5°C. After various periods of storage, triplicate samples from both packaging treatments for the three pathogens and the corresponding uninoculated controls were removed and subjected to microbiological analysis. None of the three pathogens was found as a natural contaminant of the commercial product. In vacuum-packs all three psychrotrophic pathogens were able to grow during storage at 3°C. Reduction of the storage temperature to − 1.5°C retarded but did not prevent pathogen proliferation. Under carbon dioxide, only A. hydrophila was able to grow at 3°C and then only after a 21-day lag period. None of the psychrotrophic pathogens was able to grow under carbon dioxide at − 1.5°C. With the possible exception of A. hydrophila , pathogen numbers did not decline in carbon dioxide packs during 155 days storage at − 1.5°C. It is concluded that provided gross contamination with psychrotrophic pathogens prior to packaging does not occur, a 100% carbon dioxide controlled atmosphere can be used to extend the product life of smoked blue cod during storage at or below 0°C without compromising its safety in respect to growth of A. hydrophila, L monocytogenes or Y. enterocolitica.     

The Coloration of Wool with Disperse Dyes

Work is described which shows that, by treating wool with certain amides, polyhydric alcohols or carboxylic acids, the affinity of the fibre for disperse dyes can be greatly enhanced. The most suitable compounds, with regard to effectiveness, price and commercial availability, are thiodiglycol and glycerol. Particular reference is made to the sublimation transfer-printing technique; the fibre is pretreated by pad-dry application of the compounds, and prints of excellent yield and clarity are obtained using standard disperse dye transfer papers. Yellowing and fibre damage during transfer printing are minimized by the inclusion of sulphamic acid in the pad-liquor. Wet-fastness properties of the prints are poor, but may be improved to a certain extent by the use of selected disperse dyes.     

Amylolytic activity in cooked luncheon meat

Glucose accumulated in chub packed luncheon meat cooked at 66°C. Glucose was also released from pork starch slurries, but not similar slurries prepared with beef or mutton. The amylolytic activity of pork was not inactivated by heating at 60°C, and this thermostable activity appears to account for the accumulation of glucose in pasteurized chub packed luncheon meat stored under conditions that preclude bacterial growth.     

Extension of the chilled storage life of smoked blue cod (Parapercis colias) by carbon dioxide packaging

Commercially prepared smoked blue cod ( Parapercis colias ), packaged aerobically, under vacuum and in carbon dioxide controlled atmosphere packs, was stored at + 3°C and - 1.5°C. Product stored aerobically on overwrapped polystyrene trays spoiled by 14 and 28 days respectively, and that in vacuum packs spoiled by 14 and 35 days respectively, when held at 3°C and - 1.5°C. In contrast, product in carbon dioxide packs remained acceptable until the 3°C and - 1.5°C storage trials ended after 49 and 113 days respectively. Microbial spoilage was first evident in overwrapped product stored aerobically and in vacuum-packed product as offensive putrid amine-like odours on pack opening. These odours were associated with the development of a predominantly Gram-negative spoilage microflora. Extension of product life afforded by the use of carbon dioxide controlled atmosphere packaging is attributable to a significant extension of the lag phase before spoilage microflora proliferation commenced and to the selection of a low-spoilage-potential lactic-acid-bacteria-dominated flora. Although the use of carbon dioxide packaging offers an export potential for chilled smoked blue cod, caution must be advocated until product safety, in respect to the growth of cold tolerant pathogens in the case of temperature abuse (>3°C), can be more fully evaluated.     

Recovery of High-Temperature Creep-Resistant Substructure in Rutile

Recovery of creep-resistant substructure in rutile was studied at 1000°, 1020°, and 1040°C. Specimens were crept under a stress of 10,000 psi to a strain early in the secondary stage of creep and then allowed to recover for varying periods under a residual stress of 400 psi. Recovery was detected by the increased creep strain which occurred when the 10,000 psi stress was reapplied. An apparent activation energy of 135,000 cal/mol was obtained for the recovery process. Experimental evidence suggests that the primary recovery mechanism involves the sweeping out of dislocation barriers within the material by the migration of dislocation walls or subgrain boundaries.