Enzymatic coagulation of milk by immobilized proteases, and their potential application to cheese manufacture, is reviewed. Particular emphasis is given to the immobilized protease catalyst and to the reactor design for coagulation of milk. Pepsin and chymotrypsin retained more activity and greater stability than the other immobilized proteolytic enzymes. Porous glass beads, several anion exchange resins, and the copolymer ethylene-maleic anhydride gave best results among the support materials that were evaluated. Covalent attachment of enzyme to support is preferable to adsorption techniques but may be too costly. Perhaps the best catalyst is one using a lengthy procedure for covalent immobilization of enzyme on glass beads but good results were also obtained with simpler adsorption techniques. Catalysts varied greatly in initial activity but all lost activity upon exposure to milk. Stirred tank, packed bed, and fluidized bed reactor designs were used. Continued research is required to make enzymic milk coagulation with immobilized proteases economically feasible.
One hundred and fifty beef knuckles, 140 beef ribs, and 60 arm chucks were vacuum packaged by two systems (nozzle and chamber vacuumizing machines) in bags manufactured from films differing in oxygen and moisture vapor transmission rates. Primal cuts in each system were randomly assigned to storage periods of 7, 14, 21, 28, or 35 days. In addition, leaker packages were assigned storage periods of 7, 14. or 21 days. At the termination of each storage period, cuts were evaluated for degree of vacuum, appearance of fat cover, surface discoloration, and total desirability. The combination of a chamber vacuumizing machine and use of a packaging film with a low oxygen transmission rate resulted in superior fat appearance ratings, reduced surface discoloration, and higher total desirability scores. Cuts from leaker packages usually received the lowest ratings for these attributes.
Sterile soybeans, low and full fat soy meal, soy residue, soy curd, and soy whey fortified with different nutritional supplements were inoculated with spore suspensions of Penicillium rubrum P-3290. Yeast extract-sucrose (YES); glucose-malt extract; maltose-soytone; soy whey containing 1.75, 3.5, and 5.5% dissolved solids; and a maltose-salts medium were also inoculated. Cultures were incubated quiescently at 28 C for 7, 10, or 14 days. Rubratoxins were extracted with ethyl acetate and diethyl ether and resolved by thin-layer chromatography. Greatest yields of toxin were obtained from natural rather than chemically defined media. Semisynthetic media supported formation of moderate amounts of rubratoxins. Malt extract and glucose supported greatest production of both rubratoxins A and B. Unsupplemented soy whey or soy milk did not support rubratoxin production. Although soy meal supported production of both rubratoxins A and B (0.12–0.24 mg/g and 0.55–0.71 mg/g), low fat soy meal was more suitable for toxin formation than was full fat meal. Both rubratoxins A and B were produced by P. rubrum grown in soy whey fortified with soytone, malt extract, or glucose; only rubratoxin B was produced when yeast extract or sucrose served as supplements. YES broth supported formation of only rubratoxin B. Production of toxin in soybeans was influenced by time of incubation and temperature. Maximum yields of toxin on soybeans were obtained after 14 days of incubation at 25 C, after 28 days at 28 C, after 7 days at 32 C, and after 3 days at 37 C. Rubratoxin was not produced at 40 C. Yields of rubratoxin A in soy whey media ranged from 35–40 and from 15–28 mg/100 ml when malt extract or glucose were added; values for rubratoxin B ranged from 55–100 mg/100 ml and 65–125 mg/100 ml.
A study was conducted to examine the possible bacteriostatic and bactericidal effect of rosemary spice extractive (RSE) on growth of selected microflora and total bacterial populations in mechanically deboned poultry meat (MDPM), turkey breast, and beef. Definite bactericidal effect by 0.1% RSE became evident when a pure culture of Staphylococcus aureus was tested in a bacteriological medium. Such an effect was not observed when Escherichia coli, Enterobacter aerogenes, Pseudomonas fluorescens, and Salmonella typhimurium were tested. When various types of meat were used as growth media, RSE showed a bactericidal effect on S. aureus only at 5% concentration. Such an effect was not observed on total plate counts of the meat samples.
Sources and magnitudes of thermal energy losses, as well as fuels for energy, were examined in three sauerkraut processing plants in Western New York. The fuels for thermal energy accounted for 86 to 95% of the total energy purchased by the plants. With suitable energy conservation measures, present usage of thermal energy (Btu) per case containing 24 size 303 cans can be reduced by 6 to 33% depending on characteristics of the plant.
In investigating formation of tyramine and histamine in a model system, it was found that four commercial sausage starter cultures did not exhibit appreciable tyrosine or histidine decarboxylase activity. In addition, other species of Pediococcus cerevisiae and Lactobacillus did not display appreciable decarboxylase activity. Mixtures of P. cerevisiae and Lactobacillus plantarum were also unable to produce significant levels of these amines. One species of Streptococcus tested was able to produce 34.5 μg of tyramine/hour under the assay conditions. When P. cerevisiae and L. plantarum were used as starter cultures to prepare sausages, it was found that this treatment resulted in lower tyramine levels (approximately 200 μ/g) than when the Streptococcus sp. was used as a starter culture (approximately 300 μ/g). However, the use of P. cerevisiae and L. plantarum did not result in a significantly lower tyramine level than when no starter culture was used.
Predominant microorganisms on fresh and fermenting wild rice were isolated, characterized, and then used as inoculum so their effects on processing and flavor characteristics of wild rice could be determined. During storage of wild rice at 4 C for 14 weeks, Achromobacter spp., Flavobacterium spp., coryneforms, and coliforms, and Achromobacter spp. predominated in succession. In rice stored at 21 C for 2 weeks, Pseudomonas spp. predominated. Microorganisms isolated from fresh wild rice included pseudomonads, micrococci, coliforms, Achromobacter spp., and Flavobacterium spp. Wild rice inoculated with some isolates from fermenting rice developed a variety of odors including fecal-putrid, earthy, and rotting vegetation types at 30 C, and the previous odors plus ammonia, fatty acid, and sweet-aromatic types at 7 C. Processing characteristics of wild rice inoculated with selected isolates, were not affected, but there were changes in flavor of the rice. Intensities of both tea-like and earthy flavors in wild rice were increased by inoculation of rice with Achromobacter, Pseudomonas, Flavobacterium, and Micrococcus isolates.
Wholesale cuts of beef (knuckles, ribs, chucks) were vacuum packaged in three types of packages with oxygen transmission rates (cc/100 in.2/24 h) of 0.41–0.75, 1.09, and 2.28. One type of package was sealed with a clip; the others were heat sealed. Wholesale cuts were stored for 0–35 days at 1–3 C and retail cuts from ribs and knuckles were observed under retail conditions for 5 days. Differences in psychrotrophic, mesophilic, and lactobacillus counts of knuckles and ribs resulting from differences in type of package usually were not statistically significant. Differences in psychrotrophic counts of retail steaks of knuckles and ribs resulting from differences in type of package used for the primal cuts were not significant. Psychrotrophic and mesophilic counts of cuts in defective packages (leakers) increased faster than those of cuts in intact packages. The initial microbial flora of knuckles, ribs, and chucks consisted primarily of Moraxella-Acinetobacter spp. and coryneform bacteria. During the first few weeks of storage at 1–3 C Lactobacillus spp. already were dominant on knuckles and Microbacterium and Lactobacillus spp. predominated on ribs. After 28–35 days of storage Lactobacillus spp. were dominant on both knuckles and ribs. The microbial population on chucks after 21 days of storage consisted of Lactobacillus, Microbacterium, Enterobacteriaceae. Pseudomonas, Moraxella-Acinetobacter spp. and coryneform bacteria. The microflora of cuts from defective packages was comprised of species of Pseudomonas, Microbacterium, Lactobacillus, and Moraxella-Acinetobacter.
Processing of milk into dry milk, cheese, and butter was an important part of Biblical man's survival in the desert wasteland. Meat processing was limited, and little of it was likely consumed during the 40 years of wandering of the Israelites. The Bible does mention processing of quail which were salted and dried. Locusts were a common food item for traveling Israelites and were prepared and consumed whenever found. This was done by boiling them in salt water, then baking, drying, or smoking before consuming. Cereal grain formed an important part of the Hebrews' diet. It was threshed and ground with a hand mill and then made into bread. Another method of processing was by using the mortar and pestle to make flour for bread. Manna seems to have been processed in a manner similar to that used for cereal grains. It was the sole source of food for many years while the Israelites traveled in the desert. Vegetables were not processed and are only briefly mentioned, whereas spices are referred to throughout the Old Testament. Because of the availability of natural vegetation and the difficulties of storing processed foods, extensive processing methods were not developed. Many of the processing techniques used by Biblical man are the same as those used by present-day Bedouin Arabs.
