Effect of frozen storage on the structure and enzymatic activities of myofibrillar proteins of rabbit skeletal muscle

The effect of frozen storage on the biochemical properties of myofibrils, and of their major constituents, actin and myosin, was investigated. Extractability of myofibrillar proteins increased slightly for 3 weeks during frozen storage of muscle, decreasing thereafter. The change in myofibrillar ATPase activity during frozen storage was consistent with that of a reconstituted acto-heavy meromyosin (HMM) complex prepared from frozen stored muscle at the same weight ratio of actin to myosin as in situ. However, myosin ATPase activity showed a different pattern of change when compared with myofibrillar ATPase activity. The maximum velocity of acto-HMM ATPase activity and the apparent dissociation constant of the acto-HMM complex decreased for 1 week during frozen storage, increasing thereafter, indicating that the affinity of actin for myosin was greatest in muscle which had been frozen for 1 week.     

The microbiology of instant coffee

The microbiology of a coffee production line, as well as of the final products was investigated. Lactic acid bacteria were found to be the predominant microflora with lactobacilli as the major group and L. plantarum as the dominant species. Growth kinetics of this species were examined in the presence of pure caffeine solutions and at different concentrations of total solids of instant coffee. Total inhibition of growth was obtained at 15 mg ml^?1 of a pure caffeine solution and at 60% total solids of non-decaffeinated coffee.The growth kinetics of some pathogenic bacterial strains were examined in both decaffeinated and non-decaffeinated coffee; coffee liquor was not a suitable medium for growth of these strains. The spoilage micro-organism, Saccharomyces cerevisiae, was not inactivated in coffee liquor.     

Response of malathion-susceptible and resistant strains of Tribolium castaneum (Coleoptera: Tenebrionidae) to a combination of 60Co gamma irradiation and malathion

Survival of malathion-susceptible (S) and malathion-resistant (R) strains of Tribolium castaneum (Herbst) adults exposed to gamma irradiation at 5, 10, 20 or 30 krad, followed by a 5-h exposure to malathion at 1, 8, 15 or 22 days after irradiation, was assessed for up to 5 weeks after irradiation. Exposure of S strain adults to malathion, 1 or 8 days after irradiation at all doses hastened the onset of death. Irradiation at 10, 20 and 30 krad was the dominant cause of death in the R strain. There was some evidence that exposure of the R strain to malathion at 1 or 8 days after irradiation at 10 krad accelerated mortality 2 and 3 weeks after exposure to radiation. No progeny were produced by either the S or R strains irradiated at any dose. Irradiation of S and R strains did not influence their response to malathion.     

Egg production and development of three strains of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

The numbers of eggs laid by individual females of three geographically isolated strains of C. maculatus (F.) on different numbers of cowpeas were counted. Females of strains originating in the Yemen and Brazil laid about 40 eggs when provided with a single cowpea, whilst females of a Nigerian strain laid 75. Given 40 cowpeas, females of all three strains laid between 80 and 90 eggs. Only one or two adults of the Yemen strain emerged from cowpeas irrespective of the initial number of eggs present, compared with the ten or more adults of the other two strains which emerged when the cowpea bore numerous eggs. The daily levels of oviposition did not differ among the strains when females had access to cowpeas changed daily for others bearing no eggs. The periods of development differed among the three strains, the greatest median value being 33 days in the Yemen strain where the greatest individual variation in development times was also noted. The significance of the results to the development of possible control measures for this pest is discussed.     

Incidence of histidine decarboxylating bacteria in fish and market environs

To understand the sources of contamination of fish with histidine decarboxylating bacteria (HDB), the fish market environs including fish carrying baskets, ice, market floor and water used for wetting fish, were studied for HDB counts. Fish such as seerfish (Scomberomorus guttatus) and mackerel (Rastrelliger kanagurta) were also studied for total plate count (TPC), HDB counts and levels of histamine. The results suggest that the HDB are widely distributed in the market environs and market floor and that water could be major sources of contamination of fish. While the samples of seerfish studied had very low levels of histamine, some mackerel samples had levels exceeding 10 mg%.     

Skeletal muscle characteristics in different breeds of pigs in relation to sensory properties of meat

Fibre type composition, activities of enzymes used as indicators for oxidative (citrate synthase and 3-OH-acyl-coA dehydrogenase) and glycolytic (lactate dehydrogenase and triose phosphate dehydrogenase) capacity as well as glycogen and triglyceride levels were analysed on muscle biopsies (M. longissimus dorsi and M. gluteus medius) obtained preslaughter from pure breed Hampshire (n = 5), Swedish Landrace (n = 5) and Swedish Yorkshire (n = 5) pigs. The biopsied muscles were evaluated after slaughter for the sensory properties of the meat. Fibre type composition was similar in all breeds, whereas the metabolic profile differed. The Hampshire pigs had a significantly higher oxidative capacity, lower glycolytic capacity, and greater storage of both glycogen and triglycerides compared with the Yorkshire pigs. Values for the Swedish Landrace pigs were inbetween the other breeds. Tenderness of meat was significantly lower in the Yorkshire pigs compared with the other breeds. These results suggest that of the sensory properties of meat, tenderness seems to be especially related to the metabolic profile of the muscles in the living pig.     

Some products of winged bean lipoxygenase-catalysed reaction: A note

Purified isoenzymes of lipoxygenase from winged bean were shown to catalyse the formation of hydroperoxides as well as carbonyl compounds. Preliminary experiments indicate formation of two volatile compounds by lipoxygenase in a model purified lipoxygenase-linoleic acid system which are similar to two of the volatile components of raw winged bean homogenate.     

Purification and Characterization of Four Extracellular Proteases Isolated from Raw Milk Psychrotrophs

Extracellular proteases from psychrotrophic strains of Bacillus coagulans (LY 9), Bacillus sp. (LY 10), Bacillus subtilis (LY 11), and Pseudomonas fluorescens (LY 13) were purified and characterized. The molecular weight of the purified protease from Pseudomonas fluorescens LY 13 was 4.50 × 10⁴, and from the three Bacillus species ranged from 3.35 × 10⁴ to 3.90 × 10⁴. The proteases from LY 10 and LY 13 were monomeric proteins, whereas the protease from LY 9 was in a polymeric form that contained up to 14 subunits. Only the protease from Pseudomonas fluorescens LY 13 showed trypsin-like activity. All four proteases were inhibited by ethylenediaminetetraacetate and would be classified as metallo proteases. Casein was the preferred substrate for these proteases. Susceptibility of casein fractions to attack by these proteases varied with the enzyme source. Maximum enzyme activity was between pH 6.5 and 7.5. The protease from Pseudomonas fluorescens LY 13 retained more activity after heating at 63°C for 30 min than the proteases from the three Bacillus species. Calcium ion showed a protective effect by decreasing heat denaturation of the proteases from LY 9 and LY 11. This protective effect tended to be greater in the presence of Tris-HC1 buffer (.05 M, pH 7.5) plus 10% skim milk than in buffer only.     

Pressure-heat treatment of meat: A comparison of beef and buffalo meat

A pressure-heat treatment, which disrupts the myofibrillar structure of meat but leaves the connective tissues essentially intact, was used to compare the connective tissue component of toughness in the Semimembranosus and Longissimus dorsi muscles from nine Brahman cross and nine buffalo steers, 24 to 29 months of age. For assessment of samples, peak force, initial yield force and peak force minus initial yield force values were determined from Warner-Bratzler shear force-deformation curves.

In the control, non-pressure-heat treated samples, the only breed difference detected was in peak minus initial yield force value, which was significantly lower for the beef Semimembranosus muscles. However, for the pressure-heat treated samples of both muscles, peak force and peak minus initial yield force values were significantly lower for beef than for buffalo. The pressure-heat treatment could thus be used to detect differences in the contribution of connective tissue to toughness which would otherwise be obscured by the differences in the myofibrillar toughness.     

Life history studies of internally feeding pests of stored sorghum: Sitotroga cerealella (Ol.) and Sitophilus oryzae (L.)

A laboratory study of the ecology of single species populations of Sitotroga cerealella (Olivier) and Sitophilus oryzae (L.) was made at 3 temperatures (25, 30 and 35°C) and 3 relative humidities (60, 70 and 80% r.h.). The effects of 2 lower humidities (40 and 50% r.h.) on both species were also studied at 30°C. The optimum conditions for multiplication of S. cerealella were found to be 25–30°C and 60–80% r.h. while for S. oryzae the optimum was more clearly defined (30°C and 80% r.h.). However S. cerealella could tolerate a higher temperature (35°C) and lower humidities (40 and 50% r.h. at 30°C) than S. oryzae. The results are compared with those of other workers on sorghum and other cereals, and discussed in relation to the distribution of the two species in Sudan.     

Incidence of Moraxella and other gram-negative,oxidase-positive bacteria in fresh and spoiled ground beef

A total of 1535 bacterial isolates were examined from 29 retail samples of ground beef when fresh and after aerobic spoilage at 5–7°C. Of these, 1354 (88%) were gram-negative and oxidase-positive, but only 34 were identified by API 20E as Moraxella-26 from fresh and eight from spoiled samples. Ninety-five percent of the oxidase-positive isolates were Pseudomonas spp. and 66% of these were recovered from the meats after spoilage. The findings bring into question the widely-held view that moraxellae along with Acinetobacter are rather abundant in ground beef.     

Spontaneous heating and the damage it causes to commercially stored soybeans in Israel

Spontaneous heating occurred in stored soybeans in Israel after only a few months of storage. In bins where spontaneous heating (to about 40°C) was detected early, soybean moisture content (m.c.) started to increase from the original 12–13% to 13.3–13.9% at the 2 m depth level and the free fatty acids (FFA) level, mould counts, and respiration remained at levels acceptable for commercially stored soybeans. Aeration of the bins caused a decrease in temperature at the 2 m depth level and equalised the temperature of the whole bulk. In one case, where initial heating was not detected early enough, a 30–50 tonne core of a total of 2000 tonnes burned, the core being located in the upper portion of the bulk. At the core of the heat-damaged soybeans, FFA level increased to more than 35%, while at the outer edge of the core FFA content was 22–24%. Because of the high temperature developed (up to 98°C), no fungi could be isolated from the heat-damaged soybeans. A great amount of dockage and split soybean seeds was found in the heat-damaged core. Intact soybeans around the heat-damaged bulk were not affected. In small soybean conglomerates found in the bin during the unloading process, the FFA content had increased to about 12% and mould count to about 10⁶ propagules/g. Aspergillus flavus was the only fungus isolated in all samples examined from this silo. In silos where aeration and refrigeration operations were performed periodically, seed temperature was kept low, permitting prolonged storage of soybeans. After almost 4 years storage, the FFA content of the soybeans was about 1% and fungal counts did not exceed 10² propagules/g.     

Post-mortem energy metabolism in bovine muscles studied by non-invasive phosphorus-31 nuclear magnetic resonance

Phosphorus-31 Nuclear Magnetic Resonance ((31)P-NMR) has been utilized to follow non-invasively the post-mortem metabolism of the major phosphorylated metabolites in muscles from beef slaughter carcasses. In addition to adenosine-5'-triphosphate (ATP), creatine phosphate (CP) and inorganic phosphate (P(i)) considerable amounts of glucose- and fructose-6-phosphate (G6P and F6P, respectively) as well as glycerol-3-phosphate (Glyc3P) were detected. ATP was mainly present as a Mg(2+)-ATP complex. Adenosine-5'-diphosphate (ADP) appeared to be mainly bound to muscle proteins. A good quantitative agreement was found for the levels of ATP, CP and sugar phosphates (SP) when estimated by NMR or enzymatic assays. Since the chemical shifts of the P(i) and sugar phosphate resonances are a function of the pH, the intracellular pH could be directly deduced from the NMR spectra. Values obtained in this manner were, within the errors of both methods, the same as those determined in iodoacetate/KCl homogenates. The pH gradients within the tissue never exceeded 0.3 pH units. In a final set of experiments we used (31)P-NMR 10 study the effects of electrical stimulation on the intracellular pH and post-mortem metabolism. It was concluded that (31)P-NMR, due to its non-invasive nature plus the fact that some of the NMR parameters are sensitive to the intracellular environment, provides a useful complement to existing methods for the study of post-mortem metabolism.     

Winged bean lipoxygenase—Part 1: Isolation and purification

Lipoxygenase was isolated and purified from dried winged bean seeds by ammonium sulphate fractionation, gel filtration, DEAE-Sephadex ion exchange chromatography and hydroxyapatite chromatography. Two major isoenzymes, FI and FII, were separated by ion exchange chromatography and were further purified by elution through a hydroxyapatite column. These resulted in a 105- and 171-fold purification and 7% and 9% recovery for FI and FII, respectively. FI and FII had similar Rf values of 0.25 on polyacrylamide gel electrophoresis. A minor band of Rf 0.01 was detected in ammonium sulphate fractions but was not further enriched and purified in succeeding steps.     

Protein-lipid interactions in concentrated infant formula

Radiolabeled milk proteins ([carbon-14] beta-lactoglobulin or [carbon-14] kappa-casein) were added to raw skim milk used to prepare concentrated humanized infant formula. Ultracentrifugation of the sterilized product allowed separation of three fractions: lipids and the proteins associated with them; free casein micelles and other dense particles; and the fluid phase. Distribution of radiolabeled tracer proteins or of protein measured by chemical methods among these three phases varied significantly with differences in processing conditions (time and temperature of sterilization) or amount of certain additives (potassium hydroxide or urea). In the range of 0 to 8 meq/L of potassium hydroxide added to the formula after homogenization but before sterilization, the lipid layer content of carbon-14 from [carbon-14] kappa-casein in the sterilized product decreased by 4.7% for each 1 meq/L of added potassium hydroxide. Lipid layer content of protein decreased by 2 g/L (of a total of 32 g/L) for each 1 meq/L potassium hydroxide. Such differences in the structure of the product, related to interactions of protein with lipid, protein, or calcium phosphate, may correlate with physical properties and stability of milk-based lipid-rich products.     

Winged bean lipoxygenase—Part 2: Physicochemical properties

Winged bean lipoxygenase (linoleate: oxygen oxidoreductase EC 1.13.11.12) isoenzymes FI and FII were isolated and purified according to the method of Truong et al. (1980).FI and FII were both highly specific for linoleic acid. They exhibited optimal activity at pH 6·0 and 5·8, respectively at 30°C. An activation energy of 4·5 kcal mol^?1 was calculated for this lipoxygenase within the temperature range of 30–50°C.At 0·075% Tween 20, FI and FII had K_m values for linoleic acid of 0·44 and 0·37 × 10^?3M, respectively, compared to 0·4 × 10^?3M for the crude enzyme. Maximal activity was obtained at 1·6 × 10^?3M. Higher levels of Tween 20 inhibited the lipoxygenase activity.Both isoenzymes had identical average molecular weight of 80 000 daltons by gel filtration and SDS gel electrophoresis.FI and FII isoenzymes were strongly inhibited by Hg⁺⁺, Mn⁺⁺, Mg⁺⁺ and Fe⁺⁺⁺ and activated by Zn⁺⁺, Co⁺⁺ and Fe⁺⁺. A difference in the degree of inhibition or activation was observed between FI and FII response. Ca⁺⁺ inhibited both FI and FII but the former was more sensitive to Ca⁺⁺. KCN also inhibited the two isoenzymes.Among the antioxidants tested, butylated hydroxytoluene and butylated hydroxyanisole most effectively inhibited both FI and FII at only 10^?6M. Sulphydryl reagents such as iodoacetamide and dithiothreitol have little effect on the lipoxygenase isoenzyme activity.The lipoxygenase isoenzymes were more stable at neutral pH. The enzyme in the crude extract and especially in situ was more stable to heat treatment.     

Haplotinea insectella (Fabricius) (Lepidoptera: Tineidae)—A potential pest of stored cereals in North America

The first incidence of Haplotinea insectella (Fabricius), in North America is reported from overwintered stored wheat and oats in Winnipeg, Canada. The potential of this species as a pest of stored cereals and oilseeds was tested by investigating feeding, diapause, development, and mortality on whole and crushed cereals, oilseeds and on fungi, at 25 ± 1°C and 70 ± 2% r.h. H. insectella completed egg to adult development in the absence of diapause in 49–57 days on crushed wheat, oats, barley or triticale. It did not complete its life cycle on any whole seed, crushed soybeans, crushed sunflower seed, or on cultures of Aspergillus amstelodami (Mag.) Thom and Church, A. repens de Bary, A. restictus (Smith), or A. candidus Link ex FR. These results show that H. insectella can successfully infest stored grain in Manitoba.     

An investigation of the entomogenous fungus Beauveria bassiana (Bals.) Vuill. as a potential biological control agent for Oryzaephilus surinamensis (L.)

In laboratory experiments, a soil isolate of Beauveria bassiana (Bals.) Vuill. was found to be an effective pathogen of adult Oryzaephilus surinamensis (L.) under certain conditions. Experiments on the effect of temperature showed that infection could occur down to 7°C, the lowest temperature tested. Little difference in mortality was noted when beetles were exposed to wheat treated with a range of concentrations of B. bassiana conidiospores in suspension (10⁶, 10⁵ and 10⁴ spores ml^?1), but mortality was lower at 10³ spores ml^?1. Humidity level, however, was the critical factor in allowing infection to occur. Beetles became infected at 100% r.h. but not at 90% r.h.When conidiospores of B. bassiana were applied to 50 g wheat grain cultures of O. surinamensis, the fungus proved ineffective in killing adult beetles. Breeding success, however, was sharply reduced with a 91% decrease in numbers of larvae and pupae in cultures treated with spores of the fungus mixed with the grain.