Structure of beef Longissimus dorsi muscle frozen at various temperatures: Part 2-ultrastructure of muscles frozen at -10, -22, -33, -78 and -115°C

The changes in electron micrographs of muscles frozen at -10, -22, -33, -78 and -115°C were analyzed. The ultrastructure of muscle successively changed with decreasing freezing temperature whereas light microscopy indicated anomalous behaviour at -22°C. It appeared that, in muscles frozen at -10°C, there was no freezing of water intracellularly; in those frozen at -22°C, water was frozen intracellularly (but only in the I-band region); whereas, in muscles frozen at -33°C, water was frozen inside the fibres, both in the I- and the A-bands. In muscles frozen at -78 and -115°C, water is frozen intracellularly. These findings can be explained on the basis that, in the I-band region, the major protein is actin, which has a relatively high proportion of non-polar residues and holds water weakly, whereas the predominant protein in the A-band is myosin, which contains many polar residues and has a high water-holding capacity.     

Influence of α-, γ-, and δ-tocopherol on the radiation induced formation of peroxides in rapeseed oil triacylglycerols

The effect of α-, γ-, and δ-tocopherols (enrichment: 1000 ppm) on the peroxide formation in rapeseed oil triacylglycerols (RSOTG) was evaluated. The oxidation process was initiated by gamma-irradiation with doses of 4 and 10 kGy. Whereas a pronounced antioxidant effect was observed for γ- and δ-tocopherol (sequence: δ- > γ-tocopherol), the inhibition extent of α-tocopherol was insignificant.     

Structure of beef Longissimus dorsi muscle frozen at various temperatures: Part 1-histological changes in muscle frozen at -10, -22, -33, -78, -115 and -196°C

To elucidate the relationship between the lowering of freezing temperature and the distribution of ice crystals in frozen muscle, samples of beef Longissimus dorsi muscle were frozen at -10, -22, -33, -78, -115 and -196°C. Histological preparations of these samples indicated that ice crystals were formed in muscles frozen at -10°C intercellularly, at -22°C inter- and intracellularly, at -33°C intercellularly and at -78, -115 and -196°C only intracellularly. In muscles frozen at -78°C, ice crystals in fibres were large; in those frozen at -115°C they were relatively smaller; and in those frozen at -196°C they were evenly distributed throughout the muscles. The greatest damage was caused at -22°C due to the simultaneous formation of the ice intra- and intercellularly. The results indicated that the pattern of distribution of ice crystals at the latter temperature deviates from that predicted from a linear progression of change with temperature of freezing.     

容量法测定纸浆α-,β-,γ-纤维素

前言 容量法能简单、快捷测定纸浆中的α—,β—,γ—纤维素,该方法容易恒定,重复性好,有较好的准确性。 纤维素是植物纤维中最主要成份,是造纸和制造纤维素衍生物的基本原料。纤维素大分子是由β—D—葡萄糖(1—5)通过1—4β配醣键连接起来,各种纸浆的纤维素链长各不相同,如果纤维用17.5％和9.5％氢氧化     

High-Performance Liquid Chromatography with Fluorescence Detection for Simultaneous Analysis of Retinoids (Retinyl Palmitate,Retinyl Acetate,and Free Retinol) and α-, β-, γ-, and δ-Tocopherols in Foods

A method based on high-performance liquid chromatography with fluorescence detection for the simultaneous analysis of retinoids (vitamin A) and tocopherols (vitamin E) was developed. This method consists of an isocratic solution using hexane/ethyl acetate (85:15, v/v) as the mobile phase and fluorescence detection using a time program that sets the excitation (Ex) and emission (Em) wavelengths at adequate elution times for retinoids (Ex 342 nm, Em 476 nm) and tocopherols (Ex 298 nm, Em 325 nm), respectively. The separation of three retinoids (retinyl palmitate, retinyl acetate, and free retinol) and four tocopherol homologs was achieved with sufficient reproducibility and quantitative ability. Additionally, the necessity of saponification was considered. As a result, saponification was not used in this method because of the complexity of the procedure and the loss of free retinol. The retinoid and tocopherol contents of various foods were evaluated using the developed method. Our method could evaluate the retinoid and tocopherol contents of fish (eel, Anguilla japonica, and amberjack, Seriola dumerili) muscle and liver, roasted soybean (Glycine max) flour, and Japanese torreya seed (Torreya nucifera). Additionally, our method could be applied to the determination of retinoids and tocopherols not only in foods but also in supplements and cosmetics.     

Oxidative stability of Atlantic salmon (Salmo salar,L.) fillet enriched in α-, γ-, and δ-tocopherol through dietary supplementation

The purpose of this study was to examine the effect of dietary tocopherols on the oxidative stability of Atlantic salmon fillet. The fish were fed four diets supplemented with 150mg kg⁻¹ α-tocopherol and different combinations of γ- and δ-tocopherol (50 or 100mgkg⁻¹) for 10 months, slaughtered, and stored for 16 days on ice, or 48 weeks at −30 °C. Fillet concentrations of tocopherols at slaughter were 0.101 ± 0.001, 0.091 ± 0.004 and 0.025 ± 0.002 times feed concentration for α-, γ- and δ-tocopherol, respectively. Fillet α-tocopherol, but not γ- and δ-tocopherol, was moderately lowered during iced and frozen storage. The non-α-tocopherols protected the fillet against lipid oxidation in a dose-dependent manner during frozen storage, but appeared to act as prooxidants during storage on ice. It is concluded that α-tocopherol may be better suited than mixed tocopherols as a tool to optimize the oxidative stability of Atlantic salmon fillet.     

α-Amylolysis of native potato and corn starches - SEM, AFM, nitrogen and iodine sorption investigations

Scanning electron microscopy (SEM), atomic force microscopy (AFM), as well as iodine and nitrogen sorption measurements were applied to investigate potato and corn starch granules surface after an action of Bacillus subtilis α-amylase. The SEM images revealed holes and pits (corn starch) or scratches (potato starch) on the surface of modified granules. These results were confirmed by AFM investigation which showed the presence of depressions of approximately 121 nm in diameter. Structure of the surface was not uniform. It consisted of small particles, amylopectin blocklets, of approximately 20 nm in diameter. They became more distinctive after α-amylolysis. Values of iodine binding capacity (IBC) obtained for hydrolyzed granules were lower than for native ones which indicated that the amylose and amylopectin chains building their surface were shortened. Specific surface area, volume and average diameter of mesopores increased for both starches after α-amylolysis.     

Moisture-induced aggregation of alpha-lactalbumin: effects of temperature, cations, and pH

Abstract: Alpha‐lactalbumin is an important dairy protein ingredient, and has been widely used in high‐protein foods such as infant formula and nutritional bars for its nutritional and functional properties. The purpose of this study was to investigate the moisture‐induced aggregation of alpha‐lactalbumin in premixed protein dough model systems, and to illustrate the effects of temperature, cations, and pH on the progress of protein aggregation. Our results suggested that storage temperature was a critical factor for protein aggregation in model systems, and the formation of protein aggregates became faster with increases in storage temperature. Calcium significantly improved the thermal stability of alpha‐lactalbumin and slowed down the formation of protein aggregates. The increases in pH accelerated the aggregation of alpha‐lactalbumin. Our results also suggested that the formation of intermolecular disulfide bonds together with noncovalent interactions are the main mechanisms resulting in the moisture‐induced aggregation of alpha‐lactalbumin in model systems. Practical Application: Alpha‐lactalbumin is an important dairy protein ingredient, and has been widely used in high‐protein foods such as infant formula and nutritional bars for its nutritional and functional properties. Our results suggested low storage temperature, the presence of calcium and low pH condition can make high‐protein food products containing alpha‐lactalbumin more stable.     

Electrical stimulation of red deer (Cervus elaphus) carcasses - effects on rate of pH-decline, meat tenderness, colour stability and water-holding capacity

A total of 14 female red deer were included in a study on the effects of low voltage carcass electrical stimulation on meat tenderness, colour stability and water-holding capacity. Carcasses were randomly allocated to either electrical stimulation treatment (ES; 90-95 V unipolar pulses, 7.5 ms duration, 15 Hz for a duration of 55 s) or no electrical stimulation (non-ES) (n=7 in each group). Temperature and pH decline was recorded in M.m. triceps brachii, longissimus dorsi et lumborum (at the last rib; LD) and biceps femoris, at intervals from 0.5 to 20 h post-mortem. At 24 h post-mortem, LD from the left side were excised, vacuum packaged and refrigerated at -1.5°C. Glycogen concentrations, measured at 30 min post-mortem, and ultimate pH did not differ between groups. Compared to controls, ES increased the rate of muscle pH decline and produced lower shear forces at 1 day, 1 week and 3 weeks post-mortem, but these differences disappeared by 6 and 12 weeks post-mortem. Sarcomere lengths at 24 h post-mortem were unchanged by ES. After 1 week of refrigerated storage, ES significantly reduced display life (hours of Minolta a* value ? 12), but this difference disappeared at 3, 6 and 12 weeks of ageing. ES did not affect drip at any ageing time point. The present results demonstrate that the benefits of ES on tenderness are not permanent, and the procedure is not necessary for a long-term, chilled product. This study showed no detrimental effects of using electrical stimulation on meat colour stability or drip loss.     

Microbial quality, and effect of cooking on survival of Salmonella, in Kokariç

A special preparation from the small intestine of lamb, called kokariç, is widely consumed in Turkey. In this study, Salmonella was not isolated from raw kokariç. Conventional ways of cooking, except precooking, destroyed Salmonella in artificially contaminated kokariç. The microbial quality of cooked kokariç bought from street sellers was not safe for public health consumption because of environmental contamination.     

Comparison of the properties of Ring,Solo, and Siro core‐spun yarns

In this research, core‐spun yarns with an acrylic sheath fiber and a nylon flat core have been produced on the Ring, SIRO, and Solo spinning systems and the effects of some factors were investigated. The studied factors consist of filament pre‐tension (i.e. 1, 7/5, 10, 15, 50, and 100 g), spinning system (Ring, SIRO, and Solo), and feed position of the core filament in the strands of sheath fibers (six types of feed positions). Also, their physical and mechanical properties, including strength, elongation percentage, abrasion resistance, percentage of coefficient of variation (CV%), and hairiness, were all investigated. Finally, in each stage, the best case was determined. The results show that the quality of the core‐spun yarns produced by the SIRO spinning system is better than that of the Ring and Solo core‐spun yarns.     

Effects of Parity,Bacteriological Status,Stage of Lactation,and Dry Period on N-Acetyl-β-D-Glucosaminidase Activity of Milk and Dry Secretion

Quarter foremilk samples from 61 cows were obtained at 1.5, 3, 21, and 35 wk of lactation and at 7 d after drying off. Measurements for each sample were milk SCC, NAGase activity in the milk and ability of milk to promote phagocytosis of Staphylococcus aureus by polymorphonuclear leukocytes. Milk SCC and NAGase were correlated (r = .62). The NAGase in dry cow secretion was 10-fold higher than in milk. Parity differences in NAGase activity were not significant. There were large stage of lactation trends in NAGase: NAGase activity was high in early lactation, decreased in midlactation, and increased in late lactation and in dry secretion. The increase in activity of the enzyme in milk of first parity cows in late lactation was not as great as in milk of second and third lactation cows. N-Acetyl-β-D-glucosaminidase activity of milk from quarters with intramammary infections was higher than that of milk from quarters free of pathogens.