摘要:

ABSTRACTGoldfish skeletal muscle was examined with the electron microscope to investigate the ultrastructural changes produced by freezing. Aquarium fish were used to circumvent the variables associated with catching and killing large food fish. Muscle tissue was frozen slowly in a refrigerator or quickly in liquid nitrogen. The results confirm the conclusions in the literature that fast freezing produces many small ice crystals which cause minimum dislocation of tissue ultrastructural components, whereas slow freezing generates fewer large ice crystals which distort cells and crush myofibrils. These results reveal the ultrastructural counterpart to those alterations which are visible in the light microscope using much simpler equipment and methodology [Bello et al. (1981), J. Food Sci. 46: 733].

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04945.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTEnzymic lipid peroxidation by light and dark muscle microsomes of herring (Clupea harengus) required ATP or ADP, NADH and Fe. NADPH could not effectively replace NADH. Inhibition was observed at high concentrations of ADP and NADH but not Fe. The optimal pH for the reaction of both types of microsomes was between 6 and 7. The average peroxidation rate was 362 and 1143 nmoles MDA per mg protein per hr at 6°C for the light and dark muscle microsomes, respectively. The energy of activation for the light and dark muscle microsomes was similar. The light muscle microsomes lost activity faster than the dark muscle microsomes when exposed to 35°C. Ferrous ion stimulated enzymic lipid peroxidation of light and dark muscle microsomes over that observed with ferric io

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04946.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe nutritional quality of proteins from fillets of fresh rockfish (Sebastesspp) stored in air or in a modified atmosphere (MA) of 80% CO2and 20% O2at 4°C was evaluated by the Computed Protein Efficiency Ratio (C‐PER) method. This procedure involves determination of in vitro digestibility and the amino acid composition of the samples prior to computation of the C‐PER. Casein was used as a standard. Both air‐held and MA‐held fish showed similar amino acid profiles, but the air‐held fish showed lower in vitro digestibility. The C‐PER values of both types of samples were higher than the C‐PER of 2.50 for standard casein. These results suggest that storage of fish in a modified atmosphere of 80% CO2and 20% O2does not result in deterioration in the nutritional quality of the

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04947.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTMicroorganisms present on fresh beef for stew were enumerated by Aerobic Plate Count (APC) using both rinse and maceration methods. Results showed a greater recovery of microorganisms with maceration than with rinse procedures. Scanning Electron Microscopy (SEM) techniques were used to examine the surface of the beef for stew to demonstrate the presence of microorganisms before and after rinsing. Sterile stainless steel chips (6 mm × 6 mm) were placed on both the unrinsed and rinsed beef surfaces. Contact was maintained at 4°C for 4 and 24 hr. The contacting surfaces of the stainless steel chips were examined by SEM. Transfer of microorganisms from the beef surface was seen in all cases with the organisms demonstrating clearly defined attachment fibrils. A reference experiment, using the same beef for stew and a culture ofPseudomonas fragi(ATCC 4793) was also carried out. Similar attachment fibrils were observed with the pseudomona

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04948.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTGlutathione peroxidase (GSH‐Px) activity was measured and selenium (Se) values obtained on beef semitendinosus muscles. TBA numbers were determined on stored, ground beef patties prepared from the same samples. Factors affecting the assay and the stability of the enzyme in post‐rigor beef were examined. According to these studies, GSH‐Px activity could be assayed directly from the muscle extract. The enzyme was viable throughout the rigor process and exhibited activity within the expected meat pH range. A statistically significant correlation between GSH‐Px and muscle Se was obtained. The correlation coefficient was only moderately high (0.65). Comparison of the muscle Se values obtained in this study to a suggested minimum for nutritional adequacy in cattle indicated that values for several of the muscles in the present study were similar to or below this minimum value. Studies encompassing the total GSH‐Px system are needed to determine if this system can serve to protect raw beef from oxidative deterioration durin

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04949.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTTemperature fluctuations produced during storage and transport of frozen food lead to activation of the recrystallization processes, causing enlargement of the ice crystals and diminishing advantages obtained in quick freezing of products. A model for interpreting recrystallization of ice in frozen beef was established considering that in this phenomenon the driving force is the tendency to a decrease in surface energy of the crystalline phase and that rate of movement of the grain boundary is proportional to its curvature. Meat samples were frozen and submitted to higher storage temperatures. Histological analysis of tissues immediately after freezing and of samples stored at different times made it possible to measure evolution of ice crystal size and obtain kinetic constants for proposed recrystallization model. Mechanisms for interpreting the phenomena were discussed, determining that transition of molecules occurs preferently through the liquid phase.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04950.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTConditions for gel formation of heated globin and inhibition of thermocoagulation of ovalbumin and bovine serum albumin by globin were investigated. Globin was highly soluble even when heated at 100°C at pH below 5. Globin also considerably inhibited thermocoagulation of ovalbumin and serum albumin near their isoelectric point. A great increase of viscosity was observed when 1% globin solution was heated at above 80°C in the narrow pH range between pH 5.2 and 5.4. Heated globin formed a transparent gel at concentration above 3% under well controlled heat condition

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04951.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe reaction of nitrite with cytochrome c in the presence or absence of sodium ascorbate was studied. The amount of ferrocytochrome c nitrosyl compound I (cytochrome c · Fe2+‐NO+) formed in the absence of ascorbate was dependent on pH both at initial equal concentrations of nitrite or nitrous acid; the amount formed was very small at pH above 5.0. The presence of ascorbate significantly enhanced the extent of the reaction in the pH range 5.0–6.0. The reaction decreased rapidly at pH above 6.0, but application of heat was effective in giving a large formation of the product. Ascorbate reduced compound I to ferrocytochrome c nitrosyl compound II (cytochrome c · Fe2+‐NO). The relative amounts of the two compounds formed was influenced by pH; at pH below 3.6, a mixture of compound I and II was formed, but only compound II was formed above pH 3.6. Compound II easily gave rise to ferrocytochrome c Cytochrome c probably reacts with nitrite in cured meat if ascorbate or erythorbate

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04952.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTAlterations in colloidal properties resulting from heat treatment and/or freezing of whole egg magma were studied. Both heating and freezing led to increases in apparent viscosity and in surface tension. All viscosities are non‐Newtonian. Increasing rates of shear followed immediately by decreasing rates resulted in open hysteresis loops; repeated cycles showed only one decrease in viscosity. Polyacrylamide gel electrophoresis demonstrated changes incurred by heat treatments of 60°C, 3.5 min; 64.4°C, 2.5 min; and 68°C, 1 min. Scanning electron microscopy pointed out morphological modifications caused by heating and/or freezing. Sucrose and D‐glucose preserved lower viscosity during frozen storage. In conclusion, a preliminary postulation of colloidal structure in whole egg is pre

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04953.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTRemoval of calcium from skim milk by electrodialysis was logarithmically related to the extent of demineralization (log% calcium removed = 0.18% ash removed + 0.53). This removal of calcium caused a logarithmic dissociation of micellar to serum (sub‐micellar) casein (log% total casein in serum = 0.020% calcium removed + 0.70). Increases in protein stability for skim milk and concentrated skim milk were related to this dissociation of micellar casein, and the initial degree of dissociation persisted throughout frozen storage. Protein stability was>53 wk at –8°C when 80% of the casein in unconcentrated skim milk was dissociated. Concentrated skim milk was stable for>30 wk at –8°C when 45% of the casein was dissociated. Control samples (7–9% casein dissociated) were stable for only 4–8

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1982.tb04954.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY