EFFECT OF VACUUM PACKAGING ON CHANGES ASSOCIATED WITH FROZEN COD FILLETS

Protein solubility of cod fillets sealed under vacuum was significantly higher at all sampling times than from fillets sealed in presence of air during an 18 months storage study at −25°C. Frozen storage resulted in substantial loss of protein from all of the bands of the PAGE pattern, with more pronounced loss from the myosin heavy chain, actin and tropomyosin bands. Dimethylamine and malonaldehyde concentrations were not significantly different between the air and vacuum pack. Significant losses in flavor and textural quality during frozen storage were detected. Crosslinking, responsible for the observed reduction in protein solubility of raw tissue, appears to be of relatively weak nature, since little toughening was detected in the cooked tissue.     

调味烤鳕鱼片生产工艺研究

以鳕鱼为原料,对调味烤鳕鱼片的加工工艺、操作要点进行研究.     

COMPARISON OF 2-THIOBARBITURIC ACID REACTIVE SUBSTANCES DETERMINATION METHODS IN VARIOUS TYPES OF FROZEN, FRESH MEAT

Triplicate batches of chicken breast (CB), chicken thigh (CT), fresh ground beef (GB), ground beef patties frozen 2 years (BP), veal (V), pork roast (PR), ground pork frozen 1 year (GP) and lamb (L) were homogenized and subjected to each of five 2-thiobarbituric acid reactive substances determination methods (n = 3 TBARS determinations/sample/method/replicate). Distillation methods resulted in higher (p < 0.05) TBARS values than extraction methods for all types of samples. TBARS ranges were CB=0.21–0.55; CT=0.21–0.40; GB=0.26–0.89; BP=1.14–4.00; V=0.18–0.82; PR=0.67–2.09; GP=1.17–4.01; and L=0.58–2.18. Distillation methods in which antioxidant was added did not consistently produce lower TBARS than distillation without antioxidant. Distillation methods produced TBARS approximately 2 times those produced by extraction methods in less oxidized samples (CB, CT, GB, V); distillation methods produced TBARS 2.75 times those produced by extraction methods in more oxidized samples (BP, PR, GP). Recoveries were quite different (ranging from about 65% to 95%) for the various methods indicating the need to run both standard curves and recovery rather than using published conversion factors in TBARS calculations.     

COMPARISON OF PHYSICAL METHODS FOR ESTIMATING THE MATURITY OF RAW, FROZEN AND COOKED PEAS

The back extrusion cell, Maturometer, Kramer shear press, FMC Tenderometer, and Ottawa Texture Measuring System wire extrusion cell gave useful estimates of the maturity of raw peas but, two viscosity methods gave unsatisfactory estimates. None of the instruments gave useful estimates of maturity of frozen peas that had been thawed or cooked because blanching conditions and the rate of freezing of the peas affected the readings. The most reliable estimate of raw pea maturity from thawed frozen peas was the alcohol insoluble solids content.     

PROPERTIES OF DIFFERENT FISH PROCESSING BY-PRODUCTS FROM POLLOCK, COD AND SALMON

Individual fish processing waste stream components can be used to make feed ingredients or other products. Waste stream components obtained from commercial fish processing plants included heads, viscera, frames, and skins from Alaska pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus); and heads, and viscera from pink salmon (Oncorhynchus gorbuscha). The protein content of heads from all three species ranged from 13.9 to 16.4%; and the fat content ranged from 0.9 to 10.9%. Viscera protein content ranged from 13.0 to 15.3%, and the fat content from 2.0 to 19.1%. After heating to 85C the percent soluble protein in salmon heads was different (P < 0.05) from pollock or cod heads. Percent soluble protein of pollock and cod skin increased 8fold (P<0.05) after the 85C heat treatment. Connective tissue content was calculated from chemical determination of hydroxyproline content, and large differences in percent connective tissue content were found (1% for pollock viscera to 46% for skin). Estimated rat PER values ranged from a low of 2.1 for skin to a high of 3.1 for viscera and fillet samples (P<0.05).     

海藻油微胶囊中DHA检测预处理方法的比较

对糊精、酪蛋白与变性淀粉、蔗糖两组壁材组合制备的海藻油微胶囊,采用酶法破壁与超声波法破壁,然后分别用氯仿-甲醇法、碱性乙醚法和酸水解法提取油脂,甲脂化后气相色谱分析二十二碳六烯酸(DHA)含量.结果表明:对于同一种微胶囊样品,破壁方法和油脂提取方法的不同均会对DHA的含量测定有影响.同一种破壁方法,采用碱性乙醚法提取油脂测得的DHA含量较其它方法高;同一种油脂提取方法,酶法破壁测得的DHA含量比超声波法测得的含量高.     

COMPARISON OF FROZEN, FOAM-SPRAY-DRIED, FREEZE-DRIED AND SPRAY-DRIED EGGS

SUMMARY —Coagulation patterns of slurries prepared with milk and frozen, foam-spray-, freeze-and spray-dried whole eggs, yolks and albumen were studied. All slurries were heated and stirred at constant rates using a Brabender Visco/Amylo/Graph. Ranked in order of initial gelation temperatures were slurries prepared with frozen, freeze-, spray- and foam-spray-dried whole eggs. Slurries prepared with frozen yolks or albumen showed initial gelation at lower temperatures than those prepared with dried yolks or albumen. Viscosity data indicate detrimental effects of drying to gelation properties of whole eggs, yolks and albumen.     

COMPARISON OF WET-CHEMICAL METHODS FOR DETERMINATION OF LIPID HYDROPEROXIDES

Five methods for determination of lipid hydroperoxides were evaluated, including two iodometric procedures involving a titration and a spectrophotometric micro method, and three other spectrophotometric methods namely the ferro, International Dairy Federation (IDF) and FOX2 (ferrous oxidation in xylenol orange). Peroxide values determined in a range of food products by these five methods gave different results. The ferro method required large amounts of solvent (50 mL/sample); the FOX2 method had a low range (0.005–0.04 μmol hydroperoxide); the end point detection of the titration method was subjective and required a large amount of sample (1 g); and the micro method was sensitive to interruptions during execution. Therefore, only the modified IDF method was chosen for further testing and validation. Stability tests of the standard curve showed a variation coefficient of 4% and within runs the highest variation was 5.9% (for blank) and a maximum of 9.6% between runs variation for the lowest concentration. Among the antioxidants tested, only ethylenedi-aminetetraacetic acid (EDTA) affected the peroxide determinations.     

IMPROVED METHODS FOR DETERMINATION OF CERTAIN ORGANIC ACIDS IN PASTEURIZED AND UNPASTEURIZED LIQUID AND FROZEN WHOLE EGG

ABSTRACT— This work was supported in part by National Institutes of Health Contract Ul-00131-06.
Liquid whole egg to which acetic, butyric, lactic, propionic and succinic acids were added, or which had previously been incubated at room temperature to different microbial populations, was pasteurized at 60.5°C for 3.5 min. A liquid-liquid extraction method, including the centrifugation of the denatured egg, was developed for extraction of all 5 acids. The recovery of the 5 acids was evaluated by an improved gas-liquid chromatographic procedure. Lactic and succinic acids were recovered from the liquid whole egg samples and chromatographed as their butyl ester derivatives and acetic, propionic and butyric acids were recovered and chromatographed as the acids per se. The fresh egg samples containing small amounts of acetic and lactic acid and liquid whole egg product, incubated until a microbial population of 4.5 × 10⁶ was obtained, con tained only these 2 acids at a higher concentration. The pasteurization process did not affect concentration of the added short-chain organic acids or those which accumulated during the incubation period; thus, accurate and valid analyses of the short-chain organic acids can be accomplished in pasteurized whole egg products.     

COMPARISON OF TWO ANALYTICAL METHODS FOR THE DETERMINATION OF DIMETHYLNITROSAMINE IN BEER AND ALE, AND SOME RECENT RESULTS

The results obtained by a rapid Celite column extraction method for the determination of dimethylnitrosamine (DMN) in beer and ale were compared with those obtained by a more elaborate vacuum distillation method. The end determination in both cases was done by gas-liquid chromatography using a thermal energy analyzer (TEA) detector. The two sets of results for 28 samples of beers from various countries were highly comparable. Recent survey results for both Canadian and imported beer and ales suggest a significant decrease in the levels of DMN in these beverages from that observed 2–3 years earlier. This decrease is probably due to the improvements in the malt drying techniques instituted in Canada as well as in other countries.     

A COMPARISON OF MICROBIOLOGICAL AND RADIOIMMUNOASSAY METHODS FOR THE DETERMINATION OF PANTOTHENIC ACID IN FOODS

Seventy-five foods were analyzed for the vitamin pantothenic acid using a microbiological assay and a new radioimmunoassay (RIA). The food sample extract used in both assays was the result of dialysis after enzyme hydrolysis. In the method used previously, the food-enzyme mixture had been filtered.
A very high correlation (r²=.94) between the results from the RIA and the microbiological assay was found. There was a statistically significant difference between the two assay results for all foods and for the subgroups meats, breads and cereals, and fruits and vegetables at p=.05. At p = .01 breads and cereals and fruits and vegetables did not have significantly different results between the two assay methods. For all foods and all subgroups, the microbiological assay produced a higher mean result than the RIA.
The RIA is an acceptable method for assaying pantothenic acid in breads and cereals and fruits and vegetables. Futher study is needed to determine how components of meat interact with one or both assay systems.