摘要:

SUMMARYThe antioxidant activities of several flavone glycosides and cinnamic acids were determined in lipid‐aqueous systems. Flavone glycosides, except rutin, possessed approximately the same antioxidant activity as their respective aglycone. Rutin was not as effective as its corresponding aglycone, quercetin. Quercetin derivatives were the only glycosides isolated from green onions, green‐pepper pods, green‐pepper seeds, and potato peels. Green‐onion tops also possessed a glycoside of myricetin. Caffeic acid was an effective antioxidant hut chlorogenic acid had no antioxidant a

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01833.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYFresh, diced onions were dehydrated under different regimes (high‐, intermediate‐, and low‐temperature, and lyophilization). Rehydration volumes were determined for the dice. Water vapor sorption properties and X‐ray estimates of crystallinity were obtained for the cellulose extracted from the dice and for control samples of cellulose that had been extracted from fresh onions and then dehydrated. Rehydration occurs most rapidly in lyophilized tissues, in which at 24°C and at 91°C approximately the original fresh volume is attained in 15–30 min. The final rehydrated volume in other treatments is reached more slowly and is considerably smaller than the fresh volume. The highest crystallinity of cellulose is found in the lyophilized materials, probably as a freezing effect. Freezing also produces large, internal voids. Cellulose crystallinity is essentially unaffected by temperature differences during the dehydrat

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01834.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe main simple polyphenols of immature dates (Phoenix dactyliferavar. Deglet Noor) are flavans, flavonol glycosides, caffeoylshikimic acids, and a cinnamic acid derivative. Tannins are both water‐soluble and ‐insoluble condensed tannins of the leucoanthocyanidin type. Of the simple polyphenols, the flavans and caffeoylshikimic acids undergo the greatest decrease during maturation and storage. Tests with date phenolase show these compounds to be the most susceptible to enzymic browning. Several new phenols form during storage. Treatment of the tannins with hot strong acid produces cyanidin chloride, suggesting the presence of leuco‐cyanidin units in the ta

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01835.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe effect of sulfite on the reaction of mushroom polyphenol oxidase with o‐diphenols was studied in model systems at pH 6.5. Spectrophotometric, manometric, chromographic, electrophoretic, and radiosotopic evidence is presented that sulfite prevented browning in the systems by combining with the enzymatically produced o‐quinones and stopping their condensation to melanins. During preincubation of polyphenol oxidase with sulfite a gradual loss of the property of the enzyme to cause browning was obser

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01836.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe effect of gamma radiation upon the quality of sweet cherries was studied. Softening was detected which progressed rapidly above a threshold dose of approximately 50 kilorads and was related to the degradation of pectic constituents of the fruit. Although respiratory O2consumption and CO2evolution were stimulated during irradiation, the response subsided slowly after irradiation ceased. Color bleaching occurred only at the high doses. Despite a marked initial reduction in microbial contamination, extended storage periods showed increased microbial spoilage. A reduction in the development of brown‐rot during high‐temperature short‐time storage resulted from kilorad doses of radiation. There was a slightly increased rate of sulfur dioxide bleaching and increased yield of brined cherries, but this was accompanied by loss of texture of the finished pr

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01837.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYChemical changes in the longissimus dorsi muscle of 5 beef carcasses were followed from less than 10 min after death through 20 days post‐mortem. The average initial pH value of 6.99 declined to 5.46 at 48 hr and was 5.57 at 480 hr. Initial values for creatine phosphate, total acid‐soluble phosphate, ortho‐phosphate, lactic acid, total reducing sugars, and glycogen were respectively 9.i, 54.9, 22.1, 13.1, 7.9 and 56.7 μM/g of tissue. Creatine phosphate declined rapidly to only 16% of the initial value by 12 hr post‐mortem, and was not detectable by 24 hr. Ortho‐phosphate, lactic acid and total reducing sugars increased approximately 1.5; 6.5, and 2.25 times from their initial levels during 480 hr post‐mortem. Glycogen appeared to be stoichiometrically degraded to lactic acid and reducing sugars, since the sum of these constituents was approximately constant at all times post‐mortem, if expressed in terms of glucose equivalents. Results suggest that the onset of rigor occurred at 12–15 hr post‐mortem. Development of rigor mortis was virtually complete 24 hr after death. The pattern of chemical changes observed with intact beef carcasses subjected to commercial cooling practices is in essential agreement with earlier results with isolated beef muscle strips.An enzymic method for determining ATP levels was compared with the more commonly used method of acid hydrolysis. ATP values at 24 hr post‐mortem were negligible when determined by the enzymic method, but amounted to about 27% of the original level when determined by acid hydrolysis. Reasons for the discrepancy in the two m

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01838.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe thermal conductivities of freeze‐dried slabs of starch, gelatin, pectin, cellulose gum, and egg albumen gels were determined under a variety of conditions, using a guarded hotplate apparatus. The effects of temperature, gas pressure, and gas composition on a starch gel were studied in detail. The thermal conductivities of dry materials at atmospheric pressure varied from 0.921 × 10‐4cal cm‐1°C‐1sec‐1(gelatin) to 1.337 × 10‐4(cellulose gum). In vacuum this variation was from 0.218 × 10‐4(starch) to 0.467 × 10‐4(cellulose gum). The difference between atmospheric pressure and vacuum was equal to the thermal conductivity of air for all the materials except cellulose gum, which gave a greater difference. The thermal conductivity of starch gel increased linearly with increasing temperature from 0 to 70°C, and decreased with decreasing pressure, as porous materials normally do, to a constant value below 0.1 mm Hg. A helium atmosphere gave a higher thermal conductivity than air or nitrogen. The thermal conductivity was higher in all freeze‐dried gels containing adsorbed water than after the removal of all the water. The thermal conductivity of pectin gels increased with the density. Thermal conductivity was affected by the type and size of pores of the dried materials. In general, changes in thermal conductivity were significant with pressure, type of gas, and nature of the material, particularly the fibrous structure, but less important with temperature and a

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01839.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe equilibrium isotherms and the rates of adsorption and desorption of water vapor by selected freeze‐dried food materials were studied between −20 and 50°C with a spring‐balance sorption apparatus. In simple freeze‐dried gels (starch, gelatin) the quantity of adsorbed water at equilibrium increased as the temperature was lowered from 50 to 0°C, and it remained almost constant below 0°C. In freeze‐dried foods (potato, peach, and raw beef) and sugar‐containing starch gel, adsorption was maximum at between 10 and 30°C. The equilibrium vapor pressure of simple gels followed the Clausius‐Clapeyron equation throughout the temperature range studied, and the same relationship applied to the foods at the high and low temperature regions, with a change of slope at about 20°C. The rates of adsorption and desorption at a pressure of 0.1 mm Hg remained constant at temperatures below 0°C, and they increased linearly as the temperature was increased from 0 to 50°C. As the pressure was raised from 0.1 mm Hg to atmospheric, the rates of adsorption at 30°C decreased by a factor of about 100. The adsorption rates at atmospheric pressure increased exponentially with the temperature between 0 and 50°C. The results are discussed in relation to the f

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01840.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYTests made with chickens frozen before rigor, during rigor, and after rigor showed that the amount of drip exuded on thawing was greatest in poultry frozen during rigor. The loss of nitrogenous constituents and ribose increased proportionally with the amount of drip. Protein solubility was minimum, and cooking losses maximum, in poultry frozen during rigor. The factors responsible for drip loss in poultry appear to be similar, regardless of the stage of rigor mortis at which the meat was frozen. It is probable that more water froze out of muscle during the state of rigor, causing higher solute concentrations in the tissue. The higher solute concentration in the muscle tissue frozen during rigor may affect the solubility of proteins and their ability to reabsorb water on thawing, and thus affect tenderness and loss of drip.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01841.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYHypoxanthine concentration is a useful index of the quality of flesh foods. A rapid manual assay of the purine was automated by modifying commercially available proportioning and spectrophotometric equipment. Extracts are sampled serially and mixed with xanthine oxidase and buffer. After reaction at 37° in a time‐delay coil, the mixture passes through a low‐volume flow‐through cell, where its absorption at 290 mμ (and hence uric acid production from hypoxanthine) is monitored continually. Concentrations are estimated by reference to standards and

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1965.tb01842.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY