摘要:

ABSTRACTThe effect of peroxidase on food flavor and quality is discussed, and its use as an index of blanching fruits and vegetables reviewed. Peroxidase is considered the most heat stable enzyme in plants. If inactivated, all ofher enzyme systems are usually inactivated in the product. There is an empirical relationship between residual peroxidase activity and the development of off‐flavors and off‐odors in foods. Peroxidase activity has been detected in products stored at — 18°C and under moisture conditions as low as 12.5% moisture. Any activity detected following severe heat treatments is usually due to the enzyme not being wholly inactivated. Inadequate thermal processing may result in regeneration of the

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01204.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTSoluble high molecular weight conjugates of catalase were prepared by intermolecular cross‐linking with glutaraldehyde at pH 7.0. The same reagent was used to prepare high molecular weight soluble conjugates of glucose oxidase with and without catalase activity. For cross‐linking of glucose oxidase the reactions were carried out at pH 4.5 in the presence of bovine serum albumin. No difference in Kmvalues was observed between samples of catalase conjugates and untreated enzyme, either soluble or immobilized. When soluble glucose oxidase‐catalase conjugates were incubated at 55°C for 18 min, only 20% of the original glucose oxidase activity was lost while the untreated enzyme lost 90% of its activity under the same cond

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01205.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTSamples of vegetable pear (mirliton),Sechium edule, SW, fresh tissue were analyzed for moisture and dry matter. Dry matter was further analyzed for crude protein, ether‐extractable material, pectin, crude fiber, ash, selected minerals, and nitrogen‐free extract. Fresh mirlitons contain 94% moisture. Carotene was not detected. The mirliton does not contain detectable amounts of lipoxygenase or polyphenol oxidase activity (compared to activity in mushroom). Amino acid concentrations in the seed were approximately twice those of the flesh. Methio‐nine was detected in the seed but not in the tissue. The data suggest that the mirliton can be a new fresh vegetable crop for the southern area and for processing into frozen food pro

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01206.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTChippewa and Katahdin potatoes were examined for susceptibility to enzymatic darkening in relation to lipid content. Comparisons were made between the bud and stem regions of Katahdin tubers for 3 consecutive years and between Chippewa and Katahdin tubers for 1 yr. Enzymatic darkening was always greater and lipid content lower in the stem than the bud region. This relationship was exhibited by both the pith and cortex tissues. The phospholipid fraction followed the same trend as crude lipid, being higher in the bud than the stem end. Chippewa potatoes had a greater crude lipid and phospholipid content than Katahdin potatoes and were less susceptible to enzymatic darkening. The lipid content of the tuber, although present in relatively small amount, is important in determining cellular integrity and resistance to bruising.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01207.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTAnthocyanins were extracted from taro with 50% methanol, isolated by adsorbtion on insoluble polyvinylpyrrolidone, and purified by thinlayer chromatography. The pigments were identified by chromatographic and spectrophotometric methods as pelargonidin 3‐glucoside, cyanindin 3‐rhamnoside and cyanidin 3‐glucoside. Levels of anthocyanins were highest in the skin of the corm, 16.0% mg%, with equal amounts, 4.29 mg%, in both corm and petiole. Anthocyanogens also were pr

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01208.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTStorage treatments (12°C, 95% RH) were applied to freshly harvested mushrooms for 0, 24 and 72 hr. Canned product yields were determined on replicated samples processed by a standardized procedure. Canned product yields increased 19% after 72 hr storage and total free amino acid content of the tissues increased proportionately. Electrophoretic analyses employing sodium dodecyl sulfate gels demonstrated that degradation of larger molecular weight proteins occurred during storage with a corresponding increase in the lower molecular weight fractions. Water‐binding capacity and water‐holding capacity of partially purified proteins prepared from treated lots increased as storage time progressed. Data substantiated the hypothesis that qualitative changes in mushroom proteins are a factor in the increased product yields obtained by postharvest storage of mushr

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01209.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTDirect comparisons were made on the content and retention of thiamine, pyridoxine, niacin and folacin in quick‐cooking (large Lima, pinto, pink, blackeye) beans prepared from authentic, chemically characterized lots of commercial dry beans. Significant losses occurring during cooking and their relationship to cooking time differentials were determined and the vitamin levels in cooked beans compared with ofher outstanding sources of B‐complex vitamins. Data show dry beans are a good source of B‐complex vitamins, but levels vary considerably with bean type and processing/cooking methods. Cooked, quick‐cooking Lima and blackeye beans had slightly higher levels of all four vitamins than standard cooked beans, but standard cooked pink and pinto had higher levels of thiamine, pyridoxine and niacin; folacin differences were inconsistent. There was no consistent relationship between vitamm content and cooking time. Cooked blackeye, large Lima and pink were equivalent or higher than beef liver or wheat germ with respect to thiamine, better sources of pyridoxine than yeast or wheat germ, but lower in niacin than liver. With respect to folacin, blackeye beans are a better source than liver, wheat germ or yeast and large Lima and pink are equal or better than beef liver o

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01210.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTRheological properties of cell wall material suspensions recovered from pressed cranberries were studied with rotational viscometers at 25°C. The general power law equation was found to be an adequate model, the flow behavior index decreasing, and the consistency coefficient and yield stress Increasing, as concentration increased. Time dependency and pseudoplastic or mixed‐type flow behavior were observed. Large yield stresses at low concentrations suggested potential use of cell wall material as a food. thicken

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01211.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTThe volatile emanations of cultivars of muskmelon were isolated by three procedures: direct sampling of melon cavity gases via a septum‐sealed glass probe cemented to the melon, entrapment of large volumes of headspace gas on porous polymer traps, and steam distillation‐extraction of pieces of melon fruit tissue. Essences were subjected to gas chromatographic analysis in high resolution wall‐coated open‐tubular glass capillary columns. Identifications were based on mass spectra, gas chromatographic retentions, and occasionally infrared spectra. Forty‐seven compounds, dominantly esters, were identified and their concentrations during ripening were followed. The biogenetic pathways for selected esters were studied by radioassay of volatiles produced by melon tissue incubated with selected radio‐labeled

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01212.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTThe biochemical properties of polyphenoloxidase (PPO) from Lerman and Fuerte avocado varieties, which differ in their rates of browning, were studied. The partially purified PPO from either source had a pH optimum around 5.5–6.5 and was characterized by a relatively high stability to heat. PPO of Lerman and Fuerte avocado exhibited fairly similar substrate specificity, with a higher activity toward 4‐methyl catechol, pyrogallol or dopamine and a lower one toward catechm, caffeic acid or chlorogenic acid. No lactase or cresolase activity was detected with either enzyme. The effect of several types of PPO inhibitors was tested and it was found that, with minor exceptions, the two enzymes responded similarly. PPO of both sources exhibited similar relative activities toward most of the o‐dihydroxyphenols tested and, as reported earlier, similar isoenzyme patterns were obtained with DL‐DOPA, caffeic acid, chlorogenic acid, and 4‐methyl catechol. It can therefore be concluded that the higher rate of browning observed when freshly cut Fuerte is exposed to air, as compared with Lerman, is unlikely to result from a difference in the properties of the PPO enzymes in each of these varieties. Instead, it may be directly correlated to the amount of PPO activity present per gram wet weight and/or the concentrations of the natural substrate

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1977.tb01213.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY