摘要:

Starches in the juices of yellow passion fruit,Passiflora edulis f. flavicarpa, and purple passion fruit,P. edulis f. edulis, were isolated and characterized. Starch granule sizes for the yellow variety (7.8 μm) and purple variety (6.4 μm) were similar. Gelation temperature ranges for the yellow variety (58.5–67.0 ° c) and purple variety (58.5–66.5 ° C) were also similar. The amylose content was slightly higher in the yellow variety (8.7%) than in the purple variety (5.8%). Viscosity differences between juices of the two varieties after treatment with heat and α‐amylase were attributed to differences in pH and starch content between the yellow variety (pH 2.8, 0.06% starch) and the purple variety (pH 4.2, 0.74% starch). α‐amylase was effective in reducing the viscosity of passion fruit juice in which the starches ar

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02918.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Headspace analysis of volatile compounds is complicated when components are present above their limit of solubility and/or when a second solid or liquid phase exists. A technique is presented which is based upon controlled dilution to a concentration where the solubility limit is no longer exceeded, coupled with a correction for extraction into the additional solid or liquid phase(s). The method is demonstrated for the determination of d‐limonene contents of synthetic emulsions and orange juic

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02919.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Experimental results are presented for the retention of d‐limonene during freeze drying of sucrose solutions, for 10% and 25% solution concentrations, for fast and slow freezing, and for various levels of d‐limonene addition ranging from below to considerably above the solubility limit. The results show decreasing percentage retentions with increasing initial levels of d‐limonene, reaching an asymptotic value at high initial d‐limonene contents. These results are interpreted quantitatively in terms of both microscopic observations and a simple model which allows for the collection of emulsion droplets at the ice‐concentrate interface during the freezing step, with subsequent loss of those droplets during freeze drying. Retention experiments with n‐hexyl acetate and acetone lend additional support to this interpretation and demonstrate the importance of the ratio of emulsion droplet size to the thickness of the interstitial webs of

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02920.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Retention of d‐limonene during freeze drying of citrus juices from several sources was investigated as a multi‐phase problem. Reconstituted to 25 and 10° Brix, commercial frozen concentrates show high retention (between 90 and lOO%), whereas fresh‐squeezed juice shows a relatively low retention (about 30%), comparable to that found previously for synthetic emulsions. Retention data for pasteurized fresh juice after substantial agitation and for never‐concentrated, commercial pasteurized juices show an intermediate value (between 60 and 70%). Presence and stability of cloud are shown to correlate closely with improved d‐limonene retention in commercial frozen concentrates. On this basis, a simple model is developed which predicts the retention level for this type of juice in the asymptotic region. The results for the other types of juice studied are interpreted with the aid of microscopic determinations of oil droplet size and the model derived for synthetic

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02921.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Beauty Seedless grape pigments were isolated and identified by chromatographic, spectral and chemical properties. The pigments were identified as delphinidin‐3‐glucoside, petunidin‐3‐glucoside, malvidin‐3‐glucoside, peonidin‐3‐glucoside, malvidin‐3‐glucoside acylated with caffeic acid and malvidin‐3‐glucoside acylated with p‐coumaric acid. Beauty Seedless grapes contained 62 mg anthocyanins per 100g fresh grapes and malvidin derivatives accounted for 73%

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02922.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Excision of asparagus spears triggered increased peroxidase activity and a shift in isozyme species. Changes in peroxidase occurred within 8 hr after harvest at the cut end of the spear and progressed to the tip end after 24 hr storage at 20 °C and 85% relative humidity. Isozyme changes were accelerated by exogenous ethylene gas. Ethylene production by cut spears and rate of spear toughening were greatest when spears were cut above ground. It is suggested that wound ethylene triggers a shift in peroxidase isozymes which participate in lignin biosynthesis and results in spear toughening after harvest

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02923.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Thermal degradation of methylmethionine sulfonium ions was determined in sodium citrate buffers ranging in pH from 4.0–8.0. Reaction temperatures of 82 °, 88 °, 93 ° and 99 °C were studied at reaction times of 20, 40, 60 and 80 min. The same conditions were used to study the degradation of naturally occurring methylmethionine sulfonium ions in sweet corn and tomato serums. In each solvent system, the thermal degradation of these salts occurred according to first order kinetics; the reaction rates doubled for a 5–6 °C increase in temperature and activation energies of the reaction in the various media were comparable. The characteristic degradation kinetics provides a means of identifying methylmethionine sulfonium salts in fresh foods without having to resort to involved isolation pr

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02924.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Mucilage found in hulls of yellow mustard seed was investigated. The isolated mucilage was a cold water‐swellable hydrocolloid of low to medium viscosity and exhibited thixotropic properties. Viscosity increased with addition of alkali or acid. Mucilage produced synergistic increases in viscosity when combined with guar, locust bean, or carboxymethylcellulose. Solutions were opaque, bland tasting and slightly acidic. Solutions showed stability to acidity down to pH 3.5 and also to cooking and cooling cycles. The mucilage lowered the surface tension of water and the interfacial tensions of oil and water emulsions. Emulsification was achieved in model salad dressing formulations. The mucilage exhibited excellent suspending propertie

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02925.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The effects of varying atmospheric pressures on the properties of starches were investigated. Four types of starches‐corn, rice, potato and wheat‐were studied for their water‐binding capacity and viscosity behavior. Photomicrographs of starch suspensions were taken at five altitudes and temperatures of 22 °, 60 °, 70 °, 80 ° and 90 °C respectively. Measurements of the photomicrographs showed corn, potato and rice starch granules to increase in size on changing elevation from sea level to 10,000 feet. Wheat starch was not affected. Water‐binding capacity increased for corn and potato starches as the altitude increased, but rice and wheat starches were not affected. The viscosity of corn, rice and wheat starch suspensions decreased initially with increasing altitudes but increased at the higher altitudes. The viscosity of potato starch suspensions did not change at increase

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02926.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Cerebroside (hexosylceramide) was isolated from rice grain, identified and examined for composition of fatty acid, sugar and long‐chain base constituents. The cerebroside was observed to contain 12 fatty acids; hydroxyarachidic (59.0%), hydroxylignoceric (19.7%) and hydroxybehenic (10.3%) acids were predominant. Glucose was the only sugar constituent. Three component long‐chain bases were found: two were identified as sphingosine (72.9%) and dehydrophytosphin‐gosine (17.3%). It is thus suggested that the major species of rice grain cerebroside is N‐hydroxyarachidyl‐glucosyl‐

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1974.tb02927.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY