bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzyme induced loss of sucrose in berry fruit juices
Authors: PLOWMAN J. E. , LOVE J. L. , HERBERT B. R. 
Published: July 2010

SummaryVaried concentrations of sucrose have previously been reported in freshly picked berry fruits. We have observed that sucrose in juice extracts from berries decreased markedly with time. The loss of sucrose added to raspberry and loganberry juice is attributed to the action of the enzyme, invertase. Heat inactivation immediately after picking reduced the loss of sucrose in raspberries and blackberries. Knowledge of these changes might influence the methods of harvesting, storage and processing.
Effect of heat on the fatty acids and aldehydes of veal meat phospholipids
Authors: FOGERTY A. C. , WHITFIELD F. B. , SVORONOS D. , FORD G. L. 
Published: July 2010

SummaryReactions involving phospholipids contribute considerably to the flavour and aroma of cooked meat. The effect of heat on the fatty acids and fatty aldehydes of phospholipids from veal was studied using aqueous model systems wherein extracted phospholipid fractions were heated in the presence or absence of ribose or glycine. After 1 h at 132°C, ethanolamine‐containing phospholipids rapidly lost most of their component aldehydes but not their fatty acids, whereas choline‐containing phospholipids lost their aldehydes much more slowly. In both cases, the presence of ribose or glycine had little effect on the loss of aldehydes. In the meat itself, after heating at 132°C, there was a 90% loss of aldehydes which was similar for both the ethanolamine‐ and choline‐containing phospholipids, but the latter lost fatty acids more slowly than the former.
Enzyme activities in quinoa (Chenopodium quinoa)
Authors: LORENZ K. , NYANZI F. 
Published: July 2010

SummaryThe amylase, protease, cellulase and hemicellulase activities were determined in the flour of untreated quinoa seeds, and again after mechanical abrasion and after water and heat treatment to remove saponins. Optimum pH for amylase activity was approximately 5.0 and for protease activity it was 4.2In comparison with a non‐malted wheat flour, which generally would have a Braben‐der unit (BU) reading of over 2000 in the Amylograph, values for quinoa were very low, indicating a high α‐amylase activity. Mechanical abrasion, which removed about 18% of kernel weight, increased α‐amylase and protease activities of the seeds because of removal of layers low in activity. Only toasting of seeds at 170°C after saponin removal reduced activities of these enzymes substantially.Total amylase, cellulase and hemicellulase activities were highest in the unprocessed seeds. Activities decreased after mechanical abrasion of seeds. Heat treatment after saponin removal caused a further decrease in activity of these enzymes.
Objective measurement of banana pulp colour
Authors: WAINWRIGHT H. , HUGHES P.A. 
Published: July 2010

SummaryTwo methods for determining the colour of banana pulp were compared by using either visual matching with colour charts or a portable tristimulus colorimeter. Pulp colour of ripe and unripe bananas was evaluated in both the darker central carpellary zone and the outer pulp zone near the skin of the fruit. Colour coordinates L* and b* were highly correlated (r = ‐0.89 and 0.87 respectively) with the visual matching colour charts, the central carpellary region giving higher correlations than the outer pulp zone. Results obtained show that the colour of banana pulp can be objectively measured by the combined use of L* and b* coordinates determined in the carpellary zone. The potential use of a reproducible and defined method for determining banana pulp colour is discussed.
Extraction of ginger rhizome: kinetic studies with acetone
Authors: SPIRO M. , KANDIAH M. 
Published: July 2010

SummaryGround sieved Jamaican ginger rhizome has been treated with acetone under various conditions and, in each case, the concentration of [6]‐gingerol extracted was measured as a function of time. The results could be expressed by two intersecting first‐order plots and an initial intercept, representing very rapid initial extraction, followed by a fast stage and a subsequent slow stage. At 30°C the rate constant of the slow stage was c. 95 times smaller than that of the fast stage and its activation energy was 3.6 times larger. The fast stage was not affected by solvent flow into the ginger particles, or by an increase in the stirring speed. These findings, together with the fact that both first‐order rate constants were inversely proportional to the square of the radius of the particles, pointed to [6]‐gingerol diffusion through the solid ginger as the rate‐determining step. The data could also be fitted by the equation of So and MacDonald (1986). The relevance of the research to the industrial production of ginger oleoresin is pointed out.
Reduction of Streptococcus thermophilus in a whey protein isolate by low moisture extrusion cooking without loss of functional properties
Authors: QUÉGUINER C. , DUMAY E. , CAVALIER C. , CHEFTEL J. C. 
Published: July 2010

SummaryA whey protein isolate powder (WPI) (4–5% water) inoculated with 5x105 viable Streptococcus thermophilus per g, was continuously processed in a twin screw extruder under the following conditions (barrel length = 500 or 1000 mm; screw profile = forward transport and compression elements; moisture content during extrusion = 4–5%; feed rate = 10 kg h‐1; barrel temperature (Tb) = 80–204°C; speed of screw rotation = 50 r.p.m.). The minimum residence time determined by pulse injection of erythrosin was 20–25 s (500 mm barrel) or 35–40 s (1000 mm barrel).Reduction values of viable Streptococcus thermophilus of 104.2‐fold (500 mm barrel, Tb= 143°C) or 104.9‐fold (1000 mm barrel, Tb= 133°C) were obtained without any modification of protein solubility or gelling properties. WPI extruded at the highest barrel temperatures (182–204°C) underwent limited browning and reduction of protein solubility. Gel permeation and hydrophobic interaction chromatography of the soluble constituents did not show any aggregates of β‐lactoglobulin or α‐lactalbumin.Gels prepared from control or extruded WPI (Tb 143°C with a barrel length = 500 mm or Tb 133°C with a barrel length = 1000 mm) were identical, as judged by scanning electron microscopy and rheological evaluations.
The heat stability and isoenzyme composition of peroxidases in Ohane grapes
Authors: ROBINSON D. S. , BRETHERICK M. R. , DONNELLY JUDITH K. 
Published: July 2010

SummarySoluble and ionically bound peroxidases have been obtained from homogenized Ohane grapes. The soluble fraction contained the highest level of peroxidase activity and accounted for approximately 87% of the total enzymic activity. Plots of the percentage of heat inactivation for the grape peroxidases against time were non‐linear with approximately 90% of the peroxidase activity being destroyed after 10 min at 80°C. Following heat inactivation there was no significant regeneration of enzymic activity. Using isoelectric focusing six isoperoxidases with isoelectric points ranging from approximately pI 3.5 to 9.8 were detected.
An investigation of enzyme activities found in thaumatin preparations
Authors: RAMSOHOYE PAMELA V. , KOZLOV I. A. 
Published: July 2010

SummaryA new alkaline cathodic gel has been developed which improves on the acidic cathodic gel of Reisfeld, Lewis and Williams (1962) when resolving thaumatin isoproteins in commercial thaumatin by electrophoresis. This new gel was used in the investigation of protease and esterase activities in commercial thaumatin and thaumatin isoprotein preparations. Enzyme activity stainings of the thaumatins on the new gel indicate that these activities do not belong to thaumatin but to contaminating enzymes. Other data, such as the decrease in the protease and esterase activities as a result of further purification of the thaumatins and the titration of the proteolytic activities with the specific inhibitor, E‐64, also support this conclusion.
Physical properties of cassava mash
Authors: GEVAUDAN A. , CHUZEL G. , DIDIER S. , ANDRIEU J. 
Published: July 2010

SummarySorption and thermophysical properties (desorption curves, density and specific heat) of native and gelatinized cassava mash and of cassava starch were determined, in order to gain a better understanding of the heat and mass‐transfer phenomena involved in gari cooking and drying.Desorption isotherms of native cassava mash are given at four temperatures from 40 to 90°C; the experimental data were described using the GAB model with a maximum root mean square error (RMS) of 5%.The net desorption enthalpy, calculated from the desorption data, decreases from 902.0 to 80.2 kJ/kg when the moisture content increases from 0.04 to 0.24 kg of water/kg dry matter. Desorption curves are not significantly affected by the degree of gelatinization of the starch, but at constant water activity, native cassava mash has a higher equilibrium moisture content than the other samples.The density of cassava mash increases from 1239 to 1509 kg/m3 when it is dehydrated from 51.8 to 6% (wet basis), and the specific heats of dry cassava starch and dry cassava mash, determined by differential scanning calorimetry, vary linearly over the temperature range ‐20°C to 96°C from 1.128 to 1.760 and from 0.979 to 1.591 kJ/kgxK.
The palm oil bleaching capacity of various Nigerian clay deposits
Authors: OKPALA K. O. , NWOKE M. N. 
Published: July 2010

SummaryThe ability of clay deposits from six different locations in Nigeria to bleach palm oil was assessed. Each clay was analysed for gross mineral composition. Degummed and steam‐sparged palm oil was heated with different quantities of each fine clay for 30 min. The degree of bleaching was determined by comparing the absorbance of residual pigment at 452 nm with that of unbleached oil. Performance was assessed with a modified form of the Freundlich adsorption isotherm (X/M = KCn), where X/M is the mass of pigment adsorbed per unit weight of adsorbent, C is the equilibrium concentration of pigment, and the constant K provides an index of performance for each clay. The exponent n was 2 for all clays, and K values varied from 120 to 2950, apparently with the Fe2O3 content of the clay. Clays with high iron content should be tested further, for use in bleaching palm oil.
Degradation of polysaccharides by immobilized depolymerizing enzymes
Authors: TURECEK P. L. , PITTNER F. , BIRKNER F. 
Published: July 2010

SummaryPolysaccharides in fruit and vegetable juices can be efficiently degraded using co‐immobilized amylolytic and pectolytic enzymes combined with naringinase. The enzymes were immobilized on silica carriers for use in fining procedures to remove cloudiness.
Changes in the electrical conductivity of foods during ohmic heating
Authors: HALDEN K. , DE ALWIS A. A. P. , FRYER P. J. 
Published: July 2010

SummaryOhmic heating is a food processing operation in which heat is internally generated within foods by the passage of alternating electric current. The process enables solid particles to heat as fast as liquids, thus making it possible to use High Temperature Short Time sterilization techniques on particulate foods. Ohmic heating rates are critically dependent on the electrical conductivities of the foods being processed, about which little information is available. This paper reports experiments to determine the changes in electrical conductivity which occur during ohmic heating of some common foods. A number of effects which occur during conventional heating, such as starch transition, melting of fats and cell structure changes, are shown to affect the electrical conductivity. In some cases the presence of an electric field induces enhanced diffusion of cell fluids in the food which increases the rate of change of conductivity with temperature above that found by conventional heating. Preheating is found to increase the electrical conductivity of some foods, making them acceptable for ohmic processing.
An improved high‐pressure homogenizer for making fine emulsions on a small scale
Authors: BURGAUD I. , DICKINSON E. , NELSON P. V. 
Published: July 2010

SummaryA reliable high‐pressure laboratory homogenizer is described for the small‐scale production of emulsions with highly reproducible droplet‐size distribution. A key feature of the design of this ‘jet homogenizer’ is the inclusion of separate chambers for oil and aqueous phases, thereby eliminating the necessity for premixing prior to homogenization, with its associated problems of air incorporation. To illustrate the performance characteristics of the jet homogenizer, data are presented for the effect of homogenization pressure and equipment dimensions on the droplet size of n‐tetradecane‐in‐water emulsions stabilized by sodium caseinate.
Chemical and nutritional quality of Indonesian dried‐salted mackerel (Rastrelliger kanagurta)
Authors: MARUF F. W. , LEDWARD D. A. , NEALE R. J. , POULTER R. G. 
Published: July 2010

SummaryIndonesian mackerel (Rastrelliger kanagurta) were sun dried or salted and sun dried and stored at 30°C for up to 20 weeks in air. During processing and storage polyunsaturated fatty acids oxidized to form thiobarbituric acid (TBA) reactive substances and fluorescent compounds. TBA values increased with increasing salt content (range 2.3–20.7%). Positive, highly significant correlations were found between the odour of the stored products and both fluorescent pigment production and the degree of browning. Amino acid analysis indicated loss of lysine, glutamic acid, serine, histidine, arginine and the sulphur containing amino acids, but these losses were far too small to account for the massive decreases found in net protein utilization (NPU) of the stored products, measured by rat‐feeding trials. The latter were highly correlated with the fluorescent pigment content and degree of browning in products of intermediate (∼ 14%) salt content.
Amino acid composition of whole mackerel (Scomber scombrus) stored anaerobically at 20°C and at 2°C
Authors: HAALAND H. , ARNESEN E. , NJAA L. R. 
Published: July 2010

SummaryTotal amino acid composition of whole mackerel (Scomber scombrus) and of milt and roe from mackerel stored at different conditions were studied. During storage at low temperature, no obvious changes were found. When stored at high temperature (20°C), the contents of several of the amino acids decreased, and phenylethylamine, tyramine, putrescine, histamine and cadaverine were formed the formation of cadaverine was higher than the loss of lysine.
A comparison of modified atmosphere and vacuum skin packing for the storage of red meats
Authors: TAYLOR A. A. , DOWN N. F. , SHAW B. G. 
Published: July 2010

SummaryThe performances of two commercially available packaging systems for prolonging the shelf‐life of fresh meat were compared at 1°C and during simulated retail display. Beef and pork loin steaks in modified atmosphere packs (MAP), containing 75% O2 and 25% CO2, developed an initial bright red (beef) or pink (pork) colour, which gradually changed to brownish‐red or ‐pink after 12 days; similar samples in vacuum skin packs (VSP) remained purple‐red throughout the storage period. Off‐odours developed more rapidly in MAP (8–12 days), possibly due to more extensive growth of Brochothrix thermosphacta and the effects of aerobic conditions on the metabolites of lactic acid bacteria, which predominated in both types of packs. Evidence of rancidity, using thiobarbituric acid assay, was demonstrated in MAP beef after approximately 8 days, but not in VSP. Drip losses in MAP increased after 6 days' storage, but remained generally low in VSP. Physical texture (shear force values of cooked samples) of beef was unaffected by packaging method, but pork in VSP was significantly more tender (P < 0.001) than in MAP.
Effects of controlled atmospheres on microbial spoilage, electrolyte leakage and sugar content of fresh ‘ready‐to‐use’ grated carrots
Authors: CARLIN F. , NGUYEN‐THE C. , CHAMBROY Y. , REICH MARYSE 
Published: July 2010

SummaryThe effects of controlled atmospheres (CO2 concentrations ranging from 0.03 to 40% and O2 concentrations ranging from 21 to 1%, measured in pack) were studied on fresh ‘ready‐to‐use’ grated carrots, stored at 10°C. High CO2 or low O2 conditions favour the growth of lactic acid bacteria (LAB) on grated carrots, but not in a sterile carrot medium, and induce an increased potassium ion leakage. A 25% CO2 and 2% O2 atmosphere improves retention of sugars.Grated carrots were inoculated by a strain of Leuconostoc mesenteroides, which caused increased potassium ion leakage and exudation only under an atmosphere containing 40% CO2 and 10% O2.The origin of the spoilage of ‘ready‐to‐use’ grated carrots is discussed.
Water desorption isotherms of two varieties of sweet potato
Authors: DIAMANTE L. M. , MUNRO P. A. 
Published: July 2010

SummaryWater desorption isotherms were determined for New Zealand sweet potato at 25, 40 and 55°C, and for Philippines sweet potato at 28°C. The isotherms were sigmoid in shape and of type II according to the BET classification. The data were fitted to eight two‐parameter equations reported in the literature. The effect of water activity, aw, and temperature, T°C, on the equilibrium moisture content, Me g water/100g dry solids, was best described for New Zealand sweet potato by: Me = 20.51 T‐0.204 (aw/(1‐aw)0.39 for aw= 0.06–0.81
Extraction of ginger rhizome: kinetic studies with dichloromethane, ethanol, 2‐propanol and an acetone—water mixture
Authors: SPIRO M. , KANDIAH M. , PRICE W. 
Published: July 2010

SummaryThe kinetics of extraction of [6]‐gingerol from ground Jamaican ginger rhizome have been determined at 30°C in dichloromethane, ethanol, isopropanol and an 80% (v/v) acetone + 20% (v/v) water mixture. The extractions all proceeded in three stages: an initial ‘washing’ stage, a fast stage and a subsequent much slower stage. The rate of extraction of hexahydrocurcumin in ethanol was found to follow a simpler pattern. From the first order plots, the diffusion coefficients of the extracted solubles within the ginger particles were calculated. They varied inversely with the 0.6 power of the solvent viscosity, which explained why the rates of [6]‐gingerol extraction decreased in the sequence: acetone < acetone + water < dichloromethane < ethanol < isopropanol. These results show that solvents of low viscosity should be chosen to attain fast extraction rates. The diffusion coefficient of [6]‐gingerol was also measured at 30°C in pure acetone, ethanol and isopropanol. The values in these bulk solvents were 13–20 times greater than the diffusion coefficients of [6]‐gingerol within the ginger particles for the fast stage and over 900–1800 times greater than those for the slow stage. These hindrance factors quantify the effect of the ginger matrix environment on internal diffusion.
Catalysis of the reaction between sorbic acid and thiols by surfactants
Authors: WEDZICHA B. L. , ZEB A. 
Published: July 2010

SummarySorbic acid reacts slowly with simple thiols at 80°C. The reaction involves nucleophilic attack on the sorbic acid molecule by the thiolate anion. Second order rate constants for the reactions of mercaptoethanol, mercaptoacetic acid, cysteine and glutathione are, respectively, 0.86, 0.68, 2.3 and 2.5 M‐1 h−1 at 80°C and independent of pH in the range pH 3.7–5.7. The effects of dodecyltrimethylammonium bromide (DoTAB), sodium dodecyl sulphate (SDS), lecithin, datem ester (diacetyltartaric acid ester of C18 monoglyceride) and Tween 80 on the initial rates of these reactions at pH 5.0 are reported. The greatest catalytic effect was shown by DoTAB, giving a maximum enhancement of rate by a factor of 21.4 for the mercaptoethanol reaction and 4.6 for the glutathione reaction. SDS was much less effective. The nonionic surfactants all behaved as catalysts. The mechanism of the surfactant‐catalysed reaction is discussed. Kinetically derived stoichiometries of binding of the solutes in question to DoTAB micelles depend on surfactant concentration, and for the thiols used (mercaptoacetic acid, cysteine and glutathione) it is found that each thiol molecule is associated with at least 10 surfactant molecules making up the micelles for surfactant concentrations greater than or equal to 50 mM. The implications of micellar catalysis to food additive‐food component interactions are considered.
Purification and preliminary characterization of five serine proteinases produced by Brevibacterium linens
Authors: HAYASHI K. , CLIFFE A. J. , LAW B. A. 
Published: July 2010

SummaryFive proteinases were purified from culture filtrate of Brevibacterium linens by a series of column chromatography and found to be homogeneous by polyacrylamide gel electrophoresis. All appear to be serine proteinases, being inactivated by phenyl‐methylsulphonyl fluoride and not by EDTA or p‐chloromercuribenzoic acid. They were all active against casein in alkaline pH (pH optimum of 11.0) and specific activity was within the range 2.66–3.23 units mg−1 protein. Proteinases C, D and E were more stable in higher temperature and acidic pH than proteinases A and B. Molecular weights estimated by gel filtration were 37000, 37000, 44000, 127000 and 325000 for proteinases, A, B, C, D and E, respectively.
Partial characterization of the in situ activity of pectinesterase in Bramley apple
Authors: KING KAREN 
Published: July 2010

SummaryThe characteristics of pectinesterase (PE) have been examined in waste material (peel, cores and offcuts) obtained from Bramley seedling apples barn stored for 2, 4 and 12 weeks. A crude enzyme extract was prepared by suspending the dried and milled apple waste in 0.1 m NaCl at pH 8.5. The activity of PE under standard assay conditions of 0.5% apple pectin, 0.1 m NaCl, pH 8.5 and 30°C was low, between 4 and 8 units g−1 dry matter, but activities up to 60 units g−1 dry matter were obtained at higher temperatures. The optimum temperature was 60°C with the enzyme stable up to 40°C with 5 min heating. The mean activation energy for PE in the three samples was calculated at 39.2 kJ mol−1 K−1. The optimum pH was high at 10.0 probably due to the PE assay measuring the extraction/solubilization and stability of the enzyme in addition to its activity. Optimum activity was obtained in 0.15 m NaCl with optimum stability at 0.5 m.
Evaluation of cooking time and quality of seven diverse cowpea (Vigna unguiculata (L.) Walp.) varieties
Authors: DEMOOY B. E. , DEMOOY C. J. 
Published: July 2010

SummarySeven cowpea (Vigna unguiculata (L.) Walp.) varieties, which were part of a larger collection evaluated in agronomic field trials in Botswana, were selected for characterization of cooking time and quality. Newly harvested seed was kept in the open air for 2 weeks, then stored at 4°C and 40% relative humidity for 3 months. Duplicate samples were tested for cooking time with and without 12‐h prior soaking. Varieties showed differences (P < 0.01) in cooking time and response to soaking, although the overall effect of soaking was insignificant. Cooking times ranged from 29 to 64 min without soaking and 36 to 56 min after soaking, with small‐seeded varieties having the longer cooking times. The seed coat of some varieties readily became soft, but others remained tough or split before finally softening.
Carotenoid composition and vitamin A value of some native Brazilian green leafy vegetables
Authors: MERCADANTE ADRIANA Z. , RODRIGUEZ‐AMAYA DELIA B. 
Published: July 2010

SummaryThe composition of carotenoids in five native Brazilian leafy vegetables was determined. The ranges of total carotenoid contents of Amaranthus viridis, Lepidium pseudodidymum, Xanthosoma spp., Sonchus oleraceus, and Portulaca oleracea were 347–468, 237–280, 225–361, 149–334 and 71–109 μg g−1, with lutein and β‐carotene predominating. The mean β‐carotene contents (μg−1) and vitamin A values (retinol equivalents REg−1) were 110 and 18.4, 84.6 and 14.1, 67.3 and 11.2, 62.9 and 10.5, 29.8 and 4.99, respectively. The leaves contained 54–61% of lutein plus violaxanthin, 24–34% of β‐carotene, 10–14% of neoxanthin and traces of zeaxanthin and α‐crypto‐xanthin. The native leafy vegetables were richer sources of provitamin A than the cultivated leafy vegetables analysed previously, justifying their commercial production.