bluuebunny/crossref_metadata_2025 huggingface dataset:
Glycation of bovine β‐Lactoglobulin: effect on the protein structure
Authors: Morgan François , Mollé Daniel , Henry Gwénaële , Vénien Annie , Léonil Joëlle , Peltre Gabriel , Levieux Didier , Maubois Jean‐Louis , Bouhallab Saïd
Published: March 2003

Summary Since temperature and water activity are among the most important parameters that affect the Maillard reaction, the glycation sites in pure, native bovine β‐lactoglobulin were determined after a mild heat treatment (60 °C) in an aqueous solution and after a treatment under a restricted water environment (50 °C, 65% relative humidity). In both systems, the results obtained underlined the structural heterogeneity of β‐lactoglobulin (β‐LG) glycoforms with respect to the number of lactose residues linked per protein molecule and to the binding sites involved. Subsequently, the effect of the glycation conditions on both the association behaviour and the conformational changes of the glycated β‐LG were characterised by proteolytic susceptibility, binding of the fluorescent probe 8‐anilino‐1‐naphtalene‐sulfonic acid, SDS‐PAGE and size exclusion chromatography. The results showed that dry‐way glycation did not significantly alter the native‐like behaviour of the protein while the treatment in solution led to important structural changes. These changes resulted in a specific denatured β‐LG monomer, which covalently associated via the free thiol group. The homodimers thus formed and the expanded monomers underwent subsequent aggregation to form high molecular weight species, via non–covalent interactions. The use of monoclonal antibodies with defined epitopes, raised against native β‐LG, confirmed that the protein conformation was much more modified when glycation was performed in a solution while the structural changes induced during dry‐way treatment were limited to the AB loop region of the protein.
Rheological properties of commercial whey protein samples from the MADGELAS survey
Authors: Puyol Pilar , Pérez Ma Dolores , Calvo Miguel
Published: March 2003

Summary Thermally induced gelation of commercial whey protein samples from the Molecular Basis of the Aggregation, Denaturation, Gelation and Surface Activity of Whey Proteins (MADGELAS) survey has been studied in order to develop a current status report on their rheological properties. Solutions of 10% protein (w/v) were prepared in distilled water, 200 mm NaCl or 10 mm CaCl2 at neutral pH. Small‐scale deformation of the samples was measured by dynamic oscillatory rheometry using a Bohlin CS Rheometer. Large‐scale deformation at penetration mode was measured using a Texture Analyser (Stable Micro Systems, Surrey, UK). For solutions containing salts, there was a general trend for gel point to decrease and G′ values to increase, the effect being more marked in the presence of NaCl. Similarly, force values at failure also tended to increase in the presence of salts. Results obtained with samples of similar protein composition dissolved in water were highly scattered, these differences being reduced in the presence of added salts.
Aspects of whey protein usage in infant nutrition, a brief review
Authors: Jost Rolf , Maire Jean‐Claude , Maynard Françoise , Secretin Marie‐Christine
Published: March 2003

Summary Demineralized whey, whey protein concentrates and, to a lesser extent, some other whey protein fractions are key raw materials in infant formula manufacture. An estimate of the amount of whey protein used in infant formulae annually is in the order of 30–40 000 tons. Infant formula development has been a long lasting effort to approach the nutrient composition of human breast milk while using cow's milk as the raw material. This required extensive fractionation of the bovine milk followed by subsequent recombination of specific fractions. Criteria to judge protein quality and define adequate protein quantity in infant formulae have also evolved. Early criteria for protein adequacy were based on Protein Efficiency Ratio (PER) testing in rats and/or nitrogen balance studies. More recently, the approach of essential amino acid scores, based on the amino acid pattern of mature human milk has been put forward. Regulatory authorities such as CODEX, EC Commission and more recently LSRO in its suggestions to FDA in the USA, have issued reference amino acid profiles which are based on the average amino acid composition of human milk. The same authorities have also regulated protein density in infant formulae, accounting for an observed protein mean density of 1.5–1.6 g /100 kcal in mature breast milk. The minimum protein level of cow's milk based infant formulae was fixed at 1.8 g/100 kcal by these authorities. Current infant formulae have however protein densities significantly higher than the minimum of 1.8 g/100 kcal. The higher protein density compensates for the likeliness that the protein in the best of the formulae, is not as ideal for the infant as the protein from breast milk. Even if a complete equivalence may be difficult to reach, efforts continue in the direction of further optimizing the protein quality in terms of essential and semi‐essential amino acid profiles. This is the only way to be able to lower the protein content in a formula to levels that are nearer to the low protein density of human milk. Among several possibilities, the increase in the mass proportion of bovine α‐lactalbumin is a particularly promising way to achieve this goal.
Effects of pressure‐shift freezing and conventional freezing on model food gels
Authors: Kalichevsky‐Dong Monica T. , Ablett Steve , Lillford Peter J. , Knorr Dietrich
Published: March 2003

Summary Gels of agar, starch, ovalbumin, gelatin and an industrial β‐lactoglobulin protein isolate, were frozen conventionally in a −30 °C freezer and by pressure‐shift freezing at 200 MPa at −15 °C. Thawing was carried out conventionally at 20 °C and by the application of a pressure of 200 MPa. The microscopic structure and mechanical properties of the thawed gels were compared with those of the initial gels. Microscopic examination showed that pressure‐shift freezing produces smaller and more uniform ice crystal damage than conventional freezing at −30 °C. The results also suggest that the freeze‐thaw behaviour of food gels can be categorized into two general types: (1) gels which have a reduced gel strength as a result of mechanical damage to the gel microstructure caused by ice crystal formation, and (2) gels which have an enhanced gel strength, as a result of molecular structural changes that take place in the frozen state. Agar and gelatin were found to be typical of type (1) gels, whereas starch, β‐lactoglobulin protein isolate and ovalbumin were found to be typical of type (2) gels. In the case of starch, retrogradation during thawing was found to be the most important factor.
Measurement of glass transition in native wheat flour by dynamic mechanical thermal analysis (DMTA)
Authors: Pereira Pedro M. , Oliveira Jorge C.
Published: March 2003

Summary This work describes a method to study glass transition on native starch powders, based on dynamical mechanical thermal analysis using compression tests, and was applied to wheat flour (13.5% water content). This method will allow the determination of Tg in native (unprocessed) starchy materials, with minimal disturbance of the natural structures. The influence of the test conditions (heating rate, frequency and strain) on the glass transition measurements was determined using factorial designs. The values of Tg determined as the maxima of the energy dissipation (peaks in E″) of native flour and of freeze‐dried pre‐gelatinized flour were not statistically different (around 64 °C). The heating rate did not affect the measurements in the range tested (0.25 to 1 °C min−1). An interactive effect of the strain amplitude and the frequency was detected. The significance of this interaction can be caused by differences in mechanical energy dissipation, which would indicate that not only temperature but also the total energy input may affect this transition. Slight effects of phase separation between gluten and starch were found on native flour.
The fate of cyanogens during the cooking of cassava in mumu, a traditional oven in Papua New Guinea
Authors: Sopade Peter A.
Published: March 2003

Summary Four (Alotau, Mt. Hagen, Goroka, and Rabaul) types of mumu (earth‐oven) in Papua New Guinea were evaluated to ascertain their potential to detoxify cassava. The acid hydrolysis method was used for the determination of cyanogens. Each mumu exhibited different detoxification capacity. The loss of cyanogens in the (coconut) creamed cassava dough was lower than in the uncreamed dough. This was more evident when coconut cream–cassava mixture was cooked in boiling water than in a conventional oven set at 180 °C. Certain interactions were suspected to exist between the coconut cream and cyanogens or between the coconut cream and the appropriate enzymes that are responsible for the hydrolysis of the cyanogens. Such interactions resisted the loss of cyanogens and/or their quantification by the analytical method. The results are discussed in the light of nutritional consequences of such interactions, as coconut cream is a popular dietary item in Papua New Guinea (and the South Pacific islands).
Effects of peeling methods on the quality of ready‐to‐use carrot slices
Authors: Barry‐Ryan Catherine , O’Beirne David
Published: March 2003

The effects of methods used for peeling and physiological age (over‐wintering) on the quality and storage life of carrot disks packaged in modified atmosphere were examined. Commercial mechanical abrasion peeling using fine or coarse carborundum plates, was compared with carrots peeled by hand, before slicing into disks. Slices which had been peeled by abrasion had higher respiration rates, greater microbial contamination and growth rates, higher pH values, higher rates of weight loss and shorter microbiological shelf‐lives than those which had been hand peeled. These results reflected the higher quality of the manually peeled carrots. Micrographs of the peeled surfaces confirmed that abrasion peeling inflicted greater damage. Carrots lifted in the autumn produced slices with longer shelf‐lives than carrots lifted in the spring after over‐wintering in the ground for four months.
Prodelphinidins and related flavanols in wine
Authors: de Pascual‐Teresa S. , Rivas‐Gonzalo J. C. , Santos‐Buelga C.
Published: March 2003

Summary Liquid chromatography coupled to diode array spectrophotometry and mass spectroscopy detection (LC‐DAD‐MS) has been applied to the study of the proanthocyanidin composition of red wine. Analytical conditions were optimized using several flavanols previously isolated from grape seeds and pomegranate peel. Higher sensitivity was obtained in positive than in negative ion mode and electrospray ionization (ESI) proved to be more useful than chemical ionization (APCI) for the identification of flavanols with a higher degree of polymerization, since it always provided the molecular ion. Useful information for the identification of compounds was also obtained from their fragmentation patterns (MS‐MS spectra). The application of the method of LC‐DAD‐MS set up permitted the identification of fourteen flavanols in wine: four monomers (C, catechin; EC, epicatechin; GC, gallocatechin; EGC, epigallocatechin), eight dimers (B1, B2, B3, B4, B7, GC‐4,8‐GC, GC‐4,8‐C and C‐4,8‐GC) and two trimers (EC‐4,8‐EC‐4,8‐C and C1). Two other heterogeneous dimers were detected, which were supposed to possess an epi(gallo)catechin unit. No important peaks corresponding to galloyl derivatives were found. As far as we know, prodelphinidins and flavanols containing GC units were identified in wine for the first time.
Mineral and water soluble vitamin content in the Kombucha drink
Authors: Bauer‐Petrovska Biljana , Petrushevska‐Tozi Lidija
Published: March 2003

Summary Biologically active substances (water soluble vitamins and minerals) were analyzed in ‘Kombucha’—a curative liquor, produced by the so‐called ‘Kombucha cultivation’ (Macedonian collection of microorganisms, No 734) in sweet black tea decoct. The water soluble vitamins in the Kombucha drink were separated and identified using thin layer chromatography (TLC) and quantified by the comparison of their chromatographic UV spectra with the reference compounds. Four soluble vitamins have been determinated to have the following concentrations: vitamin B1 0.74 mg ml−1, vitamin B6 0.52 mg ml−1, vitamin B12 0.84 mg ml−1 and vitamin C 1.51 mg ml−1. Mineral elements of nutritional and toxicological importance were determined in dissolved ash using atomic absorption chromatography (AAS). Mineral composition content involved determination of the essential elements: zinc, copper, iron, manganese, nickel and cobalt. Investigations of some toxic elements showed that lead and chromium were present in very small amounts, whereas cadmium was not found.
Impact of fermentation technology on the phenolic and volatile composition of German red wines
Authors: Fischer Ulrich , Strasser Mario , Gutzler Karlheinz
Published: March 2003

Homogenous grape material of the red varieties c.v. Pinot noir, c.v. Dornfelder and c.v. Portugieser were fermented on an industrial scale using a special fermenter for pump over and punch down treatment. On pilot scale, thermovinfication was carried out at 60 °C and a manual punch down treatment was used in open containers. Both the mechanical punch down and pump over treatment significantly enhanced the extraction of all phenolic compounds and their polymerization in comparison to the traditional manual punch down treatment. Applying an excess of mechanical maceration increased the extraction of seed and stem phenols, but slowed down their polymerization. Assessing volatile composition, the biggest differences occurred between wines made by thermovinification versus those fermented on their skins. Slow fermentation kinetics and low solid content in the juice enhanced ester formation in thermovinied wines. Thermal inactivation of lipoxygenase enzyme systems reduced C6‐alcohols and their subsequent esters in thermovinified wines. Only small differences occurred between punch down and pump over tanks except that the pump over regime gave all varieties of wines significantly higher quercetin levels. In conclusion, the application of modern fermentation equipment seemed to be more relevant to improve extraction and polymerization of phenolic compounds, while thermovinification yielded wines with high ester content giving a more fruity style.
Pretreatment of pigeonpea grain for improvement of dehulling characteristics
Authors: Phirke Prabhakar S. , Bhole Nivrutti G.
Published: March 2003

Summary Pigeonpea grain (c.v. C11) was used for optimization of dehulling pretreatments. Treatments applied for dehulling were soaking in urea solution and hot milling. Second order polynomial equations were developed to describe a dehulling index and dehulling time. Response surface methodology was also used. Treatment with urea solution was applied to both nonscarified and scarified grain. Different concentrations, solution‐to‐grain ratios and duration of treatments were tested in five levels as independent factors in the first set of experiments. In the second set, hot milling, heating time and heating temperature were factors in five levels. Hot milling was followed by optimized treatment with urea solution. The levels of these factors were optimized to give a maximum dehulling index and minimum dehulling time, this would yield the maximum product recovery and reduce grain scouring. The results revealed that hot milling after urea treatment of scarified grain increased the dehulling index by about 11% and, consequently, reduced dehulling time by approximately 65% when compared with the treatment followed in commercial mills. This subsequently increased the product recovery and intact pearled grain by about 19 and 23%, respectively.
Sulphite binding in ciders
Authors: Jarvis Basil , Lea Andrew G. H.
Published: March 2003

Summary The extent of sulphite binding was measured in commercial ciders, and experimentally observed binding curves were compared with theoretically derived curves based on assessment of the levels of individual sulphite binding compounds determined in the ciders. Subsequently, experimental ciders were fermented under various controlled conditions using nine different strains of cider yeasts. The results indicated considerable differences both in the levels of sulphite binding compounds produced, and in the ability of different yeast strains to produce SO2 in the cider. Juice concentration and the presence of cloud in juice had little or no effect on sulphite binding. Other factors which affected sulphite binding included the type and condition of juice (especially the effect of pectinase treatment) and, in some instances, the use of added yeast nutrients. Significant sulphite binding was also attributable to unaccountable components, probably derived from poor quality fruit, which were present in the apple juice prior to fermentation.
Effect of acetaldehyde and several acids on the formation of vitisin A in model wine anthocyanin and colour evolution
Authors: Romero Concepcion , Bakker Johanna
Published: March 2003

Summary It was found that the reaction between malvidin 3‐glucoside and added pyruvic acid (PA), leading to the formation of vitisin A in model wine solutions, was not prevented by the addition of either acetaldehyde (A) or several organic acids. The acylated forms of vitisin A (3‐acetylvitisin A and 3‐p‐coumarylvitisin A) were formed through the interaction of malvidin 3‐acetylglucoside and malvidin 3‐p‐coumarylglucoside. Disappearance of the three main anthocyanins (malvidin 3‐glucoside, malvidin 3‐acetylglucoside and malvidin 3‐p‐coumarylglucoside) from the model wine with time followed first order kinetics. Acetaldehyde had the effect of increasing the total amount of these losses but producing smaller amounts of vitisin A. During ageing model solutions developed some browness. The brownest solution was obtained without A and a reduced rate of browning was found in the presence of A. This latter result can be explained by the assumption of a superimposition of a blueing effect upon reactions of A with anthocyanins. In the presence of PA the formation of vitisin A compounds gave an intermediate colour, contributing a reddish hue to the solution. A good correlation (r2= 0.96) between the percentage of vitisin A, of the total anthocyanins and the hue angle was observed. The addition of large amounts of organic acids that are normally found in wine into the model solutions did not lead to the formation of new anthocyanins. The linear loss of PA in all model systems indicates that a first order reaction occurs and 35.35 times more PA than total anthocyanin was lost to form the new compounds.
Copper and iron determination in edible vegetable oils by graphite furnace atomic absorption spectrometry after extraction with diluted nitric acid
Authors: De Leonardis Antonella , Macciola Vincenzo , De Felice Martino
Published: March 2003

In this article, a new method for determining copper and iron in edible vegetable oils by using atomic absorption spectrometry is discussed. The metals were extracted from low quantities of oil (1–2 g) with a 10% nitric acid solution. The acid solution obtained can be injected directly into the atomic absorption furnace. The proposed method is simple and allows copper and iron to be determined in edible vegetable oils with a precision estimated below 15% relative standard deviation (RSD) for Cu and 10% for Fe.
Detection of adulteration of Basmati rice with non‐premium long‐grain rice
Authors: Bligh Heather F. J.
Published: March 2003

Basmati rice is, on average, sold at 2–3 times the price of other rice available on the world market. As such, there is a requirement for a method that would allow the detection of non‐Basmati long‐grain rice within samples of Basmati. This paper reports the use of fluorescent simple sequence length polymorphisms (SSLPs) between known Basmati rice cultivars and likely adulterants, to detect the presence of any adulterant. The competitive nature of the fluorescent detection method also enabled crude estimations of the amount of adulteration present in blind test samples. Further, the difficulty in quantifying the level of adulteration is discussed.
Low temperature blanching effect on the changes in mechanical properties during subsequent cooking of three potato cultivars
Authors: Verlinden Bert E. , Yuksel Dogan , Baheri Mohammad , De Baerdemaeker Josse , Van Dijk Cees
Published: March 2003

Eight mechanical properties of three potato cultivars were measured during low‐temperature blanching (55, 65 and 75 °C) and subsequent cooling and cooking treatments. The mechanical properties were determined with a ring tensile test. Force‐based properties showed a decrease in value during blanching and cooking, whereas deformation‐based properties showed an initial increase during blanching, before decreasing, during cooking or after longer blanching times. This behaviour was attributed to the loss of turgor of the fresh potato tissue. Rates of change of mechanical properties during cooking depended on the pre‐blanching treatments: longer blanching times resulted in a slower decrease of the mechanical properties. The overall behaviour during blanching and cooking of the three cultivars was similar. A principal component analysis on the measured mechanical properties, for each blanching temperature separately, was used to study the blanching temperature effect and to segregate potato cultivars on their cooking behaviour.
Accelerated Cheddar cheese ripening with encapsulated proteinases
Authors: Kheadr Ehab E. , Vuillemard Jean‐Christophe , El Deeb Samy A.
Published: March 2003

Summary This work was undertaken to study the impact of bacterial and fungal proteinases encapsulated in liposomes on proteolysis and organoleptic properties of Cheddar cheese during ripening. Bacterial and fungal proteinases were encapsulated in liposomes with trapping efficiencies of 31.9 and 33.0%, respectively. The encapsulated bacterial proteinase was incorporated into Cheddar‐cheese milk in order to reach enzyme concentrations of 5 × 10–6 (B1), 1 × 10–5 (B2) and 2 × 10–5 (B3) AU g–1 cheese curd, while encapsulated fungal proteinase was added in order to reach enzyme concentrations of 1 × 10–6 (F1), 2 × 10–6 (F2) and 4 × 10–6 (F3) AU g–1 cheese curd. Experimental cheeses showed slightly higher moisture content but lower protein content when compared to control cheeses. Rheological measurements revealed that experimental cheeses were slightly less firm but more brittle as compared to control cheeses. Proteolysis and texture development of experimental cheeses were faster than control cheeses. As observed by transmission‐electron microscopy, liposome‐treated cheeses exhibited less compact microstructure and liposomes were essentially located at the fat–casein interface. The elution patterns obtained from size‐exclusion chromatography revealed that the accumulation of bitter and astringent peptides was higher in experimental cheeses than in control cheeses depending on the type and concentration of added enzyme. After 3 months ripening, the organoleptic properties of cheeses were markedly improved and no bitter off‐flavour was detected among treatments except cheeses subjected to treatments B3 and F3. The present study showed that micro‐encapsulated enzymes can be successfully used to accelerate cheese ripening and to avoid drawbacks resulting from the use of free enzymes. It was also concluded that the addition of encapsulated bacterial proteinase (up to 1 × 10–5 AU g–1 cheese curd) or encapsulated fungal proteinase (up to 2 × 10–6 AU g–1 cheese curd) could be recommended to accelerate the flavour and texture development of Cheddar cheese.
Grain, flour and bread‐making properties of eight  Pakistani hard white spring wheat cultivars grown at three different locations for 2 years
Authors: Anjum F. M. , Walker C. E.
Published: March 2003

Eight Pakistani wheat cultivars grown, at three locations (Faisalabad, Khanewal and Bahawalpur) in 2 crop years (1987–88 and 1988–89) were tested for a number of grain and dough properties. These included falling number, rapid visco‐analyser (RVA), and bread‐baking potential. Measurements by pearling, near infra red (NIR) and the Kansas State University (KSU) hardness tester indicated that the Pakistani wheats had hardness values typical of ‘hard’ wheats. NIR protein was significantly higher in one of the Pakistani wheats. Dry and wet gluten contents of Pakistani wheats were significantly influenced by cultivars, but not by crop year or growth location. The farinograms differed significantly among cultivars. Arrival time, water absorption, and dough‐development time were significantly affected by growth location. A falling number and RVA analyses indicated a low α‐amylase activity in Pakistani wheats, except for those grown in Bahawalpur during 1988–89. This suggests the use of malt for optimum bread production. Bread‐baking quality scores and loaf volumes were significantly different among growth locations, cultivars, and crop years.
Phage resistance in Lactococcus lactis subsp. lactis strains isolated from traditional fermented milk products in Turkey
Authors: Akçelik Mustafa , Sanlibaba Pinar , Tükel Çağla
Published: March 2003

Lactococcus lactis subsp. lactis strains isolated from traditional fermented milk products in Turkey were used to determine their phage resistance against three different lactic phages. The following modes of action were examined: phage adsorption inhibition in five strains, abortive infection (heat sensitive phage resistance) in three strains, restriction/modification in four strains and blocking of phage DNA injection in one strain. The genetic nature of the phage resistance systems in these strains was determined by comparison of phage proliferation parameters, e.g. adsorption (%), EOP, burst size, latent period and production of major capsid protein, between wild‐type strains and their plasmid‐cured derivatives.
Monitoring the fermentation of the traditional Bulgarian  beverage boza
Authors: Gotcheva Velitchka , Pandiella Severino S. , Angelov Angel , Roshkova Zlatka , Webb Colin
Published: March 2003

Summary For many centuries fermented foods have been produced and consumed world‐wide as they are of such great importance for human nutrition. Fermentation helps to preserve the food, provides a wide variety of textures and flavours and significantly improves the nutritional properties of the raw materials used. In this work we tested the hypothesis that the fermentation process of the Bulgarian cereal‐based traditional beverage boza was similar to other cereal‐based fermentations. Boza was prepared both from whole‐wheat grains and flour, and the effect of the raw material on product quality was studied. The main microorganisms responsible for boza fermentation, yeasts and lactobacilli, were identified and some physical and biochemical changes were monitored during the first 48 h of fermentation. A significant increase in glucose content was observed, while pH, viscosity, free amino nitrogen content and dry matter decreased during the fermentation. The use of wheat flour resulted in a product with higher viscosity and dry matter content when compared to that produced from whole‐wheat grains. The effect of temperature on fermentation rate was also tested.
Thermal damage in blood orange juice: kinetics of  5‐hydroxymethyl‐2‐furancarboxaldehyde formation
Authors: Arena Elena , Fallico Biagio , Maccarone Emanuele
Published: March 2003

Formation of 5‐hydroxymethyl‐2‐furancarboxaldehyde (HMF) was studied kinetically by HPLC in blood orange juice and model systems of fructose, glucose and sucrose at different acidic pH values and temperatures. The ultraviolet absorption of the solutions changes during reaction by forming an enediol intermediate, which slowly converts into HMF. Pseudo first order rate coefficients were used for comparing reactivity of sugars in model systems and in fortified juices. Glucose degrades much more slowly than fructose, while the reactivity of sucrose depends on pH value and temperature. The activation energy for sucrose was about 20 kcal mol‐1 higher than fructose, and such a difference can be ascribed to the rate‐determining contribution of the preliminary hydrolysis step. First order rate coefficients in orange juices were similar to those of model systems at comparable pH and temperature, indicating that sugar degradation occurs without any interference of other components, thus excluding the presence of the Maillard's reaction. HMF content constitutes an index of juice deterioration, therefore it should be included among the parameters of quality for commercial blood orange juices.
Three‐dimensional MRI mapping of minimum temperatures achieved in microwave and conventional food processing
Authors: Bows John R. , Patrick Maria L. , Nott Kevin P. , Hall Laurie D.
Published: March 2003

Microbiological assurance protocols for food preservation are based on the ‘worst‐case’ slowest heating point within the food product. For conduction‐limited processing, this leads to well‐known overheating near surface regions of products, with resultant quality loss. For volumetric heating processes such as microwave heating, it is practically impossible to guarantee where the slowest heating point will be. Consequently, microwave heating regimes are generally excessive and product quality is often similar to conventional conduction‐limited heating processes. It is well known that Magnetic Resonance Imaging (MRI) can provide three‐dimensional (3D) images which quantify the spatial distribution of water in foods, and also that the MRI parameters of water are temperature dependent. The present study demonstrates that a combination of these two concepts has led to a new approach for the validation of thermal processing in food manufacture. The potential for on‐line assurance of minimum and maximum temperatures for manufacture of microbiologically assured, minimally processed, high quality food is discussed.
A magnetic resonance study of water uptake in whole barley kernels
Authors: Gruwel Marco L. H. , Chatson Brock , Yin Xiang S. , Abrams Suzanne
Published: March 2003

The water uptake by barley kernels was followed by 1H NMR spectroscopy. A model was used to explain the first 7 h of imbibition. Measurement of the 1H spin‐lattice relaxation rate, R1, showed that during the first 7 h of imbibition, water uptake is dominated by a purely diffusive process with a
dependence, where D is the diffusion constant and t is time. While increasing during the first 7 h of imbibition, R1 slowly but continuously decreased afterwards. The observed changes in R1 with imbibition time allowed discrimination between the first two phases in water uptake, as generally observed in germinating seeds. The second phase was characterized by a slow but continuous decrease in R1, indicating a redistribution of water within the kernel. Observed spin‐lattice relaxation rates, R1, were treated as a superposition of rates from water molecules in two different physical phases; a mobile and a less mobile phase. Using the Stokes–Einstein–Debye theory for viscosity, the overall water viscosity within the kernel was determined using the two‐phase model to describe water mobility.
Effect of commercial fat replacers on the microstructure of low‐fat Cheddar cheese
Authors: Aryana Kayanush J. , Haque Zahur U.
Published: March 2003

This objective of this study was to determine the effect of protein‐ and carbohydrate‐based fat replacers on the microstructure of low‐fat Cheddar cheese. Microstructure was studied by transmission and scanning electron microscopy. Protein‐based fat replacers were Dairy Lo™ (DL) and Simplesse™ (SIMP), while the carbohydrate‐based fat replacers were Novagel™ (NOV) and Stellar™ (STEL). Low‐fat Cheddar cheese was manufactured using these commercial fat replacers and aged for 6 months at 5 °C. Low‐fat control (LFC) and low‐fat Cheddar cheese made with SIMP and DL showed a rippled surface microstructure while incorporation of NOV and STEL resulted in cheese with an undulated and rough surface microstructure. Cheese made with SIMP showed void areas around the SIMP particles. Fat replacers SIMP and NOV softened low‐fat Cheddar cheese by imparting discontinuity to the casein matrix. A method in which fat replacers DL and STEL appeared to soften low‐fat Cheddar cheese was by having the fewest layers (that conceivably resist crushing) at the fat–protein interface. Microstructure of low‐fat Cheddar cheese was effected by fat replacers.
Determination of optimum hazelnut roasting conditions
Authors: Saklar Sena , Katnas Sinan , Ungan Suat
Published: March 2003

The objective of this study was to test the hypothesis that the roasting conditions used for hazelnuts, such as the air temperature, air velocity and roasting time (independent variables), could be optimized by using Response Surface Methodology. Effects of independent variables on sensory and physical characteristics were determined. A consumer test was used to determine the acceptable samples. Very dark and very light roasted samples, corresponding to 165 °C, 3 m/s, 25 min and 125 °C, 1 m/s, 15 min process conditions, respectively, were unacceptable. Superimposed contour plots were used to determine the values of independent variables and these showed the process conditions where all product characteristics were acceptable to consumers. At low velocity (0.3 m/s), acceptable products were produced at about 165–179 °C for 20–25 min. When air velocity increased, air temperature shifted to lower temperatures. Samples roasted at 145 °C, 2 m/s, 28 min, 165 °C, 1 m/s, 25 min and 145 °C, 3.7 m/s, 20 min produced the most acceptable products. The sample roasted at 165 °C, 1 m/s, 25 min required the least air velocity and was the most economical in terms of energy consumed among the samples rated most acceptable by consumers.
Kinetic parameters for thermal inactivation of cut green beans lipoxygenase calculated using unsteady‐state methods
Authors: Garrote Raúl L. , Silva Enrique R. , Bertone Ricardo A.
Published: March 2003

Kinetic parameters describing lipoxygenase inactivation during heating of cut green beans were determined using two unsteady‐state procedures. The model used an analytical solution for heat conduction in a finite cylinder to predict time–temperature profiles, and a trial and error and a non‐linear regression of experimental lipoxygenase retentions to estimate kinetic parameters. Thermal diffusivity and convective heat transfer coefficient were determined experimentally, but thermal conductivity was estimated. Mean values obtained, with standard deviations between parenthesis, were k76°C=27.2 (9.4) s–1; k82°C=92.9 (7.5) s–1; k88°C=212.1 (52.7) s–1; k94°C=407.8 (56.7) s–1; Ea=160.7 (8.1) KJ mol−1 using the trial and error procedure; k85°C=150 (26.3) s–1 and Ea=164 (4.7) KJ mol−1 using the non‐linear regression method. Predicted and observed lipoxygenase retentions showed good agreement.
Functional properties of surimi powder from three Malaysian marine fish
Authors: Huda Nurul , Abdullah Aminah , Babji Abdul Salam
Published: March 2003

Lizardfish (Saurida tumbil), threadfin bream (Nemipterus japonicus) and purple‐spotted bigeye (Priacanthus tayenus) surimi were freeze‐dried to produce surimi powder. The resulting surimi powder contained 72.8–73.4% protein and 16.8–17.5% carbohydrate. Functional properties such as solubility, gelation capacity, water‐holding capacity (WHC), emulsification, foaming properties and colour varied from species to species. The surimi powder formed gels and produced about 90% emulsification at a concentration of 1.0%. Threadfin bream was found to be the best source for surimi powder production, followed by purple‐spotted bigeye and lizardfish, respectively.
Influence of controlled atmosphere storage on polyphenoloxidase activity in relation to colour changes of minimally processed ‘Jonagored’ apple
Authors: Rocha A. M. C. N. , Morais Alcina M. M. B.
Published: March 2003

The effects of the storage atmosphere composition (2% O2 + 4% CO2; 2% O2 + 8% CO2; 2% O2 + 12% CO2) on polyphenoloxidase activity and phenolic content of the ‘Jonagored’ apple variety during cold storage was evaluated, and the relationship with enzymatic browning investigated. Controlled atmosphere storage inhibited the polyphenoloxidase (PPO) activity of apple cubes during storage. It seems that the higher the concentration of carbon dioxide in the storage atmosphere the higher inhibition of PPO and the lower browning achieved. At the substrate‐enzyme levels investigated, the phenolic content, substrate level was the major factor determining darkening.
Development of an extruded plantain/corn/soy weaning food
Authors: Njoki Paul , Faller James F.
Published: March 2003

A weaning food was developed from a plantain/soy/corn blend by extrusion cooking. A two factor factorial study was conducted at three levels of feed moisture (22, 26 and 30%) and three levels of relative residence time (RRT: 1, 0.75 and 0.6). Feed moisture content had a greater effect on product attributes than did RRT. Water absorption index reached a maximum (3.05) at a feed moisture content of 26% and decreased again as the moisture increased further. Water solubility index was not affected by RRT or feed moisture. Product discolouration decreased with decreasing feed moisture content, whereas trypsin inhibitor activity decreased with increasing feed moisture. Much of the discolouration, believed to be owing to a reaction between iron from corn and the extruder parts and phenolic compounds from plantains, was effectively controlled by chelating agents such as EDTA and citric acid.
A review on microwave baking of foods
Authors: Sumnu Gülüm
Published: March 2003

Summary Microwaves interact with polar molecules and charged particles of food to generate heat. There are differences between the heating mechanisms of microwave and conventional heating. The use of microwave heating has the advantage of saving energy and time, improving both nutritional quality and acceptability of some foods by consumers. Microwave ovens are successfully used both in homes and in the food service industry. However, there are still problems in perfecting microwave baking, therefore it is a popular research area. The main problems found to occur in microwave‐baked food products are low volume, tough or firm texture, lack of browning and flavour development. Recent studies aim to improve the quality of microwave‐baked products. This article reviews the basic principles of microwave baking, problems commonly occurring in microwave‐baked products and finally studies published concerning microwave‐baked products.
Effects of acid adaptation on the survival of Listeria monocytogenes on modified atmosphere packaged vegetables
Authors: Francis Gillian A. , O'Beirne David
Published: March 2003

The survival and growth of Listeria monocytogenes and L. innocua on ready‐to‐use (RTU) packaged vegetables (lettuce, swedes, dry coleslaw mix, bean‐sprouts) were studied. The effects of acid adaptation of Listeria spp. on their survival during subsequent storage were also investigated. Listeria innocua behaviour was similar to that of L. monocytogenes on all vegetables examined. The survival and growth patterns of Listeria varied with the packaged product. Populations on packaged lettuce and swedes significantly increased (P < 0.05, by 1–1.5 log cycles) during a 14‐day storage period. During the same period, Listeria counts gradually decreased (by 1–1.5 log cycles) on coleslaw mix. Acid adaptation enhanced survival of Listeria spp. during storage in packages of vegetables which had relatively high in‐pack CO2 levels (i.e. 25% in packaged coleslaw, bean‐sprouts). It is concluded that adapting listerial cells to mildly acidic conditions rendered cultures more resistant to relatively high (25–30%) CO2 atmospheres.
Electrosynthesis of potato starch–casein complexes
Authors: Zaleska Hanna , Ring Steve , Tomasik Piotr
Published: March 2003

Starch–casein complexes were separated by electrosynthesis at 12 V cm–2 from aqueous potato starch:casein 1:0.5, 1:1, 1:2, 1:3, 1:4 and 1:5 blends. Complexes were separated on the stainless steel anode. The composition of complexes was dependent on the biopolymer composition of the bathing solution. Kinetic measurements and analysis of thermogravimetric thermograms suggested that there was a preference for the formation of the starch:casein 1:1 complex. In baths containing a small excess of protein the 1:1 complex coprecipitated with casein. Complex formation involved peptide and amino moieties of casein and, phosphate moieties as well as hydroxyl groups of starch. Electrosynthesis of protein–polysaccharide complexes provides a precise means of control of the parameters of synthesis and reproducibility of the properties of the products.
The effect of storage at tropical ambient temperature on the quality and shelf life of grouper (Plectropomus maculatus)
Authors: Surti Titi , Anthony Taylor  , Farid Ma'Ruf
Published: March 2003

Groupers (Plectropomus maculatus) were harvested from holding tanks and stored in ice until assessment rated them unacceptable. Groupers were also subjected to periods (2–12 h) of storage at tropical ambient (29–31 °C) immediately after harvest but prior to cooling in ice. The storage life of grouper stored continuously in ice was 18 days. A 2‐h delay before cooling in ice approximately halves the storage life and for every further hour of malstorage the shelf‐life was further reduced by approximately 1 day. The total volatile basic nitrogen (TVBN) and hypoxanthine contents were found to be good indicators of freshness in groupers, which were only acceptable with contents <31 mg N 100 per g and <2.0 μmoles g–1, respectively and all unacceptable at >37 mg N 100 per g and 2.3 μmoles g–1 respectively. TMA‐N was found not be a reliable indicator of freshness.
Effect of membrane pore size on quality of ultrafiltered apple juice
Authors: Zárate‐Rodríguez Elpidio , Ortega‐Rivas Enrique , Barbosa‐Cánovas Gustavo V.
Published: March 2003

Fresh apple juice was processed using an ultrafiltration (UF) unit, with polysulphone membranes of 10 000 and 50 000 daltons pore size. Trans‐membrane pressures of 103, 120.5, 138 and 155 kPa were studied. Recovery percentages of 0, 25, 50 and 75 were tested for the smaller pore membrane, as well as 0, 10, 20, 30, 40, 50 and 60 for the larger pore membrane. The responses to these factors were evaluated for the quality attributes pH, acid content, soluble solids and colour. In general terms, pH, acid content, and soluble solids did not change but presented less variability for the smaller pore membrane treatment. Relative colour changes were observed for both membranes, with an evident browning trend, which was more detectable for the larger pore membrane treatment.
Water activity at 35 °C in ‘sugar ’ + water and ‘sugar ’ + sodium chloride + water systems
Authors: Comesaña José F. , Correa Antonio , Sereno Alberto M.
Published: March 2003

Water activities of aqueous solutions of xylose, glucose, fructose and sucrose, and of these sugars with sodium chloride, were measured and correlated with a simple empirical equation proposed by Lin et al. (1996). Parameters for the equation were obtained and, from them, values of water activity were calculated with an average relative deviation of less than 0.14% for all the systems studied.
The impact of both the season of collection and drying on the volatile constituents of Origanum vulgare L. ssp. hirtum grown wild in Croatia
Authors: Jerković I. , Mastelić J. , Miloš M.
Published: March 2003

Samples of Origanum vulgare ssp. hirtum were collected from the same geographic area in the south of Croatia at different seasons of growth. The maximum fluctuations found for the main components from fresh plant material were: thymol [149.2–1124.4 mg (100 g)–1], carvacrol [51.6–564.3 mg (100 g)–1], p‐cymene [20.2–220.9 mg (100 g)–1] and γ‐terpinene [50.1–217.5 mg (100 g)–1]. The oregano that was analysed belonged to a thymol/carvacrol chemotype. The season of collecting affected the qualitative and quantitative composition of the essential oil. The most impressive difference was the increase of p‐cymene content in August. After the drying of the plant material, all samples showed a minor decrease in essential oil yields when compared with fresh plants. Drying, at room temperature, had no effect on the qualitative composition of oregano oil. Because of the variability of essential oil compositions from seasonally collected fresh and dried oregano, it would be important to check the quantity and quality of such components before usage.
Effect of dietary α‐tocopheryl acetate supplementation on the shelf‐life stability of reduced nitrite cooked ham products
Authors: Dineen N. , Kerry J. P. , Buckley D. J. , Morrissey P. A. , Arendt E. K. , Lynch P. B.
Published: March 2003

Colour stability (Hunter ‘a’ values) and lipid oxidation (TBARS (thiobarbituric acid reactive substances) values) of overwrapped cooked ham slices and cooked ham patties were measured at 2‐day intervals for 10 days. Ham products were manufactured from α‐tocopheryl acetate supplemented and control M. gluteobiceps which were halved and cured with either 25 or 100 mg nitrite (kg meat)–1. Vitamin E supplementation had a beneficial effect on reduced nitrite hams in terms of colour and oxidative stability.
Effect of autoclaving cocoa nibs before roasting on the precursors of the Maillard reaction and pyrazines
Authors: De Brito Edy S. , García Nelson H. Pezoa , Amancio Allan C. , Valente Antonio L. P. , Pini Gláucia F. , Augusto Fabio
Published: March 2003

Nibs of raw cocoa (N) were roasted (R) at 150 °C for 38 min. Some samples were autoclaved at 121 °C for 15 min (A) and roasted (AR) at 150 °C for 38 min. The samples were then analysed for moisture content, water activity (aw), reducing sugar and amino group (α‐N) levels and, absorption at 275 nm (A275) for a trichloro acetic acid (TCA) extract and at 280 nm (A280) for the distillate. Tri‐ and tetramethylpyrazines were quantified by solid phase micro extraction‐gas chromatography (SPME‐GC). There was a reduction in the levels of α‐N, in the order N > A > R > AR. The same sequence was observed for reducing sugars. The tetramethylpyrazine had an Areapyrazine/Areainternal standard of N < R < A < AR and for trimethylpyrazine the order was N < A < R < AR. After autoclaving, the Atetra/Atri decreased from 31.30 (N) to 11.06 (A). With roasting, this ratio was 2.18 (R) and 2.58 (AR). Autoclaving nibs before roasting significantly influenced the levels of compounds which contribute to cocoa flavour formation and increased the concentration of tri‐ and tetramethylpyrazines in the headspace of cocoa samples. Autoclaving prior to roasting also affected the sensory properties of the samples.
Manufacture of Mozzarella cheese from highly‐concentrated skim milk microfiltration retentate depleted of whey proteins1
Authors: Brandsma Randall L. , Rizvi Syed S. H.
Published: March 2003

A cheese‐making process was developed which utilizes concentration factor (CF) 8, pH 6.0 skim milk microfiltration (MF) retentate to produce low‐moisture, part‐skim (LMPS) Mozzarella cheese. The compositional and proteolytic effects of different levels of rennet concentration, coagulation temperature, and post‐coagulation curd cutting time were evaluated, with rennet concentration having the strongest influence. A post‐coagulation curd cutting time of 15–20 min was found to normalize the extent of κ‐casein hydrolysis during coagulation of concentrated MF retentate. Optimal cheese manufacturing parameters were determined to be 80–100 μL rennet kg–1 MF cheesemilk, coagulation temperature of 32–36 °C, and post‐coagulation curd cutting time of 15 min. As compared with ultrafiltration (UF) retentate cheese manufacture, cheese made from MF retentates has potential for improved textural and functional qualities, along with recovery of highly functional whey proteins (WP) from permeate.