Showing papers in "Lwt - Food Science and Technology in 1993"
TL;DR: Fresh minced beef muscle inoculated with Citrobacter freundii, Pseudomonas fluorescens or Listeria innocua was subjected to high hydrostatic pressures from 50 to 400 MPa for 20 min at 4, 20, 35 and 50°C to study the effects of pressure.
Abstract: Fresh minced beef muscle inoculated with Citrobacter freundii, Pseudomonas fluorescens or Listeria innocua was subjected to high hydrostatic pressures from 50 to 400 MPa for 20 min at 4, 20, 35 and 50°C. At 20°C, complete inactivation (more than 5 log cycles) was observed at pressures above 200 MPa for P. fluorescens, above 280 MPa for C. freundii and above 400 MPa for L. innoccua. Higher (50 or 35°C) or lower (4°C) temperatures enhanced the effects of pressure. The greatest reduction was obtained at 50°C. At a given pressure, surviving microorganisms decreased exponentially with time, and a decimal reduction time could be calculated for each microorganism (23.8 min at 150 MPa for P. fluorescens, 14.7 min at 230 MPa for C. freundii and 6.5 min at 330 MPa for L. innocua). Partial discoloration of meat was observed after 10 min pressurization above 150 MPa. Minced beef muscle lost its red colour and became grey after 10 min pressurization above 350 MPa.
197 citations
TL;DR: Inactivation of the yeast at low aw could be achieved by pressure treatment at increased temperature, and at atmospheric pressure, processing temperatures of 70 to 80°C were required to accomplish the same effects.
Abstract: High hydrostatic pressure (200 to 400 MPa) treatment of Rhodotorula rubra suspended in solutions of sucrose, glucose, fructose or sodium chloride resulted in water activity (aw) dependent barotolerance. The protective effect started at values below aw = 0.92 to 0.88. Increase in time of treatment over 15 min had a small influence. In sucrose, the effect was independent of pH between pH 3.0 and 8.0. Inactivation of the yeast at low aw could be achieved by pressure treatment at increased temperature (45°C). At atmospheric pressure, processing temperatures of 70 to 80°C were required to accomplish the same effects.
177 citations
TL;DR: In this article, the odour activity values (OAV; ratio of concentration to odour threshold) were calculated from quantitative data determined by means of stable isotope dilution assays and from odour thresholds in oil.
Abstract: Sensory evaluation of five different kinds of butter revealed an Irish sour cream butter (ISC) and a farmer sour cream butter (FSC) with the highest overall odour intensities Nineteen odour-active compounds were detected by aroma extract dilution analysis in a distillate of the ISC butter The highest flavour dilution (FD)-factors were found for δ-decalactone, skatole, [Z]-6-dodeceno-γ-lactone and diacetyl followed by [E]-2-nonenal, [Z,Z]-3,6-nonadienal, [Z]-2-nonenal and 1-octen-3-one Odour activity values (OAV; ratio of concentration to odour threshold) were calculated from quantitative data determined by means of stable isotope dilution assays and from odour thresholds in oil Diacetyl followed by δ-decalactone and butanoic acid showed the highest OAVs in the ISC butter and a cultured butter with creamy, sweet odours In contrast, a sweaty, rancid odour predominated in the FSC butter in which butanoic acid showed the highest OAV The odour of a mixture of diacetyl (034mg/kg), δ-decalactone (49 mg/kg) and butanoic acid (36 mg/kg) in sunflower oil was in very good agreement with the odour of the cultured butter containing the same amounts of these odorants The data suggest that the three odorants should be useful as indicators for the objective assessment of the buttery odour note in milkfat-containing products
175 citations
TL;DR: In this paper, the repeatability and reproducibility of nitrogen fractions of cheeses were evaluated using standardized methods including the determinaiton of total nitrogen (TN), water soluble nitrogen (WSN), nitrogen soluble at pH 4.4 and nitrogen soluble in phosphotungstic acid (PTA-N).
Abstract: This study was carried out within the framework of the European COST 902/FLAIR-programme (European Cooperation in the Field of Scientific and Technical Research). The first objective was the harmonization of certain techniques currently used for the determination of nitrogen fractions of cheese. The second objective was to determine the repeatability (r) and reproducibility (R) of the standardized methods including the determinaiton of total nitrogen (TN), water soluble nitrogen (WSN), nitrogen soluble at pH 4.4 (SN 4.4), ethanol soluble nitrogen (ESN), nitrogen soluble in trichloroacetic acid (TCA12-N) and nitrogen soluble in phosphotungstic acid (PTA-N). The r- and R-values for TN were in the range of O.3 to 1.4 and 1.4 to 2.5 g/kg, respectively. For all other methods tested, the r-values were in the range of 0.1 to 1.1% of TN, the R-values were below 3.3% of TN except for ESN (5%). For most cheeses tested, the WSN and SN 4.4 results were highly correlated, as were the TCA12-N and ESN results. Therefore, only a limited number of methods should be applied in practice, other aspects should be considered such as practical and environmental aspects (e.g. toxicity of solvents) and future use of the fractions and the kind of cheese. The difference between the TCA12-N and PTA-N values as well as the difference between SN 4.4 and TCA12-N values were used to characterize protein breakdown.
120 citations
TL;DR: In this article, a first order kinetic model was assumed to analyse thermal inactivation of enzyme systems which consist of heat labile and heat resistant fractions, and lipoxygenases and peroxidases were used as blanching indicator enzymes during the experiments.
Abstract: Peroxidase and lipoxygenase inactivation and ascorbic acid retention were studied during water and microwave blanching of peas, green beans and carrots. A first order kinetic model was assumed to analyse thermal inactivation of enzyme systems which consist of heat labile and heat resistant fractions. Lipoxygenases and peroxidases were used as blanching indicator enzymes during the experiments. Ascorbic acid retention during blanching was higher in vegetables when lipoxygenases were selected as the indicator enzymes for the blanching treatments. Also ascorbic acid retention was found to be higher in microwave compared to water blanched vegetables.
118 citations
TL;DR: In this article, the effects of steam blanching, surfactant pretreatment and drying conditions on the drying rate and on the chlorophyll and colour retention of air-dried basil were studied.
Abstract: The effects of steam blanching, surfactant pretreatment and drying conditions on the drying rate and on the chlorophyll and colour retention of air-dried basil were studied. Colour was monitored by recording the L * , a * , b * values. Chlorophyll and pheophytin levels were assayed by HPLC. Temperature was the main factor in controlling the rate of drying. The influence of air velocity and air humidity were less pronounced and significant only at the beginning of the drying period. Steam blanching and surfactant pretreaments increased drying rates by a factor of 10 and 14, respectively. Both pretreatments resulted in a better retention of the overall green colour of the basil leaves. Higher chlorophyll retention confirmed the protective effect of steam blanching. In order not to impair quality, low air drying temperatures were necessary for non pretreated samples while high air drying temperatures were acceptable for steam blanched and surfactant pretreated samples.
84 citations
TL;DR: In this paper, the influence of fermentation on the neutral/basic volatile fraction of the French bread dough was investigated by GC-MS and GC/olfactometry analysis of the corresponding aromatic extracts obtained by vacuum desorption.
Abstract: The influence of the fermentation on the neutral/basic volatile fraction of the French bread dough was investigated. Three types of dough were compared by GC-MS and GC/olfactometry analysis of the corresponding aromatic extracts obtained by vacuum desorption: (YF) control dough obtained by the straight dough method, (YNF) yeasted but not fermented dough (which was conditioned just after the mixing step) and (NYF) not yeasted but fermented dough (like the control one but without incorporation of the baking yeast in the system). More than 40 components were identified among with 20 alcohols, seven esters, six lactones, six aldehydes, three alcanes and one sulphur compound. Except for the aldehydes and the alcanes, all these classes of compounds increased with the activity of the yeast Saccharomyces cerevisiae [from (NYF) to (YF)], notably the alcohols due to the formation of fusel alcohols. The 2,3 butanedione, 3-methyl 1-butanol, 2-methyl 1-butanol, methional, 2-phenyl ethanol and two unidentified components with a pungent an a mushroom-like odour, were the most odourant compounds generated during the fermentation of the dough, as shown by the aroma extract dilution analysis of the three aromatic extracts.
77 citations
TL;DR: In this article, a model was developed for osmotic dehydration of fruit, which took into account outgoing water, incoming solute and shrinkage of fruit during the process, and the model was experimentally verified by laboratory dehydration of apple slices using 55 g/100 g glucose syrup at 45°C.
Abstract: A model was developed for osmotic dehydration of fruit which takes into account outgoing water, incoming solute and shrinkage of fruit during the process. The model was experimentally verified by laboratory dehydration of apple slices using 55 g/100 g glucose syrup at 45°C. The model adequately described experimental results in terms of lost water, gained solids, reduction of water activity and shrinkage during osmosis. By fitting the model to experimental values, apparent diffusivity values at 45°C for outgoing water and incoming sugar were 1.9 × 10 -10 and 1.5 × 10 -10 m 2 /s, respectively.
75 citations
TL;DR: In this paper, the shelf-life of sunflower oil and olive oil were estimated using an Accelerated Shelf-life Testing (ASLT) method and these were compared with the values in long term storage.
Abstract: Shelf-lives of sunflower oil and olive oil were estimated using an Accelerated Shelf-life Testing (ASLT) method and these were compared with the values in long term storage. In addition, the effect of type, oxygen permeability, and transparency of the packages on the shelf-lives of oils were investigated. The determinations were based on the oxidative stability of oils by measuring their peroxide values. The limiting peroxide value corresponding to the end of shelf-life was obtained from the FAO/WHO standards. The shelf-lives of sunflower and olive oil samples in retail store conditions were estimated as 10.6 and 20.8 mo, respectively. Storage lives of sunflower oil in polyethylene tere-phthalate (PET), clear glass and colour glass bottles under a 10 W fluorescence lamp were 10.4, 11.1 and 11.8 mo at 10°C, and 4.8, 5.1 and 6.5 mo at 20°C, respectively. Long term storage lives of olive oil in PET, clear and coloured glass were 17.5, 17.8 and 18.3 mo at 10°C, and 8.0, 8.4 and 8.7 mo at 20°C, respectively. These long term storage lives were then compard with the ASLT results obtained from the modified active oxygen method using a simple shelf-life plot approach.
69 citations
TL;DR: In this paper, the effects of enzymatic oxidation of polyphenols associated with active filtration and membrane filtering were evaluated, in terms of juice characteristics and stability, using low molecular weight cut-off membranes.
Abstract: Stabilization against discolouration and clouding is a major problem in fruit juice production. Effects of enzymatic oxidation of polyphenols, associated with 'active filtration' and membrane filtration were evaluated, in terms of juice characteristics and stability. Laccase oxidation produces a significant decrease in the phenolic content of juices, associated with a remarkable colour increase. Active filtration by polyvinylpolypyrrolidone and activated charcoal partially decolourates the oxidized juices and stabilizes these products, removing a high quantity of phenolic compounds. Membrane filtration demonstrates to be an effective technique in terms of stabilization only if performed using low molecular weight cut-off membranes.
63 citations
TL;DR: In this paper, the authors examined the influence of salt and phosphate brine as well as tumbling and heating on the microstructure of cooked hams through scanning electron and transmission electron microscopy.
Abstract: This study examined the influence of salt and phosphate brine as well as tumbling and heating on the microstructure of cooked hams through scanning electron and transmission electron microscopy. The observed morphologies were used to explain mechanisms of technological, biochemical and quality characteristics of the products.
TL;DR: In this article, the authors performed single compression, double compression and penetration tests to determine mechanical and texture properties of the apple flesh (failure stress and strain, modulus of deformability, juiciness, cohesiveness and firmness).
Abstract: Selected commercial apple cultivars (Golden Delicious, Stark Delicious, Renetta, Annurca, Granny Smith, Emperor) were studied to discriminate among the cultivars and the different levels of merceological quality for their mechanical and texture characteristics, by instrumental and sensory methods. Single compression, double compression and penetration tests were carried out to determine mechanical and texture properties of the apple flesh (failure stress and strain, modulus of deformability, juiciness, cohesiveness and firmness). Sensory responses were obtained by the descriptive technique of texture profile analysis and by the pairwise ranking test (paired comparisons of more than two samples) for the following parameters: fracturability, firmness, cohesiveness, mealiness and juiciness. Annurca and Granny Smith cultivars showed the highest values for almost all the instrumental and sensory parameters measured. The instrumental methods indicated that the internal variability of flesh structure influenced the differences among the cultivars, although some significant differences were clear. Results from the correlation study between instrumental and sensorial parameters were affected by the non-homogeneous distribution of the values in the correlation plots, probably due to the low number of samples considered. Principal component analysis applied to the instrumental results showed that the first two components described about 85% of the total variance. The first component was a linear combination of five variables, excluding the failure strain, while the second was a failure strain factor. It seems that only two parameters, the failure stress for instance and the failure strain, would be sufficient to point out differences among the cultivars and the merceological quality levels considered.
TL;DR: In this article, a group for the sensory analysis of cheese was formed as part of the FLAIR COST 902 project in order to harmonize the training of the tasting panel and to develop a common method for characterizing hard and semi-hard cheese.
Abstract: Dans le cadre du programme FLAIR COST 902, un groupe d'analyse sensorielle des fromages s'est forme pour harmoniser l'entrainement des jurys de degustation et pour avoir une methode commune pour caracteriser les fromages a pâte dure et semidure. Cinq fromrages d' 'Appellation d'origine controlee' (AOC) ont ainsi ete etudies. Il s'agit du Comte (Jura francais), du Parmigiano-Reggiano et de la Fontina (Italie), du Mahon (Espagne) et de l'Appenzeller (Suisse). Apres avoir defini l'importance de la texture des fromages entre l'apparence et la flaveur et avoir constate qu'aucune methode de la litteratare n'etait directement applicable, le groupe s'est mis d'accord sur la facon d'apprecier la texture des fromages. Les caracteristiques de surface, meaniques, geometriques ainsi que d'autres sensations kinesthesiques et intra-buccales ont ete etudiees. Pour preciser les perceptions et leurs intensites, des produits alimentaires de reference autres que des fromages sont indiques. Il s'agit, par exemple, de pomme, de biscuit ou de l'interieur d'une peau de banane. De plus, pour permettre l'etude des relations entre l'analyse instrumentale et sensorielle—objectif principal de FLAIR COST—les caracteristiques mecaniques ont ete precisees par des definitions physique et sensorielle, ainsi que par une technique d'evaluation originale. L'ampitude de la perception est donnee par une echelle de sept niveaux, dont trois sont fixes par un produit de reference standardise et connu de tous les pays europeens. Les difficultes semantiques et socio-culturelles ont ete prises en compte. Si ce guide a ete elabore originalement en francais, des traductions en italien, espagnol, allemand et anglais sont prevues dans le cadre de FLAIR COST. Elles sont placees sous la responsabilite des divers auteurs de cette methode. Sensory Evaluation of the Texture of Hard and Semi-hard Cheeses. A Collaborative Study A group for the sensory analysis of cheese was formed as part of the FLAIR COST 902 programme in order to harmonize the training of the tasting panel and to develop a common method for characterizing hard and semi-hard cheese. After placing the importance of cheese texture between its aspect and flavour and having noted that no method described in the literature was directly applicable, the group agreed on a method to appreciate the texture of cheese. The characteristics of surface, mechanical, geometrical and other kinaesthetic and oral sensations were studied. Other reference foods besides cheese, e.g. an apple or a biscuit or the inside of a banana skin, were used to clarify perceptions as well as their intensities. Also, in order to study the relationship between the instrumental and sensory analysis—the principal object of the FLAIR COST project—the mechanical characteristics were clarified by physical and sensory definitions as well as by an original assessment technique. The magnitude of perception is measured on a scale of seven, three of which are set by a standard reference product known in all European countries. Semantic and socio-cultural difficulties were taken into consideration. This guide was originally prepared in French, however, translations into Italian, Spanish, German and English will be made in the future as part of the FLAIR COST project. They are placed under the responsibility of the various authors of this method.
TL;DR: Aroma extract dilution analysis of the volatile fraction of stewed beef revealed a compound that smelled tallowy and beef-like as discussed by the authors, which was identified as 12-methyltridecanal (MT) and had a sensitivity odour threshold of O.1 μg/kg in water.
Abstract: Aroma extract dilution analysis of the volatile fraction of stewed beef revealed a compound that smelled tallowy and beef-like. The compound was identified as 12-methyltridecanal (MT) and had a sensitivity odour threshold of O.1 μg/kg in water. Using a stable isotope dilution assay, 431 μg/kg of MT was found in stewed beef. The lipid fraction was isolated from the lean meat of different animal species and then hydrolysed. High amounts (expressed as μg/g lipid) were liberated from beef (44 to 149), lower from veal, lamb, springbuck and red deer (5 to 19) and very low amounts from chicken, turkey and pork (0.3 to 2.7). Plasmalogens were detected as the precursors of MT.
TL;DR: In this article, a simple coating technique involving the chemical cross-linkage of alginate by calcium was used to sufficiently extend the shelf life of mushrooms, and the effects of the coating itself were investigated.
Abstract: Mushrooms (Agaricus bisporus) were coated with different concentrations of alginate film. A simple coating technique involving the chemical cross-linkage of alginate by calcium was used. The ability of this coating method to sufficiently extend the shelf life of mushrooms, and the effects of the coating itself were investigated. After coating, mushrooms were stored at room temperature (20°C) or at 4°C. At room temperature 1% alginate-coated mushrooms, and in cold storage 1 and 2% alginate-coated mushrooms were found to have higher L values, indicating lighter colour and a better appearance than the uncoated controls. At room temperature, the rate of water evaporation from the coated vegetables decreased. Coated mushroom strength as checked by a Universal Testing Machine, and integrity were maintained for a longer period of time than that of the uncoated controls, and the former therefore more closely resembled fresh, intact mushrooms. These positive effects were more pronounced in the cold-stored mushrooms.
TL;DR: In this article, a crude commercial canola oil (Westar) and an oil obtained from a genetically reduced linolenic acid cultivar, were laboratory processed under commercial conditions to finished, deodorized oils.
Abstract: A crude commercial canola oil (Westar) and an oil obtained from a genetically reduced linolenic acid cultivar, were laboratory processed under commercial conditions to finished, deodorized oils. Fatty acid analysis indicated that the linolenic acid content of the low linolenic canola oil (LLCO) was 3.1%, compared to 11.5% for Westar. The LLCO exhibited markedly improved stability during accelerated storage at 60°C (Schaal Oven Test) as evident by negligible changes in chemical indices of rancidity. No significant changes were observed in overall odor intensity or odor pleasantness for the LLCO over the 12 d storage period, whereas significant changes were found for the Westar oil. Comparison of volatiles produced by these oils during storage confirmed enhanced storage stability of LLCO.
TL;DR: In this paper, the authors investigated the effect of MAG and soy fiber on corn meal extrusion with two-screw extrusion of corn meal with monoacylglycerol (MAG) and soy fibers.
Abstract: Twin-screw extrusion of corn meal with monoacylglycerol (MAG) and soy fiber was investigated. The treatment variables studied were MAG and soy fiber contents, screw speed, and feed rate. MAG addition reduced torque, specific mechanical energy, and dough temperature, but increased die pressure. The significant increase in die pressure was caused by an increased length in filled flights. Die pressure and dough mass temperature increased with soy fiber addition at lower MAG contents ( 0.4 g/100 g). Moreover, MAG-starch complexation increased with MAG addition but was impeded by soy fiber addition.
TL;DR: The moisture sorption isotherms of conventional (from 100% durum wheat semolina) and diet (high protein) spaghetti were constructed at 22, 30, 37 and 45°C, using a computerized inverse gas chromatographic method (CIGC).
Abstract: The moisture sorption isotherms of conventional (from 100% durum wheat semolina) and diet (high protein) spaghetti were constructed at 22, 30, 37 and 45°C, using a computerized inverse gas chromatographic method (CIGC). Conventional spaghetti exhibited a higher sorption capacity than diet spaghetti. This is attributed to the higher carbohydrate content of conventional spaghetti as compared to diet spaghetti. Good agreement was observed between moisture sorption isotherms obtained from the CIGC method and the gravimetric static method. BET (Brunauer, Emmett and Teller), GAB (Guggenheim, Anderson and De Boer) and 'Local' isotherm models were tested to fit the experimental sorption data. Goodness of fit, standard deviation and the applicable range of water activity (a w ) indicated that GAB and 'Local' isotherm models could explain the data well over a wide a w range up to 0.80.
TL;DR: In this paper, high performance size exclusion chromatography (HPSEC) was used for analysing the quality of vegetable oils during the industrial refining process and the main interest focused on the contents of high molecular weight autoxidation products: oxidized triacylglycerols (PTAG) and triacylsglycerol dimeric compounds (TGD).
Abstract: High performance size exclusion chromatography (HPSEC) was used for analysing the quality of vegetable oils during the industrial refining process. The main interest focused on the contents of high molecular weight autoxidation products: oxidized triacylglycerols (PTAG) and triacylglycerol dimeric compounds (TGD). The diacylglycerol and free fatty acid contents of the oils were also monitored. Three vegetable oils (sunflower oil, soya bean oil and low erucic acid rapeseed oil) were used as test materials. In crude oils, the content of PTAG compounds ranged from 5.3 to 9.0 g/kg of oil and that of diacylglycerols from 6.1 to 12.6 g/kg, indicating the different autoxidative and hydrolytic qualities of the raw materials. No dimeric or higher oligomeric TAG compounds were detected in crude oils. The major change during the refining process detected by HPSEC analyses was the increase in TGD content after bleaching and deodorization. In refined oils, the TGD content ranged from 1.2 g/kg for rapeseed oil to 2.3 g/kg for sunpower oil. A slight decrease in PTAG content after bleaching was detected in each of the samples. The content of PTAG compounds in refined oils was comparable to that in crude oils. The decrease in free fatty acid content after neutralization was clear but there was no change in the diacylglycerol content during the processing. HPSEC analysis is a suitable method for monitoring the level of high molecular weight autoxidation products during the processing of edible oils and for analysing the autoxidative quality of oils after industrial refining.
TL;DR: In this paper, the inactivation of commercial soybean lipoxygenase was studied at various temperatures using conventional and microwave heating, and the activation energies (Ea) were 119, 113 and 180 kJ/mol, respectively, for the conventional, mixed and microwave mode heating.
Abstract: The inactivation of commercial soybean lipoxygenase was studied at various temperatures using conventional and microwave heating. Conventional heating was carried out in a temperature controlled water-bath, while a custom designed microwave temperature control system was used to maintain test samples at selected temperatures either by full exposure to microwaves (microwave heating) or partial exposure by immersion in water (in a beaker) maintained at the desired temperature using the microwave oven (mixed mode). Lipoxygenase inactivation was evaluated using first-order reaction kinetics. Conventional and mixed mode heating produced somewhat similar results while the microwave mode resulted in a more rapid inactivation of the enzyme. The activation energies (Ea) were 119, 113 and 180 kJ/mol, respectively, for the conventional, mixed and microwave mode heating. Higher enzyme inactivation rates under microwave heating conditions were ascribed to possible non-thermal effects.
TL;DR: In this article, a mathematical model is employed to describe the water diffusion and gelatinization of white rice, and experiments are performed to measure change of water content of rice during soaking.
Abstract: A mathematical model is employed to describe the water diffusion and gelatinization of white rice. Experiments are performed to measure change of water content of rice during soaking. The oberved data are used to estimate the effective diffusion and reaction rate coefficients. Both temperature-dependent coefficients are shown to obey the Arrhenius equation with a distinct break point where rapid gelatinization of rice begins. The enhanced gelatinization process is seen to cause a considerable increase in the activation energies.
TL;DR: In this paper, the effect of storage time and temperature on the colour of concentrated juice of prickly pears (Opuntia ficus indica) was studied, and mathematical models were developed to predict colour variation of concentrated and reconstituted juices, as a function of the CIELAB parameters.
Abstract: The effect of storage time and temperature upon the colour of concentrated juice of prickly pears (Opuntia ficus indica) was studied. Mathematical models were developed to predict colour variation of concentrated and reconstituted juices, as a function of the CIELAB parameters (official measure system of the Commission Internationale de l'Eclairage). An increase in a * and a marked modification of the hue angle H * with time and temperature was observed in the concentrated juice. Parameters a * and b * also increased in the reconstituted juice and increased even more at higher temperatures and longer times. The sensory evaluation of the colour acceptability indicated that reconstituted juices were more acceptable at shorter storage times than the respective concentrated juices. An equation which predicts the sensory response as a function of the CIELAB parameters was also derived.
TL;DR: In this article, a list of acidic volatile components isolated and identified by GC-MSD in a pool of five mature, first class Swiss Gruyere cheeses was reported; the compounds found were principally fatty acids such as ethanoic, butanoic and propanoic.
Abstract: Part IV first reports a list of acidic volatile components isolated and identified by GC-MSD in a pool of five mature, first class Swiss Gruyere cheeses. The analysis of the outer zone (including the smear-coated rind), the middle and central zones revealed concentration gradients for some of the volatile components. The compounds found were principally fatty acids such as ethanoic, butanoic, propanoic, hexanoic, 2-methylbutanoic, 2-methylpropanoic, 3-methylbutanoic, pentanoic, octanoic and decanoic acids ranked by decreasing concentration, and hydroxybenzene (phenol). Changes in the content of these acidic volatile substances were then studied in two zones of eight first class Swiss Gruyere cheese over a 12-month ripening period. Quantitative determination of main constituents were performed separately by GC-TCD for the eight loaves. Semi-quantitative analyses of minor compounds were carried out by GC-MSD or GC-FID only in a pooled sample. The content of 2-methylpropanoic, 2-methylbutanoic, 3-methylbutanoic, 4-methylpropanoic, hexanoic (particularly in the inner zone), octanoic, and decanoic acids as well as hydroxybenzene increased in an approximately exponential way during the ripening period. On the other hand, concentrations of total volatile fatty acids, ethanoic, propanoic, butanoic, pentanoic and hexanoic (particularly in the outer zone) showed a more linear increase. Some possible metabolic pathways for the formation of these cheese flavour components are reviewed.
TL;DR: In this paper, raw and parboiled white and brown rice from three Australian cultivars (Calrose, Doongara and Waxy) were analysed for total and enzymically resistant starch (RS), and for water-soluble and water-insoluble non-starch polysaccharides (NSP).
Abstract: Raw and parboiled white and brown rice from three Australian cultivars (Calrose, Doongara and Waxy) were analysed for total and enzymically resistant starch (RS), and for water-soluble and water-insoluble non-starch polysaccharides (NSP). Raw white and brown rice from these cultivars were also analysed for starch and RS after cooking in a microwave oven or rice cooker and cooling or freezing of the cooked rice. Generally, starch was higher in white rice samples than in the corresponding brown rice and was higher in parboiled white and brown Calrose but not Doongara or Waxy. The starch content of white and brown rice was maintained or increased by cooking in a microwave oven or rice cooker except with Waxy. In extruded and drum-dried rice flour, rice-pop and rice cakes, starch content was the same as in the corresponding raw material. RS was higher in rice products and in brown and parboiled rice than in white rice and was often increased by cooling or freezing cooked rice but it never exceeded 1.5% of total starch. Total NSP were lower in white (1.8-2.3%) than brown rice (3.1-3.5%) and were increased slightly by parboiling. The ratio soluble/insoluble NSP was higher in white rice than in brown rice. NSP sugar composition varied between the three cultivars and, in products made from Calrose, was also affected by procesing.
TL;DR: In this article, a continuous spectrophotometric assay modified for fungal pectinesterases is reported, which is based on that developed by Hagerman and Austin for plant pectine-terases.
Abstract: A continuous spectrophotometric assay modified for fungal pectinesterases is reported. This method is based on that developed by Hagerman and Austin for plant pectinesterases. The amount of carboxylic groups released during the assay is calculated from the decrease in absorbance of a pH indicator added to the reaction mixture with a pKi value within the pH range of maximum enzyme activity. Bromocresol green was chosen for our modified method as fungal pectinesterases have an optimum activity at acid pHs (4.6 to 5.1) which are within the pH range of color change (3.8 to 5.4) for this dye. Our methodology was tested by employing a commercial pectinase product as the source of pectinesterases. Statistical analysis using the Student's t-test showed good agreement between the reference titrimetric method and that reported herein.
TL;DR: In this paper, the authors evaluated the effects of individual seal-packaging in low density polyethylene (LDPE) films and waxing treatments on the storage quality of bell peppers.
Abstract: The objective of this study was to evaluate the effects of individual seal-packaging in low density polyethylene (LDPE) films and waxing treatments on the storage quality of bell peppers. Waxed and unwaxed fruits were packaged in two LDPE bags of different thickness and permeability, and stored at 10°C and 75% relative humidity (RH) for up to 40 d. The thickness and permeability to oxygen and water vapour of the films were determined. The O 2 and CO 2 levels of the package atmosphere were determined at 3-d intervals. Pepper fruits were also evaluated at 10-d intervals for changes in colour, weight loss, soluble solids, titratable acidity, pH, % decay and sensory characteristics. The activity of alcohol dehydrogenase was used as an indicator of anaerobiosis. Packaging plus waxing significantly delayed fruit senescence, reducing the change of colour, weight loss, firmness, and % decay with respect to the waxed and unwrapped fruits. No abnormal flavours were detected in peppers stored at 10°C for up to 40 d. These results demonstrate that LDPE bags plus waxing can be efficiently used to prolong the shelf-life of the bell peppers up to 20 d, without significant alteration of the postharvest quality of peppers.
TL;DR: In this paper, Cheddar cheese from a split lot of cheese curd was prepared with or without added NaCl, KCl or mixtures of NaCl/KCl (2:1, 1:1 1: 1, 1 :2 and 3:4, all on wt/wt basis) to achieve final salt concentrations of approximately 15.0 or 17.5 g/kg.
Abstract: Cheddar cheese from a split lot of cheese curd was prepared with or without added NaCl, KCl or mixtures of NaCl/KCl (2:1, 1:1, 1:2 and 3:4, all on wt/wt basis) to achieve final salt concentrations of approximately 15.0 or 17.5 g/kg. Cheeses were ripened at 3 ± 1°C and proteolysis was determined over a 36 wk period. Peptide material soluble in trichloroacetic acid (120 ml/L) (TCA sol-N) and free amino acids measured as phosphotungstic acid-soluble amino N (PTA sol-amino N) increased in all cheeses during ripening through 36 wk. There were no significant (P > 0.05) differences attributable to various salt treatments in levels of TCA sol-N and PTA sol-amino N of cheeses tested after 12, 24 and 36 wk of ripening. Unsalted cheese generally had more proteolysis than salted cheeses. Peptide extracts of selected cheeses from trials 1 (made with Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris) and 2 (made with L. lactis subsp. lactis) were chromatographed using a Sephadex G-25 column. Sensory evaluation indicated that only eluent fractions of cheeses from trial 1 were slightly to markedly bitter. In trial 2, fractions from unsalted cheese were slightly bitter and those from cheeses made with NaCl or NaCl/KCl mixtures were not bitter. Thus it is unlikely that KCl was responsible for bitterness in cheeses of trial 1.
TL;DR: In this article, the authors evaluated the tolerance and responses of mango (Mangifera indica L. var. Keitt) fruits to a modified atmosphere (MA) of 0.03 to 0.26% O2 and 72 to 82% CO2 (balance N2) for 0 to 4 days at 20°C, and to a controlled atmosphere (CA) of 2% O 2 + 50% CO 2 (balance n2), and they concluded that MA and CA delayed fruit ripening.
Abstract: The tolerance and responses of mango (Mangifera indica L. var. Keitt) fruits to a modified atmosphere (MA) of 0.03 to 0.26% O2 and 72 to 82% CO2 (balance N2) for 0 to 4 days at 20°C, and to a controlled atmosphere (CA) of 2% O2 + 50% CO2 (balance N2) for 0 to 5 days at 20°C, were evaluated. MA and CA delayed fruit ripening. Both MA and CA increased the activity of ATP:phosphofructokinase, alcohol dehydrogenase, and pyruvate decarboxylase, but did not affect the activity of pyruvate kinase. MA decreased the activity of PPi:phosphofructokinase. Although the atmospheres used caused changes in the activity of some glycolytic enzymes, there was no indication of any injury and fruits ripened normally. Sensory evaluation did not indicate the presence of off-odours and off-flavours. This work indicates a potential application of MA/CA for post-harvest insect control in mango fruits.
TL;DR: The effect of removal of phenolics and amino acids, and initial oxidation of ascorbic acid on nonenzymic browning in kiwifruit juice concentrate during storage at 20°C was investigated in this paper.
Abstract: The effect of the removal of phenolics and amino acids, and initial oxidation of ascorbic acid on non-enzymic browning in kiwifruit juice concentrate during storage at 20°C was investigated. Kiwifruit juice was passed through cation exchange resin Dowex 50W and/or adsorbent resins Amberlite XAD-4 and XAD-2, to remove amino acids and phenolic compounds. The extent of the initial oxidation of ascorbic acid which occurred during treatments was determined before concentration. After the initial storage period, during which products from ascorbic acid oxidation were most reactive, the browning rates in concentrates which had approximately 90% of the amino acids removed were half that of the control. Initial oxidation of ascorbic acid led to an initially accelerated browning rate, which affected the overall browning occurring during storage. Removal of amino acids with minimal oxidation of the juice produces a kiwifruit juice concentrate with the least overall browning during storage, while removal of phenolic compounds does not appear to be a beneficial procedure for the control of browning in kiwifruit juice concentrate.
TL;DR: In this article, the authors proposed several methods for the reduction of cholesterol in commonly eaten foods with the aim of lowering dietary cholesterol, including biological (microorganisms, enzymes), chemical (solid-liquid-extraction, extraction with organic solvents, complex formation) or physical processes (distillation, crystallization, supercritical fluid extraction).
Abstract: Of the indicators of increased early-onset coronary heart disease, raised serum cholesterol is a risk factor or risk marker, but not the cause. Strategies to reduce morbidity and mortality from coronary heart diseases generally involve reduction of plasma total and low density lipoprotein cholesterol through lowering the intake of total and saturated fat and of dietary cholesterol. Several methods for the reduction of cholesterol in commonly eaten foods have been developed successfully over the past few years with the aim of lowering dietary cholesterol. These approaches are biological (microorganisms, enzymes), chemical (solid-liquid-extraction, extraction with organic solvents, complex formation) or physical processes (distillation, crystallization, supercritical fluid extraction). While the application of these procedures to animal foods, especially to dairy products, is technically feasible, the relatively small contribution of dietary cholesterol to raised plasma cholesterol does not appear to justify the costs involved or to be scientifically justified.