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  • 1
    ISSN: 1431-4630
    Keywords: Key words Boiled beef ; Aroma ; Screening ; Potent odorants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  After boiling, beef was extracted with dichloromethane, and the volatile fraction including the solvent was distilled from the non-volatile material. The distillate was divided into two portions; one-half was subjected to aroma extract dilution analysis (AEDA), and the other to aroma extract concentration analysis (AECA). In the latter case, the AECA was accompanied by a series of gas chromatography-olfactometry (GCO) analyses, whereas in the former (i.e. AEDA) the extract was first concentrated to a small volume and then diluted stepwise for GCO analysis. Both screening procedures confirmed the presence of 32 odorants which were all identified after a 250-fold concentration of the extracts. However, the ranking of the compounds in order of odour potency was different due to losses of the odorants in AEDA. 2-Furfurylthiol and 4-hydroxy-2,5-dimethyl-3(2H)-furanone followed by 2-methyl-3-furanthiol and a group containing 3-mercapto-2-pentanone, 1-octen-3-one and (E)-2-non-enal were indicated by AECA to be the most potent odorants of boiled beef.
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  • 2
    ISSN: 1431-4630
    Keywords: Key words Honey ; Flavonoids ; Botanical origin ; Apis ; Melipona
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Profiles of flavonoid compounds of Apis mellifera and Melipona spp. honeys from Venezuela were analysed to evaluate entomological-dependent differences. The presence of ellagic acid was a characteristic of A. mellifera honeys from Venezuela, but its presence was variable in Melipona spp. samples. The number of flavonoid types present in individual samples did not exceed six and occasionally only one phenolic type was present. The diversity of flavonoid compounds in tropical honeys from Venezuela was lower than that previously measured in temperate honeys. Flavonoids such as myricetin, an unidentified chalcone and a flavonol glycoside were only found in Melipona honeys but not in all the samples; therefore, they cannot be foreseen as entomological markers to differentiate between the Apis and Melipona honeys under study. A preliminary discussion is made regarding flavonoids present in Melipona honeys and their probable link with the putative anticataract action of stingless bee-honeys.
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  • 3
    ISSN: 1431-4630
    Keywords: Key words Raisins ; Figs ; Drying ; Control ; Hunter Lab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Shewhart control charts are constructed by using the Hunter Lab color scale parameters to assure maintenance of the color of raisins and dried figs during storage in modified atmosphere packages, vacuum packages, or nylon bags. These control charts may be used to maintain the quality within acceptable limits and make it possible to readjust storage conditions if the acceptable limits should be violated.
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  • 4
    ISSN: 1431-4630
    Keywords: Key words Green pea seeds ; Yellow pea seeds ; Emulsifiers ; Pea processing ; Macaroni
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Pea flour from green and yellow mature pea seeds (Pisum sativum) was processed by adding emulsifiers (Glycerol-monostearate GMS, and Amidan 250B polar type monoglyceride, A250). Doughs obtained were cooked for 15 min and 30 min in order to investigate the effect of the presence of emulsifiers and cooking treatment. The quality of macaroni was examined, cooking properties were defined and sensory assessment established. Changes in protein structure were studied by solution fractioning and SDS-PAGE. Modification of the monosaccharide, disaccharide and α-galactoside contents and trypsin inhibitor activity (TIA) were also studied. The addition of emulsifiers improved dough quality. Emulsifiers fundamentally change the solubility of protein fractions, and they were able to promote the soluble fraction molecular weight distribution and the infiltration of low molecular weight fractions into the protein network. The soluble carbohydrate content was not modified by the addition of emulsifiers whilst cooking time affected its content. α-Galactoside content and TIA were reduced after the addition of emulsifiers and the cooking of peas.
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  • 5
    ISSN: 1431-4630
    Keywords: Key words Carotenoids ; Peroxyl radicals ; Alkoxyl radicals ; Electron spin resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The influence of eight commonly occurring carotenoids on (1) the production of spin adducts, (2) the hyperfine splitting constants a H and a N of the spin adduct electron spin resonance (ESR) spectra, and (3) the production of the oxidized N-tert-butyl-α-phenylnitrone (PBN) derivative N-benzoyl-N-tert-butylnitroxide (PBNOx) was investigated in ESR spin-trapping experiments, in which radicals were thermally generated from 2,2′-azobis(2,4-dimethylvalero nitrile) (AMVN) and trapped by PBN. In the polar solvent acetone under air, all carotenoids except β-carotene were shown to diminish the number of spin adducts formed by about 20%. A prooxidative effect of β-carotene was even demonstrated at a higher concentration. In the less polar solvent toluene under air, most carotenoids lowered the amount of spin adducts, but effects were not as large as in acetone, and differences were found between (1) the more effective carotenoids with two cyclohexene rings conjugated to the polyene backbone (and lycopene), and (2) carotenoids with zero or one conjugated cyclohexene ring. The formation of PBNOx in toluene, which was essentially due to breakdown of peroxyl spin adducts, was significantly inhibited by astaxanthin, canthaxanthin and lycopene. Throughout, only alkoxyl radical adducts of PBN were observed. However, a significant difference was found between the a H values of zeaxanthin and the carbonyl carotenoid astaxanthin, indicating structural differences of the spin adducts.
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  • 6
    ISSN: 1431-4630
    Keywords: Key words Glucose oxidase reactor ; FIA ; Glucose ; Spectrophotometric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A stopped-flow injection analysis system for the determination of glucose is described, based on the iodometric measurement of hydrogen peroxide generated in a glucose oxidase reactor. The detection of the iodine–starch complex was carried out spectrophotometrically. The calibration curve was linear up to 2 mmol l-1 glucose, with a correlation coefficient, r, of 0.9996. The relative standard deviation was 1.6% (n=5) for 1.0 mmol l-1 glucose. A sample frequency of 25 samples h-1 was achieved. This method was applied to the determination of glucose in fruit products and the results obtained using this method were in good agreement with those of a routine enzymatic method. A high dilution of the sample avoided interference from ascorbic acid. The enzyme reactor was stable for 1 month after 200 measurements with no loss of activity.
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  • 7
    ISSN: 1431-4630
    Keywords: Key words Vacuum leaching ; Gelation ; Protein solubility ; Proximate composition ; Sardine mince
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  In order to determine the effect of the vacuum level and leaching time used during the washing process on the gelation characteristics and water-holding capacity (WHC) of sardine mince, a Response Surface Methodology was used. The use of vacuum leaching for short time periods was highly efficient and produced a 50% decrease in the fat content of the washed mince. The leaching under atmospheric pressure produced minces characterised by a low water content and a high residual fat content. The minces’ WHC was shown to be conditioned exclusively by the vacuum pressure produced during stirring, with the lowest WHC results corresponding to the highest fat contents in the minces, which result from the leaching at atmospheric pressure. The determination of gel strength showed that the highest values are obtained with intermediate values of air pressure, and correspond to minces with high protein contents. Harder gels were also obtained with intermediate levels of vacuum. In general, the gels tended to be more cohesive when medium levels of vacuum are used (200–300 mmHg, 26.7–40.0 kPa) for short periods (5 min), or low vacuum levels (550– 650 mmHg, 73.2–86.5 kPa) for longer periods. Hardness, as well as gel strength and breaking force, presented a behaviour that followed the evolution of the protein content in the mince, i.e. higher values were measured at higher protein contents.
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  • 8
    ISSN: 1431-4630
    Keywords: Key words Texture properties ; Wheat dough ; Dough functionality ; Bread quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Texture properties of wheat doughs were determined with a texturometer by using texture profile analysis (TPA) as well as Chen and Hoseney methodologies. The time elapsed between two compressions and strain were optimized so that meaningful values were obtained for TPA. Single effects and interactions between flour type, the breadmaking process and anti-staling additives (i. e. monoglycerides, diacetyl tartaric ester of monoglycerides, sodium stearoyl lactylate, carboxymethylcellulose and hydroxypropylmethylcellulose) on dough texture properties (i. e. springiness, resilience, hardness, cohesiveness, adhesiveness, chewiness, gumminess and stickiness) were estimated. The breadmaking process and addition of hydrocolloids had the most important effects and interactions on TPA. Hydrocolloids and α-amylase increased dough stickiness. Dough cohesiveness was a good predictive parameter of bread quality. Water content, acidity values and gluten quality were the main factors determining the texture properties of dough.
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  • 9
    ISSN: 1431-4630
    Keywords: Key words Yeast identification ; SDS-PAGE ; NIR technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The suitability of near infrared reflectance spectroscopy (NIR) for the rapid identification of different yeasts was tested. Yeasts were grown in batch culture and samples were taken from the exponential and stationary growth stages; later samples were divided into aliquots, one of which was heat-shocked. The four yeasts tested were morphologically different. Optimal growth temperatures were all in the range of 30 – 35°C and at 30°C growth rates of mixed cultures did not differ significantly from those of monocultures. NIR spectra of the strains investigated were significantly different. The growth stage or heat-shock treatment had significant effects on the spectrum. Mixtures of two pure cultures (0, 10, 20 . . . 90% “infection”) had NIR spectra which were intermediate to those of the pure culture and even 10% contamination caused a significant difference.
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  • 10
    ISSN: 1431-4630
    Keywords: Key words Garlic-based products ; Garlic ; Allium ; Alliin ; Dithiins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Garlic Samples (n = 34) used as a spice and/or health preparations were analysed for their content of the major amino acid found in garlic, i. e. alliin and its five major decomposition products: 2-vinyl-[4H]-1,3-dithiin; 3-vinyl-[4H]-1,2-dithiin; diallyl disulphide; allylmethyl disulphide and diallyl trisulphide, using two high-performance liquid chromatographic methods. The obtained data were subjected to principal components analysis (PCA) which distinguished these samples into different individual categories according to the similarity of their chemical composition. The four distinguished groups were: fresh garlic bulbs, dry garlic products (powders, granulates and tablets), macerates in vegetable oils (salted garlic pastes, soups and bouillon cubes, which had a very similar chemical composition) and garlic essential oils.
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