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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 51 (1986), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An acid distillation (AD) method, followed by ion chromatography (IC) resulted in incomplete extraction (50-65% recovery) of sulfite from shrimp samples fortified with various levels of sodium metabisulfite (Na2S2O5). AD-IC accounted for approximately 30% of the sulfite as determined by the AOAC Monier-Williams method (M-W), when shrimp were treated with a standard sulfite dip. An IC method involving extraction of shrimp samples with an alkaline-formaldehyde solution (AFE-IC) or water (WE-IC) gave residual sulfite levels which averaged 97% of those obtained by the M-W method. Fresh shrimp treated with 0.5% and 1.25% Na2S2O5 dips were found by the M-W and WE-IC methods to have mean residuals of 31 and 83 ppm as SO2, respectively, which were below FDA's legal limit of 100 ppm as SO2.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 48 (1983), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of temperature, iron and ascorbate fortification, and oxygen concentration on the stabilities of folic acid (FA) and 5- methyltetrahydrofolic acid (5-CH3-THF) were examined in liquid model food systems. Small retort pouches were used as reaction vessels and the model systems were processed at 100°C, 120°C, and 140°C. A cation-exchange procedure was devised to provide sample extract purification before quantitation using high-performance liquid chromatography (HPLC). FA and S-CH3-THF were found to be very stable under these conditions. Lactose, protein, iron and ascorbate were all found to be capable of reducing the oxygen partial pressure within the model systems, thereby enhancing the stability of FA and 5-CH3-THF. FA and 5-CH3-THF degradation was not zero or first order but possibly second order as a result of limiting oxygen concentrations.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 45 (1980), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Storage stability of α-tocopherol in a model food system containing no fat was shown to be a function of water activity (aw), storage temperature, and the molar ratio of oxygen:α-tocopherol. The degradation rate of α-tocopherol increased as the water activity was increased in the range 0.10–0.65 aw, as the storage temperature was increased from 20 to 37°C, and as the molar ratio of oxygen:α-tocopherol was increased from approximately 15:l to 1450:1. Degradation data of α-tocopherol from all storage conditions best fit the first order rate kinetics model. Experimental activation energies ranged from 8.85–13.05 Kcal mol−1.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dehydrated food systems were employed to study the stability and bioavailability of vitamin B6 as affected by roasting at 180°C for 25 min. The roasting conditions were selected to permit estimation of the maximum effects of the roasting process on the B6 vitamers and are above those which would be normally used for commercial processing. The relative degradation of pyridoxine, pyridoxamine, and pyridoxal phosphate was found to be 50-70% by both microbiological and semi-automated fluorometric assay methods. Estimates of biologically available vitamin B6 in the roasted model systems, as determined by rat bioassay correlated closely with microbiological results. Thus, vitamin B, remaining after roasting at 180°C for 25 min was biologically available and active. Semiautomated fluorometric values for total vitamin B6 in untreated and roasted systems were 1.65-3.63 times higher than corresponding microbiological assay data. Fluorescence spectra studies of samples prepared for the semiautomated assay revealed no detectable interfering compounds. Microbiological assay provided an accurate evaluation of available vitamin B6 in the roasted model food system as shown by the rat bioassay. The consistently high results from the semiautomated fluorometric method indicate that further work is required before this method can be accurately used to quantitatively determine the level of vitamin B6 in foods.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 48 (1983), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The degradation of pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM) during thermal processing was evaluated in casein-based liquid model food systems. Limited evaluation of various potentially reactive ingredients suggested that vitamin B6 stability is not strongly a function of food system composition. Rapid interconversion of PL and PM was observed. Kinetic analysis of B6 vitamer degradation revealed approximately 2.5- to 3.5-fold greater stability of PN than the other nonphosphorylated vitamers, with activation energies of 27.3, 23.7, and 20.8 kcal/mol for the loss of total vitamin B6 after initial fortification with PN, PM, and PL, respectively. Limited studies with pyridoxal 5′-phosphate indicated that it is approximately 1.5- to 2-fold less stable than PL.
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  • 6
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The results of reverse phase high performance liquid chromatographic (HPLC), competitive binding radiometric, and Lactobacillus casei methods were compared for the determination of total folacin in raw cabbage, a fortified cereal, and a fortified infant formula. A cation exchange procedure was developed which permitted the analysis of cabbage folacin by reverse phase HPLC after hydrolysis of folacin polyglutamates with endogenous conjugase. Although general agreement was observed between assays for the cereal product, marked variation was found for cabbage and the infant formula. These results suggest that the accuracy of the radiometric and L. casei assays may be influenced by the distribution of folacin derivatives present and other sample components. Reverse phase HPLC provides a direct analysis which is not subject to such variability.
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  • 7
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous research has suggested that dietary fiber can reduce the bioavailability of certain micronutrients by ionic binding or physical entrapment. In this study, the ability of eight purified polysaccharides, lignin, and wheat bran to bind B-6 vitamers was examined in vitro using equilibrium dialysis under physiological conditions. The polysaccharides used were cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, methyl cellulose, citrus pectin, xanthan gum, sodium alginate, and gum arabic. No significant binding was detected when pectin was dialyzed to equilibrium at, 0.5, 0.75, and 1% levels in the presence of 0.1 or 0.1 mM pyridoxine, pyridoxamine, or pyridoxal. When 1% wheat bran, lignin, and the test polysaccharides were incubated overnight with 0.1 mM pyridoxine prior to dialysis, to allow for any slow binding process to occur, no in vitro binding of pyridoxine by any of the test materials could be observed on equilibrium dialysis. These results are consistent with findings of in vivo experiments which showed that cellulose, pectin, and bran did not significantly decrease the bioavailability of vitamin B-6 when fed to the rat and/or the chick.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 45 (1980), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The results of microbiological and high performance liquid chromatographic (HPLC) methods for total vitamin B-6 were compared with rat bioassay results for biologically available vitamin B-6 in nonfat dry milk and a rice base breakfast cereal product. Excellent agreement was observed between assay values for total and available vitamin B-6 in the nonfat dry milk, indicating full bioavailability. In contrast, the rat bioassay results indicated that the bioavailability of the vitamin B-6 in the cereal product was low. The factors responsible for the apparently poor absorption or utilization of the vitamin B-6 from the cereal product are not known. The results of this study indicate that the bioavailability of vitamin B-6 may be strongly influenced by food composition.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The retention of biologically available vitamin B6 during storage was examined using dehydrated food systems fortified with various B6 vitamers. Storage conditions of 37°C and 0.6 water activity (aw) were selected to permit estimation of maximum rates of nonenzymatic browning and vitamin degradation typically encountered in food storage. The stability of the vitamers during storage was evaluated by periodic assay with a high performance liquid chromatographic (HPLC) method. Losses of pyridoxine (PN), pyridoxamine (PM), pyridoxal (PL), and pyridoxal phosphate (PLP) could be described by fist order kinetics. When stored in small volume metal containers, the first order rate constants were 0.015–0.020 day−1 for PL, PM and PLP, and 0.0049 day−1 for PN degradation in food systems. Storage in metal cans which provided a large headspace volume resulted in significantly lower rates of browning and degradation of the B6 vitamers. The only significant degradation mechanism identified was the binding of PLP to proteins to form e-pyridoxyllysine. Correlation of rat bioassay results with microbiological and HPLC assay data indicated that the B6 vitamers remaining after storage for 128 days at 37°C retained full vitamin activity. Determination of the model system vitamin B6 content by the semiautomated fluorometric procedure yielded consistently high results, as found in previous research. These studies indicate that HLPC and microbiological assay results accurately reflect the content of biologically available vitamin B6 in dehydrated food systems after storage at 37°C and 0.6 aw for 128 days. They also demonstrate the potential for application of the HPLC assay to the determination of vitamin B6 in foods.
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  • 10
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A soluble model system was utilized to study the interactions of pyridoxal (PL) and pyridoxal phosphate (PLP) with proteins during the thermal processing of foods. Heat stable peptides, rather than intact proteins, were used in the model system to maintain solubility and permit subsequent evaluation of the peptide binding of the B6 vitamers. Ultraviolet and visible difference spectra and fluorescence emission spectra confirmed the binding of PL and PLP to the peptides during processing. Total peptide-bound PLP (as the sum of Schiff base, pyridoxylamino, and substituted aldamine derivatives) comprised about 21% of the model system PLP. Approximately 60% of the peptide-bound PLP was bound via nonreducible linkages, suggesting the possible formation of biologically unavailable pyridoxylamino complexes. The acid stability of the PLP complexes, tested to simulate gastric conditions, indicated that most of the nonreducible bound PLP was in the form of pyridoxylamino complexes. Therefore, approximately 10% of the model system PLP was rendered biologically unavailable during these process conditions. The presence of ascorbic acid and/or glucose in the model systems had no significant effect on the extent or manner of peptide-binding of the B6 vitamers; however, glucose-induced browning appeared to slightly inhibit pyridoxylamino complex formation. The results of this study indicate that losses of vitamin B6 bio-availability during thermal processing may be lower than previously reported.
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