ASSESSMENT OF STORAGE EFFECTS ON VITAMIN B6 STABILITY AND BIOAVAILABILITY IN DEHYDRATED FOOD SYSTEMS

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Abstract
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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