Characteristics of viableBrevibacterium linenscells, methionine and cysteine in milkfat-coated microcapsules

Abstract

The potential for microencapsulation of viable Brevibacterium linens with methionine or cysteine in milkfat to produce sulphur compounds was examined in this study. More than 80 per cent of B. linens cells were encapsulated and then numbers inside capsules increased about three-fold during 48 h at 26 degrees C under anaerobic conditions before a slow decline. Most of micro-organisms (7 x 10(7)/ml) were still viable in the capsules after 15 days. More than 90 per cent of cysteine and methionine were encapsulated and 90, 80 and 60 per cent of the encapsulated amino acids were maintained in the capsules at 4, 12 and 26 degrees C, respectively, after 24 h. Most of the cysteine was oxidized to cystine during microencapsulation but still available to micro-organisms whereas methionine remained in the reduced form. Partition coefficients of methionine and cysteine to milkfat were 0.117 and 0.275, respectively, indicating that most of these substrates would be available to cells of B. linens in the capsules.

Encapsulation of bifidobacteria in whey protein-based microcapsules and survival in simulated gastrointestinal conditions and in yoghurt

“…Milk fat and other hydrophobic substances have previously been reported as potential cell immobilization matrices (Kim & Olson, 1985;Modler & VillaGarcia, 1993;Sunohara et al, 1995;Champagne, Raymond, Mondou, & Julien, 1995;Baba, Kubota, Horishita, & Matsunobu, 1996). Diffusion of H + , organic acids, water, and oxygen across membranes of lipid capsules is limited.…”

Production of methanethiol in milk fat-coated microcapsules containingBrevibacterium linensand methionine

“…The loss of methanethiol in milk fat capsules under anaerobic conditions may result from the reactions with degradation products of milk fat such as free radicals and unsaturated carbonyl compounds. The adverse effects of milk fat on sulphydryl groups was illustrated previously by the rapid oxidation of cysteine in aqueous extracts of milk fat whereas cysteine in buffer was not oxidized (Kim & Olson, 1985).…”

“…Growth conditions of B. linens (ATCC 9174) and preparation of bacterial cells for encapsulation were described previously (Kim & Olson, 1985). Encapsulation was carried out by the methods of Magee & Olson (1981) and Braun & Olson (1986) except that 0 0 5 % Tween 60 was added to the dispersion fluid.…”

“…Numbers of cells in cell suspension were estimated by the same method as was used previously (Kim & Olson, 1985). Two sets of controls were used.…”

“…At high temperatures, methanethiol is more likely to react with degradation products of milk fat or other compounds than at low temperature. Also, more methionine should be available over a longer time to microorganisms at low temperature because less substrate would diffuse from the capsules (Kim & Olson, 1985). Methanethiol production was slow at 12 °C but levels increased continuously and eventually reached almost the same concentrations as those at 26 or 32 °C; levels at 4 °C were almost the same as those at 26 or 32 °C after 6 d because less methanethiol was lost even though the initial production rate was much lower.…”