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SummaryYogurt starter B3 was grown in cows' milk, goats' milk I (obtained 2–3 weeks after parturition) and goats' milk II (8 months after parturition), and a number of biochemical and bacteriological parameters were recorded at intervals during incubation for 8 h at 43°C. No appreciable differences between the milks were observed for total viable count, bacteriological ratio of rods to cocci, or decrease in pH. Production of acetaldehyde, however, was considerably lower in goats' milk I (6·2 ppm) and goats' milk II (8·9 ppm) than in cows' milk (18 ppm). Formation of diacetyl and acetoin showed similar patterns in all three milks. The highest production of α-acetolactic acid was observed in goats' milk II, apparently coincident with the highest production of CO2 in this milk.

Ultraviolet (u.v.) laser irradiation has been used to inactivate Bacillus subtilis spores deposited on to planar aluminium-and polyethylene-coated packaging surfaces. Kill kinetics were found to be diphasic, with an initial rapid inactivation phase followed by tailing. Although no de®nitive evidence was obtained, it is thought that spores located within packaging crevices/pores were primarily responsible for the observed tailing. Surviving spores were also found on the unexposed underside of cards and, to a lesser extent, within clumps. The log count reduction in B. subtilis was dependent on spore loading and total u.v. dose. In comparison, packaging surface composition,¯uence (2±18 Jm À2 ) and frequency (40±150 Hz) had only a negligible effect. By irradiating boards carrying 10 6 spores, with a dose of 11Á5 J cm À2 , a log count reduction >5 was obtained. The mode of spore inactivation was primarily through DNA disruption. This was con®rmed by the high sensitivity of spores lacking protective, small, acid-soluble proteins, in addition to the high frequency of auxotrophic and asporogenous mutations found amongst survivors.

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The sensory and chemical shelf-life of UHT-milk stored at room temperature and at 6 degrees C in aluminium-foil, non-foil barrier (X-board) and PE cartons were investigated. UHT milk in aluminium-foil stored in the dark has a minimum shelf-life of 6 months, while the shelf-life is 4-5 months in X-board and PE cartons. When PE cartons and X-board cartons are stored with strong light exposure at 6 degrees C, a development of light-induced off-flavour is detected after 2 and 8 weeks, respectively. The light-induced off-flavour effect is more pronounced than the effect of non-light induced oxidation of unsaturated lipids.