THE EFFECTS OF FILLING ULTRA‐HIGH‐TEMPERATURE STERILIZED MILK INTO CONTAINERS UNDER NON‐STERILE CONDITIONS

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Abstract
Summary: The spoilage of UHT milk filled into sterilized‐milk bottles and capped with Crown cork seals, into pasteurized milk bottles capped with aluminium foil, and into cartons has been investigated. Spoilage was determined by organoleptic examination, clot‐on‐boiling, and methylene blue reduction. When both types of bottle were filled cold, there was rapid spoilage and no improved keeping quality compared with pasteurized milk controls. Similar results were obtained with milk filled hot into pasteurized‐milk bottles. UHT milk filled cold into cartons had a slightly longer keeping quality than the pasteurized milk. Significant improvement in quality was only obtained by filling hot UHT milk into sterilized‐milk bottles and sealing the bottles with Crown seals. Spoilage was then about 40 per cent after six days at 22o C. (72o F.). Tentative identification of the spoilage bacteria showed that Bacillus cereus was responsible for spoilage occurring within the first two to three days, and that corynebacteria were mainly responsible for spoilage occurring later. Experiments with sterile bottles and with ordinary bottles filled by hand suggested that contamination was arising about equally from the washed bottles and from the filling process. Con‐tamination from the bottles might be eliminated (for example by the introduction of a steaming stage) but it is unlikely that filler contamination caused by the entry of unsterile air could be eliminated without a drastic redesign of the filler.

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