Effect of temperature on the spoilage of stored peas by Rhodotorula glutinis

Abstract

The population of the psychrotrophic pink yeast Rhodotorula glutinis FMT157 increased in numbers on blanched, surface sterilised peas stored at temperatures in the range −18 to +15 °C. The duration of lag phase and rate of growth were directly related to incubation temperature. Yeast growth was limited by the total quantity of carbohydrate available in the peas. Flavour changes determined by the analysis of headspace volatiles showed that although alcohols and ethanal were isolated from both inoculated and uninoculated pea samples, considerably more hexanal was detected in yeast inoculated samples earlier in the incubation period, indicating a higher level of lipid oxidation due to lipoxygenase activity. Thus it would appear that yeast derived enzymes were compensating for loss of similar pea derived enzymes destroyed by the blanching process prior to freezing. In addition 2-methyl furan was formed in yeast inoculated peas at temperatures <5 °C leading to a more objectionable flavour change than in inoculated peas incubated at higher temperatures. Thus control of the yeast contamination on peas and storage at temperatures <18 °C appear to be necessary to ensure a commercially acceptable shelf-life for frozen peas.