Factors affecting the quality and shelf-life of cooked chilled foods with special reference to full meal vending.

Abstract

A nation wide survey of the vending industry indicated that the shelf-life of chilled menu items served from vending machines rarely exceeded 24 hours. This necessitated food production and distribution to vending sites on a daily basis. The short life coupled with unpredictable consumer demand may result in high food wastage rates. Vacuum and modified atmosphere packaging (MAP) are known to improve stored raw food quality. In order to optimize the quality and shelf-life of vended foods, the effects of these techniques and length of storage time on menu items were studied. Chicken drumsticks and chicken a la king were either individually cling wrapped, vacuum packed or packed under modified atmosphere (70% CO , 30N 0) and stored for up to 21 days in a chilled foot vending machine. The growth of naturally occurring micro-organisms was delayed in vacuum packed samples, compared with cling wrapped samples. However, direct inoculation studies indicated that this effect was dependent on the nature of the initial microflora. The public health risk of serving cooked food from vending machines was assessed by means of a survey of the operating temperatures of chilled food vending machines and a review of the growth characteristics of the major food poisoning micro-organisms. Th8 surveyed machines were able to maintain temperatures below 5 C, although this temperature was not universally found. The sensory quality of the chicken samples was examined by two trained taste panels and also a consumer panel. Stepwise discriminant analysis of the trained panel scores indicated that packaging and length of storage had a distinctive and unique effect on the sensory quality of both products. The mean consumer scores were used to construct significant (p<0.05) regression models, which showed that on average consumers preferred the fresh unpackaged sample and least preferred the cling wrapped samples. However, when the consumer scores of individuals were examined by means of Prefmap analysis, subgroups were found to exist within the population that held polar viewpoints in opinion. The results show that MAP and vacuum packaging may be used in place of cling wrapping to extend the shelf-life of certain vended menu items, but of more immediate importance to the vending industry is the implementation of proper temperature control to ensure a hazard free syste