1989

Ahvenainen, Raija

Interest in the use of gases in the packaging of cooked food products has increased considerably in recent years.Therefore the quality as well as the microbiological and sensory shelf life of selected chilled cooked meat products and ready to eat foods packed using nitrogen and carbon dioxide (gas packaging) were studied and compared with those of regularly packed products (air or a vacuum).In addition, to obtain full benefit from gas packaging, the effects of some basic factors, such as the optimal gas compositions, gas permeability of packaging materials, head space volume and initial microbiological quality, were studied.Furthermore, the quality of gas packed ready to eat foods stored in both opened and leaking packages was investigated.Gas packaging improved the sensory quality and shelf life of several meat and ready to eat products.The best gas composition for cooked meat products was a mixture of 20 % CO2 + 80 % N2, whereas for ready to eat products the optimal gas composition was very dependent on the product. However, gas packaging did not improve the shelf life of mayonnaise based potato salad.Gas also had an obvious residual inhibitory effect on the quality deterioration of minced meat steaks, but it lasted only some days.On the other hand, the quality retention of minced meat steaks was even poorer in leaking gas packages than in sealed air packages.Among the factors studied, the length of the delay in packaging had the most significant effect on the quality and shelf life of gas packed products.So called high barrier materials, e.g. materials including EVAL or PVDC layers, did not lengthen the shelf life of gas packed products.Instead, high barrier materials essentially improved the shelf life of vacuum packed products.A gas volume in which a product was not yet compressed was sufficient.This study also showed very clearly that in shelf life studies involving new preservation techniques applied to food products attention should be paid to the retention of sensory quality in conjunction with microbiological parameters.Furthermore, the appearance of unopened packages is important.