Lipid stability of dehydrated beef strips stored in two packaging types

Abstract: Meat is an excellent source of many essential nutrients and makes an important contribution to a balanced diet. Vacuum frying is the technique of deep frying foods under vacuum, and is essentially a dehydration process that develops the desirable sensory properties of traditional fried foods. Vacuum frying has been demonstrated to great effect on fruits and vegetables, but has been used only rarely with animal products and, until now, not with beef. In this study, strips of marinated beef were vacuum fried and stored in two different packaging materials in order to determine the effects on lipid quality of packaging and storage. The packaging types were polyethylene terephthalate (PET) and aluminium foil laminate. Vacuum fried beef samples were stored at 11°C, 15°C, 25°C, 35°C and 39°C for 3, 5, 10, 15 and 17 weeks and the samples and extracted oil was analysed. Response surface methodology (RSM) was used to analyse the responses and the equations generated were also used to predict responses during storage up to 32 weeks at 15, 20 and 25°C. Moisture content and water activity (aw) were only affected following storage in PET packaging. Lipid decomposition was evidenced by significant increases in free fatty acids (FFAs) for both packaging types and Totox value with PET packaging, though these changes were considered to be minor with FFAs reaching only 4.0 (% oleic acid) during 17 weeks of storage and predicted to increase to over 8% after 32 weeks of storage and Totox value not exceeding 32 even after 32 weeks of storage. There were no significant changes in the unsaturated fatty acid content but the levels of polyunsaturated fatty acids, linoleic and linolenic acids decreased during 17 weeks of storage, and average levels were higher in the aluminium foil packaging, indicating that less oxidation had occurred. The tocopherol content decreased significantly from initial concentrations and mean levels were higher in the oil from vacuum fried beef strips stored in aluminium foil laminate packaging, but the response could not be satisfactorily modelled by RSM. Sterol oxidation products (SOPs) were also measured but were unable to be modelled, although higher average levels were found in the oil from vacuum fried beef strips stored in PET packaging. The results of this experiment suggest that vacuum fried beef strips can be stored for up to 32 weeks at temperatures 15-25°C without significant lipid deterioration. Aluminium foil laminate packaging reduced most of the changes that occurred due to lower oxygen and water vapour transmission rates. Future research into the shelf-life of vacuum fried beef strips should concentrate on the use of antioxidants to reduce oxidative changes, SOPs formation and a sensory analysis to determine the acceptability of the products after storage.