The functionality of tempeh addition to beef patties

Abstract

Red meat has been consumed for thousands of years by humans and has played an important part in human evolution. It is a nutrient rich food which is high in protein, minerals, such as iron, zinc, selenium, and many vitamins. However in recent years there has been negative consumer reaction to red meat. This has partially been due to its saturated fat content but also due to the causal link between red meat consumption and the incidence of colorectal cancer. Oxidative stress caused by excess free radical generation in vivo has been linked to the pathology of many diseases including cancers. These effects can be mitigated by consumption of dietary antioxidants, compounds which have increasingly gained consumer attention for their health benefits.

The stomach is a bioreactor where both pro-oxidative and anti-oxidative compounds from the diet interact under low pH and at a relatively high temperature of 37°C. Beef is susceptible to lipid oxidation as it contains both catalyst (free and haem iron) and substrate (lipid) of lipid peroxidation. Consumption of beef with an antioxidant was hypothesised to limit lipid peroxidation in a model stomach system.

Tempeh is a traditional fermented soy product which has antioxidant properties and is commonly consumed in vegetarian diets for nutritional benefits and meat like flavour. Tempeh could be successfully incorporated into a beef patty to provide a source of antioxidant to limit in vivo lipid oxidation. This research aimed to determine the appropriate legume for tempeh production, determine changes that occur in beef patties with tempeh addition and changes in model stomach oxidative processes which occur during consumption of tempeh with beef. During the initial phase of testing soy was chosen as the legume to produce tempeh from. It had acceptable antioxidant properties, was much less labour intensive to produce and more visually appealing than azuki tempeh.

Addition of tempeh to beef patties significantly (p < 0.05) increased water and carbohydrate contents; significantly (p < 0.05) decreased protein content and had no effect on fat content. Tempeh containing patties had an improved fatty acid profile compared to control patties as it contributed a higher level of unsaturated fatty acids. Patties with tempeh retained a lighter, redder colour for longer time during stimulated retail display than the control and were slower to brown as measured by 630-580 and 630/580 nm wavelength ratios. Tempeh containing patties had a higher PUFA content but shelf life was more limited than the control as measured by TBARS. Tempeh containing patties were softer, less cohesive and less chewy than the control patties. Focus group discussions suggested that there was a market for the product if consumers were informed of tempehs health benefits. Overall, the experiments including a pilot and full consumer sensory studies showed that inclusion of 10% tempeh was the most acceptable level of addition. There were no significant (p > 0.05) differences between control and 10% tempeh patties for overall acceptability or acceptance of flavour. However, 10% tempeh patties were found to be more tender and juicier than the control (P < 0.05). The in vitro digestion results showed no significant difference between control and 10% tempeh patties for TBARS. As there is an apparent antioxidant effect in tempeh which is negated by the high PUFA content a defatted tempeh product may be more successful.

Overall there is market potential for a novel beef patty product incorporating tempeh which has several benefits compared to a conventional control patty.