The optimum temperature and pH to hydrolyse meat proteins with an enzyme complex from kiwifruit
Sarcopenia is the loss of skeletal muscle mass in elderly people. It is usually considered an inevitable part of ageing, but results from AUT University doctoral study by Donaldson (2008) suggest that a combination of higher stomach pH and lower pepsin secretion into the stomach of the elderly limits the nutritional benefits of protein in the diet, eventually resulting in muscle wasting. To aid digestion, the proteolytically-active fruit kiwifruit, is increasingly used in clinically validated therapies to improve geriatric nutrition. An alternative strategy is to use protein preparations previously hydrolysed by kiwifruit protease complex as a non-bitter dietary supplement. The best conditions for hydrolysis are currently unknown. The hydrolysis of meat protein by an enzyme complex isolated from kiwifruit (Zyactinase®) was studied to evaluate the influence of temperature (35, 40, 45 and 55°C), and pH (1 to 8) on the protein solubility. In a typical experiment, each trial was incubated for two hours, which followed by centrifugation. The post-centrifugation supernatant was divided into two parts: the first part was undertaken Kjeldahl method; the second part after dilution was carried out an ultraviolet scanning. Once the optimum conditions were determined, a characterisation of the protein hydrolysate was carried out by using sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE). It was found that the highest Zyactinase-dependent solubility occurred at 35°C and pH 2 by Kjeldahl method while the highest total protein solubility occurred at 45°C and pH 2. However, the biggest Zyactinase-dependent absorbance was at 40°C and pH 2 by UV scanning. The optimum conditions of hydrolysis were optimised using response surface methodology. The optimum conditions were determined as 40°C and pH 2. The SDS-PAGE profiles in the hydrolysate from optimum conditions included myosin, actinin, actin and tropomyosin.