The present study aimed to investigate the effect of dietary
actinidin on the kinetics of gastric digestion of beef
muscle proteins and on the rate of stomach emptying in growing pigs. For this purpose, 120 pigs (mean
body weight 28 (sd 2·9) kg) were fed beef
muscle protein-based diets containing either
actinidin (fresh green kiwifruit pulp or
gold kiwifruit pulp supplemented with purified
actinidin) or no
actinidin (fresh
gold kiwifruit pulp or green kiwifruit pulp with inactivated
actinidin). Additionally, fifteen pigs were fed with a
protein-free diet to determine the endogenous
protein flow. Pigs were euthanised at exactly 0·5, 1, 3, 5 and 7 h postprandially (n 6 per time point for each kiwifruit diet and n 3 for
protein-free diet). Stomach chyme was collected for measuring gastric retention,
actinidin activity, individual beef
muscle protein digestion based on SDS-PAGE and the degree of hydrolysis based on the appearance of free amino groups. The stomach emptying of DM and N was faster when
actinidin was present in the diet (P< 0·05): the half gastric emptying time of DM was 137 v. 172 min ( ± 7·4 min pooled standard error) for the diets with and without
actinidin, respectively. The presence of dietary
actinidin in the stomach chyme increased the digestion of beef
muscle protein (P< 0·05) and, more specifically, those
proteins with a high molecular weight (>34 kDa; P< 0·05). In conclusion, dietary
actinidin fed in the form of fresh green kiwifruit increased the rate of gastric emptying and the digestion of several beef
muscle proteins.