Actinidin in Green and SunGold Kiwifruit Improves Digestion of Alternative Proteins—An In Vitro Investigation

Abstract

Both Hayward (green) and SunGold (gold) kiwifruit varieties contain a proteolytic enzyme, actinidin, that has been reported to enhance the upper tract digestion of animal proteins. Unlike the other gold varieties, which do not contain any actinidin, the SunGold variety contains significantly higher actinidin activity, but its activity is still much lower than that present in the green (Hayward) fruit. The objective of this study was to determine the effectiveness of actinidin in Hayward and SunGold kiwifruit in digesting alternative proteins, including pea protein, almonds, tofu, and quinoa. The protein sources were digested using a three-stage in vitro oral-gastro-small intestinal digestion model. The findings showed that both kiwifruit extracts enhanced the breakdown (observed through SDS-PAGE) for all the studied protein sources, particularly during gastric digestion, possibly due to higher actinidin activity at gastric pH. The increase in the rate of protein breakdown was probably due to the broader specificity of actinidin compared to pepsin. For many protein sources, most of the intact proteins disappeared within the first few minutes of gastric digestion with added kiwifruit extract. Green kiwifruit extract, due to its higher actinidin activity, had a higher effect on protein breakdown than the SunGold extract. However, for some proteins and under certain digestion conditions, SunGold extract resulted in higher protein breakdown. The latter, in the absence of any digestive enzymes, also led to some protein breakdown during the small intestinal digestion phase, which was not the case for the green kiwifruit extract. The green kiwifruit extract led to the greater breakdown of polypeptide chains of Pru-du 6, a major allergen in almonds. The results, for the first time, suggest that both Hayward and SunGold kiwifruit can lead to improved breakdown and digestion of alternative proteins when consumed as part of a meal; and therefore, have the potential to be used as a digestive aid in population groups looking to achieve faster and greater protein digestion such as athletes, elderly and people with the impaired digestive system.

Effects of gold and green kiwifruit juices on the physicochemical properties and tenderness of pork loin and antioxidant activity during incubation (24 h) in a pork model system

“…We determined that GRJ (38.05±1.08) had a higher protease activity than GOJ (30.13±2.95) (p<0.05). This result was consistent with the previous study that green kiwifruit had a higher specific protease activity than gold kiwifruit [18]. Chao [19] reported that actinidin content determined protease activity even among kiwifruit species with similar protein concentrations.…”

A comprehensive review of phytochemical and pharmacological properties of Actinidia deliciosa

“…The results for the first time indicate that both SunGold and Hayward kiwifruit can improve the breakdown and digestion of other proteins when eaten as part of a meal. As a result, they have the potential to be used as a digestive aid in populations like athletes, the elderly, and those with impaired digestive systems who want to achieve faster and greater protein digestion [28] .…”

Correction of Exocrine Pancreatic Insufficiency by Plant-Derived Enzymes (Literature Review)

“…It is important to note that there is a large interindividual difference in response to enzyme preparations [32], which requires a more detailed study in the future of the optimal response to enzyme replacement therapy among different population categories. In particular, there is potential for the use of actinidin as a beneficial factor to improve and accelerate the protein digestion process among certain groups of people -athletes, the elderly, and people with digestive organ pathology [33].…”