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Nutrients 2014, 6(4), 1488-1500; doi:10.3390/nu6041488

Variation in Gastric pH May Determine Kiwifruit’s Effect on Functional GI Disorder: An in Vitro Study

1,* , 1
1 Faculty of Health and Environmental Sciences, AUT University, Private Bag 92006, Auckland 1142, New Zealand 2 Institute of Food, Nutrition and Human Health, Albany Campus, Massey University, Auckland 0745, New Zealand
* Author to whom correspondence should be addressed.
Received: 7 February 2014 / Revised: 24 March 2014 / Accepted: 27 March 2014 / Published: 11 April 2014
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Consumption of kiwifruit is reported to relieve symptoms of functional gastrointestinal (GI) disorder. The effect may be related to the proteases in kiwifruit. This in vitro study aimed to measure protein hydrolysis due to kiwifruit protease under gastric and duodenal conditions. A sequence of experiments incubated meat protein, with and without kiwifruit, with varying concentrations of pepsin and hydrochloric acid, at 37 °C for 60 min over the pH range 1.3–6.2 to simulate gastric digestion. Duodenal digestion was simulated by a further 120 min incubation at pH 6.4. Protein digestion efficiency was determined by comparing Kjeldahl nitrogen in pre- and post-digests. Where acid and pepsin concentrations were optimal for peptic digestion, hydrolysis was 80% effective and addition of kiwifruit made little difference. When pH was increased to 3.1 and pepsin activity reduced, hydrolysis decreased by 75%; addition of kiwifruit to this milieu more than doubled protein hydrolysis. This in vitro study has shown, when gastric pH is elevated, the addition of kiwifruit can double the rate of hydrolysis of meat protein. This novel finding supports the hypothesis that consumption of kiwifruit with a meal can increase the rate of protein hydrolysis, which may explain how kiwifruit relieves functional GI disorder.
Keywords: kiwifruit; protease; gastric protein digestion; functional gastrointestinal disorder kiwifruit; protease; gastric protein digestion; functional gastrointestinal disorder
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Donaldson, B.; Rush, E.; Young, O.; Winger, R. Variation in Gastric pH May Determine Kiwifruit’s Effect on Functional GI Disorder: An in Vitro Study. Nutrients 2014, 6, 1488-1500.

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