Centre for Nutrition and Food Sciences, The University of Queensland, Hartley Teakle Building, room S426, St Lucia, QLD 4072, Australia.
Eur J Nutr. 2011 Feb;50(1):31-40. doi: 10.1007/s00394-010-0112-0. Epub 2010 Apr 29.
Organic acids from plant food have been shown to play an important role in the prevention of chronic diseases (osteoporosis, obesity), inherent to western diets, but little is known about their bioavailability in the small intestine, information that needs to be determined in order to quantify likely effects on human health.
An in vitro model of human digestion was carried out, comprising simulated oral, gastric and pancreatic digestion followed by an in vitro model of small intestine absorption using Caco-2 cell monolayers. As models for fruits and vegetables, freeze-dried or raw samples of banana and sweet potato were used.
Organic acids have been found to be slowly released from the food matrix during simulated digestion of both banana and sweet potato, either raw or after freeze-drying. In the Caco-2 cell assay, malic and oxalic acids were absorbed more than citric acid. Oxalic and citric acids, but not malic acid, were transported across the cell monolayer. The release and uptake of major organic acids from model fruits and vegetables using established in vitro simulation processes was not quantitative and varied with acid type.
Partial uptake is consistent with a dual nutritional role for organic acids as alkalinising agents (fraction which is taken up) and as modulators of large intestinal function (fraction which is not taken up in the small intestine). Studies of in vivo digestive release and uptake are needed in order to identify the contribution of organic acids to the nutritional value of fruits and vegetables.
植物性食物中的有机酸已被证明在预防与西方饮食相关的慢性疾病（骨质疏松症、肥胖症）方面发挥着重要作用，但它们在小肠中的生物利用度知之甚少，为了定量评估其对人类健康的可能影响，需要确定这方面的信息。
采用体外人消化模型，包括模拟口腔、胃和胰腺消化，随后使用 Caco-2 细胞单层进行体外小肠吸收模型。香蕉和甘薯的冻干或生样本被用作水果和蔬菜的模型。
在模拟香蕉和甘薯（无论是生的还是冻干的）消化过程中，有机酸从食物基质中缓慢释放。在 Caco-2 细胞测定中，苹果酸和草酸的吸收多于柠檬酸。草酸和柠檬酸，但不是苹果酸，被跨细胞单层转运。使用既定的体外模拟过程，从模型水果和蔬菜中释放和摄取主要有机酸是非定量的，且随酸的类型而变化。
部分吸收与有机酸作为碱化剂（被吸收的部分）和作为大肠功能调节剂（在小肠中未被吸收的部分）的双重营养作用一致。需要对体内消化释放和吸收进行研究，以确定有机酸对水果和蔬菜营养价值的贡献。
