Preliminary tests for the safety evaluation of new enological agents containing polyaminoacids : in vitro assessment of digestibility and intestinal absorption

Each step in the winemaking process must be carefully planned and controlled to optimize the quality of wine. Among others, tartaric stabilization is one of the most critical steps in enology. Although effective, the usual practices for wine stabilization present some qualitative limitations, and show important economical and environmental impacts. For the reasons reported above, the wine producers are searching for alternative practices, with particular interest in the area of organic products. Biopolymers are among the possible alternatives in this field. The selection and the characterization of new biopolymers is the object of the European project STABIWINE. The first group of biopolymers analyzed were polyaminoacids and, in particular, polymers of L-aspartic acid (PAA), which can be used as enological additives for tartaric stabilization. The aims of the research here described were: 1) to evaluate the proteolysis of PAAs, using an in vitro model, which simulates the gastrointestinal digestion, and 2) to estimate the intestinal absorption by using CaCo2 cells. To simulate the human digestion, PAA samples were assayed by in vitro gastrointestinal models, using a sequential proteolytic attack with pepsin and pancreatin. Proteolysis was measured by quantifying: the undigested proteins by microbiuret method [1], and the release of free aminoacids by ninhydrin method [2]. The absorption through intestinal barrier was measured, with the same methods indicated above, in apical and basolateral portion after the addition of PAAs to CaCo2 cell layer. From the proteolytic profiles obtained, it was shown that PAAs were very poorly digested by gastrointestinal enzymes, justifying the data found in CaCo2 cells, where most of PAA (approximately 70%) was found in the apical area after 24 h from addition (very limited absorption). REFERENCES 1) Itzhaki RF and Gill DM. 1963. A micro-biuret method for estimating proteins. Analytical Biochemistry 9: 401-410. 2) Moore S and Stein WH. 1954. A modified ninhydrin reagent for the photometric determination of aminoacids and related compounds. The Journal of Biological Chemistry 211: 907-913. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 314903. It has been carried out within the STABIWINE project (www. stabiwine.eu). This report does not necessarily reflect the Commission views or its future policy on this areas.