Influence of particle size and intestinal conditions on in vitro lipid and protein digestibility of walnuts and peanuts

A static in vitro model was used to assess walnuts and peanuts macronutrient digestion of with two different particle size. Nuts were digested under different intestinal conditions of pH (6 or 7), bile concentration (1–10 mM) and pancreatic concentration (1000 to 4000 LU/g fat) the matrix degradation index (MDI), proteolysis and lipolysis were analyzed. Results showed that nuts particle size affects proteolysis and MDI the most; intestinal pH was more relevant in free fatty acids release. Lipolysis extent was lower under suboptimal intestinal conditions of pH 6 and bile salts 1 mM, and in peanuts it was lower than walnuts (567, 585, 134 and 398 mg FFA/g fat in large and small walnuts, and large and small peanuts, respectively). The higher the pancreatic concentration the higher the proteolysis extent in walnuts; in peanuts, protein digestibility was limited even at high pancreatic concentration at pH 6 and bile concentration 1 mM.