Changes in bioactive compounds present in beef burgers formulated with walnut oil gelled emulsion as a fat substitute during in vitro gastrointestinal digestion

Abstract BACKGROUND The partial or total substitution of animal fat by a gelled emulsion elaborated with cocoa bean shell and walnut oil in beef burgers was assessed in terms of the stability of the bioactive compounds (polyphenolic and methylxanthines compounds, and fatty acid profile), bioaccessibility, colon‐available indices (CAIs), and lipid oxidation after in vitro gastrointestinal digestion (GID). RESULTS No free polyphenolic compounds were detected in the soluble fraction after the GID of reformulated beef burgers. Reductions were obtained in the bound fraction with respect to the undigested sample from 47.57 to 53.12% for protocatechuic acid, from 60.26 to 78.01% for catechin, and from 38.37 to 60.95% for epicatechin. The methylxanthine content decreased significantly after GID. The theobromine content fell by between 48.41 and 68.61% and the caffeine content was reduced by between 96.47 and 97.95%. The fatty acid profile of undigested samples was very similar to that of digested samples. In the control burger the predominant fatty acids were oleic acid (453.27 mg g −1 ) and palmitic acid (242.20 mg g −1 ), whereas in reformulated burgers a high content of linoleic acid (304.58 and 413.35 mg g −1 ) and α ‐linolenic acid (52.44 and 82.35 mg g −1 ) was found. As expected, both undigested and digested reformulated samples presented a higher degree of oxidation than the control sample. CONCLUSIONS The reformulated beef burgers with cocoa bean shells flour and walnut oil were a good source of bioactive compounds, which were stable after in vitro gastrointestinal digestion. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.