Development and characterization of new functional accorn beverage

Abstract

Acorns are fruits from trees belonging to the genus Quercus. Portugal is one of the world's biggest producers of this fruit, however only a small part is used for animal feed, and the remaining is frequently left unharvest in the field. For many years, the acorn makes part of our diet being consumed at meals as a substitute for walnuts, peanuts or olives, incorporated into bread or cookies, or used to produce liqueurs and coffee substitutes. Acorn has high nutritional value containing components that can exert health benefits, for example the presence of non-hydrolysable starch. Given this, and knowing that today the consumer and industry seek more diverse and active functional foods, this work aimed at the development and characterization of a functional beverage made from acorn with and without incorporation of probiotic bacteria. So, acorn beverage was evaluated as matrix for incorporation of probiotic bacteria − Lactobacillus plantarum, L. acidophilus, L. paracasei and Bifidobacterium lactis B94, studying the impact of beverage supplementation with glucose, yeast extract, or both. After proving the positive effect of yeast extract on the growth of selected bacteria, the growth of each microorganism in the original beverage and beverage supplemented with yeast extract, as well as its the viability throughout 28 d of refrigerated storage was characterized. The antioxidant capacity and phenolics content as well as the protein content were evaluated in all stages. For the non-fermented acorn beverage and fermented beverage with appropriate blend of probiotics, an in vitro evaluation of the impact of beverage in a batch system with human faecal inocula of two volunteers was assessed for 48 h. In order to evaluate the potential benefits of the beverage in the balance of the intestinal microbiota and metabolites produced by it, several groups of bacteria were quantified in faecal samples by implementing the qPCR technique, as well as the measurement of the content of short-chain fatty acids (SCFA) generated during 48 h. It was found that the plain beverage maintain the growth of each microorganism tested, reaching 107 CFU/mL after 24 h, which was maintained throughout the 28 days of refrigerated storage. The antioxidant capacity of this beverage was 0.501 ± 0.00 g of AAE/L, the phenolic content 0.312 ± 0.01 g of GAE/L and protein content 0.893 ± 0.00 g/L. Along the 28 days of refrigerated storage there was the reduction of antioxidant activity to 0.287 ± 0.06 g of AAE/L. The positive impact of fermented beverage and non-fermented beverage on the intestinal microbiota was confirmed mainly by the selective increase of SCFA, since the implemented qPCR technique did not allow reliable results in the selective quantification of representing groups from microbiota. Thus, the beneficial effect of non-fermented and fermented beverage was demonstrated by the significant increase of SCFA (propionic acid and acetic acid) and especially lactic acid, with increments even superior to those observed for the inulin, used as a positive control. Thus, it was possible to develop an acorn beverage with prebiotic properties and a symbiotic acorn beverage by incorporating probiotics, demonstrating both the potential ability to modulate the intestinal microbiota, in addition to its antioxidant potential.

Date of Award	2014
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Maria Manuela Pintado (Supervisor)