Application of soaking and cooking waters as prebiotics

CARBONI, ANGELA D; MARTINS, GONÇALO N.; HUGO, AYELÉN AMELIA; GOMEZ-ZAVAGLIA ANDREA; CASTILHO, PAULA C.

Castelo Branco

Encuentro; XVI Encontro de Quimica dos Alimentos; 2022

Pulses contain oligosaccharides with prebiotic effects, including galacto-oligosaccharides (GOS). GOS are prebiotic compounds composed of a variable number of galactose units, between 2 and 10 (e.g., degree of polymerization, DP = 10), linked via glycosidic bonds, and a terminal glucose (or sucrose) unit.1 The processing of legumes before consumption by soaking and/or cooking enhances the bioavailability of certain nutrients, improves organoleptic characteristics such as texture or flavour, and reduces undesirable effects after consumption.2 These treatments usually involve the use of large amounts of water, generating wastes and high levels of environmental pollution. Reusing industrial by-products or discards is an important strategy to improve the sustainability of food production. Lactic acid bacteria (LAB) are a group of probiotic microorganisms significant for the food industry. GOS can help in the growth of LAB.3 The objective of the present work was to evaluate a possible application for different samples of waste waters obtained through the processing of lentils and chickpeas, on the growth of LAB.GOS-containing extracts were obtained by either soaking, cooking after soaking, or cooking dry seeds of commercially obtained lentils (Lens culinaris Medikus var. variabilis) or chickpeas (Cicer arietinum L.) in water. The same seed to water was used in all experiments. Every extract was analysed using High Performance Liquid Chromatography with Refractive Index (HPLC-RI) for the determination of carbohydrates. Their content was estimated by comparison with Vivinal® GOS Syrup (Vivinal) as a standard.The prebiotic effects of the obtained GOS were evaluated over two strains of LAB Lactiplantibacillus plantarum CIDCA 83114 (LP114) and Lactobacillus delbrueckii subsp bulgaricus CIDCA 331 (LB331). For this, the extracts were added at 0.3 % to de Man, Rogosa and Sharpe (MRS) culture medium (without glucose as carbon source) and then, bacterium were inoculated in a concentration of 2.3E+07 CFU/mL (1% v/v). These results were compared to the same experiment using conventional sugars or none.Chickpeas appear to be a richer source of saccharides compared to lentils, both in terms of the overall number of species present in the extracts, (shown by the larger number of peaks detected in the chromatograms); as well as the larger amount in which each compound seems to be present. Although GOS can be found in higher quantities in the chickpea extracts, lentils provided far less monosaccharides and DP = 2 sugars, which usually require removal. The cooking methods produced extracts with higher GOS’ contents than the soaking processes (Figure 1). The results obtained for the microbiological assays for LP114 were similar for all saccharides tested, i.e., the bacteria grew in all conditions. However, this was not the case for the assays carried out with the LB331 strain, in which only glucose and Vivinal were able to promote its growth.In conclusion, GOS were detected in all waste waters derived from lentil and chickpeas, as well as other saccharides. These samples showed prebiotic potential towards LP114 strain, or at least did not inhibit its growth. This behaviour was not shown towards LB331.This work proved the wastes produced during domestic and industrial treatments of legumes present bioactive compounds with possible applications in the food or pharmaceutical industries, such as prebiotic supplements.