Dietary fiber concentrates recovered from agro-industrial by-products: Functional properties and application as physical carriers for probiotics

Abstract

Traditional alcoholic extraction from by-products always discards insoluble fiber-rich residues, generating a new ‘waste’ stream. To recover these alcohol-insoluble residues (AIRs), we used an ethanol-washing method to obtain these dietary fiber concentrates from six agro-industrial by-products (blackcurrant pomace, banana peels, clementine peel, oat hull, potato peel and wheat bran) and applied them as probiotic carriers. The functionalities of absorption capacities and the antioxidant capacities in AIRs were characterized. The results showed that the alcohol-washing method to obtain AIRs did not result in a loss in the dietary fiber fraction. Fruit AIRs still contained a high content of bound phenolic compounds, displaying long-term ABTS and DPPH radical scavenging capacities during a 4-h incubation. Different AIRs varied in water and oil holding capacity and protein absorption capacity. The protective effects of AIRs on three lactobacillus strains (Lactobacillus acidophilus LMG9433T, Lactobacillus casei LMG6904T and Lactobacillus rhamnosus LMG25859) against heat shock were also investigated in Man-Rogosa-Sharpe (MRS) broth supplemented with 1% AIRs After an 18-h incubation at 37 °C, all AIRs did not influence the growth of probiotics, while they mostly increased the tolerance to the gastric digestion of Lactobacillus rhamnosus LMG25859, efficiently improved the viability of three strains after heat shock. Among six AIRs, the one extracted from clementine peel performed better in improving the viability of probiotic cells after heat shock than the other AIRs. Valorizing dietary fiber concentrate as probiotic carriers can promisingly replenish the whole chain of the food recovery from agro-industrial by-products.