Propriedades funcionais da fibra de maçã modificada química e fisicamente

Abstract

This work aimed to study the influence of acid hydrolysis and extrusion on the physicochemical and biological properties of apple pomace fibre, seeking to enhance its beneficial effects as a functional ingredient. Allied to this, it was investigated also bioactive compounds associated with plant cell wall and its relationship with the highest antioxidant protection of the organism. The different acid hydrolysis conditions of the apple fiber promoted increase in all the physicochemical properties evaluated, increasing the capacity of the fibre to bind bile acids (55%), to inhibit pancreatic lipase activity (206%), and to retain water (11%) and fat (20%) in its structure. The hydrolysed fibre (H2SO4 1.5N for 3 h) significantly stimulated the growth of Bifidobacterium lactis and Lactobacillus acidophilus after 48 h of in vitro incubation, and the growth was larger (p <0.05) than that detected for the untreated fibre for both probiotic bacteria and similar (p > 0.05) to that seen in the positive control with inulin for B. Lactis. Regarding extrusion, this treatment caused redistribution among fibre fractions, increasing the soluble fiber content by up to 112.6% (90 ºC/ 33% of moisture). Partial degradation of cell walls was confirmed by the reduction in cellulose and hemicellulose contents and by the increase in soluble pectin levels. more aggressive experimental conditions improved the capacity of apple fibre to bind bile acids (13%), fat (22%), and to inhibit pancreatic lipase activity (by over 70%). The energy generated from extrusion led to the partial release of fibre-associated polyphenols, increasing the extractable polyphenol content. Extrusion (90 ºC/ 33% of moisture) further stimulated the growth of L. acidophilus, but it did not influence the growth of B. lactis. For the biological assay, conducted for 38 days, were used 32 male Wistar rats (21 days of age), distributed among the following treatments: CEL (control with cellulose), AP (with apple pomace fibre) HAP (with hydrolyzed apple pomace fibre) EAP (with extruded apple pomace fibre). The extrusion process increased solubility and fermentability of the fibre, boosting butyric acid production and antioxidant protection of the caecum; increased fecal excretion of the fat and cholesterol; reduced serum triglycerides, and decreased of postprandial glycemic peak. Acid hydrolysis was highlighted by potentiating the prebiotic effect of the fiber, improved the prebiotic effect of the fibre, reducing faecal pH and increasing the production of SCFAs, especially of propionic and butyric acids. Consumption of modified and unmodified apple fibres increased the concentration of polyphenols in the serum and in the intestine of experimental animals, resulting in better antioxidant protection. This shows that these fibres play an important physiological role as carriers of bioactive compounds through the gastrointestinal tract. The methods of modifying the dietary fibre of the apple evaluated in the present work were effective, intensifying some of its beneficial properties and improving its protective effect of intestinal health. It is therefore argued that the proposed methods produced differentiated active ingredients to be exploited in human functional nutrition.