Comparison of starch digestibility of a blended food prepared with and without extrusion cooking

Abstract

Objective: To compare starch digestibility from a maize-soy blended food with and without extrusion cooking.

Design: Resistant starch, soluble and insoluble dietary fibres were measured in vitro before and after extrusion. Starch digestibility was assessed in 8 volunteers who took, in a randomised order, a test meal with either 100 g extruded (EF) or non-extruded (NEF) blended flour cooked 15 min at 80°C in 500 ml of water.

Setting: Research ward for healthy volunteers.

Subjects: Healthy volunteers.

Main outcome measures: Starch digestibility was measured by ¹³C enrichment of breath samples for 8 h. Breath H₂ concentration was measured during 12 h to assess bacterial fermentation in the colon. Volunteers reported hunger on a visual scale every hour for 8 h.

Results: In vitro resistant starch, soluble and insoluble dietary fibers were higher in NEF than in EF (5.4 vs 1.1, 0.7 vs 0.5, and 13.3 vs 10.4% dw respectively). In vivo, the area under curve (AUC) for ¹³CO₂ excretion during 8 h was not significantly different for NEF and EF (10.3±1.3 vs 9.1±0.5 mmol/min, respectively). AUC for H₂ excretion during 12 h was significantly higher for EF than for NEF (26.9±5.6 vs 14.1±4.7 mL, P<0.05). AUC for satiety was marginally higher with EF (12.6±1.6) than for NEF (10.0±2.1) (P=0.06).

Conclusions: Extrusion cooking does not seem to substantially improve blended foods digestibility. Extrusion of high fibre flours may promote carbohydrate fermentation in the colon and increase satiety.

Sponsorship: Supported by a grant from Nutriset (Malaunay, France) and ANVAR (Agence Nationale de la Valorisation de la Recherche, Contract No A9703021P).