Comparison of effects of prickly pear (Opuntia ficus indica sp) fruit, arabic gum, carrageenan, alginic acid, locust bean gum and citrus pectin on viscosity and in vitro digestibility of casein

The consumption of high levels of fibres can induce a decrease in both food digestibility and nutrient availability. Prickly pear is a pectin-rich fruit and it is possible to use it to decrease plasma cholesterol levels. Its effect on food digestibility deserves attention. This effect was determined by using a mixture of a constant quantity of casein and an increasing quantity (10, 20, 25% of the casein) of prickly pear pulp, skin and seed. In parallel, the effect of similar mixtures of carrageenan, gum arabic, locust bean gum, alginic acid and citrus pectin with casein was also studied. The flow behaviour of the different mixtures was determined and their digestibilities were measured using an in vitro digestion cell device. The apparent viscosities of the mixtures with prickly pear components and gum arabic were similar. The nature and level of fibres in the diet modified nitrogen release in the in vitro digestion cell model. The pulp of the prickly pear decreased the digestibility of the casein-based diet to a greater extent than the other soluble fibres, whatever the percentage used. The results suggest that the decrease in N release in the digestion cell model is due to the interaction of the fibres with the enzymes or casein rather than to the apparent viscosity of the mixtures. (C) 2000 Society of Chemical Industry.