Détermination des propriétés sensorielles, physico-chimiques et stabilisatrices des biscuits de riz (Oryza sativa. L) enrichis au safou (Dacryodes edulis) pendant l’entreposage et leur formulation

Abstract

The majority of rice (Oryza sativa L.) husked in Sub-Saharan Africa contains a high proportion of broken rice (over 50%) and this local broken rice has low economic value in the market,it is very rich in resistant starch. In addition, safou (Dacryodes edulis) is a fruit with high lipid levels (contains essential fatty acids),vitamin C, polyphenols and minerals. It is perishable when fresh and during the harvest period consumers prefer safou from the same clone and which must not be sour. Sour safou constitutes most of the of post-harvest losses. The present study was carried out with the aim of valorising low value broken rice grains to and reduce the post-harvest losses of safou fruits through the formulation of rice biscuits enriched with safou. Sour and non sour safou powder were analyzed for their physico-chemical properties. The main objective was to formulate rice biscuits fortified with dried safou powder and to evaluate the physical, organoleptic, nutritional properties, and the stability during storage in polyprpylene and aluminium packages. The composition of the various ingredients like wheat flour, rice flour, margarine and safou powder was optimized using Response Surface Methodology (RSM), Minitab 18 software. 21 sets of 'experiments and observing responses considered on the responses of parameters such as hardness, granules, appearance, melting, crispness, aroma and overall acceptability were recorded. The results showed that the lipid, protein, fibre and vitamin C contents of the non sour safou powder were higher than that of the sour safou powder. The sour safou was richer in minerals. The optimized biscuit contained 20.24 % of wheat flour, 24.51% of rice flour; 19.09 % of margarine and 2.47% of safou powder alongside the other ingredients (salt, sugar, yeast, flavour agent). The overall acceptability of the biscuit was found to be 4.02. The optimized biscuits were analyzed for their physical, sensory, physico-chemical properties and their stability in to two types of packages. The biscuits made with the fine particles (non-sandy) of a maximum particle size of 500 μm and the safou rice biscuits were rated as "very nice", while the plain rice biscuits were rated as "nice". Fortification of rice biscuits with safou increased the protein, essential amino acid and mineral content of the biscuits. The stability of biscuits in polypropylene and aluminum packages was followed for 5 months at atmospheric conditions (T = 25 ° C, RH = 60%) with intervals of one month for each parameter. The results showed that there is no significant change in the physical parameters (hardness and colour) in each type of biscuits for the two types in packages used during storage. The relatively low humidity level, the peroxide value and malondialdehyde level in the biscuits are not very variable and is particularly lower for rice-wheat biscuits with safou. Safou rice-wheat biscuits therefore have an advantage as they are made with local ingredients and can be used to prevent cardiovascular deseases and fight against protein, iron, phophorus,potassium and zinc malnutrition.