Physico-Chemical Characterization of Some Malagasy Rice Varieties. Relationship between Digestibility and Weevil Attack

Abstract

Alkali digestibility and gel consistency of a few Malagasy rice varieties have been studied. As regard the alkali digestibility, results show three types of vari-eties: respectively varieties with low, medium and high alkali digestibility. Homogeneous translucent milled varieties are found to have a long time of un-changeableness at storage (more than two years): they were most of the im-proved irrigated rice. They agreed with low alkali digestibility (score 2 to 3) and they were difficult to be attacked by weevil. Most of the rainfed rice varieties were of intermediate alkali digestibility (score 3 to 5), and they have a semi-translucent caryopsis. High alkali digestibility (score 5.5 to 7) was among heterogeneous caryopsis rice (white belly rice, cracked rice, structured paddy). They are even though in the class of rice easy to cook on culinary considera-tion. They were remarkably easy to be attacked by weevils or fungi. Hybrid 885 retained water in the slot and was breakable as example. About gel con-sistency, most of the varieties were of hard gel consistency (score less than 40 mm). The low gel consistency (score more than 60 mm) was found with par-boiled rice varieties and some varieties such as 27 GM, 28 GM, Manjamena, which reflects a good culinary quality: tenderness longtime after cooking and cooling. In every case, varieties with a low gel consistency and easy to cook are highly sought varieties by urban consumers.