EFFECTS OF PRE-DECORTICATION TREATMENTS ON THE MILLING PROPERTIES AND FLOUR CHARACTERISTICS OF BAMBARA GROUNDNUT (Vigna Subterranea L.) VARYING IN SEED COAT COLOUR
N. DANBABA *
Food Technology and Value Addition Research Program, National Cereals Research Institute, Badeggi, Nigeria and Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
P. Y. IDAKWO
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
A. L. KASSUM
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
S. D. MALGWI
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
O. A. IGWEGBE
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
H. K. LAWAN
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
A. I. MAIJALO
Department of Food Science and Technology, Faculty of Engineering, University of Maiduguri, Nigeria.
I. NKAMA
Department of Food Science and Technology, University of Nigeria, Nsukka, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Variability in the milling behaviour, flour colour, particle size distribution and chemical composition of pre-treated bambara groundnut varying in seed coat colour were studied. Pre-decortication treatments were soaking, steaming, boiling, roasting and germination. Treatments improved decortication efficiency and split yield and reduced broken splits. Decortication efficiency ranged between 81.10 – 94.05% (cream), 83.91 – 97.31% (black) and 83.61 – 89.11% for red. Colour characteristics of flour indicated mean lightness (L*), redness (a*) and yellowness (b*) of 59.07, 6.88 and 32.72 respectively, with significant difference between treatments and cultivars (p<0.05). The highest L* value (61.30) was observed in black cultivar when steamed, while the least L* values (50.22) was found in all the roasted cream sample. Significant percentage of all the flours were retained on the 1 mm sieve except black coated seed when pre-treated by soaking where the highest retentions (26.18% and 37.06%) were observed at 500 and 150 µm sieves respectively. Protein content of flour ranged from 16.35 to 17.67% and gross calorie from 353.07 to 397.03 kcal/100 g. Significant improvement in protein was observed in pre-treated flour when compared with raw flour. Overall, water related treatments (soaking, boiling and steaming) improved milling performance, while roasting and germination reduced lightness index of flour colour and all the treatments improved protein content.
Keywords: Bambara groundnut, colour, decortication, flour particle size, milling, protein.