Selection of the best method for inherent tannin reduction and high nutrient retention

Abstract

Raw legume seeds used in feed contain high antinutritive factors, such as tannins, which threaten livestock farming. Hence, the aim of the study was to (1) carry out single (raw plus dehulling [R + D]; soaking plus dehulling [S + D]; autoclaving plus dehulling [A + D]; infusion plus dehulling [I + D]; microwaving plus dehulling [M + D]; cooking plus dehulling [C + D] and combination [S + A + D; S + I + D; S + M + D; S + C + D; I + M + D, I + A + D]) processing methods on Cicer arietinum, Arachis hypogaea, and Phaseolus vulgaris; (2) determine dry weight yield and tannin reduction; (3) perform proximate and mineral analysis; (4) select the best method based on cost-effectiveness, high tannin reduction and high nutrient retention. The legume seeds were processed, dried, ground, and analysed for dry weight yield, tannin reduction, and proximate (ash, moisture, protein) and mineral (magnesium [Mg], zinc (Zn], copper [Cu], iron [Fe]) contents. A microplate reader and inductively coupled plasma were used as analytical tools. The results showed the highest (97.7%) and lowest (53%) dry weight yields in R + D and I + A + D, respectively. Effective tannin reductions were recorded in I + D (97.8%), S + D (93.9%), S + C + D (96.6%), S + M + D (92.2%), S + I + D (93.8), C + D (91.8%) and S + A + D (84.6%) methods with statistical significance (p < 0.05). Furthermore, ash, moisture, proteins and mineral retention had a range of 29% – 62% to indicate that tannin removal had no effect on nutrient compositions. Although S + M + D (62%) had the highest nutrient retention, S + D (53%) was selected as the best method as it satisfied all the requirements.
Contribution: An effective processing method for use in rural farming to reduce tannins without compromising nutrition of the legume seeds was introduced.