EFFECTS OF MALTING AND FERMENTATION ON THE NUTRITIONAL, PHENOLIC COMPOSITION, ANTIOXIDANT AND ANTIDIABETIC POTENTIALS OF WHEAT (Triticum aestivum L.)

Abstract

Malting and fermentation are bioprocessing methods that transform the nutritional composition, antioxidant and anti-diabetic potentials of foods generally. This study investigated the effects of malting and fermentation on the nutritional composition, antioxidant and antidiabetic potentials of wheat (Triticum aestivum). The wheat grains were subjected to two different processing methods; fermentation and malting, thereafter the proximate and mineral composition, glycemic indices, amylose and amylopectin ratio and high performance liquid chromatography with diode-array detector (HPLC-DAD) quantification of phenolics of the unprocessed, fermented and malted wheat were evaluated. Additionally, the phytochemical screening, ex vivo and in vitro antioxidant assays, of the unprocessed, fermented and malted wheat were also investigated. The proximate values of malted wheat (MW) and fermented wheat (FW) were significantly higher (p<0.05) with the exception to the fat and moisture content of the fermented wheat, compared to the unprocessed wheat (UW), however the carbohydrate content were significantly lower for both malted and fermented samples. Similarly, the major (Na, K, Ca, and Mg) and trace minerals (Fe, Mn, Zn, Cr, and Pb) of the MW and FW were slightly higher than the UW. Similarly, the antioxidant properties of the MW and FW improved significantly (p<0.05) when compared with the UW, with FW having the highest antioxidant properties as assessed by total phenol, total flavonoid, 1,1-diphenyl-2-picryl-hydrazyl radical scavenging ability, 2’-azinobis 3-ethylbenzothiazoline-6-sulfonic acid radical scavenging ability, nitric oxide scavenging ability, hydroxyl radical scavenging ability, ferric reducing antioxidant power, superoxide dismutase activity, reduced glutathione and lipid peroxidation methods. Malting and fermentation showed a better in-vitro anti-diabetic activity as assessed by α-amylase and α-glucosidase inhibitory assays, glycemic index, amylose and amylopectin ratio protocols, when compared with the UW. The glycemic indices of the treated samples are as follows: unprocessed wheat (42.51); fermented wheat (42.23) and malted wheat had (41.93). The amylose and amylopectin content of the various wheats were 28.66% and 71.34% for unprocessed wheat flour; 43.15% and 56.85% for FW flour, 44.11% and 55.89% for MW flour, respectively. The malted wheat at concentration 50 mg/mL, effectively inhibited α-amylase activity at (82.28 %), whereas fermented wheat at 50 mg/mL, effectively inhibited α-amylase activity at (77.53%) and unprocessed wheat at 50 mg/mL, had a significantly (p<0.05) lower inhibitory α-amylase ability at (71.60%). Likewise, the α-glucosidase activity for the malted wheat extract was significantly (p<0.05) higher at 50 mg/mL (81.59%) while the fermented wheat at 50 mg/mL, effectively inhibited α-glucosidase activity at (78.28) and the unprocessed wheat showed a significantly (p<0.05) lower α-glucosidase inhibitory potency (72.89%). However, the slight reduction in the phenolic compounds of FW, and MW as against UW was not significantly different. Thus, malting and fermentation may serve as a method of improving functional value of wheat in the management of Diabetes mellitus.