Enzyme and Antioxidant Activities of Malted Bambara Groundnut as Affected by Steeping and Sprouting Times

Effect of malting on physicochemical, antioxidant, and microstructural properties of finger millet (Eleusine coracana) flours

Finger millet (Eleusine coracana L. Gaertn.) is a gluten-free crop with a high amount of fiber, calcium and iron, outstanding malting qualities and a low glycemic index. The study aimed to determine the physicochemical, functional, antioxidant and microstructural properties of malted finger millet (light and dark brown) flours. The two varieties of finger millet grains were germinated for 0, 24, 48 and 72 h and kilned for 8 h. The lightness (L*) values of malted finger millet flours significantly increased, with light brown having the highest L* value of 76.62. The hue angle and total color differences (ΔE) of the malted finger millet flours increased significantly (p ≤ .05.), and values ranged from 63.43° to 71.20° (light brown) and 2.12° to 4.32° (dark brown), respectively. The moisture, ash, fiber, protein, total phenolic, total flavonoids contents and DPPH activity of both malted finger millet flours significantly increased. On the contrary, the fat, carbohydrate, energy contents and FRAP activity significantly decreased with each malting period of both finger millet flours. Both malted finger millet flours' solubility index, water and oil absorption capacity increased significantly while the packed and loose bulk density decreased. Malting had no significant effect on the viscosity of the cold paste; however, a significant decrease in the viscosity of the cooked paste in both finger millet flours was observed, with values ranging from 285 to 424.00 cP (light brown) and 271.33 to 418.00 cP (dark brown), respectively. Malting resulted in changes in the thermal properties of finger millet flours with an increase in the onset, peak and conclusion temperatures. Fourier-Transform Infrared Spectra showed that malting slightly changed the peaks of both finger millet flours. Scanning electron microscopy showed that malting altered the microstructural characteristics of finger millet flours. The results showed that malted finger millet flours are promising raw materials for gluten-free bakery products.

Effect of soaking and air-resting on the phytochemical, antioxidant, and antimicrobial properties of Piper guineense (Schum and Thonn) seeds

BACKGROUND

Soaking and air-resting are processing steps in malting. This has been reported to increase metabolic and enzyme activities in rice paddy as a result of exposure of the grain to atmospheric oxygen. The present study evaluated the effect of soaking and air-resting on the phytochemical composition of Piper guineense seeds. The seed extracts were prepared by: soaking the seeds in water for 4 h; air-resting for 30, 60, 90, and 120 min; and re-soaking for another 4 h. The out-of-steep seeds were milled and an extract was formed by tissue homogenization and maceration using ethanol. The phytochemical, antioxidant, and antibacterial properties of the seed extract were determined using standard methods.

RESULTS

The alkaloid, flavonoid, saponin, tannin, and total phenol contents were 0.126-0.268, 0.091-0.172, 0.080-0.123, 0.00-0.107, and 0.447-0.908 g kg^-1 respectively. The antioxidant properties (reducing power) of the seed extracts were concentration-dependent and were in the range 1.08-3.24 g kg^-1 at 8 mg mL^-1 , 1.14-3.47 g kg^-1 at 16 mg mL^-1 , 1.30-3.35 g kg^-1 at 24 mg mL^-1 , 1.26-3.11 g kg^-1 at 32 mg mL^-1 , and 1.13-3.04 g kg^-1 at 40 mg mL^-1 , respectively. The antibacterial activities against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa showed that, at 100 mg mL^-1 , the inhibition zone diameters of the seed extracts were in the range 10-23 mm.

CONCLUSION

Soaking and air-resting of P. guineense seeds increased the phytochemical components of the seeds. The extracts from the seeds air-rested for 30 min showed the highest phytochemical contents and had the highest antioxidant and antimicrobial properties. © 2022 Society of Chemical Industry.

Physicochemical Characteristics of Bambara Groundnut Speciality Malts and Extract

Speciality malts and their extracts have physicochemical characteristics such as colour, flavour, and aroma sorted for in food production. Speciality malts used in food production are mostly produced from cereal grains. Hence, this study aimed to produce speciality malts from Bambara groundnut (BGN) seeds and analyse their physicochemical characteristics and metabolites. The base, toasted, caramel, and roasted malt were produced by drying at different temperatures and times. Syrups were produced isothermally from the speciality malts. The speciality malts and syrups were assessed for colour, pH, protein, α and β-amylases, total polyphenols, antioxidants, and metabolite profiling. The BGN speciality malts were assayed for fatty acid methyl esters (FAME), hydrocarbons, sugar alcohols, sugars, acids, amino acids, and volatile components using capillary gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame ionisation detection (GC-FID). The colours of the speciality malts and syrups were significantly (p = 0.000) different. The protein content of the BGN speciality malts was significantly different (p = 0.000), while the protein content of the syrups was not significantly different. The amylase activities of the BGN speciality malt decreased with the change in kilning temperatures and time. The α- and β-amylase activities for the specialty malts were 1.01, 0.21, 0.29, 0.15 CU/g and 0.11, 0.10, 0.10, 0.06 BU/g. The total polyphenols and antioxidant activities differed for all BGN speciality malts. There were twenty-nine volatiles detected in the BGN speciality malts. Fifteen amino acids consisted of seven essential amino acids, and eight non-essential amino acids were detected in the speciality malts. Fatty acid methyl esters (FAME) identified were palmitoleic, oleic, linolelaidic, linoleic, and arachidic acid. The sugars, organic acids, and sugar alcohols consisted of lactic acid, fructose, sucrose, and myo-inositol. The BGN speciality malts exhibited good physicochemical characteristics and metabolites that can make them useful as household and industrial ingredients for food production, which could be beneficial to consumers.