Physicochemical Characteristics and In Vitro Starch Digestibility of Spontaneously Combined Submerged and Solid State Fermented Cassava (Manihot esculenta Crantz) Flour

Catalytic efficiency and thermal stability promotion of the cassava linamarase with multiple mutations for better cyanogenic glycoside degradation

In our previous study, we found that cassava cyanogenic glycosides had an acute health risk. Therefore, to solve this problem, the improvement of specific degradation of cyanogenic glycosides of cassava linamarase during processing is the key. In this study, the catalytic activity and thermal stability of enzymes were screened before investigating the degradation efficiency of cyanogenic glycosides with a cassava linamarase mutant K263P-T53F-S366R-V335C-F339C (CASmut) -controlled technique. The CASmut was obtained with the optimum temperature of 45 °C, which was improved by 10 °C. The specific activity of CASmut was 85.1 ± 4.6 U/mg, which was 2.02 times higher than that of the wild type. Molecular dynamics simulation analysis and flexible docking showed there were more hydrogen bonding interactions at the pocket, and the aliphatic glycoside of the linamarin was partially surrounded by hydrophobic residues. The optimum conditions of degradation reactions was screened with CASmut addition of 47 mg/L at 45 °C, pH 6.0. The CASmut combined with ultrasonication improved the degradation from 478.2 ± 10.4 mg/kg to 86.7 ± 7.4 mg/kg. Those results indicating the great potential of CASmut in applying in the cassava food or cyanogenic food. However, challenges in terms of the catalytic mechanism research is worthy of being noticed in further studies.

Physicochemical Composition and Antioxidant Activity of Five Gari Processed from Cassava Roots (Manihot esculenta Crantz) Harvested at Two Different Maturity Stages and Two Seasons

Gari is a partially gelatinized roasted fermented granular white or yellowish product made from storage roots of cassava. It is consumed as fast foods in many countries across the world. Physicochemical composition, particle size, colour, and antioxidant activities of five gari (92/0326, 96/1414, IRAD4115, EN, and AD) processed from fresh storage roots harvested at 12 months after planting (MAP) and 15MAP compared to four (4) commercial gari (M1, M2, M3, and M4) were evaluated. The analytical results revealed that colour value b∗ and particle size varied significantly (p < 0.05) among the gari samples. Bound flavonoid contents were lower than free flavonoids (3.93 to 10.50 mgQE/100 g and 2.40 to 8.85 mgQE/100 g, respectively). Fourier transform infrared confirmed the functional groups in all gari samples. The antioxidant activity of the bound phenolics showed significantly (p < 0.05) higher DPPH scavenging ability than free phenolics (gari M2: 2.70 μgTE/g). Similarly, the bound phenolics showed significant (p < 0.05) variation of HRSA scavenging activity (0.18-35.09 μgTE/g). However, the best HRSA scavenging activity was found with bound phenolics of gari 96/1414, whereas HRSA scavenging activity was not detected in gari 92/0326, 96/1414, and AD. The value of ABTS scavenging activity of gari varied significantly (p < 0.05) from 20.60 to 30.17 μgTE/g and from 20.70 to 34.39 for free and bound phenolics, respectively, while free phenolics showed higher FRAP value (7.97 mgTE/g) than the bound phenolics (4.59 mgTE/g). Additionally, phenolics and antioxidant activities showed significantly (p < 0.05) a positive correlation. The present study has provided an insight into the physicochemical composition, bioactive compounds, and antioxidant activities of various gari processed at different season and maturity period of harvesting. It reveals that consumers of cassava gari can get health benefits apart from the nutritional values.

Effect of ultrasonic pretreatment on eliminating cyanogenic glycosides and hydrogen cyanide in cassava

Traditional soaking method takes days to remove cassava cyanide. Ten minutes of ultrasonic pretreatment (UPT) was found to be a new effective method to eliminate both cyanogenic glycosides and hydrogen cyanide in cassava. Here, the parameters of UPT were optimized and the underlying mechanisms were investigated. 40.36% and 24.95% of hydrogen cyanide and cyanogenic glycosides in cassava juice were eliminated under 10 min of UPT (45℃, 81 W). UPT before boiling enhanced the total cyanide elimination to 41.94%. The degradation patterns of hydrogen cyanide and cyanogenic glycosides were different. Ultrasound directly eliminated hydrogen cyanide and indirectly degraded cyanogenic glycosides through promoting enzymatic hydrolysis. The β-glucosidase activity was increased by 17.99% induced by ultrasound. This was supported by the movement of hydrophobic residual and the rearrangement of the secondary structure of the molecular as found in fluorescence, CD, FTIR, DSC and TG analysis. This study revealed that UPT acted as a fast and simple technical way in improving cassava safety.