A Novel Enzymatic Process to Produce Oxalate Depleted Starch From Taro

Abstract

A novel process comprising treatment of Taro (Colocasia esculenta (L.) Schott) tuber flour with oxalate oxidase enzyme is developed to deplete the oxalate content. Oxalate oxidase enzyme produced by an endophyte, Ochrobactrum intermedium CL6 is employed to treat taro tuber flour. The treatment followed by extraction of starch results in a 97% reduction in total oxalate content. Further, several physicochemical properties such as paste clarity, swelling power, solubility, amylose content, granule size of starch produced out of enzyme treatment are studied and compared with properties of taro starch produced without enzyme treatment. The study reveals that enzyme treatment does not bring appreciable changes in the studied parameters. The taro starch produced by enzyme treatment shows very low paste clarity (9.38%), high swelling power (15.32 g/g), very low solubility (21.66%), and low amylose content (7.52%) at 100 C compared to potato and sweet-potato starches. X-ray diffraction data reveal that taro starch possesses an A-crystalline form, unlike the B-crystalline form found in potato and sweet potato starch. To the best of the authors knowledge, for the first time, the use of oxalate oxidase to produce oxalate depleted taro starch is reported. One of the interesting food industry applications of oxalate-depleted taro starch, among many other uses could be for baby food formulation because of its small granule size.

Evaluation of Enzymatic and Chemical Treatments to Produce Oxalate Depleted Starch from a Novel Variety of Colocasia esculenta Grown in Joida, India

“…An increase in swelling power of the NT, ET, and PT with an increase in temperature indicates high hydrating ability under different temperatures and excess water. These results corroborate the findings of Kumar and Belur [2] and Tattiyakul et al [49] The solubility of NT, ET, and PT was quite low at a temperature of 65 °C (Figure 4b). But as the temperature increased from 65 to 100 °C, the solubility increased for all three starches.…”

“…These results were in agreement with the trend seen eddoe type of taro. [2] The paste clarity (2% (w/v) starch suspension) was much higher for the native starch of eddoe starch (10.44%) compared to the dasheen type taro starch taken in the current study. The paste clarity of taro starch was in the range of 37.51-42.1% transmittance in the taro cultivated in Jharkhand, India, and 1.5-2.5% transmittance in the taro cultivated in South Africa.…”

“…Kumar and Belur had reported an oxalate content of 790 mg 100 g −1 flour produced out of eddoe type of taro sourced in Mangalore, a west coast city in south India. [2] It had a soluble oxalate content of 639 mg 100 g −1 and insoluble oxalate content of 150 mg 100 g −1 dry weight of taro flour. Hang reported that total oxalate content varied between 127 and 550 mg 100 g −1 taro flour in seven cultivars of C. esculenta grown in central Vietnam.…”

Physicochemical properties and in vitro digestibility of flours and starches from taro cultivated in different regions of Thailand

“…The granular sizes of taro starches were even smaller than those of rice starches (4.33-5.57 μm) reported by Tangsrianugul et al (2019). Due to its small granular sizes, the taro starch has been suggested to provide a better mouth feeling as a potential lipid substitute and baby food formulation (Kumar & Belur, 2018).…”

“…Besides starch, it also contains significant amounts of ash (3.5-5.7%), protein (2.5-5.4%), fibres (0.3-3.8%) and fats (0.3-0.7%) (dry basis) (Mbofung et al, 2006). However, the presence of anti-nutritional factors, for example, trypsin inhibitors and oxalates, make it unfit for consumption without processing (Kumar & Belur, 2018). Taro is commonly processed and used in the preparation of various food recipes, for example, taro paste, taro chips, taro bread and infant foods (Nip, 1997;Arici et al, 2020).…”