Physicochemical and thermal properties of taro (Colocasia esculenta sp) powders as affected by state of maturity and drying method

Physicochemical Characterization of Resistant Starch Type-III (RS3) Obtained by Autoclaving Malanga (Xanthosoma sagittifolium) Flour and Corn Starch

The feasibility of obtaining resistant starch type III (RS3) from malanga flour (Xanthosoma sagittifolium), as an unconventional source of starch, was evaluated using the hydrothermal treatment of autoclaving. The physicochemical characterization of RS3 made from malanga flour was carried out through the evaluation of the chemical composition, color attributes, and thermal properties. In addition, the contents of the total starch, available starch, resistant starch, and retrograded resistant starch were determined by in vitro enzymatic tests. A commercial corn starch sample was used to produce RS3 and utilized to compare all of the analyses. The results showed that native malanga flour behaved differently in most of the evaluations performed, compared to the commercial corn starch. These results could be explained by the presence of minor components that could interfere with the physicochemical and functional properties of the flour; however, the RS3 samples obtained from malanga flour and corn starch were similar in their thermal and morphological features, which may be related to their similarities in the content and molecular weight of amylose, in both of the samples. Furthermore, the yields for obtaining the autoclaved powders from corn starch and malanga flour were similar (≈89%), which showed that the malanga flour is an attractive raw material for obtaining RS3 with adequate yields, to be considered in the subsequent research.

Aroids as underexplored tubers with potential health benefits

Colocasia esculenta (L.) Schott and Xanthosoma sagittifolium (L.) Schott are the most popular tubers among the Araceas family. Their chemical composition related to their nutritional benefits could make these rhizomes a valid option for the nutritional and technological improvement of food products. This chapter provide a clarification about the correct nomenclature of both tubers giving an insight around the principle components and their health effects. The scientific literature review has primarily highlighted several in vitro and animal studies where the consumption (leaves and whole tuber) of Colocasia esculenta (L.) Schott and Xanthosoma sagittifolium (L.) Schott was related with certain antihyperglycemic, antihypertensive, hypoglycemic and prebiotic effects. Owing to their functional properties, different component from these rhizomes, specially starch, mucilage and powders are being used by the food industry. Their ability to behave as thickener and gelling agent has allowed their incorporation in baked food, food paste and beverages. This chapter suggests the development of more research around these rhizomes since they could potentially play, with other crops, an important role in the future sustainable strategies to feed the planet.

Proximate and starch composition of marama (Tylosema esculentum) storage roots during an annual growth period

The aim of this study was to determine the most suitable time for harvesting marama (Tylosema esculentum) root as an alternative source of novel starch by evaluating the quality of marama root and its starch during growth periods of 12 months. The effects of time on the proximate analysis of marama roots as well as the thermal properties, size and physicochemical properties of the starch were also investigated. Marama was planted in September and total starch of marama roots on both as is and dry bases increased significantly (p<0.05) from 24 g/kg to 115 g/kg and 259 g/kg to 601 g/kg, respectively, from 2 to 12 months after planting. Amylose content significantly (p<0.05) decreased from about 50.7% to 21.4% of the starch for the same time period. The size of marama root starch granules significantly (p<0.05) increased from 8.6 μm to 15.1 μm. The marama root harvested after 2 months had the highest crude protein content (33.6%). In terms of thermal properties, the peak temperature decreased significantly with time (ranging from 93.0 °C to 73.4 °C), while the ΔH increased significantly with time. The findings indicate that marama should be planted early in summer and harvested between 4 and 8 months for optimal starch before winter. Significance: Proximate and starch characteristics of marama storage roots differ significantly with time of harvest. This suggests that desired functional properties can be achieved by controlling growth time. The marama root harvested at 4 months is highly nutritious, it has high protein content, starch that is high in amylose and is suitable for consumption as a fresh root vegetable in arid to semi-arid regions where few conventional crops are able to survive. Marama root is a climate smart crop and it could potentially contribute to food security in arid regions. The results obtained in this study suggest that the optimum time for harvesting marama as a root vegetable is at 4 months while the optimum time for harvesting marama for its starch is at 8 months. Younger roots have higher amylose, and hence higher gelatinisation temperatures, and therefore may be more suitable to be used as a coating during frying.

Mucilage chemical profile and antioxidant properties of giant swamp taro tubers

The yellow (YP) and white (WP) sections of giant swamp taro (GST) contain 40.0 g/kg and 51.5 g/kg (dry wt) respectively of pure mucilage made up of D-glucose (44.95-78.85 %), D-galactose (8.70-25.35 %), D-mannose (3.20-10.45 %), D-arabinose (2.45-5.20 %) and small amounts of glucuronic acid and rhamnose. Arabinogalactan-proteins (5.30-8.83 g/kg) contain mainly arabinose and galactose (in a 1:1 proportion) and also significant amounts of rhamnose, xylose, glucuronic acid and mannose. Antioxidant activity of YP was higher than those of WP while chelating ability and reducing power increased with mucilages content. Generally YP and WP showed better reducing power (1.06 ± 0.35 at 5 mg/mL) than ascorbic acid (0.89 ± 0.22). WP and YP chelated ferrous ions by 20.0-76.0 % and 16.4-71.0 % respectively. Effective concentrations (EC50) of mucilages (WP 1.28 ± 0.05 mg/mL; YP 1.42 ± 0.04 mg/mL) were lower than those of citric acid (1.58 ± 0.04 mg/mL). Generally mucilage from the WP and YP sections are excellent sources of chelating agents.