Purple carada (Dioscorea trifida L.f.) and cará-de-espinho (Dioscorea chondrocarpa Griseb.) as new sources of Amazonian starches - Extraction and characterization

Purple yam (Dioscorea trifda L.f.) and spiny yam (Dioscorea chondrocarpa Griseb.) are Amazonian tubers cultivated and consumed by family farmers, playing an important role in this population's diet. They are of great importance for food and nutritional security due to their nutritional characteristics, promising productivity, adaptation to soil and climate conditions, and a good source of starch, a polysaccharide that contributes a portion of the calories in the human diet. Studies show that, due to their high carbohydrate content, these tubers are ideal for starch extraction, offering opportunities for value-added addition and applications in various food products. Therefore, the objective of this work was to extract and characterize the native starches of purple yam (ACR) and spiny yam (ACE). The tubers were purchased from agroecological farms in Manaus, Amazonas, and their starch content was obtained through exhaustive aqueous extraction. After dehydration in an air-circulating oven at 40°C for 72 hours, they were characterized for water activity (Aw), moisture, ash, protein, crude fiber, total carbohydrates, and pH using official methods, and their technological paste properties were determined using a Rapid Visco Analyzer (RVA). The starch extraction yield was 8.34% for ACR and 18.97% for ACE, values ​​higher than those of previous studies, a result dependent on the cultivation soil and harvest. The ACR and ACE presented, respectively, 7.97% and 8.10% moisture, 0.25% and 0.23% Aw, 0.19% and 0.13% ash, 0.81% and 0.90% protein, 0.07% and 0.08% crude fiber, 90.96% and 90.79% carbohydrates, and 6.05 and 6.99 pH. These results are similar to those in the literature for starches from other tubers. Paste property data from RVA showed, for ACR and ACE, respectively, paste temperatures of 80.10°C and 85.12°C, viscosity breakdown of 3,774cP and 620cP, final viscosity (FV) of 1,743cP and 4,114cP, and retrogradation of 208.67cP and 1,320cP. ACR showed low final viscosity and retrogradation. ACE demonstrated a higher paste temperature and lower viscosity breakdown. Therefore, ACR is promising for application in liquid or semi-solid foods, where the texture does not need to be firm, while ACE is better suited for products that require a firm and resistant structure. ACR and ACE have distinct nutritional compositions and rheological properties, with potential for diverse food applications and the enhancement of Amazonian tubers.