Pinhão and corn starches are submitted to phosphating with sodium tripolyphosphate and their properties are evaluated by thermogravimetry, differential scanning calorimetry, viscoamylography, X‐ray powder diffractometry, field emission gun‐scanning electron microscopy analysis. The phosphating process is divided into three steps to analyse the behaviour of the sample on exposure to phosphate groups. After the modification, there is a decrease in the transition temperatures and gelatinisation enthalpy of both starches. During the three phases of phosphating, small differences are observed in the thermal stability of the modified samples, but a lower value is obtained for corn starch after the third stage. The decrease in pasting temperature is accompanied by an increase in the peak viscosity of the starch suspensions, however, higher values for setback and breakdown are also recorded. The degree of relative crystallinity of the phosphated starches increases, and from microscopy it is possible to observe the presence of crystals of sodium tripolyphosphate during phosphating process.

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HIGHLIGHTS  Unconventional starches from ginger (Zingiber officinale) and yam (Dioscorea sp.) were investigated.  Lower thermal stability was found for unconventional starches when compared to maize starch.  Greater relative crystallinity and enthalpy of gelatinisation was recorded for ginger starch.  Yam starch had the highest peak viscosity, and corn starch had the highest breakdown. Oliveira, C.S.; et al.