Steady shear and yield stress data of fresh and frozen/thawed mashed potatoes: Effect of biopolymers addition

Five different hydrocolloids (amidated low-methoxyl (ALM) and high methoxyl (HM) pectins, kappa- and iota-carrageenans (κ-C and i-C), xanthan gum (XG)) and two dairy proteins (whey protein (WP), sodium caseinate (SC)) were added, at five different concentrations to fresh (F) and frozen/thawed (F/T) mashed potatoes to investigate their effectiveness in preventing deleterious effects caused by processing. Rheological behaviour was characterized using steady shear measurements, and instrumental colour and sensory analysis were also carried out. All tested biopolymers can be used to improve viscosity/consistency of F and F/T mashed potatoes. The effects were highly dependent on the type and level of biopolymer added. Adding higher levels of ALM and HM pectins (3–8 g kg−1) increased rheological properties of F/T mashed potatoes as compared to their fresh counterparts, suggesting their usefulness as texturizers in F/T mashed potatoes. F and F/T samples with added κ-C and i-C were more structured. Freezing and thawing did not significantly affect the steady data of the product with added carrageenans and xanthan, highlighting the potential of these gums to stabilize the texture of frozen and microwave-thawed mashed potatoes, as compared with fresh counterparts. Addition of biopolymers affected parameter a* (greenness) more than yellowness index (YI), although XG and WP affected less the colour of the mashed potatoes. When (0.5–1.5 g kg−1) XG were added XG, both F and F/T samples were judged more acceptable than F control thanks to their creamy mouthfeel. Conversely, WP and SC affected the taste and odour of the mashed potatoes and were judged unacceptable.