Effect of addition of cryoprotectants on the mechanical properties, colour and sensory attributes of fresh and frozen/thawed mashed potatoes

Abstract

Cryoprotectants such as hydrocolloids (amidated low-methoxyl (ALM) and high methoxyl (HM) pectins), kappa- and iota-carrageenans (k-C and i-C), xanthan gum (XG)) and dairy proteins [whey protein (WP), sodium caseinate (SC)] were added to mashed potatoes to investigate ways of improving the effects of freezing and thawing. It was found that each hydrocolloid and protein, depending on concentration, affected the mechanical properties [instrumental textural profile analysis (ITPA), cone penetration (CP) test], the total colour difference (ΔE) with respect to fresh control (FC) and the sensory attributes of fresh (F) and frozen/thawed (F/T) mashed potatoes in a different way. In the F/T samples, adding 5 and 8 g kg-1 ALM, 3, 5 and 8 g kg-1 k-C, 1.5, 3, 5 and 8 g kg-1 i-C and 1.5, 5 and 15 g kg-1 WP significantly increased ITPA consistency. Also, adding 2.5 and 5 g kg -1 XG significantly increased ITPA consistency of the F/T product. In both F and F/T samples, k-C provided the highest ITPA consistency and also high CP average force evidencing a stronger synergistic effect in κ-C/denatured milk protein systems, although the excessive thickening and stickiness provided was judged undesirable by the panellists. Adding 8 g kg -1 HM pectin had a disruptive effect on the mashed potatoes and decreased both ITPA consistency and CP average force. In all cases, freezing and thawing reinforced the gel structure of the products as compared to F and FC counterparts. The ΔEvalues were higher in F samples containing ALM and HM pectins. Dairy proteins affected the taste and odour of the mashed potatoes and were judged unacceptable in the sensory analysis. Samples containing 0.5 and 1.5 g kg-1 added XG were preferred organoleptically due to the creamy mouthfeel it produced. ITPA consistency correlated well with sensory texture attributes. © 2007 Springer-Verlag.