EFFECT OF CRYOPROTECTANT MIXTURES ON RHEOLOGICAL PROPERTIES OF FRESH AND FROZEN/THAWED MASHED POTATOES

摘要

Hydrocolloids and protein were added to fresh (F) and frozen/thawedn(F/T) mashed potatoes in the form of mixtures of: (1) amidated low-methoxyln(ALM) pectin and xanthan gum (XG); (2) kappa-carrageenan (k-C) and XG;nand (3) sodium caseinate (SC) and XG. F and F/T mashed potatoes withoutnadded biopolymers and with XG at 1.5 g/kg were also analyzed. Flow curvesnfit the power law and Casson models well – and preferentially the first of these.nThe Cox–Merz rule was not applicable to the steady and dynamic shear datanon all of the mashed potatoes. In the F products, the departure of mashednpotatoes–biopolymer mixtures from the Cox–Merz rule was XG concentration-ndependent. It was concluded that most of the F mashed potatoes followed thenlinear modified Cox–Merz rule, with h*(w) and ha(u0002 γ ) well superimposed.nHowever, after processing, the linearity – or otherwise of the relationshipnbetween viscosities – was more dependent on the type of biopolymer mixture.nAlso, in the case of the F/T mashed potatoes without added biopolymers andnwith added ALM/XG binary mixtures, the relationships may be considerednlinear. Conversely, in the case of F/T mashed potatoes with added XG alonenand mixed with k-C and SC, small amplitude dynamic properties cannot benused directly to predict changes in texture perceived in the mouth given that thenrelationship between these properties and steady shear measurements is non-nlinear. The effects of addition of either XG alone or binary mixtures to F andnF/T mashed potatoes were very dependent on the magnitude of the strainndeformation applied to the system (i.e., low strain in oscillatory shear and highnstrain in steady shear).