Heat and NaOH penetration during chemical peeling of patatoes.

The effect of NaOH concentration (40-200g/kg), process temperature (55-95°C) and time (1-7 min) on heat and NaOH penetration during a one stage chemical peeling of potatoes was studied using response surface methodology. The progression of starch gelatinization within potato was followed microscopically on potato tissue histologically prepared and coloured by the PAS method, meanwhile NaOH penetration was read on tissue coloured with phenolphthalein using a magnifying glass. The statistical models developed were adequate for heat ring penetration thickness and tangent of NaOH penetration thickness, and showed no significant lack of fit. The effect of independent variables on NaOH penetration and heat ring characteristics are analysed, estimating process conditions that determine equal NaOH and heat ring penetration thickness. Adequacy of the model equations obtained were tested and no statistical differences were found between predicted and experimental results. Analysis was also performed using time-temperature simulation to determine potato starch gelatinization temperature at maximum heat ring penetration thickness; a value of 57.16 ± 1.95°C was obtained (p < 0.01).