1997. Chicken breasts with skin were packaged either in air, under vacuum or in modified atmospheres of (i) 30% CO 2 /70% N 2 and (ii) 70% CO 2 /30% N 2 . After 3, 7, 14 and 21 days of storage at 4°C, the samples were evaluated for spoilage microbial growth, odour and overall aspect. As expected, pseudomonads grew well in air or under vacuum, but growth was suppressed in both types of modified atmosphere packaging (MAP). However, growth of lactobacilli, Enterobacteriaceae and Brochothrix thermosphacta was not inhibited in MAPs. Modified atmosphere packaging (ii) extended shelf-life up to 21 days compared to 5 days for air-packed samples.

Using Response Surface Methodology the effects of NaOH concentration (4-20%), process temperature (55-95°C) and time (l-7 min) was determined on the yield, peeling quality, unpeeled skin and total usage of NaOH. Also evaluated were titratable NaOH in the potato tissue, NaOH penetration and "heat ring" depths during one stage chemical peeling of potatoes (Huincul variety). The best peeling quality, maximum yield and minimum total usage of NaOH was obtained for the following ranges: concentration, ll-13%, time 5-5.70 min and temperature, 90-95°C. The maximum temperature for which the "heat ring" and NaOH penetration depths were equal was 72°C where, at 20% NaOH and 7 min, peeling quality was very good and "heat ring" was absent.

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).Se ha estudiado el efecto que la concentraci6n de NaOH (40-200 g/kg), la temperatura (55-95°C) y el tiempo (1-7 min) tienen sobre la penetraci6n de calor y de NaOH en patatas peladas quimicamente en una etapa, utilizando la metodologia de la superficie respuesta. El avance de la gelatinizaci6n del almid6n se siguió por microscopia 6ptica en un tejido de patata histol6gicamente preparado y coloreado por el m6todo PAS, mientras que la difusi6n de NaOH se midi6 en el tejido coloreado con fenoftaleina, utilizando una lupa con medida de contraste. Los modelos estadisticos obtenidos fueron adecuados para el espesor del anillo termico y la tangente del espesor de penetraci6n de NaOH, siendo la falta de ajuste no significativa. Se analiz6 el efecto de las variables independientes estudiadas en la penetraci6n del NaOH en el tejido de patata y en las caracteristicas del anillo termico, y las condiciones de tratamiento que permiten lograr espesores coincidentes de penetraci6n de NaOH y del anillo termico. No se detectaron diferencias significativas entre los valores dados por los modelos matemdticos obtenidos y los valores experimentales. Se realiz6 tambi6n una simulaci6n de tiempo-temperatura para predecir la temperatura de gelatinizaci6n del almid6n de patata, en la que se utiliz6 los espesores maximos de penetracion del anillo t6rmico, y se obtuvo un valor de 57,16 ± 1,95°C (P < 0,01).Palabras clave: patatas, pelado, difusi6n, hidr6xido s6dico, superficie respuesta