Pardeamiento no enzimático en sistemas acuosos conteniendo vitamina C.

ROJAS A.M.L.; GERSCHENSON L.N. Y ALZAMORA S.M.,

Montevideo, Uruguay.

Congreso; VIII Seminario Latinoamericano y del Caribe de Ciencia y Tecnología de Alimentos,; 1994

Asociación Latinoamericana y del Caribe de Ciencia y Tecnología de los Alimentos (ALACCTA).

The anaerobic destruction of L-ascorbic acid in sweet aqueous model systems (water activity=0.94) of pH 3.5 was studied. Ascorbic acid degraded as a function of time and temperature with a behaviour that, in general, could be described by first order kinetics. The influence of the humectants tested (glucose, sucrose and sorbitol) on nutrient destruction depended on the temperature studied: at lower temperatures (24, 33 and 45ºC), humectants protected L-ascorbic acid from destruction, sugars being the most effective due to the structure-forming effect they have; at higher temperatures characteristic of processing (70, 80 and 90ºC), humectants with active carbonyls (glucose and sucrose) promoted ascorbic acid destruction, non-enzymic browning reactions probably being responsible for these results. The effect of sodium bisulphite presence was only significant at the lower temperature range producing inhibition of destruction; at higher temperatures the prevalence of non-enzymatic browning seemed to nullify the effect of this additive. It is concluded that not only water activity or additive effect but also solute-solvent interaction and other reactions taking place must be considered when analysing the effect of humectants and additives on ascorbic acid degradation. The anaerobic L-ascorbic acid (AAs) destruction in glucose aqueous model systems (water activity, aW, 0.94) of pH 3.5, 4.1 and 5.0 was also considered. The AAs degraded as a function of time and temperature (70, 80 and 90ºC) with a behaviour that, in general, could be described by first order kinetics except for AAs in the system containing L-lysine, in which the results adjusted to zero order. The increment of pH from 3.5 to 5.0 accelerated AAs destruction and browning reactions. The addition of tin(II) and lysine to the glucose medium, increased AAs loss and browning. No difference was observed in AAs degradation and colour intensity when sorbic or propionic acid were used as antimycotics, at pH 3.5. Packaging the glucose system of acid pH with an air chamber, produced a faster destruction of AAs and browning of the solution than the one observed for the same system in anaerobic condition. In aerobic condition, the presence of glucose produced a lesser degradation of AAs than the one observed in the system without humectants.