A kinetic model for the formation of acrylamide in a glucose-asparagine reaction system is pro-posed. Equimolar solutions (0.2 M) of glucose and asparagine were heated at different temperatures (120-200 degrees C) at pH 6.8. Besides the reactants, acrylamide, fructose, and melanoidins were quantified after predetermined heating times (0-45 min). Multiresponse modeling by use of nonlinear regression with the determinant criterion was used to estimate model parameters. The proposed model resulted in a reasonable estimation for the formation of acrylamide in an aqueous model system, although the behavior of glucose, fructose, and asparagine was slightly underestimated. The formation of acrylamide reached its maximum when the concentration of sugars was reduced to about 0. This supported previous research, showing that a carbonyl source is needed for the formation of acrylamide from asparagine. Furthermore, it is observed that acrylamide is an intermediate of the Maillard reaction rather than an end product, which implies that it is also subject to a degradation reaction.

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Total and individual glucosinolates were measured after different duration of steaming broccoli (Brassica oleracea L. var. italica). During steaming, the temperature profile, cell lysis and inactivation of myrosinase were assessed as well. Steaming resulted in high retention of total aliphatic and indolyl glucosinolates in the cooked product. Only after extensive steaming of broccoli (30 min) substantial losses of total indolyl glucosinolates of 55% and total aliphatic glucosinolates of 8.5% were observed. Steaming broccoli for more than 6 min result in complete inactivation of the hydrolytic enzyme myrosinase. However, steaming of broccoli for less than 6 min may result in a high intake of glucosinolates, in the presence of a residual active myrosinase, allowing the release of health-protective breakdown products of glucosinolates after consumption.