CONICET | Buscador de Institutos y Recursos Humanos

Previous studies demonstrated that Glabrous canary seed (CDC-Maria variety) have a unique protein composition of high catalytic activity that can be used for the formulation of different food products. For this reason, its extraction and subsequent enzymatic fractionation was performed. The enzymatic extraction process was carried out with a specific protein buffer solution and a subsequent centrifugation. The supernatant was called crude extract (EC). Subsequently, a fractionation using an isoelectric point precipitation process between pH 4.5 and pH 5.5 was performed. Finally, the enzymatic fractions were preserved by lyophilization. The effect of addition of the EC and the enzymatic fractions obtained in gluten free breads were studied. This study allowed select as optimum sample the enzymatic fraction obtained at pH 5.3. Maillard reactions have a great influence on the quality degradation of enzymatic products. This process include a series of reactions that generate the formation of the 5-hydroxymethylfurfural intermediate (HMF), a compound with activity in the UV spectrum-visible. In this work the stability of the EC and the enzymatic fraction obtained at pH 5.3 was studied. For that, a determination of the deterioration kinetics was made from a spectrophotometric measurement of HMF at 280 nm using the Carrez I (potassium ferrocyanide at 15%) and Carrez II (30% zinc acetate) reagents. Subsequently, the shelf life time was calculated at a temperature of 8 °C. The samples were stored in flexible Pet /Al /Pe containers at different temperatures: EC at 20 °C, 30 °C and 40 °C and the fraction obtained at pH 5.3 at 20 °C and 30 °C for 50 days and at 7 °C per one year. The results showed that all samples presented a consistent multivariate kinetics of zero order. In a first instance the production of the measuring compound (HMF) is generated from various chemical reactions. Subsequently, it is consumed when reacting with an amine forming undesirable browns pigments. The reaction rate constant of the HMF production no presented statistically significant difference between the studied samples (EC: 0.0057 day-1; pH5.3: 0.0094 day-1). This may be due, that the lower pH of the sample obtained at pH5.3 decreases the reactivity of the amino groups and increases the reactivity of the carbonyl groups of the reducing carbohydrates, increasing the HMF formation. However, the rate constants obtained for the HMF consumption reaction presented a statistical difference between studied samples. A lower values of reaction rate of the fraction obtained at pH5.3 was obtained (EC: 0.231 day-1; pH5.3: 0.034 day-1). This may be due to its lower pH value (isoelectric point pH) that decreases the reactivity of the amino groups by a reduction of the net proteins surface charge. This demonstrated the strong influence of pH in the last phases of the reaction. Therefore, the freeze-dried fraction obtained at pH 5.3 at a storage temperature of 8 °C presented a higher shelf life time (EC: 21 months and pH 5.3: 25.4 months).