Flavour retention in sodium caseinate – Carboxymethylcellulose complex coavervates as a function of storage conditions

Abstract

Flavour retention in freeze-dried complex coacervates prepared with sodium caseinate and carboxymethylcellulose was followed over storage for 20 days at two relative humidities (0 and 54%) and temperatures (25 and 45 °C). Beta-pinene was used as a model volatile compound. Avrami’s equation mathematical model was equipped to describe the correlation between release rate and storage time. In general, volatile’s retention in the dried powder was considerably affected by the storage conditions along with the wall material characteristics (e.g. protein/polysaccharide ratio, presence of reticulating agents, i.e. glycerol and tannic acid) as a greater rate of release was observed at high relative humidity (RH) and temperature values and low biopolymer addition levels. Moreover, the Arrhenius activation energy Ea was reduced by increasing RH from 0 to 54% while it got either positive or negative values indicating that the release of β-pinene was either related or not to temperature. Rehydration of dried powders in high humidity air conditions and the induced reduction of their effective surface area may account for the decrease of β-pinene retention. Glycerol addition resulted in higher retention of the volatile compound in the powder stored at low RH and temperature (0% RH, 25 °C) as compared to other storage conditions, which was further confirmed by the remarkable increase of half-life release t1/2 from 29 to 9303 days, as this was calculated from the Avrami’s equation mathematical model.