Spray drying and rehydration of macadamia oil-in-water emulsions: Impact of macadamia protein isolate to chitosan hydrochloride ratio.

The utilization of oils in the food industry can be facilitated by converting into a powdered form using microencapsulation technologies. In this study, coatings formed from macadamia protein isolate (MPI) and chitosan hydrochloride (CHC) were assessed for their ability to facilitate the microencapsulation of macadamia oil by spray dried, and all encapsulation efficiency was higher than 87.0%. The physicochemical properties of macadamia oil powders were then characterized. In addition, changes in the particle size, aggregation state, and creaming stability of rehydrated emulsions were analyzed during storage. The addition of CHC significantly enhanced the water-solubility and wettability but decreased the flowability of microencapsulated oil. Powdered macadamia oil produced at MPI/CHC = 5:1 had the highest encapsulation efficiency (94.2%), best oxidation stability (<4 meq/kg), and best rehydration properties. Overall, MPI/CHC could be used as a good emulsifier for producing stable rehydrated emulsion, which may therefore be useful in certain food applications.

Microwave pretreatment promotes the annealing modification of rice starch.

Early indica rice starch can only be modified to a small extent by annealing treatment (ANN), which limits its application. Microwave pretreatment (MW) with different intensity was used to enhance the effectiveness of ANN, and single ANN or MW treatments were used as controls. MW pretreatments per se exhibited insignificant or minor effect on the starch. However, MW pretreatment with appropriate intensity could significantly promote the structural and physicochemical modification of the starch in subsequent ANN, including the enhancement of long- and short-range crystalline structures, the increases in gelatinization enthalpy, particle size, peak viscosity, breakdown and G' value, and the decreases in tan δ value. The MW pretreatment could untangle the entanglements between starch chains by inducing violent movement of the chains, which facilitated the molecular rearrangement and interaction during subsequent ANN, thereby promoting the structural and physicochemical changes. This study provided new insights into the annealing mechanism of starch.