Orange oil stability in spray dry delivery systems

The oxidation stability of orange oil flavours encapsulated in carbohydrate based spray dry delivery systems is assessed through accelerated shelf life testing, compatible with the physical state of the delivery system. It is demonstrated here that the oxidative shelf life stability is limited by the diffusion of oxygen through the carbohydrate matrix. Determination of the evolution of orange oil oxidation products with time and correlations with simple but accurate sensory data allows for prediction of absolute shelf life. The oxidative shelf life appears to be dependent only on the number average molecular weight of carbohydrates in the matrix and is not affected by the substitution of small sugars (e.g., maltose for sucrose). A maximum of 2 years shelf life at 25 °C is predicted if sugar dimers are the predominant species in the matrix. The drawback to extended oxidative stability is a low physical stability under humid conditions promoting local softening in the sample. Maltose, having low hygroscopicity, improves the physical stability compared to sucrose. The best compromise between physical (caking) and chemical (oxidation) stability is obtained for carbohydrate compositions with number average molecular weight of 560 g mol−1 that do not contain sucrose (stability against oxidation: 20 months at 25 °C and stability against humidity: 50% RH at 25 °C).