Development of powder and beverage products from cranberry: Exploration of drying mechanism, bioactive stability and changes in volatile and phenolic profiles

Abstract

Cranberry (Vaccinium macrocarpon Ait.) is rich in phytochemicals or bioactives, especially phenolic compounds, which are beneficial to human health. However, cranberry is rarely consumed fresh due to its unfavourable taste and they are mainly processed into products. While there have been a variety of commercial cranberry products available in the market, indepth studies on processing and its effect on bioactive stability and flavour profile of cranberry have been limited. Due to the reported health benefits of cranberry, it is important to understand the above area to provide consumers with high quality cranberry products. Therefore, the goal of this research is to develop cranberry products with good retention of bioactive compounds and sensory palatability. To achieve this, two processing techniques were investigated, spray drying and fermentation. New Zealand grown cranberry cultivars were used in current research. Spray drying microencapsulation of cranberry juice using four different wall materials (GA (gum Arabic), M1 (maltodextrin, DE 7-10), M3 (maltodextrin, DE 17-20) and GAM1 (GA and M1 at 1:1, w/w)), and stored at different temperatures (4, 25 and 45 °C) for a period of 12 weeks to study the stability of the encapsulated bioactive compounds in the powders. Results showed high stability of cranberry phenolics during processing, as increase of phenolics were observed after spray drying, and also during storage (with highest increase in myricetin-3- galactoside and quercetin-3-galactoside). The enhancement of phenolics during storage was caused by phenolic polymer decomposition by phenolic profiling using HPLC-DAD and LCMS/ MS analyses. Microencapsulated cranberry powder showed different phenolic stability after drying and during storage, which was correlated with the drying mechanisms of different cranberry juice samples as influenced by the wall materials used. The drying behaviours and particle structure formation process of cranberry juice samples were studied using single droplet drying (SDD) approach, which mimics the spray drying process. The SDD results clearly demonstrated the effect of wall material and drying temperature on the particle crust forming process, dissolution property and morphology of cranberry particles, which could be used to predict the physico-chemical properties of the corresponding spray-dried powders. Furthermore, the drying kinetics were modelled and predicted using the Reaction Engineering Approach (REA). The master activation energy curves revealed the energy requirements for moisture evaporation of the particles as in this order: M3 < M1 < GAM1 < GA. The shrinkage models demonstrated most shrinkage of the particles containing M3. The results show that REA could be useful in scale-up of spray drying of cranberry juice in industry. On the other hand, three cultivars of cranberries were fermented into low alcoholic beverages through three vinification methods (Red, White, and Thermo). The phenolic and volatile profiles of the wine products were identified by HPLC-DAD-MS/MS and GC-MS, respectively. The phenolic composition of cranberry wines showed similar pattern to that of the corresponding juice. However, high total phenolic content in the original juice (especially proanthocyanins) inhibited the generation of volatiles during fermentation. Furthermore, 41 key aroma-active compounds identified volatiles were determined as major aroma contributors in wines by GC- O/MS, with most of them being fermentation-derived ester and alcohols. The potential synthesis pathways of the volatiles in the wines were also investigated, especially for the key aromatic compounds. This research has provided fundamental knowledge on spray drying microencapsulation of cranberry juice by exploring the phenolic stability and mechanism of drying as influenced by different wall materials. The research also gave insight into the changes of phenolic and volatile compounds as affected by cranberry cultivar and vinification methods during fermentation.