Effect of spray drying and storage on the stability of bayberry polyphenols
Highlights
► Spray drying is a good technique for retention of bayberry polyphenols. ► We evaluated the polyphenol stability of bayberry powder during storage. ► Spray dried bayberry powder should be stored at less than 25 °C and aw of 0.33. ► Anthocyanin in bayberry powder is more readily degraded than other phenolic compounds.
Introduction
Bayberry (Myrica rubra Sieb. et Zucc) is a berry fruit originating from China, which was first introduced to Australia in about 2000. Bayberry fruits have a special sweet/sour taste that has made them one of the most popular and valuable fruits in Chinese markets. In China, the fruit has traditionally also been used to treat gastric intestinal problems, such as diarrhoea and gastroenteritis (Chen, 1996). Bayberry fruits are rich in polyphenols, including anthocyanins, flavonols, and phenolic acids (Bao et al., 2005, Fang et al., 2007, Fang et al., 2009). Polyphenols have been demonstrated to act as antioxidants and are assumed to have beneficial health effects for humans (Tomás-Barberán & Robins, 1997). There is evidence that the strong antioxidant capacity of bayberry fruits (Bao et al., 2005), juice (Fang et al., 2009), and jam (Amakura, Umino, & Tonogai, 2000), is highly correlated with their polyphenolic content.
However, bayberry fruits easily decay and are often processed into juice for wider and longer-term consumption (Fang, Zhang, Sun, & Sun, 2006), but bayberry juice colour can show browning deterioration due to enzyme and phenolic reactions in the liquid state (Fang, Zhang, Sun, & Sun, 2007). Another concern that limits the potential application of bayberry polyphenols is that phenolic compounds are generally sensitive to adverse environmental conditions, including unfavourable temperatures, light, pH, moisture, and oxygen, and are therefore susceptible to degradative reactions during product processing and storage. Encapsulation of the bayberry polyphenols and conversion of the liquid bayberry juice into a solid state might potentially increase the stability of the product, and also make it easier to handle for circulation and application.
In the food industry, microencapsulation techniques have been widely used to protect food ingredients against deterioration, volatile losses, or premature interaction with other ingredients (Shahidi & Han, 1993). Various kinds of microencapsulation techniques such as spray drying, spray chilling/cooling, coacervation, extrusion, fluidized coating, liposome entrapment and molecular inclusion, have been developed (Gouin, 2004). Among these, spray-drying is the most commonly used technique, on account of it being a continuous, low cost process that produces dry particles of good quality, and for which the machinery required is readily available. Spray drying is especially useful for the encapsulation of heat sensitive food ingredients, as the drying process is very rapid and the core is heated to temperatures generally much lower than 100 °C (Masters, 1991). As polyphenols are a group of phytochemicals sensitive to heat processing, spray drying might have the potential for the encapsulation of bayberry polyphenols. This technique has been successfully used for the encapsulation of a number of polyphenol rich materials, including black carrot extract (Ersus & Yurdagel, 2007), Hibiscus sabdariffa L. extract (Chiou & Langrish, 2007), soybean extract (Georgetti, Casagrande, Souza, Oliveira, & Fonseca, 2008), grape seed, apple and olive leaf extracts (Kosaraju, Labbett, Emin, Konczak, & Lundin, 2008), and procyanidins (Zhang, Mou, & Du, 2007).
The aim of this study was to develop a spray drying method for encapsulation of bayberry polyphenols. The polyphenol stability and antioxidant capacity of the spray dried products were monitored during 6 months storage under different combinations of temperature and humidity. This study is regarded as having potential for the industrial use of bayberry polyphenols.
Section snippets
Chemicals and solvents
The chemicals gallic acid, cyanidin 3-glucoside, quercetin 3-galactoside, quercetin 3-glucoside, Folin–Ciocalteu’s phenol reagent, and DPPH (2, 2-diphenyl-1-picrylhydrazyl) were purchased from Sigma–Aldrich (Castle Hill, NSW, Australia). Acetonitrile and methanol (HPLC grade) were purchased from Merck (Darmstadt, Germany), while ethyl acetate and formic acid (analytical grade) were obtained from Ajax Finechem Pty Ltd. (Taren Point, NSW, Australia). Polyphenolic standards were dissolved in
Product recovery, TPC and ACN retention
The spray dried bayberry powder was recovered from the collection vessel only, and any particles deposited on the dryer chamber were discarded. Product recovery was calculated as the ratio of the mass of solids collected from cyclone to the solid mass in the infeed solution (on a dry weight basis). The powders were immediately sealed after collection to prevent subsequent moisture uptake. The water activity and moisture content were then quickly measured after the powder’s temperature dropped
Conclusions
The stability and antioxidant capacity of bayberry polyphenols during spray drying and storage were studied. Bayberry powder was successfully obtained when the juice was spray dried with maltodextrin (DE 10) as the carrier, with inlet and outlet temperatures of 150 °C and 80 °C, respectively. The retentions of total TPC and ACN during drying process were about 96% and 94%, suggesting spray drying was a satisfactory technique for drying heat sensitive polyphenols. Under an aw of 0.11–0.44 and
Acknowledgements
This work was supported by a Postdoctoral Research Fellowship of The University of Queensland, Australia. We thank Professor Daryl Joyce, from the School of Agriculture and Food Sciences, The University of Queensland, and Dr. Garth, from the Maroochy Research Station, Department of Employment, Economic Development and Innovation, Queensland, for providing the bayberry fruits used in the study. The authors also thank Dr. John Schiller of the University of Queensland for his professional proof
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