Antioxidant capacity, phenolic composition and microbial stability of aronia juice subjected to high hydrostatic pressure processing
Introduction
Aronia (chokeberry) (Aronia melanocarpa) constitutes an attractive research material due to its multiple health-promoting properties (Kedzierska et al., 2013). It has a unique composition of bioactive compounds including high levels of anthocyanins and procyanidins; with their concentrations being as high as 2% and 5% in the berries' dry matter, respectively (Kokotkiewicz, Jaremicz, & Luczkiewicz, 2010). Polymeric flavan-3-ols of the chokeberry are mainly composed of (−)epicatechins which are constitutive units of procyanidins. In turn, anthocyanins are a mixture of four different cyanidin glycosides: 3-galactoside, 3-glucoside, 3-arabinose and 3-xylose (Kokotkiewicz et al., 2010). In addition to these two main groups of phenolic compounds, aronia berries are also rich in phenolic acids (chlorogenic and neochlorogenic acids) (Slimestad & Solheim, 2002). In contrast, flavonols were found to constitute only 1.3% of the total phenolic compounds in aronia (7849.21 mg/100 g of dried matter) (Oszmiański & Wojdyło, 2005). The content and unique composition of aronia phenolics is strongly correlated with their high functional properties and biological activities (Zheng & Wang, 2003).
The production of fresh aronia is limited to a relatively short time period. Its black berries are borne in clusters and ripen in early September in Northern and Eastern Europe. Aronia berries are rarely consumed fresh because of their several negative sensory attributes like bitterness and astringency (Troszyńska, Lamparski, & Kmita-Głażewska, 2003). They are rather used for the production of jams, juices, wines and anthocyanin colorants (Oszmiański & Wojdyło, 2005). In the case of jam and juice production, a heat treatment is required to prolong the shelf life of these aronia products. However, the processing involves temperature treatment, such as blanching of berries and pasteurization and/or hot-filling of wine/juices, which strongly diminishes the product's quality due to changes in the quantity and quality of thermolabile phytochemicals (Cao et al., 2012). As reported in literature, approximately 80% loss of anthocyanins from blackberries may be attributed to thermal degradation. The pasteurization of non-clarified and clarified juices obtained from black raspberries was reported to lead to the loss of anthocyanins by 19% and 23%, respectively (Howard, Prior, Liyanage, & Lay, 2012). Likewise, aronia juice subjected to pasteurization (100 °C) yielded a similar drop in anthocyanin content, which in turn was accompanied by a reduction in its antioxidant capacity (Arancibia-Avila et al., 2012).
High hydrostatic pressure (HP) is an innovative processing technology, wherein food is exposed to pressure (up to 600 MPa) for a short duration with or without exposure to different temperatures (Nguyen et al., 2010). A number of attempts have been made to use HP instead of high temperatures to inactivate food-spoiling microorganisms (Liu, Li, Wang, Bi, & Liao, 2014) and undesired food enzymes (Mujica-Paz, Valdez-Fragoso, Samson, Welti-Chanes, & Torres, 2011) while maintaining all the quality and safety parameters of the products (Zhang et al., 2012, Ferrari et al., 2010). Because chemical or enzymatic reactions can be enhanced or retarded by HP, the content of some bioactive compounds may be indirectly altered upon pressurization (Oey et al., 2008, Corrales et al., 2008). It has been reported that the levels of phenolics, anthocyanins, flavonols and tannins in red wine are distinctly affected by HP (250–650 MPa for 15–120 min at ambient temperature) (Tao et al., 2012). In contrast, no significant changes in anthocyanin and ascorbic acid contents were found after pressurization (400–600 MPa for 15 min at 10–30 °C) of strawberry and blackberry purees (Patras, Brunton, da Pieve, & Butler, 2009). Blueberry juices pressurized at 600 MPa and at 42 °C for 5 min had reduced levels of ascorbic acid, which accounted for < 5% of the initial content (Barba et al., 2012).
The effect of high pressure on the quality of aronia juice has not been extensively studied in literature. The aim of the present study was, therefore, to characterize the effect of high hydrostatic pressure (200–600 MPa/15 min) on the antioxidant capacity, polyphenol content and composition, as well as microbiological stability of aronia juice. Taking into consideration that the storage of berries (temperature, time, amount of light and oxygen) may also be a key factor affecting phytochemicals stability (Patras et al., 2010, Howard et al., 2012), all the aforementioned evaluations were also performed on pressurized juices that were stored at 4 °C for 0, 20, 40, 60 and 80 days.
Section snippets
Aronia juice
Aronia juice was procured from the Farm Specialist Plantation of Aronia (Aronia melanocarpa) in Bielawki, Pelplin, Poland. It produces cold-pressed juices without any addition of sugar, water or preservatives. According to the producer, the juice had a pH of 3.5, and a total solids content of 15.4 °Brix.
Naturally cloudy, cold-pressed juice was immediately packed in dark glass bottles to a volume of 0.75 L, and subsequently transported in cold state (6 ± 2 °C) to the Institute of Animal Reproduction
Total phenolic content
The fresh and untreated juice yielded a significantly higher total phenolic content compared to juices treated with the pressures of 200, 400 and 600 MPa for 15 min (Table 1). However, the reduction in total phenols noted for the HP-treated juices was not correlated with the pressure applied. Juice pressurized at 200 MPa yielded a 12% drop in total phenols, whereas juice pressure-treated at 600 MPa yielded an 8% loss in antioxidants compared to the untreated and fresh samples. The opposite results
Conclusions
The results presented here characterized and compared the antioxidant concentration, composition and antiradical potential of aronia juice subjected to HP treatment (200–600 MPa for 15 min at ambient temperature) and storage (4 °C for 80 days). Irrespective of the pressure applied, pressurization significantly affected the phenolic concentration in aronia juice. The regression analysis proved explicitly that the antioxidants concentration greatly affected the antiradical potential. A total of 6
Acknowledgment
The work was supported by the Institute of Animal Reproduction and Food Research, Polish Academy of Sciences (Statutory research 2015) in Olsztyn, Poland within the statutory research.
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