The application of high hydrostatic pressure for the stabilization of functional foods: Pomegranate juice
Introduction
Rapid developments in science and technology, increasing healthcare costs, changes in food laws affecting label and product claims as well as increasing interest in attaining wellness through nutrition are among the main factors supporting the request for foods with clear effects on human health, generally defined “functional foods”. On the other hand, scientific research indicates that there are many clinically demonstrated and potential health benefits from particular biologically active components, known as “functional compounds”, due to having health benefits or desirable physiological effects. Pomegranate juice represents one of the foods recently promoted for its health benefits. For instance, a glass of pomegranate juice contains about 40% of the Recommended Daily Allowance (RDA) of Vitamin C. It also contains Vitamin A, Vitamin E and folic acid in reasonable quantities. Furthermore, pomegranate juice is an important source of anthocyanins, such as 3-glucosides and 3,5-diglucosides of delphinidin, cyanidin, and pelargonidin (Du et al., 1975). Moreover, several studies have highlighted the antioxidant and antitumoral activity of pomegranate tannins (punicacortein) and the antioxidant activity of the fermented pomegranate juice (Schubert et al., 1999). The main antioxidant compounds in pomegranate juice are hydrolysable tannins, but anthocyanins and ellagic acid derivatives also contribute to the total antioxidant capacity of the juice (Gil et al., 2000). Moreover, the antioxidant activity of the pomegranate juice can be correlated to the phenolic composition. In particular, it has been demonstrated that the consumption of this juice decreases the susceptibility of LDL (Low Density Lipoprotein) to aggregation and retention. Unfavorably, the bioactive compounds are quickly affected by exogenic factors such as oxygen, light, and especially pH and temperature. Therefore, there is a real need to minimize the degradation of the functional molecules during the pasteurization process and storage time of the pomegranate juice, in order to secure an optimal sensorial and nutritional quality. The thermal treatment of the juice and subsequent storage at room temperature represent the critical phases of the pomegranate transformation chain. Therefore, the challenge to preserve the nutraceutical properties suggests the application of non-thermal innovative technologies for the sanitation of the pomegranate juice. Among these technologies, high pressure processing (HPP) has the potential to produce high-quality foods that display characteristics of fresh products, are microbiologically safe and have an extended shelf life (Hogan et al., 2005, Patterson, 2005). Moreover, HPP has been used for processing several red-fruit based products (Rastogi et al., 2007, Talcott et al., 2003; Zabetakis et al., 2000).
The present paper aims at analyzing the effects of pressure, temperature and processing times on the main parameters related to the quality of pomegranate juice: the color parameters, the content of tannins, anthocyanins, polyphenols, the aroma composition. A detailed analysis of the experimental data will allow the optimal combination of the processing parameters to be selected as well as verify the possible implication of HPP application on the selected juice.
Section snippets
Pomegranate juice extraction
Pomegranates (Punica granatum) obtained from the local market, were used for the extraction of the juice. This fruit is nearly round, 2-1/2 to 5, crowned at the base by a prominent calyx. The tough, leathery skin or rind, is typically yellow overlaid with light or deep pink or rich red. The internal seeds are separated by a membranous walls and white, spongy, bitter tissue and filled with sweetly acid red juice. The extraction process is deeply described by Alper et al. (2005). The pomegranates
General aspects
In order to test the effect of high pressures on the stabilization as well as nutritional and sensorial properties of red fruit juices, HP cycles were carried out on samples of pomegranate juice under different operating conditions. The performed research activity will create general criteria for the selection of process conditions in terms of the time–pressure–temperature combination able to ensure the preservation of the functional properties of pomegranate juice. This will be achieved
Conclusions
The application of high pressures results to be particularly interesting on the pomegranate juice, characterized by a high added value, due to the high content of nutraceutical components (anthocyanins, polyphenols, tannins). The experiments, by analyzing the effect of the main processing variables (pressure, temperature and time) on both the microbiological stability as well as the properties responsible for the sensorial and nutraceutical quality of the investigated products, demonstrate that
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