Quality and antioxidant properties of a reduced-sugar pomegranate juice jelly with an aqueous extract of pomegranate peels
Highlights
► We produced a reduced-sugar pomegranate juice jelly added with pomegranate peel (PE). ► Guar, xanthan and tragacanth gums and aqueous PE extract were used. ► The combination of three gums presented the better rheological behaviour. ► The addition of PE increased the antioxidant content and activity. ► PE did not affect the physical, rheological and sensory properties.
Introduction
Pomegranate (Punica granatum Linn.) is a fruit that belonging to the Punicaceae family. Almost all parts of a pomegranate have biological activities and are used for the treatment of numerous diseases. In Unani and Ayurvedic folk medicines practiced in India, pomegranate flowers are used to manage type 2 diabetes mellitus (Saxena & Vikram, 2004). Clinical in vivo and in vitro assays have shown that juice, flower and fruit extracts have antioxidant and anti-inflammatory activities and create positive effects on glycemia, insulin, dyslipidemia, blood pressure and foam cell formation; additionally, some mechanisms of these effects have been reported (Jurenka, 2008, Katz et al., 2007, Lansky and Newman, 2007). Gallic, ellagic, chlorogenic, p-coumaric acids, catechin, epigallocatechin 3-gallate, quercetin, rutin and luteolin are only some of the active phenolic compounds present in juice and flowers (De la Fuente and Manzanaro, 2003, Ippoushi et al., 2009, Kang et al., 2009, Li et al., 2008, Moon et al., 2006, Nakagawa and Yokozawa, 2002, Pannala et al., 1997, Xie et al., 2008). However it is important to mention that some these active compounds can be also present in pomegranate peel (Lansky & Newman, 2007). In Mexico in 2008, the total annual pomegranate production was 3740 tons (SIAP, 2008); pomegranate peel comprises 30–40% of the total weight of the fruit (Al-Maiman and Ahmad, 2002, Fadavi et al., 2005), thus generating 1122–1496 tons of agro-industrial residue. Pomegranate peel (skin, rind or husk) could have medicinal or industrial applications however, is considered an agro-industrial residue.
The development of products as functional food enriched with pomegranate peel active compounds, could be useful for the treatment of certain diseases such as the diabetes mellitus (DM). In addition, consumers worldwide are more conscious about the relationship between dietary habits and disease risk, such as that between obesity and DM and cardiovascular and gastrointestinal diseases (Espín, García-Conesa, & Tomás-Barberán, 2007). These facts have prompted the development of new foods to satisfy the new demands of the market and it is important to evaluate the food quality of these possible functional foods, before to studied theirs biological activities or theirs therapeutic properties.
Therefore, the objective of this work was to develop a reduced-sugar pomegranate juice jelly with the aqueous extract of pomegranate peel and to analyze its physical, chemical, antioxidant, microbiological and sensory properties.
Section snippets
Preparation of peel pomegranate extract
Pomegranate peels were acquired from an orchard located in the region of Arteaga, Coahuila, Mexico in September 2008; they were identified by the department of Botany, Universidad Autónoma Agraria Antonio Narro, Mexico. The husks were washed with distilled water, dried at room temperature and pulverized in a manual mill. The powder was stored in dark glass bottle. For decoction, pomegranate husk (40 g) was added to 300 mL of boiling distilled water for 10 min. The product was filtered and the
Jelly selection
The pH, °Brix and Aw of jellies with and without PE are shown in Table 2. The °Brix and Aw values obtained for the jelly samples were not similar to those of commercial jelly. The pH and Aw of jellies with PE was significantly (P < 0.05) lower than those of jellies without PE, unlike the °Brix values. The effects of PE on pH, °Brix and Aw were not relevant to selection. The rheological properties were influenced by gums but not by PE addition (Fig. 1). The T and TE had the lowest viscosities in
Discussion
The increase in the prevalence of DM and obesity has been an important factor in producing reduced-calorie and functional foods. Traditionally, pectins are used in the food industry to produce jams and jellies. Rich methoxyl pectins require exposure to boiling point temperatures, low pH (3–5) and high concentrations of sugar (>55% of sucrose) to obtain acceptable jellies. Low-methoxyl pectins produce gels in the presence of calcium and do not require large amounts of sugar (Acosta, Vízquez, &
Conclusions
Compared to commercial jelly, all of the jellies produced had major Aw values and minor total soluble solid contents. The jelly produced with a mixture of xanthan, guar and tragacanth gum produced the most similar rheological behaviour to commercial jelly. The rheology of J and JE was similar at 0 and 8 weeks. The addition of PE diminished the pH but increased the antioxidant content and activity in fresh jelly samples. Both jellies exhibited co-pigmentation, and the colour and antioxidant
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