Pomegranate is an important source of bioactive compounds, such as anthocyanins, other phenolic compounds, and ascorbic acid. In the present work an in vitro availability method has been used to assay the influence of the physiological conditions in the stomach and small intestine. This method enables the study of the release of anthocyanins, vitamin C, and total phenols from the pomegranate juice and their transformations during gastrointestinal digestion. Results have shown that pomegranate phenolic compounds are available during the digestion in a quite high amount (29%). Nevertheless, due to pH, anthocyanins are largely transformed into non-red forms and/or degraded (97%), and similar results are obtained for vitamin C (>95% degradation).

Our recent work shows that in pomegranate juice the destructive effect of ascorbic acid on anthocyanins is not well correlated with changes in the observed colour. However, the addition of vitamin C to this juice has no additional bene®t, since ascorbic acid degradation is very rapid and a slightly orange hue results, after a period of storage, in those juices to which ascorbic acid was added. Data are also included on the in¯uence of storage temperature on juice colour stability, indicating that this parameter is more speci®c for colour alteration and anthocyanin degradation.

Pomegranate juices were assessed after pasteurisation and storage in different packaging materials: transparent and green glass, and paperboard carton with polyethylene layers (Minibrik-200). The main objective was to establish the influence of the container on the stability of colour and bioactive compounds (anthocyanins, ellagic acid and other non-coloured phenols). Results showed that noncoloured phenols and ellagic acid were quite stable during the storage period. In contrast, anthocyanins degraded, to an extent directly proportional to colour loss, less for those juices stored in glass bottles than for those stored in Minibrik. These results indicated that these paperboard carton containers are oxygen permeable, and that oxygen has a greater influence on anthocyanin, and consequently on colour degradation, than light on pomegranate juice during storage. Nevertheless, the antioxidant activity was not influenced by the packaging material employed.

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Plums were treated with calcium or heat (45 °C) and then stored at 2 °C for 28 d. Fruit firmness, ethylene, and CO 2 production rates were investigated. The concentrations of endogenous polyamines (free, conjugated-soluble, and cell wall-bound) were also studied. Both treatments improved fruit firmness by increases in Magness-Taylor force and force-deformation ratio, and decreases in flesh deformation. No differences were found in either ethylene or respiration rate production among fruits due to the low storage temperature. Calcium-treating plums increased the conjugated forms of putrescine (conjugated-soluble and cell wall-bound), which are related to higher firmness. Heat-treated plums mainly increased cell wall-bound spermidine, inducing a greater cell wall stability and plum firmness.