Deposition Form and Bioaccessibility of Keto-carotenoids from Mamey Sapote (Pouteria sapota), Red Bell Pepper (Capsicum annuum), and Sockeye Salmon (Oncorhynchus nerka) Filet.

The ultrastructure and carotenoid-bearing structures of mamey sapote (Pouteria sapota) chromoplasts were elucidated using light and transmission electron microscopy and compared to carotenoid deposition forms in red bell pepper (Capsicum annuum) and sockeye salmon (Oncorhynchus nerka). Globular-tubular chromoplasts of sapote contained numerous lipid globules and tubules embodying unique provitamin A keto-carotenoids in a lipid-dissolved and presumably liquid-crystalline form, respectively. Bioaccessibility of sapotexanthin and cryptocapsin was compared to that of structurally related keto-carotenoids from red bell pepper and salmon. Capsanthin from bell pepper was the most bioaccessible pigment, followed by sapotexanthin and cryptocapsin esters from mamey sapote. In contrast, astaxanthin from salmon was the least bioaccessible keto-carotenoid. Thermal treatment and fat addition consistently enhanced bioaccessibility, except for astaxanthin from naturally lipid-rich salmon, which remained unaffected. Although the provitamin A keto-carotenoids from sapote were highly bioaccessible, their qualitative and quantitative in vivo bioavailability and their conversion to vitamin A remains to be confirmed.

In situ inactivation of polyphenol oxidase in mamey fruit (Pouteria sapota) by microwave treatment.

Polyphenol oxidase (PPO) is the enzyme responsible for quality loss in most fruits and vegetables. Quality loss is mainly because of oxidative chemical reactions which generate the darkening of tissues. Mamey fruit (Pouteria sapota) after harvesting suffers a rapid quality decay trough activation of PPO. However, PPO may be inactivated in situ by chemical or thermal treatment. In food processing, microwave treatment (MT) has been used recently as an alternative for PPO inactivation. In this study, it was observed that mamey fruit pulp subjected to a gently MT resulted in a higher PPO activity as the generated heat induced in situ the increase in PPO activity. In contrast, PPO was completely inactivated after long MT by using a high microwave power. Temperature in mamey pulp after MT reached a maximum of 79 °C; although PPO was active up to 60 °C. PPO was completely inactivated when conventional blanching treatment was performed but required a higher temperature (92 °C/300 s). The optimum energy intensity (E(opt)) for PPO inactivation by MT was 0.51 kJ/g or 937 W/165 s. Under this condition, the remaining PPO activity was inversely proportional to energy intensity (E). Interestingly, MT resulted in a negligible damage in microstructure of mamey pulp, although blanching treatment resulted in large damaging effects on tissue organization and shape. Therefore, MT is proposed as an effective way to completely inactivate PPO without causing any significant damage to fruit tissues and shape; as preservation of color, flavor, and taste would be favored.