Stability and bioavailability of lycopene, lutein and zeaxanthin in fruits and vegetables as affected by thermal processing

Purpose of review: Dur ing food production, most fruits and vegetables undergo various mechanical and heat-related processing operations t hat could potentially influence their carotenoid bioavaila bility. The aim of the present review is to provide an overview of the effects of thermal processing on the stability of some non-provitamin A carotenoids. Mai n findings: Th e effects of thermal processing on the bioavailability of lycop ene depend mainly on the severity of the thermal treatm ents applied. At lower temperature ranges (60–100°C), which are used for blanching, pasteurisation and drying, plant tissues are d isrup ted and cell walls and membranes are destroyed, leading to an i ncrease in carotenoid extraction and retention, whereas isomeris ation is n egligible. Higher temperatures (>100°C), practiced for canning and sterilisation, cause major cis- isomerisation favouring carotenoid up take. Carotenoids found in canned or sterilised products tend to have a high storage stab ility. In contrast, carotenoids in fre sh produ ce, and frozen and dry products are very susceptible to oxidati ve deterioration, especially during production and storage of conven ience produ cts (eg, pizza). For any bioavailability estimation, only data concerning carotenoid stability and isomerisation deriv ed from r eal food matrices are valid. D irections for future research: C anning of food enhances lycopene isomerisation, facilitat es its absorption, enhances its bioavailability in humans, and provides high storage stability. This effect shoul d be used to create innovative food products with a special interest in lutein- and zeaxanthin-containing fruit or vegetable matrices. Furthermore, knowledge about the effects of different processin g (t hermal, mechanical, chemical) and oxygen-excluding storage methods on lycopene, lutein and zeaxanthin stability in specific fru it and v egetable matrices is needed. Special emphasis should be g iven to production and storage of convenience products. Ke ywords: Ly copene; lutein; zeaxanthin; thermal processing; extractability; cis-tra ns-i somerisation