Low temperature-induced lycopene degradation in red ripe tomato evaluated by remittance spectroscopy

Tomatoes are mostly harvested at the orange and red-ripe stages. A survey among consumers indicated that tomatoes are most often stored in the refrigerator well below 10 °C, a temperature considered harmful for chilling sensitive products such as tomato. Also during distribution, tomatoes may be exposed to chilling temperatures. The effects of storage at chilling temperatures on quality aspects of tomatoes were investigated. The colour and lycopene content of red ripe tomatoes of two cultivars (cocktail and round type) was evaluated during 20 days of storage at 4, 8, 12 and 16 °C. Colour was repeatedly measured over time by tristimulus colour measurements, RGB image analysis and colour intensity was scored by eye using a consumer panel. Lycopene content was repeatedly assessed by following the NAI index over time. This index, obtained from remittance VIS spectroscopy, was found to relate closely to the lycopene level as measured by HPLC measurements of pericarp tissue. Temperatures below 12 °C resulted in lycopene loss in ripe-red tomatoes and substantial colour loss well assessed by visual evaluation. Colour measurement using tristimulus colour measurements and RGB image analysis did not correlate well with lycopene content. Prior hot water treatment did not prevent lycopene loss. Results show that storage of red ripe tomatoes at chilling temperatures reduces the nutritional and presumed health promoting value and affects fruit visual quality.

► Low storage temperatures cause discolouration in red ripe tomato fruit.
► Low storage temperatures reduce lycopene contents of red ripe tomatoes.
► Hot water treatments do not alleviate discolouration and lycopene reduction of tomatoes stored at chilling temperatures.
► VIS remittance spectroscopy better estimates tomato lycopene content than tristimulus colorimetric measurements.