Modified atmosphere generated during storage under light conditions is the main factor responsible for the quality changes of baby spinach

• Baby spinach was stored under modified atmosphere.
• In light high pO2 and low pCO2 while in darkness low pO2 and high pCO2.
• Leaf quality and senescence changed due to gas composition and not to light exposure.
• High O2 promoted oxidative damage and microbiological growth.
• High CO2 increased pH and leaf damage and also off-odours.

Minimally processed products are generally exposed to low temperature and uncontrolled light conditions during the supply chain. The positive effect of low temperature on quality of baby spinach is widely reported, but there is little information available about the light effect. The objective of this study was to obtain insight about the cause-effect of light exposure of baby spinach on leaf quality and senescence parameters. Minimally processed baby spinach was stored in passive Modified Atmosphere Packaging (MAP) and in Controlled Atmosphere (CA) under different light conditions. In passive MAP, three very different headspace gas compositions within the bags due to photosynthesis and respiration reactions were generated that strongly affected the quality characteristics. To isolate the light effect from the atmosphere composition influence, and thus understand the mechanisms causing the quality changes, baby spinach was stored under two CA of 0.5 kPa O2 + 10 kPa CO2 (low O2 + high CO2 levels) and air combined with 2 light conditions (continuous light and darkness). The changes observed under the different light conditions were mainly caused by the differences in gas composition. Under light, MAP with high O2 partial pressure (pO2) and low CO2 partial pressure (pCO2) was detrimental because of the growth of Pseudomonas spp. and the progress in tissue senescence due to oxidative stress, increasing cell damage, lipid peroxidation and chlorophyll degradation. Under darkness, MAP with low pO2 and high pCO2 was also detrimental because of the intense off-odour developments, the increase in pH and electrolyte leakage and the reduction in chlorophyll fluorescence. Our results showed that the modified atmosphere generated with exposure to the different light conditions affects the quality of baby spinach mainly because of the high pO2 under light and high pCO2 under darkness.

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