Off-odour development in modified atmosphere packaged baby spinach is an unresolved problem

A major problem associated with minimally processed baby spinach (Spinacia oleracea L.) is strong off-odours when stored under modified atmosphere packaging (MAP) with low O2 and high CO2. Although the influence of O2 and CO2 levels on the quality and shelf-life of baby spinach has been extensively studied, results have been inconsistent and the benefits and disadvantages are not well understood. In this study, the effects of 3 different MAP conditions with low O2 with CO2 (stabilizing near 1% O2 + 11% CO2), low O2 alone (stabilizing near 1% O2, CO2 scrubber) and moderate O2 with CO2 (stabilizing near 10% O2 + 9% CO2) were studied during storage at 7 °C for 12 days. Different parameters related to physiology, tissue structure, microbial population and metabolite production were evaluated. Samples exposed to low O2 with CO2 had the lowest quality at the end of storage due to high development of off-odours, while off-odours of spinach in low O2 alone were intermediate but higher than in moderate O2 with CO2. Increasing CO2 concentration significantly increased tissue damage with ammonia release and decreased protein content. Decreasing O2 concentration significantly reduced the development of aerobic psychrophilic bacteria and Pseudomonas. Senescence occurred more rapidly in baby spinach held in moderate O2 with CO2. Baby spinach quality remained acceptable during 7 days of storage at 7 °C, independent of MAP conditions tested. Appropriate MAP for baby spinach must be associated with maintenance of quality and extension of shelf-life.

Transverse section (a) and details of cells (b) of baby spinach at d 0 (A) and after 12 d at 7 °C in MAP of low O2 with CO2 (B) or moderate O2 with CO2 (C).Figure optionsDownload as PowerPoint slideHighlights
► Low O2 with CO2 reduced shelf-life of baby spinach because of the development of strong off-odours.
► MAP with CO2 was directly correlated with tissue damage, protein decrease, ammonia accumulation and pH increase.
► Moderate O2 with CO2 controlled the development of off-odours but reduced-shelf life by accelerating senescence and cell death.
► Decreasing O2 concentration preserved the physiological integrity of the tissue and reduced aerobic psychrophilic bacteria and Pseudomonas.
► Baby spinach quality remained acceptable for 7 days at 7 °C, independent of MAP conditions.