High Helium Controlled Atmosphere Storage Decreases Microbial Growth and Preserves Quality on Fresh-Cut Mizuna Baby Leaves

The industrial sector of fresh-cut or minimally fresh processed products is very competitive and it is forced to seek technological solutions in order to satisfy the consumer's demands, by offering new, safer, nutritious and high overall quality products. In the recent years, the market of oriental baby leaves, and among them mizuna (Brassica rapa var. nipposinica), has noticeably raised. However, the scientific information about their postharvest behaviour is still very scarce. The object of this work was to study the effect of non conventional high helium controlled atmosphere storage (He-CA) versus air and a low oxygen controlled atmosphere on natural microflora development and on changes in nutritional and sensory quality on fresh-cut mizuna baby leaves during 8 days at 5°C. After harvest, the raw material was air pre-cooled at 5°C, pre-washed with tap water at 5°C and disinfected by immersion in a solution at 5°C with 100 ppm NaClO. Subsequently, the mizuna was spin dried to eliminate water excess and it was placed inside 1.5 L gastight glass jars. Four different humidified CA were assayed: 20.9 kPa O2 + 0.03 kPa CO2 + 79 kPa N2 (control); 1 kPa O2 + 20 kPa CO2 + 79 kPa N2; 83 kPa He + 15 kPa CO2 + 2 kPa O2; 98 kPa He + 2 kPa O2. Both He-CA storage decreased 1 log cfu g-1 the total aerobic mesophilic load after 8 days at 5°C while control and low oxygen atmosphere exceeded the maximum recommended of 7 log cfu g-1. However, the sensory quality was acceptable for consumption in all treatments. After shelf life, no differences among treatments were found in total antioxidant activity and phenolics content which preserved their initial values of 35 g eq ascorbic acid kg-1 fw and 850 mg eq clorogenic acid kg-1 fw, respectively. As main conclusion, when compared to air or low oxygen atmospheres, He-CA storage combined or not with moderate CO2, improved the overall quality of minimally processed mizuna baby leaves up to 8 days at 5°C.