Survival of Listeria Strains and Shelf Life Determination of Fresh Blueberries (Vaccinium corymbosum) Treated with Cold Atmospheric Plasma.

Fresh blueberries are delicate, hand-picked, packaged, and refrigerated fruits vulnerable to spoilage and contamination. Cold atmospheric plasma (CAP) is a promising antimicrobial technology; therefore, this study evaluated the CAP treatment effect on acid-tolerant Listeria innocua and Listeria monocytogenes and evaluated changes in the quality of the treated fruit. Samples were spot-inoculated with pH 5.5 and 6.0 acid-adapted Listeria species. Samples were treated with gliding arc CAP for 15, 30, 45, and 60 s and evaluated after 0, 1, 4, 7, and 11 days of storage at 4 °C and 90% humidity for the following quality parameters: total aerobic counts, yeast and molds, texture, color, soluble solids, pH, and titratable acidity. CAP treatments of 30 s and over demonstrated significant reductions in pathogens under both the resistant strain and pH conditions. Sixty-second CAP achieved a 0.54 Log CFU g-1 reduction in L. monocytogenes (pH 5.5) and 0.28 Log CFU g-1 for L. monocytogenes (pH 6.0). Yeast and mold counts on day 0 showed statistically significant reductions after 30, 45, and 60 s CAP with an average 2.34 Log CFU g-1 reduction when compared to non-CAP treated samples. Quality parameters did not show major significant differences among CAP treatments during shelf life. CAP is an effective antimicrobial treatment that does not significantly affect fruit quality.

Survival of Spray-Dried Rhodotorula mucilaginosa Isolated from Natural Microbiota of Murta Berries and AntagonisticEffect on Botrytis cinerea.

The aim of this study is to evaluate the survival rate and effective antagonistic activity against Botrytis cinerea, responsible for grey mould on harvested fruits and vegetables, of yeast Rhodotorula mucilaginosa, isolated and identified from the natural microbiota of murta (Chilean guava) berries, after spray drying at different inlet air temperatures, mass per volume ratio of encapsulating agent (maltodextrin) and feed flow rates. The 100% survival of the yeast was obtained after spray drying with 18% maltodextrin at 130 °C inlet temperature and a feed flow rate of 9.25 mL/min. The dried yeast obtained under such conditions had the highest antagonistic activity in vitro and in vivo on apples, which showed that spray drying is a valid method to produce active dried cells of R. mucilaginosa that can be used for biocontrol of grey mould spoilage. It was also found that the encapsulating agent maltodextrin improved the in vitro antagonistic activity of R. mucilaginosa.