Gaseous storage effects on fruit quality, shelf life, and some pathogens on Tifblue blueberry (Vaccinium ashei L.)
Tokitkla, Angsana
Ph.D., Mississippi State University, 2004, 131 pages
2004
บทคัดย่อ
In efforts to extend shelf life of fresh-packed stored blueberries and to eliminate Escherichia coli 0157:117 and Salmonella on the fruit, the use of three gases was examined on Rabbiteye blueberries cv 'Tifblue'. Two experiments were conducted to compare the effectiveness of gases on postharvest fruit quality, shelf life and control of E. coli O157:H7 and Salmonella infection on blueberries. The first experiment studied the effects of gases on fruit quality and shelf life of 'Tifblue' blueberries. Fruits were placed in clamshell containers, then loaded into SLX ® containers and fumigated with 15.5% O3 , 193 PPM SO2 , 18.8% CO2 , and normal air. Fruit were then stored at 2°C and 95% relative humidity, and sampled periodically for a period of 48 days. The second experiment studied the effectiveness of the above listed gases in inhibiting E. coli O157:H7 and Salmonella in stored blueberries. In this experiment, blueberries were inoculated with bacterial cell suspensions, packaged, fumigated and stored as described in first experiment. At timed storage intervals, berry samples were removed from each treatment and microbial load was determined. Results indicated that fruit decay was greater on berries stored in normal air compared to other treatments. In all gas treatments, change in weight loss did not differ with the time. Acidity decreased during storage, particularly for the samples stored in SO2. Firmness was increased when berries were stored under O3 gas. Berries treated with SO2 had higher anthocyanin and antioxidant content. However, blueberries stored under SO 2 and O3 showed higher levels of phenolic content. Berries stored under SO2 had higher hue values, 'a' values and chroma, than the other treatments. The control and O3 -treated berries had higher 'L' and less 'b' values. Sensory evaluations showed that blueberries stored in O3 had more acceptable qualities than did berries kept under other storage conditions. Treatment with O3 and SO2 resulted in greater reduction in populations of E. coli O157:H7, Salmonella, and yeast and mold growth. Ozone and SO2 may, therefore, be considered useful gases under modified atmosphere packaging (MAP) to extend shelf life and inhibit growth of pathogenic bacteria on blueberries.