Effects of ultrasonication in combination with selected sanitizer and surfactant on the quality and microbial safety of produce

Ultrasound;sanitizer;surfactant;quality;lettuce;carrots

Palma Salgado, Sindy ; Feng ; Hao

关键词: Ultrasound;    sanitizer;    surfactant;    quality;    lettuce;    carrots;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/45366/Sindy_Palma%20Salgado.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In the United States, outbreaks of foodborne illnesses caused by pathogenic microorganisms associated with consumption of fresh and fresh-cut produce is a recurring problem. It is estimated that 1 in every 6 US residents contracts a foodborne illness every year. There is an urgent need to develop better sanitization methods and sanitizing agents that are effective against pathogens, safe for operators, environmentally friendly, and with minimal negative impact on produce quality. This study was undertaken to address the need for the development of more effective sanitization strategies and better sanitizers. Specifically, the effects of a new sanitization strategy and a set of sanitation combinations on reduction of microorganisms on produce, as well as the potential impact of these treatments on produce quality, were examined.To examine if lettuce will be floating or submerged in a washing solution, the water absorption and thus changes in specific gravity of whole head Iceberg lettuce at two storage (5 C and 23°C) and two washing solution (4 C and 23°C) temperatures were first investigated. The reduction of Escherichia coli O157:H7 population during a sanitization treatment as affected by produce surface area to weight ratio was examined with whole baby carrots and baby carrots cut into sticks and shreds. The decay of chlorine and peroxyacetic acid at different surface to weight ratios was evaluated. The reduction of E. coli O157:H7 on Iceberg lettuce by two washing sequences, i.e. “cutting-before-washing” and “washing-before-cutting” was compared by treating the samples with water, and combinations of ultrasound with chlorine (free chlorine concentration 20 mg L-1) and Tsunami (final acid concentration 80 mg L-1) was examined.Iceberg lettuce stored at 23oC and washed at 4oC had the highest percentage increase in weight and specific gravity. Chlorine and peroxyacetic acid availabilities decreased when the surface-to-weight ratios increased, and chlorine was consumed faster than peroxyacetic acid. Correspondingly, a lower reduction of E. coli O157:H7 counts on carrot samples having high surface area-to-weight ratio was found, evidencing the effect of chlorine decay on inactivation of microorganisms. In sanitizer-only washing tests, the E. coli count reduction for lettuce treated by “washing-before-cutting” was higher by 0.79 and 0.80 log10 CFU/g in chlorine and peroxyacetic wash, respectively, compared to the traditional “cutting-before-washing” process. When ultrasound was used in combination with a chemical sanitizer, a further increase in the E. coli population reduction of 0.68 and 0.37 log10 CFU/g (again, for chlorine and peroxyacetic acid, respectively) was achieved by the “washing-before-cutting treatment”, reaching total reductions of 2.43 and 2.24 log10 CFU/g for the chlorine and peroxyacetic washes, respectively. In tests to evaluate the effects of sonication in combination with 2 sanitizers (chlorine and Tsunami) and sodium dodecyl sulfate (SDS) on the quality of fresh-cut Iceberg and Romaine lettuce, lettuce samples were sonicated for 1 minute in a custom-designed ultrasonic (US) tank containing one of the following treatment solutions: tap water, chlorine (100 mg L-1 free chlorine), Tsunami (80 mg L-1 peroxyacetic acid), and a combination of Tsunami with 0.1% (w/v) SDS. Washed samples were bagged and sealed under modified atmosphere conditions and stored at 4 C for up to 14 days. Changes in headspace gases, texture, color, tissue damage, visual quality, and populations of aerobic mesophiles and yeasts and molds were determined. The oxygen concentrations and CO2 accumulation in Romaine lettuce were not significantly different among the treatments. In Iceberg lettuce, lower O2 and higher CO2 concentrations in the samples treated with Tsunami and Tsunami + SDS were recorded. After 14 days of storage, the tissue damage measured by electrolyte leakage rate (ECR), total color differences, firmness, and total aerobic plate counts were not significantly different for all the treatments in both types of lettuce samples (P>0.05). Treatments of Iceberg lettuce with sonication in combination with Tsunami or Tsunami + SDS do not cause more quality changes compared to the chlorine treated samples. For Romaine lettuce, chlorine treated samples had a significantly higher overall quality score than those from the other treatments