Fresh-cut Produce Wash Water Reuse Affects Water Quality and Packaged Product Quality and Microbial Growth in Romaine Lettuce

Abstract

Washing is a critical step for maintaining quality and safety of fresh-cut produce during its preparation and is often the only measure taken to reduce microbial populations and remove tissue fluids. However, little is known about the effect of washing method on water quality or its consequence on microbial growth and finished product quality. This study was conducted to evaluate the effect of wash water reuse on changes in water quality and its subsequent effect on microbial growth and product quality of packaged fresh-cut Romaine lettuce (Lactuca sativa L.). Romaine lettuce leaves were sliced and washed in water with chemical oxygen demand levels ranging from 9.8 mg·L−1 (fresh water) to 1860.5 mg·L−1 (reused water) and product-to-water ratios of 1:20 and 1:150. The washed samples were dried and placed into packages prepared from films with an oxygen transmission rate of 8.0 pmol·s−1·m−2·Pa−1 and stored at 5 °C for 14 days. Microbial growth and product quality were monitored at days 0, 4, 8, 11, and 14 during storage. Results indicate that as the quantity of lettuce dipped in 40 L of water increased from 2.0 kg to 18.0 kg, water chemical oxygen demand increased from 124 mg·L−1 to 1721 mg·L−1 and biological oxygen demand increased from 140 mg·L−1 to 526 mg·L−1, whereas free and total chlorine levels declined from 151.5 mg·L−1 to 4.7 mg·L−1 and from 171 mg·L−1 to 31.5 mg·L−1, respectively. Thoroughly washed lettuce in clean water with a small product-to-water ratio had the least off-odor development. Samples without wash treatment and those washed with reused water had 0.8 to 1.6 log cfu·g−1 higher populations of lactic acid bacteria than those washed with clean water at the end of storage.