Quality control shredded littuce during preservation and distribution

Abstract

Storage temperature of shredded lettuce (5×5cm) vacuum-packed (200 mmHg) into Nylon/Poly-ethylene 60μm (NY/PE60) pouch during Practical distribution, such as refrigerator in processing Plant, delivery refrigerator truck and refrigerator at user's shop, was examined in summer season (atmospheric temperature : 22-32°C). Chemical, microbiological and organoleptic properties of shredded lettuce were investigated during storage at 1, 5, 10 and 20°C in laboratory scale, along with developing a simple cold delivery system using crushed ice, coolant and polystyrol container. The results were obtained as follows.
(1) In summer season, a series of temperature through the refrigerator in the processing plant, the refrigerator truck and the refrigerator at user's shop were 5-12°C. It was considered that the shelf life of shredded lettuce would be less than 3 days in this condition.
(2) The model investigation in laboratory scale suggested the storage stability of shredded lettuce was for 14 days at 1°C, for 5-7 days at 5°C, for 3-5 days at 10°C and for 1-3 days at 20°C, The deterioration factor was the ferment-like off-flavor formation. One of major components was ethyl alcohol, and the degree of ethyl alcohol formation enhanced with the increase of storage temperature.
(3) The preferable and simple delivery system was developed that the shredded lettuce (1kg×10 packages) pre-cooled to 1°C placed into polystyrol container with crushed ice 2kg. This system ex tended shelf life of shredded lettuce more than 5 days in atmospheric temperature : 20°C. It was showed that pre-cooling played an important role in practical delivery.