Assessment of Nitrite Toxicity in Hydroponically Cultivated Lettuce (Lactuca sativa L.) during Post-Harvest Storage

Lettuce (Lactuca sativa L.) is a common vegetable in daily meals and is widely grown hydroponically in Vietnam. The purpose of this study was to investigate the changes in Nitrite toxicity after harvest under different storage conditions. The study selected extraction methods, mainly grinding, crushing, and filtration, and chemical analysis methods suitable for the practical conditions of laboratories in vegetable farms. The results showed that at temperatures above 28°C after harvest, the nitrite content increased significantly, and the lettuce began to spoil after 24 hours. At temperatures below 25°C, the lettuce suffered less damage within 48 hours. When stored in a refrigerator at 4°C to 5°C, spoilage only began after 4 days. In conclusion, the Nitrite content in lettuce increased rapidly when stored at temperatures above 25°C. At temperatures below 5°C, intrinsic enzymes are inhibited and the growth of nitrate-reducing bacteria is almost completely halted.