The hot water treatment (HWT) is already used in commercial practice for whole horticulture commodities such as pepper, tomato, apple, citrus fruit etc. This treatment is developed for fungal and insect control as well as other postharvest disorders. The treated product maintains better postharvest quality because of better firmness (apples) better colour (broccoli, asparagus) and lack of chilling injury (pepper).
The research team led by Maria Grzegorzewska at Research Institute of Horticulture (InHort, Skierniewice, Poland) has just concluded the deliverable N. 4.26, whose objective was to obtain a protocol for the hot water treatment of fresh-cut vegetables: Chinese cabbage (Brassica rapa L. var. pekinensis), salad rocket (Eruca sativa M.) and melon (Cucumis melo). Moreover, the estimation of fresh-cut vegetables durability during short term storage was also carried out.HWTs were conducted by dipping the fresh-cut vegetables into the water bath at temperatures ranging between 38–60°C and time durations of: 20 min. – 3 sec. The parameters of hot water were evaluated in successive tests depending on results obtained earlier for particular vegetables.
The samples were stored at different temperatures: 0°C, 5°C, 10°C, 15°C and 18-20°C (depending on experiment). The quality of fresh-cut products was estimated every 2 - 3 days during storage and based on nine grade scales. Additionally, the sensory, chemical, microbiological and microscopic analysis were performed for samples of selected treatments.
Results showed that Chinese cabbage cv. Bilko F1 was positively affected by short term dipping in hot water of temperature 53 – 55°C (time duration 3 – 5 seconds). The browning of cut leave surface was retarded as well as the fresh cut cabbage maintained better sensory quality during short term storage. Grzegorzewska concludes: "On the basis of these results, it was possible to provide a HWT protocol for potential implementation at industrial level".
As for fresh-cut rocket, the short dipping (3 – 5 seconds) in hot water at temperatures of 50 – 55°C reduced leaves yellowing during short term storage. On the other hand, HWT influenced the better sensory quality of the following melon types:
1. Galia melon treated at 55°C during 3 s. and stored at 5°C and 18-20°C,
2. Cantaloupe melon treated at 53°C over 1.5 min. and stored at 0°C and 18-20°C.