Effect of Vacuum Cooling on Shelf Life of Organic Chayote Shoot （Sechium edule Sm.）

The effect of vacuum cooling on shelf life of organic chayote was investigated. Vacuum cooling processes of organic chayote shoot packed in perforated polyethylene package using different vacuum pressure reserving operation modes were experimented. The holding final pressures for vacuum-cooled organic cilantro packed in holed polyethylene bags were set at two different levels, namely at 10 and 11 millibar. The pressures were experimented with 3 levels of reserving time of 3, 4 and 5 minutes. The weight loss percentage of chayote shoot during precooling to the temperature of 8 ~ 1 ~C using reserving pressure of 10 milibars for 3, 4, and 5 minutes were 0.5, 0.7, and 0.9, respectively. For the weight loss percentage during precooling using reserving pressure of 11 milibars for 3, 4, and 5 minutes were 0.4, 0.5, and 0.5, respectively. The optimum parameter for vacuum cooling process of organic chayote shoot at the initial temperature of 19-23 ℃to 8 ±1 ℃was the reserving pressure of 11 mbar with reserving time of 5 minutes. The precooled organic chayote shoot was then stored at 8 ℃ for quality analysis. The results showed that vacuum cooling had no effect on the change of color, chlorophyll a, b and total chlorophyll. However, precooled organic chayote shoots showed better appearance than non-precooled vegetables. Vacuum cooling can reduce weight loss percentage. The amount of total soluble solids in organic chayote shoots increased with storage time. Precooled organic chayote shoot had longer shelf life of 8 days compared to normal storage life of 5 days.

Simulation approach for optimal design of vacuum cooling on broccoli by simulated annealing technique

Water-spraying is regarded as an effective method to reduce the weight loss of product during vacuum cooling process.This study aimed to investigate the effect of vacuum cooling factors on the weight loss of postharvest broccoli,and attempted to optimize the treatment conditions by simulated annealing(SA)technique.An algorithm based on simulated annealing meta-heuristic technique was developed to identify the optimum condition for vacuum cooling treatment of broccoli.Results demonstrated that the SA algorithm could adjust well with the simulation of the broccoli cooling process.The best condition was at 200 Pa of pressure,274 g broccoli,6% of water volume and 40 min processing time.Under this condition,a product with only 0.35% of weight loss and 1.48℃ final temperature was obtained.The developed method may help to effectively control the weight loss during vacuum cooling process and reducing the economic loss.

Design Evolution and Analysis of the ITER Cryostat Support System

The cryostat is a vacuum tight container enveloping the entire basic systems of the ITER tokamak machine,including a vacuum vessel,a superconducting magnet and thermal shield etc.It is evacuated to a pressure of 10^-4Pa to limit the heat transfer via gas conduction and convection to the cryogenically cooled components.Another important function of cryostat is to support all the loads from the tokamak to the concrete floor of the pit by its support system during different operational regimes and accident scenarios.This paper briefly presents the design evolution and associated analysis of the cryostat support system and the structural interface with the building.

Comparison of different cooling methods for extending shelf life of postharvest broccoli

This study aimed to investigate and compare the effects of vacuum cooling,cooling water and cold room methods on the shelf life of broccoli.The experiments were divided into four groups:vacuum cooling(A),ice-water cooling(B),cold room cooling(C)and control.The cooling rate and changes of weight loss,respiratory rate,chlorophyll,vitamin C,reducing sugar content and sensory properties were measured at intervals of five days.The results indicated that vacuum cooling was the most effective method for extending the shelf life of postharvest broccoli in terms of cooling rate,respiration rate,chlorophyll,vitamin C,reducing sugar and sensory properties.Moreover,spraying the broccoli with water during the vacuum cooling process resulted in a significant reduction in weight compared with the other two cooling methods and did not reduce the quality of the broccoli.Consequently,vacuum cooling treatment can be applied to broccoli after harvest in the field to maintain quality during transportation and storage.Additionally,the application of water spraying during vacuum cooling can considerably reduce the negative influence caused by vacuum cooling.