| Broccoli(Brassica oleracea L. Var. Italica)is one of popular vegetables which is full of nutritions such as protein, vitamin, minerals and anticancer glucosinolates. The quality of broccoli including visual quality and nutrient quality is essential to its price and market competition. Currently, researches on post-harvest technology of broccoli mainly focus on storage, and few studies on the whole cold-chain logistics process are reported. Thus, from field precooling to transportation, then to storage, finally to sales, the dissertation studied the effects of different precooling methods, transportation methods and sales method on the quality of broccoli, as well as the preservation technology of cold storage and controlled atmosphere combined. The results were as follows:1. study of the effect of different precooling methods on precooling rate and weight loss of broccoliEffect of carton and plastic case on average precooling rate and weight loss of broccoli by pressure cooling and cold-room cooling and the precooling rate of pressure cooling, cold-room cooling, ice water(10min) + pressure cooling and ice water(10min)+pressure cooling were studied. The results showed that the precooling rate of broccoli packaged by plastic case was faster, the weight loss of broccoli packaged by carton and plastic case were below 1.5%. The precooling rate of pressure cooling and cold room cooling were 0.232℃/min,0.094℃/min respectively. The precooling rate of ice water(10min) + pressure cooling was fastest in four precooling methods.2. study of the effect of different transportation methods on nutrient quality and visual quality of broccoliBroccolis packaged by expanded polystyrene case with ice were placed in normal temperature to simulate insulated van transporting broccoli. Broccolis packaged by expanded polystyrene case with ice and carton with film were placed in cold room to simulate refrigerator cat transporting broccoli. The effect of three transportation methods on broccoli was studied. The results showed that the central temperature of broccoli packaged by expanded polystyrene case with ice was increased from 0℃to 25℃after 33 hours under 30℃and comprehension value was about 3 points. So broccoli packaged by expanded polystyrene case with ice can't be transported for more than 33 hours under 30℃, or visual quality and nutrient quality would be affected seriously. Broccolis packaged by expanded polystyrene case with ice for refrigerated transportation were better than ones packaged by carton with film, and comprehensive evaluations of both were 4.07 points,3.93 points separately.3. study of the effect of different film packages on physiology and biochemistry of broccoliThe effect of 0.02mm polyethylene (PE), 0.06mm polyvinyl chloride (PVC), shrink film and without plastic film on nutrient quality, antioxidant enzymes activity and visual quality of broccoli during 44 days storage at (0±0.5)℃were studied. The results showed that the weight losses of broccoli packaged by film were below 5%. All film packages delayed the degradation of chlorophyll, slowed the increase of yellow index and reduced the decrease of soluble protein content. However, broccolis in 0.02mmPE and 0.06mmPVC were better. The comprehensive evaluations of broccoli in 0.02mmPE and 0.06mmPVC were 3.51points, 3.42points separately. Broccoli in 0.02mmPE and 0.06mmPVC had commodity value, but ones in shrink film had not food value.4. study of the effect of low oxygen on physiology and biochemistry of broccoli in cold storageTo investigate the changes of broccoli in low oxygen, the effect of 5%10%O2, 2%5%O2 on broccoli were studied according to the indices of chlorophyll, VC, soluble sucrose, soluble protein, free amino acids and antioxidant enzyme activity. The results showed that low oxygen in cold storage effectively slowed the decrease of chlorophyll, VC, soluble sugar and soluble protein as well as the increase of free amino acids, inhibited the decrease of CAT and the increase of POD. After 60 days, the chlorophyll contents of broccoli in 5%10%O2, 2%5%O2 were 30.39mg/100g, 36.48mg/100g respectively; the VC contents were 105.88mg/100g, 128.29mg/100g respectively. Broccolis in 2%5%O2 were better than in 5%10%O2.5. study of the effect of different sales methods on nutrient quality of broccoliBroccolis without shrink film, with shrink film and with humidification were placed in 20℃to simulate cabinet and cabinet with humidifying chamber selling broccoli respectively. Broccolis without shrink film and with shrink film were placed in 4℃to simulate preservation cabinet selling broccoli. The results showed that broccolis with shrink film had lower weight loss and higher nutrient quality than ones without shrink film in 20℃or 4℃. The weight losses of broccoli with humidification were lower than ones without humidification. Broccoli with humidification looked more luster, because humidifying treatment can increase the water to complement the water used by surface evaporation. Broccolis with shrink film in 4 were the best and had the longest shelf life. |
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