Development Of New Citrus Wax Coating And Its Physiological Effects On Citrus Fruit

China is the native place for citrus production with a long history of cultivation. In 1999, China had the area of 1.49 106 ha. and 1,011 104t of citrus fruit The value of it is just second to crop and vegetable. The citrus industry plays an vital role to improve life standard of growers in southern part of China.Waxing citrus fruit is a standard procedure in citrus production countries. In general, there are four reasons for waxing fruit: 1.To reduce shrinkage due to water loss. 2. To provide a barrier to free gas exchange. 3. To improve appearance and marketability by application of a shiny, sweat-resistant film, 4. To provide a carrier for decay-control fungicides and growth regulators. Therefore, USA, Japan, Italy, Australia, Israel, Spain, Cuba and South Africa pay more attention to the research of fruit wax coating, and develop many varieties of wax coating for citrus to different cultivars, conditions and needs. The fresh citrus fruit can not be permitted to sale in supermarkets unless they are coated with waxes there.Currently, the consumer require more higher quality of citrus fruit, and more and more citrus growers use packingline to treat fruit for fresh sale. Based on we conducted the research. The main research contents and results are as followed:Experiment 1 The Epicuticular Wax and Artificial Wax Coating of 'Valencia' Orange Fruit and Their Relationship to Weight Loss1.1 Materials and MethodsFor SEM observations and weight loss measurements, 'Valencia' orange fruits, stored at 21 ,90%RH, were left into the following treatments: (1) naturally occurring waxed orange,(2) washed with water only ,(3) washed and dewaxed, and (4) washed, dewaxed and coated with Budshine A. The naturally occurring wax was removed by dipping the orange in a solvent solution of 2:1 chloroform-methanol at room temperature for 1min, manually rubbing the surface, rinsing in running water and wiping the fruit dry. To add artificial wax, the orange was brushed of Budshine E wax.1.2 Results1.2.1 SEM observationsThe results show that the natural wax platelets on the surface of fruit are irregular in shape and size. Most natural platelets can be removed by dipping the orange in a chloroform-methanol solution. With the surface cleared, open stomata were visible. Waxing partially or completely plugs stomatal pores.1.2.2 Weight lossThe epicuticular wax is very important retarding water loss, and is found to be inversely correlated to weight loss of 'Valencia' orange (y = -35.994x + 10.249, R2 = 0.7915) .Removal of natural wax platelets resulted in heavy loss of water in the fruit. Waxing can effectively reducesI 7. 11the weight loss of fruitExperiment 2 Properties for 17 Wax Coatings on Citrus2.1 Materials and Methods17 commercial coatings were evaluated in the 1998-99 season These coatings from American, Spain, Australia, Israel, Italy, Argentine and Uruguay were Tag, Vbichem, Briteseal, Italy wax, Citroacril HM10, Frupel SL, Frupel TR, Rexin A, Emulcol MTH, Primafresh, Clearfresh, Primafresh 7K Primafresh 72, Primafresh 73, Primafresh 74, Sta-Fresh360HS and Water wax. .2.2 ResultsAll citrus coatings were alkaline but the pH range was rather extensive, 7.7 to 10.2. Percent solids, which are important as it relates to application rates, surface coverage and drying characteristics, ranged from 8.9 to 30.7%..Specific gravity values had a value from 0.991 to 1.051 and 0.991 to 1.038 at 15 and 25 , respectively, and viscosities from 2.21 to 16.93 mPa.s and 0.21 to 13.1 mPa.s, respectively. As expected,strong correlations existed between specific gravity and solid contents and between viscosity and solid contentWater vapor transmission rates represent a combined resistance of the coating material and filter paper to which the coating was was applied. No significant relationship was found between these water vapor transmissio...