STUDY TO IMPROVE TECHNOLOGY IN COOLING AND COLD TRANSPORTING LITCHI TO MARKET IN SOUTH OF VIETNAM

Reported by Vietnamese groupNguyen Manh Khai, Dinh Thai Hoang, Huynh Thi Thanh Tuyen

Khon Kaen, 11/2011

IMPROVE TECHNOLOGY IN COOLING AND COLDTRANSPORTING LITCHI TO MARKET IN SOUTH OF VIETNAM

I. IntroductionLitchi is one type of important tropical fruit with high nutrition value. Litchi has high economic value with high competition and is exported with high foreign currency for many countries.Recently, Vietnameses production of litchi increase incessantly with about 300,000 to 500,000 tons per year. However, harvesting season of litchi is very short (only around 30 days) with only one season in year. Moreover, life of fruit after harvesting is very short, too (only about 3 days). These make many difficulties for consumption, therefore price of litchi fruit fell continuously, this cause no small damage about economic for producer.

To commercialize litchi, it is necessary to maintain quality until it is transported to consumer. However, the most difficult problem when managing quality of litchi after harvesting is that color of fruits cover change into brown after fruit cut from plant. This characteristic of litchi fruit is one no small restriction for ability extending consumption market. Therefore, finding maintaining and transporting methods to maintain quality of fruit during commercial route, but conducting method must be simple and can deploying with large scale in practice with highest economic effect is extremely necessary.One of effective method to ensure quality and to lengthen maintaining time is decreasing rapidly temperature of fruit after harvesting to appropriate maintaining temperature.

II. ObjectivesGeneral objective- To restrict lose after harvesting fruit- To determine cooling and cold transporting litchi fruit Specific objective- To study on effect of pre-cooling method to quality of litchi fruit- To evaluate ability of replacing old method by new method

III. Materials and methods3.1. Object and materialsObject: Thanh Ha cultivar is planted in Thanh Binh commune, Thanh Ha district, Hai Duong province, VietnamMaterials: Fruits are harvested when 50 percent of cover area changing color to red in the early morning. Fruits are cut down leaf then bundling into bunches with average weight about 2.0 kilogram and transporting rapidly to packing house.

3.2. Experiment designBruches after being transported to packing house will be pre-cooled according to 2 methods below:Experiment 1 (Exp. 1): Bruches is packed into foam containers lined by polyethylene (about 8 bunches per container), then transporting immediatly into cold storage with temperature about 2oC within 10 hours.Experiment 2 (Exp. 2): Soaking each bunch into frozen water with temperature about 2 4oC within 3 minutes, lifting in a sieve within around 2 minutes, after that putting them into foam containers lined by polyethylen (about 8 bunches per container) then transporting immediatly into cold storage with temperature about 2oC within 3 hours.

Control: Bunches are treated and transported according to current process (Fresh fruits are transported to packing house, after classifying they are bundled into bruch with weight about 2.0 kilogram per bruch. Soaking them into frozen water with temperature about 5oC within 3 minutes, then putting into foam containers lined by polyethylene (about 8 bunch per container with about 8 kilogram of ice). After storing in cold storage as above, the litchi fruits of 2 experiments and control are transfered to lorry with cold hold (temperature in cold hold about 0oC) to transport to Ho Chi Minh city within 48 hours. Immediatly after, litchi containers are transported to Can Tho city by ordinary lorry within 18 hours (including waiting and transporting time).

3.3. Studied targetsWeight lose level (%)Color changeDetermining change in color of fruits cover by NR 3000 machine. The result is reported by indexes including: L, a and b. Where;L: index showed light level of fruits cover, with values range from 0 to 100.a: index showed color range from green to red, corresponding with value from 60 to + 60b: index showed color range from sea blue to yellow, corresponding with value from 60 to + 60.

Changing to brown index of fruit' coverDetermining by method of Wrolstad (1982) with grades ranging from 1 to 5. Grade 1 with fruits having natural red and grade 5 with fruits having over 50 percent of fruits cover area changing to brown.Damaged rate (%)Total sugar content (%)Temperature of fruit after transportingVitamin C content (mg%)Evalutating quality by sence methodConducting to evaluate quality of fruit basing on standard TCVN 32 1579 of Vietnameses Ministry of Agriculture and Rural Development with targets, including: color of fruits cover, color of fruits pulp, state of fruit, state of fruits pulp, tase of fruit.

TargetGrade rangeImportant coefficient1234Color of coverBlackBrownRed-greyRed-yellow0.9State of fruitVery softSoftQuite softHard0.85Color of pulpRed-whiteMatteMatte whitePure white0.45State of pulpVery wetWetQuite wetDry0.85TasteSmelly, sour/ tastelessOdorless, little sweetPerfumed, sour, sweetVery perfumed, sweet0.95IV. ResultsTable 1: Effect of cooling methods on temperature of litchi fruit after transporting

MethodInitial temperature(oC)Temperature after transporting (oC)Control5.018.8Exp. 15.020.4Exp. 25.018.4Slow increase of temperature process after taking fruit out ordinary temperature condition will help maintain better quality of fresh litchi fruits Table 2: Changing color of fruit after transporting

MethodRaw material fruitFruit after transportingControl081.40 aExp. 1080.59aExp. 2078.22bEffect of cooling method on color of fruits cover was determined by three indexes: L, a and b with only index: Eab = square of (L2 + a2 + b2) which is easy to compare changing color of fruit in maintaining process between methods

Table 3: Effect of cooling method on natural weight lose level of litchi after transporting

MethodInitial weight(g)Weight after transporting (g) Natural weight lose level (%)Control16.715.010.00cExp. 115.815.23.80aExp. 217.817.23.37bIn the same packaging and transporting condition, treating fruit by frozen water delayed losing weight speed of fruitTable 4: Effect of cooling method on total dissolved matter content of litchi fruit after transportingLitchi fruit cooling by soaked into frozen water method has total dissolved matter level less than ordinary methodMethodRaw material fruitFruit after transportingControl18.115.80aExp. 118.116.62aExp. 218.117.24bTable 5: Effect of cooling method on vitamin C content (mg %) of pulp after transportingTreating fruit by method soaked into frozen water before pre-cooling by cold air has good effect restricting process of declining vitamin C content in pulp of fruitMethodRaw material fruitFruit after transportingControl15.209.00aExp. 115.209.15aExp. 215.209.54bTable 6: Effect of cooling method on sense quality of litchi fruit after transportingMethodControlExp. 1Exp. 2Color of cover2.442.502.64Color of pulp4.004.004.00Taste3.553.753.82State of cover3.053.073.21State of pulp3.403.503.64Summing without important coefficient 15.5016.3817.32Summing with important coefficient13.4613.5813.95V. Conclusion and suggestion5.1. ConclusionTreating fruit by method soaking into frozen water within 3 minutes, then putting into cold storage with temperature about 2oC within 3 hours, after that transporting in cold lorry with temperature about 0oC gained the best effect in comparison with method which was not cooling treated and controlTreating fruit by method soaking into frozen water and packaging by foam container lined polyethylene, then transporting in cool lorry maintained the most sense quality and nutrition quality of fresh litchi fruit in comparison with method which was not cooling treated and control.

5.2. Suggestion It is necessary to continue researching with more large scale to affirm effect of treating and transporting methods to quality of fruit during transporting and maintaining to can hand over quickly research results into reality production.It is necessary to research more about combining using substance against fungus and methods to restrict changing brown of fruits cover to improve quality and to lengthen maintaining time with fresh litchi fruit, to restrict seasonal, to extend consumption market for this special fruit.

Thanks for your attention