Research On Quality Evaluation Of Fresh Litchi

Litchi(Litchi chinensis Sonn.) is one of the most popular fruit in China. It has been known as the "Best fruit south of the Five Ridges". There are a large number of litchi cultivars in China which counts for about80%in planting area and production around the world. It is mainly marketed for fresh fruit. Industrial investigation analysis revealed that cultivar selection and development of excellent cultivars would be important project for the future. Quality evaluation can be used as an important reference and guide for production and extension of the selected excellent cultivars.Thus, quality evaluation of fresh litchi was conducted in this study by the building and selecting of evaluation factors which would be used as the basis for establishing an evaluation system of fresh litchi. Thus, the excellent cultivars could be selected by this method and used for the development of litchi industry.The selection of evaluation parameters was the crucial factor in quality evaluation of fresh litchi. Twenty litchi clultivars with excellent qualities, favor and storage qualities were selected for quality analysis. Taking the consideration of all the known factors affecting litchi quality, seventeen quality evaluation parameters were established. The seventeen quality parameters were selected as the primary evaluation parameters which including appearance, eating, nutritional value, and other characteristics. By analysis of the quality of twenty excellent litchi cultivars, crucial parameters affecting litchi quality were detected. Another sixty litchi cultivars were selected for farther analysis. With consideration of variation of quality parameters between different cultivars, correlation analysis, multi linear regression analysis between sensory evaluation value and the seventeen quality parameters, the main quality parameters were selected in evaluation of fresh litchi. The evaluation method of the sixty litchi cultivars was conducted by principal component analysis. The sixty cultivars were evaluated by the above method to classify the cultivars into three kinds from which the excellent cultivars were selected for the production. The model could be used as a guide for cultivar plantation and extension.The main results and conclusions of current study are as follows: 1. Cultivars with excellent quality selected from twenty cultivars were ’Nuomici’,’Guiwei’,’Baitangli’, while other cultivars such as ’Shuangjianyuhebao’,’Feizixiao’,’Huaizhi’,’Dadingxiang’had inferior quality comparatively.2. Detecting methods of quality parameters were established with consideration of previous studies for all the qualiy parameters in experiment.3. Correlation analysis between every quality parameters illustrated that significant correlation can be found between sucrose, fructose and glucose; color a*and b*, b*and L*; TA, malic acid and pH. So sucrose, color a*, pH were selected as the representative parameters for sugar, color and acid, respectively.4. Multi linear regression analysis between the quality parameters and sensory evaluation value revealed that the ratio of TSS to TA, a*and single fruit weight were the crucial parameters in deciding of sensory evaluation values. The model of multi linear regression was:sensory evaluation value=71.045+0.25xratio of TSS/TA+0.23*a*-0.285×single fruit weight. The model acted well with R2=0.843.5. The quality evaluation parameters were selected as:juice yield, TSS, edible rate, ratio of TSS to TA, a*, single fruit weight, sucrose, pH, Vc, crude protein.6. Six components were extracted from the ten quality parameters which explained82.22%of initial variables in principal component analysis, and the formula of quality evaluation of fresh litchi was as follow:F=0.15×edible rate-0.03×juice yield+0.009×color a*+0.18×single fruit weitht+0.09×TSS+0.12*pH+0.12×crude protein+0.02RVc+0.13×ratio of TSS to TA+0.12×sucrose.7. Cultivars with good quality selected form the sixty cultivars were:’Mili’-.’Guiwei(Guangdong)’、’Baitangying(Guangdong)’、’Xijiaozi’、’Lizhiwang’、’Jiapili’、’Feizixiao(Guangxi)’、’Baitangying(Guangxi)’、’Midingxiang’、’Ednali’. The result was in agreement with the actual findings.