Study on suitability of different citrus varieties of for juice manufacturing based on principal component analysis

Abstract: 【Objective】Fruit and vegetable juice has a broad prospect for development as a nutritious and healthy drink. In 2015, the output value of fruit and vegetable juice in China reached 120 billion yuan, and is increasing at a rate of 7%-15% per year. Development and production of nutritious juice products has become an important development direction in fruit and vegetable processing industry. Citrus juice accounts for two thirds of juice produced. But at present, the variety of citrus juice is very narrow and dominated by orange juice. Besides sweet orange, our country has a rich citrus resource, especially Satsuma mandarin. In Japan, studies have been carried out on the function and processing of Satsuma mandarin, and some products have been commercialized. However, there are few studies on the NFC juice processed from different citrus varieties in Zhejiang. In order to select citrus varieties suitable for manufacturing NFC orange juice, 19 citrus cultivars produced in Zhejiang province were evaluated for suitability for juice production.【Methods】At present, there are many methods of evaluating citrus juice, and each method has its advantages and disadvantages. Fresh mature fruit samples were collected from four directions of tree canopy from mid-November to mid-December. A part of the samples were used for weighing and juicing, and the pulp recovery and juice recovery were determined at the same time. The processed juice were stored in a cryogenic refrigerator (-18 ℃) . The determinations of 6 parameters were carried out according to national standards or Ministry of Agriculture Standards. The quality characteristics analyzed included juice recovery, pulp recovery, and nutritional phyto-chemical components in citrus juice including vitamin C (VC) , total soluble solid (TSS) , titratable acidity (TA) , soluble sugar (SS) , total phenols (TP) and total flavonoids (TF) . Then, principle component analysis (PCA) was applied to evaluate the overall quality of NFC juice made from different citrus varieties.【Results】The pulp recovery of‘Niponicum'and‘Citrus Hybrid'was higher than 80%. 11 varieties had a pulp recovery between 70% and 80%. The lowest pulp recovery was found in‘Aliquam', which was63.09%.‘Niponicum'had the highest juice yield (68.50%) . There were 4 varieties with juice yield higher than 60%, including‘Satsuma Mandarin'‘Miyagawa Wase'‘Citrus Hybrid'and‘Owari'.There were 13 varieties with juice yields ranging from 50% to 60%. The juice yield of‘Aliquam'was the lowest, being only 36.84%. There was a significant influence of variety on the taste of the citrus juice. The taste of Citrus Sinensis Osbeck was very sweet because of its highest ratio of total soluble solid to titratable acidity (44.24) and low acidity. The fruits were generally high in vitamin C, total phenols and total flavonoids. The contents of vitamin C in‘Newhall Navel'and‘Aliquam'were higher, being78.26 mg · 100 mL-1 and 74.90 mg · 100 mL-1, respectively. Citrus Suavissima had the highest content of total phenols and total flavonoids, but‘Haruka Tangelo'had the lowest content. The results showed that there were significant differences in quality traits of the juice among varieties.‘Niponicum'‘Satsuma Mandarin'‘Miyagawa wase', Citrus Hybrid and‘Owari'showed good yield. However, the contents of vitamin C, total phenols and total flavonoids in their juice were relative low, leading to plain flavor. Principal component analysis showed that the characteristic values of the top three principal components were all higher than 1, and the rates of variance contribution to the three principal components were 38.267%, 35.615% and12.846%, respectively. The accumulative variance contribution rate of three principle components extracted from nine origin indices reached 86.728%, illustrating that the three principal components reflected the most parts of the original variables. The first factor reflected total soluble solid, soluble sugar, vitamin C, and total sugar; the second factor titratable acidity, RTT, and pH; and the third the total phenols and total flavonoids. The comprehensive evaluation function was F=0.38267×F1+0.35615×F2+0.12846×F3. The comprehensive quality evaluation model of citrus was constructed using the proportion of the eigenvalues corresponding to the three principal components and the sum of the extracted principal components' eigenvalues, which was used for screening citrus varieties suitable for making juice. The top 5 were Citrus Sinensis Osbeck, ‘Newhall Navel', Citrus Suavissima, Ponkan and Satsuma Mandarin.【Conclusion】The 19 citrus varieties could be divided into three categories. Citrus Sinensis Osbeck, ‘Newhall Navel'and Citrus Suavissima had the high grades.‘No. II Li Png', Satsuma Mandarin, ‘Red Sene', ‘Cocktail Citrus Paradisi'and‘Aliquam Zhongyu'were intermediate. Through this evaluation, citrus varieties with high nutritional value and good flavor and taste can be selected conveniently. At the same time, the pulp recovery, juice recovery and other factors provide an intuitive evaluation of citrus quality and provide a reference for selecting suitable raw material varieties for juice processing.