(47) Nippon Shokuhin Kogyo Gakkaishi Vol. 34, No. 2, 115～122 (1987) 〔Article〕 115 Changes in the Composition and Amounts of Volatile Compounds of Apple Juice Associated with Thermal Processing Norio KAKIUCHI*,Sanae MORIGUCHI*,Nobutomo ICHIMURA**, Yutaka KATO** and YoshiakiBANBA** * FruitTree Research Station , Fujimoto,Yatabe-machi, Ibaraki 305 ** Food Laboratory, Soda AromaticCo., Ltd, Noda-shi Chiba 270-02 Studies were undertaken to analyse the changes in the composition and concentration of volatile compounds after thermal processing of apple juice and to evaluate the suitability for processing of five main cultivars in Japan. Juice yield of the cultivars examined ranged from 65.7% in 'Kogyoku' to 77.2% in 'Hatsuaki' throughout the processing. Seventy to 80 kinds of volatile compounds were detected in chromatographic peaks of which 39 compounds were identified by gas chromatograph- mass spectrometry. The compounds of each class included 27 kinds of esters, 6 of alcohols, 2 of aldehydes, 2 of hydrocarbons, a phenol and an acid. Average percentage of retention of each class of volatile compounds of the five cultivars was highest, 71.9%, for the alcohols, followed by 50.7% for the esters and 30.5% for the aldehydes. Total amounts of volatile compounds recovered after thermal processing were highest in the cultivar 'Kogyoku' amounting to 7.58ppm followed by 'Ha- tsuaki' with 5.83ppm, 'Mutsu' 3.20ppm, 'Golden・Delicious' 1.44ppm and lastly 'Fuji' with 1.41 ppm. From these results, it was apparent that the higher concentration of volatile compounds in the juice of cultivar 'Kogyoku' and related cultivar 'Hatsuaki' after thermal processing, accounted the higher suitability of juice making of these cultivars. The quality of apple juice depends on the selected on the basis of their genetical and flavour characteristics of the raw materials breeding characteristics. which vary conspicuously with the cultivar. Materials and Methods A large number of investigations has been car- ried out on the volatile compounds of apple Fruit materials fruit, as it is a very important factor of con- Apple from five cultivars 'Hatsuaki' (Picking tributing the quality of fresh fruit1)～8) and date Sept. 26th 1983), 'Kogyoku' (Oct. 17th), 'Golden ・Delicious' (Oct processed products3)9)11). 27th), 'Mutsu' (Oct. In previous reports the authors already out- 31st) and 'Fuji' (Nov. 5th) were sampled in lined the differences of the volatile compounds the orchard of the Morioka Branch of the Na- depending on the cultivars in studies dealing tional Fruit Tree Research Station in Morioka with the fresh fruits of five apple cultivars Prefecture. including 'Kogyoku' and 'Hatuaki' which con- Twenty three kilograms of fruits of each tained a large amount of volatile compounds10). cultivar were used for the chemical analysis However, to define the quality of apple juice, of fresh fruits (5kg) and processing of juice it is important to analyse the changes in flavour (18kg) within 10 days after harvest. which may occur during the thermal proces- Apple juice processing sing of juice. The changes in the flavour of Apple juice was processed according to the apple juice associated with thermal processing flow sheet illustrated in Figure 1. A quantity have been reported only in a few cultivars3)11). of 18kg of fruits was divided into two sam- The present study was undertaken to analyse ples, weighing 2kg and 16kg respectively. the changes in the flavour and processing After washing, juice containing ascorbic acid suitability of unclarified apple juice associated and sodium chloride was prepared from the 2 with heat pasteurization in five main cultivars kg fruit sample by a hand juicer. The fruits 116 日本 食 品 工業 学 会誌 第34巻 第2号 1987年2月 (48) Fig. 1 Flow sheet of apple julce production from the 16kg sample were cut into 1/8 to 30 sec at 93℃, hot-packed in No. 4 tin cans 1/16 sections, trimmed and the core was (net wt. 430g) and cooled with tap water. removed. The fruit flesh which had been The canned samples were stored at a tem- sectioned was macerated with a micronizer perature of 5℃ until analysis. (Model MSC-50, Kokusanseiko Co., Ltd.), in Quality determination of fresh and pas- adding a small quantity of juice containing teurized juice ascorbic acid and sodium chloride continuously Fruit firmness was measured on the peeled to prevent the discoloration due to enzymatic portion of the blush and green sides of the oxidation during processing. Juice was ex- apple with a Magness-Taylor pressure tester tracted with a screw press (Model JX-100× with a tip penetration of 7/16-in. in diameter, 300, Seikensha Co., Ltd.) and passed through and a 0～30 Lb scale. The amount of soluble a 150 mesh filter to obtain unclarified natural solids of the juice were determined by Brix juice. After homogenization with a high pres- degree checked with a hand refractometer. sure homogenizer (Model H-10, Kokusanseiko Titratable acidity expressed as percent of malic Co., Ltd.), the juice was heat-pasteurized for acid was determined with 0.1N NaOH to the (49) KAKIUCHI et al.: Changes of Apple Flavour Associated with Thermal Processing 117 phenolphthalein end point. Pulp content by with FID detector and using 50m×0.25mm volume was determined by centrifuging the fused silica capillary columns coated with FFAP particles from pasteurized juice with a conical (WCOT Gaschro Ind Co., Ltd.). The instru- tube at 3000rpm for 10min. Viscosity was ment was operated at a nitrogen flow of 0.8 measured using a viscosimeter (Model B-8 L, ml/min and the oven temperature of the co- Tokyo-Keiki Co., Ltd.) The color of the juice lumn ranged from 70° to 200℃ at the rate of was tested by using a Hunter color difference 3℃/min with a sample size of 0.1μl. meter (Model SM 4-2, Suga Test Instrument A Hewlett Packard 5992 B GC-MS system Co., Ltd.). scanning at 70 eV was used to record mass Determination of volatile compounds spectra data. The columns were similar to A modification of the high vacuum distilla- those employed for analytical gas chromato- tion method10) developed previously by KATA- graphy. After an initial isothermal period of YAMA et al3) was applied in this experiment. 3min, the column was programed from 100° In case of fresh fruit, 7 or 9 apples were used to 200℃ at a rate of increase of 5℃/min. The for flavour analysis. Each fruit was cut into contents of volatile substances were expressed quarters and cored to obtain the fruit flesh in ppm for the weight of fresh fruit and pas- with the peel. Two kilograms of these ma- teurized juice. Authentic samples were ob- terials were homogenized with 400ml water tained for all the compounds which had been containing 20g of NaCl under cooled condi- detected in the apple volatile compounds and tions to prevent the deterioration due to enzy- had been identified based on retention time matic activity. In the case of pasteurized juice and mass spectrum determinations. (4 cans of 430g net wt.) was used for analy- Results and Discussion sis within two months under storage at 5℃. The fruit homogenate or pasteurized juice Quality characteristics of fresh fruit and was poured into a 5l flask as described in the pasteurized juice previous report10). The flask was attached to Table 1 shows the physical and chemical a set of four cold traps connected to a vacuum properties of fresh fruit and pasteurized juice. pump. The volatile compounds were distilled Fruit weight varied with the cultivars, ranging off under the reduced pressure of 0.1～0.2mm from 207g in 'Kogyoku' to 400g in 'Mutsu'. Hg at the temperature of 35℃ for 6 hours. Magness-Taylor firmness of fruit material Cold trap condensate containing water was showed a high value of 15 pound or more in- collected together, the apparatus was rinsed dicating that the freshness of the fruit has with 100ml of ethyl ether and the two solu- been well maintained. Soluble solid contents tions were mixed. The ethyl ether solution of pasteurized juice ranged from 11.0° to 13.4° was salted out by 200g of sodium chloride, Brix, and the acid contents also ranged from and the water phase was washed three times 0.41 to 0.58% except for the cultivar 'Ko- with ethyl ether (200ml). This solution was gyoku' which showed a higher value of 0.88 added to the original ether solution to obtain %. Juice yield of the cultivars ranged from 300ml of extracting solution for the volatile 65.7% in 'Kogyoku' to 77.2% in 'Hatsuaki' compounds. throughout the processing. The ether extract was dehydrated with 30g Pasteurized juice passed through a 150 mesh of magnesium sulfate. After filtration of this filter contained about 0.4～1.3% of pulp ex- solution, ethyl ether was evaporated by a rotary cept for the cultivar 'Golden・Delicious' which evaporator to obtain the volatile compound as showed a higher value. This higher value of a residue under a low temperature. The res- pulp content in 'Golden・Delicious' was attrib- idue was dissolved into 300μl of n-hexane uted to the fact that the fruit flesh could be containing an internal standard of butyl ben- smashed easily as the flesh was very mealy and zene and analysed by gas chromatography. fine. Juice viscosity was low in the early Gas chromatagraphic data were obtained maturing cultivar 'Hatsuaki' compared to the using a Shimadzu GC-9 A gas chromatograph other 4 cultivars. 118 日本 食 品 工業 学 会誌 第34巻 第2号 1987年2月 (50) Table 1 Physical and chemical properties of fresh fruit and pasteurized juice The juice of all the cultivars showed a deep It was interesting to note that the tota yellow color and it was difficult to discriminate amount of volatile compounds was most abun- visually the color tone.