JOURNAL OF THE SCIENTIFIC AGRICULTURAL SOCIETY OF FINLAND Maataloustieteellinen Aikakauskirja Voi. 47: 445—453, 1975 Chemical and organoleptic evaluation of some Finnish apple varieties Kerttu Voho 1) and Pertti Varo Institute of Food Chemistry and Technology, University of Helsinki Abstract. Chemical and organoleptic analyses were carried out on ten important locally grown apple varieties. Most of the varieties were characterized by high titratable acidity and fairly low total sugar concentration. Consequently the sugar-to-acid ratio (a suggested indicator of the eating quality of apples) remained low. However, some of the varieties with high acidity (Red Atlas, Raike) were scored high in the preference test, confirming that other factors in addition to the sugar-to-acid ratio have an influence on the palatability of apple juices. Generally it seems that juice from most of the studied varieties should be mixed with low acid, high sugar juices to be suitable for commerical juice production. The quality of apple products is dependent on several factors, e.g. variety, maturity, and length of storage time of the apples. Each variety has an optimum harvest time as well as storage period to develop the best quality for any intended use. For instance the aroma characteristics and the yield of juice, among other properties, can be influenced greatly by harvest and storage practices. Several extensive studies have been made on the chemical composition of apples and apple varieties (Lopetz et al. 1958, Kochan 1968, Bradley and Brown 1969, Holfelder and Eid 1970, Mohr and Adair 1970). However, the results of these investigations may not be applicable as such when consid- ering the chemical composition of apples grown in Finland since many of the commercially grown apple varieties are of local origin. Moreover, the unique weather and growing conditions of the country may be reflected in the chemical composition of apples. Since all varieties are not equally suitable for industrial use (e.g. Rotstein et al. 1969) ten locally important apple varieties (Melba, Charlottenthal, Red Atlas, Antonovka, Raike, Snygg, Erstaa, Kaneli, Lobo, and Äkerö) were screened chemically and organoleptically to find suitable cultivars for apple J) Present address; Chymos Oy, Lappeenranta. https://www.c-info.fi/en/info/?token=QOPGbkYS5SxkVOJC.qxLYz1_XoWc2dCMjKzdvcA.qvwNYkdiQxfi1keVc37bIE9AjNX10EQzrYvh45LlptzyPBZoEdeCtRfA9NDH-EIOn6nSGmXJVEo8bTRB2K00ST9b92YDfTH7abaBhgmYcHxtDlL4fmOOQQbJhhZ5xLwqAj131eYbU7U2AzKetHoIfLQeOc73j0xG8_wGqAFr-pfnySYzA-NRTrc 446 Table 1. Apple varieties, growing locations, dates of harvest, and storage periods. Growing Date of Storage period. Additional ar 'et' location harvest 1972 weeks information Snygg Kangasala Sept. 5 3 Summer variety Erstaa Kangasala Sept. 5 6 »Berry apple* Melba Lohja Sept. 6 7 Fall variety Charlottenthal Lohja Sept, 6 5 Summer variety Kaneli Kirkkonummi Sept. 11 6 Fall variety Äkerö Kirkkonummi Sept. 11 12 Winter variety Raike Piikkiö Sept. 13 4 Winter variety, novelty Red Atlas Lielahti Sept. 14 12 Winter variety Lobo Kirkkonummi Sept. 24 9 Winter variety Antonovka Lohja Sept. 27 12 Winter variety juice production. The first five varieties in the list were evaluated chemically in greater detail than the others. Similar local studies have been made on a few other varieties (Kuusi and Pajunen 1971). Materials and methods Harvest dates and growing locations of the apple varieties studied in this investigation are given in Table 1. The influence of increased storage time on the following chemical factors was determined: pH (Official methods of analysis of AOAC 1970) sugars (Schoorl and Regenbogen 1935) soluble solids (Official methods of analysis of AOAC 1970) titratable total acids as malic acid (Official methods of analysis of AOAC 1970) starch (Stoll 1969, Dubois et al. 1956) phenols (Swain and Hillis 1959) pectines as Ca pectate (Ruck 1963) dry matter (72 hours at 70° C under vacuum) ash (24 hours at 450° C) mineral elements K, Ca, Mg, and Mn by atomic absorption spectrophotometry (Hulme et al. 1958, Perring 1964, Analytical methods for AAS 1966). Instrument: Perkin-Elmer 303. The storage conditions were: temperature 5 Q C, and relative humidity 73-78 %. The samples for chemical analyses were taken immediately after the apples were received from the orchards, and later at intervals of 2—3 weeks from 2 to 4 times depending on the variety. The apples were washed and rinsed in distilled water, and the endocarps and stalks were removed. For one sample 20 apples were divided into sectors, part of which (300 g) were deep frozen in polyethylene bags until analyzed. For the determination of sugars and phenolic constituents 200 g of apple slices were homogenized and extracted with 80 % ethanol (Salminen et ai. 1969). Soluble solids, titratable total acids, and pH were determined from the juice pressed in connection with the organoleptic analyses. 447 The sugar-to-acid ratio of the apples was computed as the ratio of soluble solids and total acids as malic acid. Juice for the organoleptic analysis was pressed with a Bucher-Guyer juice press. Samples (three parallels) were taken at intervals of 1 to 3 weeks depend- ing on the variety. The size of the samples was 6 8 kg. The apples were rinsed with cold water before crushing. The juice samples were deep frozen in one liter plastic bottles until analyzed. The organoleptic quality of the apple juices was analyzed by a trained panel of 10 members. In the evaluation of juice quality three methods were used (Amerine and Pangborn 1965): 1. The storage time after which the taste of juice differs from that of non- stored apple juice was estimated by the triangle test. 2. The optimum storage time of each variety to develop the best apple flavor and the highest preference was tested with the ranking method. 3. The best juices of the varieties (according to the ranking test) were scored for their sourness, sweetness and preference using the scoring test (hedonic scale). All tests were repeated. Results The gross chemical compositions of the ten apple varieties after different storage periods are given in Table 2. The varieties Melba, Charlottenthal, Raike, Antonovka, and Red Atlas were subjected to a more detailed chemical evaluation. These results are given in Table 3. It is seen that the values of total acids and starch decrease, while pH and the sugar-to-acid ratio increase with the increasing storage time. With sugars the changes are less pronounced, and all other values seem to remain more or less constant. Juice recovery from the different apple varieties is given in Table 4. The recovery was at its maximum at the time of harvesting and decreased rapidly in the early varieties (Snygg, Charlottenthal, Melba) and more slowly in the late varieties (Äkerö, Antonovka.) The results of the triangle test are summarized in Table 5. It is seen that the taste of juice from the early varieties changed significantly from the stan- dard (O-storage juice) in 23 weeks, while that of the late varieties changed more slowly. With the ranking test it was found that the apple aroma in the varieties Lobo and Äkerö was significantly weaker at the time of harvesting than in the stored apples. No other significant differences in aroma were found. The preference did not change significantly with an increasing time of storage of the varieties Melba and Erstaa. In the other varieties significant differences were found in preference, and the results are summarized in Table 6. Accord- ing to the results the optimum storage period for winter varieties was about three weeks, with the exception of Antonovka for which it was 9 weeks. For early varieties the storage period should be no longer than 2 weeks. Table 2. Gross chemical composition of some Finnish apple varieties. Storage time. Total Solube Sugar- to-acid \arict\ weeks acids % solids % ratio Melba 0 0.78 3.29 11.5 14,7 1 0.73 3,36 12.1 16.6 3 0.65 3.37 12.3 19.1 5 0.63 3.50 12.3 19.7 7 0.60 3.43 12.6 21.1 Charlottenthal 0 1.35 3,03 9.8 7.3 1 1.32 3.05 9.5 7.2 3 1.33 3.04 9.3 7.0 5 1.18 3.17 9.3 7.9 Raike 0 1.01 3.19 11.2 11.1 2 0.88 3.15 11.5 13.1 4 0.81 3.15 11.2 13.8 Antonovka 0 1.33 2.95 11.8 8.9 3 1.28 2.97 11.9 9.3 6 1.20 2.97 11.1 9.2 9 1.02 3.12 11.4 11.1 12 0.86 3.14 11.2 13.0 Red Atlas 0 1.19 3.08 12,8 10.8 3 1.17 3.06 13.1 11.2 6 1.04 3.19 12.9 12.4 9 0.87 3.25 12.4 14.2 12 0.76 3.34 12.3 16.2 Snygg 0 0.75 3.37 10.0 13.1 1 0.74 3.35 9.3 12.6 3 0.70 3.29 9.6 13.8 Kaneli 0 0.65 3.32 10.0 15.3 2 0.63 3,36 10.9 17.5 4 0.61 3.35 10.4 17.0 6 0.59 3.54 10.7 18,2 Lobo . 0 0.57 3.35 11.4 20.0 3 0.55 3.42 11.5 20.6 6 0.50 3.65 11.7 23.3 9 0.40 3.63 10.3 25.6 Äkerö 0 0.80 3.27 11.1 13.9 3 0.69 3.35 12.5 18.1 6 0.66 3.45 12.6 19.2 9 0.58 3.45 12.3 21.3 12 0.55 3.50 11.8 21.6 Erstaa 0 1.15 3.27 12.3 10.7 2 1.10 3.22 12.6 10.2 4 1.10 3.34 12.3 11.2 6 1.11 3.34 12.7 11.4 448 Table 3. Additional chemical analyses on the varieties Melba, Charlottenthal, Raike, Antonovka, and Red Atlas. Variety/Storage time in weeks Melba Charlottenthal Raike 01357 0135 024 Sugars, total % 7.67 8.09 8.36 8.64 8.65 5.67 5.55 4.60 4.98 7.07 7.71 7.79 reducing % ... 5.93 6.34 6.28 6,46 6.94 4.65 4.68 4.02 4.50 4.48 4.78 5.06 Starch % 0.46 0.35 0.35 0.29 0.27 0.31 0.20 0.35 0.28 0.46 0.26 0.19 Ca pectate % 0.65 0,59 0,63 0.69 0.69 0.61 0.61 0.66 0.64 0.65 0.62 0.52 Phenols % 0.20 0.25 0.22 0.30 0.31 0.19 0.18 0.18 0.18 0.16 0.13 0.12 Dry matter % 11.7 11.9 11.6 13.0 12.5 9.7 10.2 9.1 9.5 11,3 11.8 11.8 Ash % 0.24 0.24 0.24 0.23 0.26 0.23 0.24 0.25 0.26 0.25 0.27 0.28 Mineral elem. mg% K 105 97 106 98 105 97 99 111 108 123 115 112 Ca 4.9 4.6 4.2 4.2 4.1 3.5 4.1 3.8 4.0 4.1 3.8 3.9 Mg 4.8 4.9 4.4 4.5 4.9 5.0 4,8 4.8 5.2 4.0 4.4 4.0 Mn 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0,02 0.03 0.02 0.02 0.02 Antonovka Red Atlas 0369 12 0369 12 Sugars, total % 8.16 7.83 7.06 7.15 7.07 8.86 8.75 8,64 8.41 8,56 reducing % .... 5.29 5.69 5.98 6.37 6.36 4.98 6.03 6.53 6.03 6.48 Starch % 0.50 0,27 0.25 0.26 0.30 0.59 0.42 0.34 0.34 0.37 Ca pectate % 0.73 0.72 0.61 0.70 0.71 0.69 0.63 0.72 0.68 0.71 Phenols % 0.13 0.16 0.18 0.16 0.17 0,20 0.18 0.19 0.19 0.19 Dry ma ter % 12.5 12.3 11.5 11.5 11.6 13.3 13.2 13.0 12.8 13.1 Ash % 0.27 0.26 0.25 0.25 0.25 0.26 0.26 0.27 0.27 0.26 Mineral elem. mg % K 96 99 93 101 103 120 122 115 124 125 Ca 2.7 2.5 3.1 2.9 3.2 3.1 3.5 3.5 4.5 3.7 Mg 4,7 4.7 4.8 5.2 5.0 4.4 4,8 5.2 4.5 4.6 Mn 0.02 0.02 0.01 0.20 0.02 0.02 0.03 0,03 0.02 0.03 Table 4. Juice recovery (%) of some Finnish apple varieties with increasing time of storage. Storage period, weeks Variety 01 2345679 12 Melba 76.0 64.3 - 65.8 - 61.8 - 52.6 - Charlottenthal 75.5 75.2 - 68.2 - 59.0 - - - Snygg 64.7 56.1 - 49.9 ______ Erstaa 73.2 - 73.7 - 66.1 - 65.6 - _ _ Kaneli 76.5 — 71.5 - 69.1 - 56.5 _ _ _ Raike 1) 76.1 - 79.5 - 79,4 _____ Lobo 74,0 - - 72.6 — - 56.0 — 46.5 - Akerö 74.0 - — 73.1 - - 71.2 — 66.3 55.8 Red Atlas 74.3 - - 66.0 — — 53.1 — 51.1 — Antonovka 76.2 — — 74.4 — — 61.0 — 58.6 50.4 *) Juice pressed with a Braun juice centrifuge 449 450 Table 5, Appearance of significant changes in taste with increasing storage time. Storage time Significance of change \ ariet\ weeks in taste1) Kaneli 2 *** Melba, Erstaa 2 • Melba, Äkerö, Lobo, Snygg 3 Charlottenthal, Antonovka 3 • Charlottenthal 5 *** Antonovka 6 **• Red Atlas 6 •• Red Atlas 9 *»* * P< 0.05 ** P< 0.01 ••• P< 0.001 *) Compared to juice from O-storage apples Table 6. Significant differences in the preference of juices within each variety Storage time Preference Variety weeks liked not liked Snygg 3 - * Charlottenthal 5 ** Kaneli 4 ** Äkerö 0 ** Äkerö 3 ** Antonovka 3 ** Antonovka 9 •• Lobo 3 »* Red Atlas 3 • * P< 0.05 ** P< 0.01 The different varieties were also scored with each other. A commercial product was used as standard. The scores were brought on the same scale by equalizing the scores of the standard. The stronger the quality tested the higher the score (maximum score for sourness was 4, for sweetness and prefer- ence 5). The results (Table 7) show that apples of low sourness and high sweetness are considered best (Raike, Äkerö, Lobo, Kaneli). The commercial products were not liked. This may be due to the changes in apple aroma caused by sterilization. Discussion The best chemical estimates for the quality of taste are the total sugar content and the sugar-to-acid ratio (Daepp 1970). The titratable acid contents of the studied varieties are high compared to some reported values (e.g. Vestr- heim 1971). As a consequence the sugar-to-acid ratios remain fairly low Table 7. Sourness, sweetness and preference scores of juices from different apple varieties1 ) Sourness 2 ) Sweetness3) Preference 4) Variety mean range mean range mean range Melba 1.7 1-3 2.5 2-3 2.9 2-4 Charlottenthal 4.1 3.5-4.5 1.6 1-2 1.9 1-3 Snygg 1.8 1-3 2.5 1-3 2.8 1-4 Erstaa 3.2 2-4 1.8 1-3 1.8 1-3 Kaneli 1.2 1-2 3.3 3-5 3.3 2-5 Red Atlas 2.3 1-3 3.2 2-4 3.1 2-4 Lobo 1.0 1 4.4 3-5 3.7 2-5 Akerö 1.5 1-3 3.7 2-5 3,7 1-5 Antonovka 3.2 1.5-4.5 2.3 1-3 2.9 1-4 Kaike 2.1 1.5-3.5 3.4 3-4 3.8 2-5 Commercial juice A 6) 2.9 2—4 2.5 1—4 2.2 1 4 Commercial juice B ... 2.5 1.5 3.5 2,9 2 4 1.9 1—3 b Juices ranked highest in the ranking test 2) 1 = weakly sour, 4 = very sour 3) 1 = weakly sweet, 5 = very sweet 4) 1 = not liked, 5 = liked very much 5) Standard although they reach acceptable values (10—25) during storage in most cases. Also the sugar content of the Finnish apple varieties is comparatively low. The correlations between the organoleptic and some chemical characteristics are given in Table 8. It shows that there is a high correlation between sugar- to-acid ratio and preference, while soluble solids (a measure of sugar content) and preference show no correlation. On the other hand, total acids and pref- erence show a fairly high negative correlation. There were exceptions from the general line in the case of Raike and Red Atlas. Juice from these apples was scored high in the preference test even though the acidity was high (Raike 0.88 % and Red Atlas 1.07 %) and the sugar-to-acid ratio low (Raike 13.0 and Red Atlas 11.4). The juice from these varieties has a strong, pleasant apple aroma, which may well account for their preference. This shows that the sugar-to-acid ratio alone is not a reliable measure of the organoleptic quality. The processing qualities and the juice yield of Antonovka in particular, but also of Äkerö and Red Atlas, are suitable for industrial juice production. However, these varieties show a fairly high acidity (Antonovka also feeble Table 8. Correlations between organoleptic and some chemical analyses. Chemical analysis Organoleptic analysis Correlation Total acids % x sourness 0.93 Soluble solids % x sweetness 0.34 Sugar-to-acid ratio x preference 0.70 Total acids % x preference —0.43 Soluble solids % x preference —O.Ol 451 452 aroma qualities), and alone they will not yield palatable juices. Of the studied varieties only Lobo has, in addition to reasonable processing qualities, a high enough sugar content and a low enough acidity to be suitable for mixing as a taste softener with high acidity juices. Acknowledgements. This study was assisted financially by the Finnish National Research Council for Agriculture and Forestry. The apple material was kindly provided by Ahtiala Orchards, Kirkniemi; Pikkola Orchards, Kangasala; Rilaksholm Orchards, Kirkkonummi; Markola Orchards, Lielahti; Institute of Horticultural Research, Piikkiö. REFERENCES Amerine, M. A., Pangborn, R. M. & Roessler, E. B. 1965. Principles of sensory evaluation of food. Academic Press, New York. Analytical method for atomic absorption spectrophotometry, 1966. Perkin-Elmer Corp., Norwalk, Connecticut, USA, Bradley, B. F. & Brown, B. I. 1969. Influence of maturity and storage of Granny Smith apples at ambient temperature on the quality of canned apple juice. Food Technol. Aust. 21: 212, 213, 215, 217. Daepp, H. V. 1970. Beitrag zur analytischen und sensorischen Qualitäts-Bestimmung von Apfelsäften, Horgen. Dubois, M., Gilles, K, A., Hamilton, J. K,, Rebers, P. A. & Smith, F. 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem. 28: 350 356. Holfelder, E. & Eid, K. The quality of 1-variety apple juice produced from dessert apples not suitable for marketing in a fresh state. Fliissiges Obst 37: 302 305. Hulme, A. C. & Wooltorton, L. S. C. J. 1958. Determination of the nonvolatile acids of pome fruits and a study of acid changes in apples during storage. J. Sci. Food Agric. 9: 150. Kochan, A. 1968. Evaluation of optimal quality of apple juice. Fliissiges Obst 35: 514 518. Kuusi, T. & Pajunen, E. 1971. Less grown apple varieties in juice production and the influence of polyphenols and added ascorbic acid on the juice quality. J. Sci. Agric. Soc. Finl. 43: 20-26. Lopetz, A., Fellers, P. J., Wood, C. B. & Johnson, J. M. 1958. Composition of ten processing and table varieties of Virginia apples. Food Res. 23:492—504. Mohr, W. P. & Adair, R. G. 1970. Processing qualities of apple varieties and selections. Canada Dept. Agric. Pubi. 1424, 19 p. Official methods of analysis of the association of official analytical chemists: 1970. 11th edit. 1015 pp. Washington, DC. Peering, M. A. 1964. Mineral composition of apples. I. Introduction, sampling methods and ashing techniques. 11. Analytical methods. J. Sci. Food Agric. 15: 739—752, 752 759. Rotstein, E., Namor, M. S. S., Sica, M. & Amand, J. 1969. Apples from Argentina: Chemical and physical characteristics useful for technology. J. Milk Food Technol. 32: 79—89. Ruck, J. A. 1963. Chemical methods for analysis of fruit and vegetable products. Canada Dept. Agric. Res. Branck. Pubi. 1154. Salminen, K. & Koivistoinen, P. 1969. A scheme for the simultaneous quantitative determination of free amino acids, organic non-amino acids, sugars, nitrogen and pectic substances in plant materials. Acta Chem. Scand. 23: 999 1006. Schoorl, N. & Regenbogen, A. 1935. Zuckerbestimmung durch indirekte Titration des Kupfer iiber Schusses. Handb, Lebensm. Chem. 2: 866, Berlin. Stull, U, 1969. Starch content and starch changes in apples. Mitt. Geb. Lebensmittels u. Hyg. 60:257-259. Swain, T. & Hillis, W. E. 1959, Phenolic constituent of Prunus domestica. I. Quantitative analysis of phenolic constituents. J. Sci. P'ood Agr. 10: 63 68. Vestrheim, S. 1971. Apple constituents as affected by time of harvest. Meld. Norges Landbr. högsk. 50: 5. 453 Selostus Eräiden suomalaisten omenalajikkeiden kemiallinen ja aistinvarainen laatututkimus Kerttu Voho ja Pertti Varo Helsingin yliopisto, Elintarvikekemian ja -teknologianlaitos, Viikki Kymmenen kotimaista omenalajiketta (Melba, Charlottenthal, pun. Atlas, Antonovka, Raike, Snygg, Erstaa, Kaneli, Lobo ja Äkerö) analysoitiin kemiallisesti ja aistinvaraisesti tarkoi- tuksena löytää sopivia lajikkeita teolliseen tuoremehun valmistukseen. Tutkituille lajikkeille tunnusomaista oli yleensä korkea tiirattava happoisuus sekä suhteellisen alhainen sokeripitoi- suus. Tästä syystä myös sokeri-happosuhde, jota on pidetty parhaana omenan makuominai- suuksia kuvaavana kemiallisena kriteerinä, jäi alhaiseksi. Toisaalta aistinvaraisessa tutkimuk- sessa arvostettiin varsin korkealle joitakin sellaisia lajikkeita (pun. Atlas, Raike; kummallakin voimakas hedelmäinen aromi), joiden sokeri-happosuhde oli alhainen. Tämä vahvistaa käsi- tystä, ettei ko. suhde yksinään anna riittävän luotettavaa kuvaa omenan makuominaisuuk- sista. Prosessointiominaisuuksiensa ja mehusaaliinsa puolesta erityisesti Antonovka, mutta myös Äkerö ja pun. Atlas soveltuisivat hyvin teolliseen tuoremehun valmistukseen. Nämä lajikkeet ovat suhteellisen happamia (Antonovka myös heikkoarominen). ja siten yksinään käytettyinä liian voimakkaan makuisia maittavan mehun raaka-aineeksi. Tutkituista lajikkeista ainoas- taan Lobo, joka prosessointiominaisuuksiltaan on tyydyttävä, on riittävän sokeripitoinen ja vähähappoinen soveltuakseen käytettäväksi seoksena happamien mehujen kanssa maun peh- mentäjänä.