2007 vol. 66, 197-203 DOI: 10.2478/v10032-007-0022-8 ________________________________________________________________________________________ INFLUENCE OF CULTIVAR AND STORAGE TIME ON THE CONTENT OF HIGHER FATTY ACIDS IN APPLE CUTICLE Marjan SIMČIČ, Melita KADUNC, Janez HRIBAR, Rajko VIDRIH Biotechnical Faculty, Dep. of Food Science and Technology University of Ljubljana Jamnikarjeva 101, 1000 Ljubljana, Slovenia Summary The main objective was to determine the fatty acid composition on the sur- face of apple peel and in seeds. 7 apple cultivars were used: Elstar, Fuji, Glo- ster, Idared, Jonagold, Pink Lady and Golden Delicious. Apple seeds contain from 8.4% to 15% of water and from 17.1% to 28.0% (f.w.) of fat. The fatty acid content in seeds ranged as follows: linoleic (55.9-62.3), oleic (23.9- 30.7%), palmitic (7.1-9.3%), stearic (1.6-2.3%), arachidic (1.2-1.6%), linolenic (0.4-0.7%. Linolic acid is prevalent fatty acid on peel as well. Ratio of linolenic acid on peel is up to 30 fold higher than in seeds. Saturated palmitic and stearic fatty acid ratio is considerably higher in peel than in seeds while is the ratio of oleic acid nearly the same as in seeds. During storage of apples the ratio of pal- mitic and oleic acid increases, while ratio of linoleic acid considerably de- creases. key words: apples, higher fatty acids, peel, seeds INTRODUCTION As far as apples are concerned fatty acids are present in seeds and in much lower concentration also on the upper part of peel. Fatty acids in apple seeds are either esterified with glycerol or are present as free fatty acids (Lu & Foo 1997). Fruits in general are coated with layers of lipids that are involved in the protection of fruits toward atmosphere conditions. Protection layers serve to adapt the fruit to the extreme temperatures and other stress conditions which in fruit may lead to different storage disorders (Marangoni et al. 1996, Saquet et al. 2000). Fatty acids build up in developing and ripening apples especially during climacteric respiratory rise. After the respiratory rise, fatty acids begin to decline and are metabolised to various lipid fractions (Meigh & Hulme 1965). On the other hand fatty acids are known to act as precursors of aroma volatile production (Fellman et al. 2000, Harb et al. 2000). Corresponding author e-mail: [email protected] © Copyright by RIVC 198 VEGETABLE CROPS RESEARCH BULLETIN 66 _____________________________________________________________________________________________________ Little is known about the role of higher fatty acids in scald appearance. Higher fatty acids are present on the skin either as free or in wax. Chemically is wax esterified with alcohol (Nelson & Cox 2000) and has a function to protect the fruit against environmental factors (Morice & Shortland 1973). Biosynthesis of waxes starts in plastids, the fatty acids are later elongated (Kunst & Samuels 2002). Typical characteristics of waxes depend on cultivar and climatological conditions like rainfall and temperature (Veraverbecke et al. 2001). Waxes not only protect the fruit in the outside, but play some protective role during fruit storage as well. During storage, waxes have a protective role against water loss while their composition is changing. Content of free fatty acids present on apple skin are changing during stor- age period (Morice & Shortland 1973). Total free fatty acids insoluble in petrol ether increased slightly during storage On the other hand, total free fatty acids soluble in petrol ether did not change significantly (Morice & Shortland 1973). Content of linolenic acid on the peel of cv. Granny smith increased signifi- cantly during storage (Morice & Shortland 1973). MATERIAL AND METHODS Fatty acid composition was analysed in seeds and on the surface of seven apple cultivars (Elstar, Fuji, Gloster, Idared, Jonagold, Pink Lady and Golden Delicious) immediately after harvest or after 3 months of staorage at +1°C. Fatty acids in seeds were analysed according to the method described by Garces & Mancha (1993). Methyl esters of fatty acids (palmitic C 16 : 0; stearic C 18 : 0; oleic C 18 :1; linolic C 18 : 2; linolenic C 18 : 3 and arachidic C 20 : 0) were analysed on GC and peaks were recorded. Content of fatty acids on apple peel was analysed in hexane extract of apple surface. 5 apples were washed with 300 ml of hexane for 2 minutes. The volume of hexane was evaporated to 50 ml. Three ml of hexane extract were used to determine the fatty acid composi- tion on apple peel according to the method described by Garces & Mancha (1993). GC: Agilent technologies 6890N; Column: SUPELCO – SPB PUFA; 30 m x 0.25 mm x 0.2 μm; Detector: FID; Column temperature: 210°C; Detec- tor temperature: 260°C; Injector temperature: 250°C (split 1: 100); Carrier gas: He 1 mL·min-1; Injection volume: 1.0 μL. RESULTS Content of total fats in apple seeds varies from 17 to 28%, Golden Deli- cious has the highest content and Jonagold the lowest (Table 1). Compared to other fruit seeds, apple seeds have lower content of total fats. Linolic acid is the prevalent higher fatty acid in apple seeds of all cultivars investigated. Apple seeds contain from 55 to 62% of linolic acid. Its content is cultivar dependent, the highest ratio was found in Jonagold, the lowest in Glo- ster (Table 2). M.SIMCIC et al. – INFLUENCE OF CULTIVAR AND STORAGE ... 199 _____________________________________________________________________________________________________ Table 1. Fruit firmness (kg) at harvest and after storage and content of total fats in apple seeds at harvest (% in dry matter) Firmness (kg) cultivar At harvest After storage Total fats (%) in dry matter Elstar 6.7 3.8 20.4 Jonagold 7.6 4.9 17.1 Golden Delicious 7.5 4.3 28.0 Gloster 8.2 5.8 26.3 Idared 7.0 4.7 22.9 Fuji 7.5 6.7 25.8 Pink Lady 8.9 8.4 23.7 Table 2. Fatty acid composition of apple seeds (as % of total fatty acids) Cultivar C 16 : 0 C 18 : 0 C 18 :1 C 18 : 2 C 18 : 3 C 20 : 0 Elstar 7.47 2.24 30.75 57.37 0.61 1.56 Jonagold 9.32 1.63 24.48 62.27 0.70 1.16 Golden 7.53 2.26 30.00 58.25 0.44 1.51 Gloster 7.37 1.84 32.93 55.94 0.64 1.27 Idared 7.85 1.77 29.65 58.90 0.52 1.31 Fuji 7.15 1.85 30.63 58.46 0.51 1.40 Pink Lady 7.35 2.15 28.17 60.31 0.52 1.50 Next to linolic fatty acid is oleic, its ratio varies from 24 to 30%. Apple seeds contain below 1% of linolenic acid. Among saturated fatty acids apple seeds contain 7% of palmitic acid, around 2% of stearic acid and 1.5% of ara- chidic acid. The sum of linolic and oleic acid is very similar for all cultivars; cultivars that contain more linolic acid contain less oleic acid and vice versa. Linolic acid is prevalent fatty acid in seeds as well as on the surface of ap- ple peel (Table 3). The concentration of total fatty acids on apple peel is rather low ca. 0.02 mg·cm-2 of apple peel. At harvest cultivars Jonagold and Golden Delicious have the highest amount of total fatty acids on peel, cultivar Elstar and Fuji the lowest (Table 3). Content of arachidic acid was below threshold level. Compared to seeds, much higher ratio of linolenic, palmitic and stearic acid was determined on apple peel (Table 4). After storage period of three months the content of total fatty acids on ap- ple peel decreased at all cultivars except Idared (Table 3). Meigh & Hulme (1965) reported a decline of fatty acids after the respiratory climacteric. Brack- mann et al. (1995) found the fatty acid content to be dependent on the storage atmosphere. Low oxygen concentration inhibited the synthesis of fatty acids and aroma volatiles. Song & Bangerth (2003) reported of an increase of unsaturated linolic and oleic acid during on tree maturation of ‘Golden Delicious apples. 200 VEGETABLE CROPS RESEARCH BULLETIN 66 _____________________________________________________________________________________________________ Table 3. Fatty acid composition of apple peel (mg·100 mL-1 hexane extract) at harvest and during storage SUM of Cultivar C16 : 0 C18 : 0 C18 : 1 C18 : 2 C18 : 3 fatty acids Elstar at harvest 1.36 0.78 1.05 1.38 0.99 5.56 after 37 days 1.28 1.16 1.77 1.94 1.17 7.32 after 68 days 1.03 0.50 0.97 1.05 0.68 4.23 after 102 days 1.43 0.50 1.09 0.88 1.06 4.96 Jonagold at harvest 6.01 3.68 8.67 17.82 2.09 39.52 after 37 days 2.14 1.43 3.93 7.28 0.96 15.74 after 68 days 1.50 0.84 1.74 2.8 0.64 7.63 after 102 days 1.04 0 0.83 0.75 0 2.62 Golden Delicious at harvest 5.19 3.26 9.60 18.25 2.79 39.09 after 37 days 4.64 2.77 9.12 15.07 2.94 35.54 after 68 days 2.19 1.06 3.43 4.23 1.23 12.14 after 102 days 2.23 0.93 3.23 3.34 0.82 10.55 Gloster at harvest 5.33 1.56 3.74 8.73 1.77 21.13 after 37 days 4.32 1.54 3.34 6.31 1.45 16.96 after 68 days 3.16 1.04 2.03 2.86 0 9.09 after 102 days 2.97 0.97 2.56 3.09 0 9.59 Idared at harvest 2.66 1.04 3.1 5.88 1.00 13.72 after 37 days 1.52 0.65 1.66 1.87 0.00 5.70 after 68 days 3.4 1.07 5.64 6.29 1.09 17.49 Fuji at harvest 1.20 1.00 2.40 3.38 0.62 8.60 after 37 days 1.81 1.44 4.80 5.34 0.81 14.20 after 68 days 1.29 0.89 3.06 2.95 0.00 8.19 Pink Lady at harvest 5.64 2.84 7.32 13.87 2.75 33.35 after 37 days 4.50 1.95 6.62 8.98 2.44 24.49 after 68 days 4.74 1.53 6.42 7.38 2.20 22.27 The ratio of fatty acids on apple peel is quite different from ratio in seeds.