Volatile Compounds Profile during Storage of Ionathan, Starkrimson and Golden Delicious Apple Varieties Elena Andruţa MUREŞAN 1, Sevastiţa MUSTE 1 *, Sonia Ancuţa SOCACI 2, Romina Alina VLAIC 1, Emil RACOLŢA 1, Vlad MUREŞAN 1 1 Food Engineering Department, Faculty of Food Science and Technology, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, Romania. 2 Food Science Department, Faculty of Food Science and Technology, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, Romania. * Corresponding author e-mail: sevastita.muste@usamvcluj.ro ISSN-L 2344-2344; Print ISSN 2344-2344; Electronic ISSN 2344-5300 DOI: 10.15835/buasvmcn-fst:10851 Abstract Apples produce volatile chemicals that are responsible for the characteristic flavour of the fruit, as well as for the attribute of the final flavour. The aroma induced by the volatile compounds is important in determining the quality of the fruit, and especially for determining consumer acceptability. Fruits from three apple varieties were analysed (Ionathan, Golden Delicious and Starkrimson) at technological maturity and consumption maturity. The analysis method was developed on a Shimadzu QP-2010 GC-MS gas chromatograph, equipped with an AOC - 5000 (CombiPAL) autosampler. The results showed that there are differences between varieties in terms of number, type and concentration of volatile compounds. Fruits at technological maturity have a high content of aldehydes while fruits at consumption maturity have a higher content of esters. Keywords: flavour, apple, storage, ripe, volatile compounds, HS/GC-MS; INTRODUCTION Fruit quality, besides nutrients, aspect, size, texture and colour also includes aroma. Fruit aroma is one of the most appreciated characteristics of fruits. Volatile compounds play a key role in determining the flavour and also in the product perception and acceptance by consumers (Cheong et al., 2010). The aroma is a complex mixture of a large num ber of volatile compounds whose composition is specific depending on the species, variety and fruit variety. Most fruits produce a significant number of volatile compounds, but many of them are produced in very small amounts that are not identified by analytical tools but can be detected by the human olfactory senses (Muna et al.,2013). Commercial interest is thus focused on develop ing suitable criteria for harvest maturity as well as appropriate storage procedures in order to assure the quality of the final product. The aroma of volatile compounds is an important factor determining final sensory quality of fruit products and hence consumer satisfaction, being directly influenced by fruit maturity (Mattheis et al., 1991). The apples aroma profile is complex, as it comprises a large number of volatile organic compounds that contribute to the overall sensory quality. Over 400 volatile organic compounds were identified in the aromatic profile of apples (Forney et al., 2009), including esters, alcohols, aldehydes, acids, ethers, acetals, hydrocarbons and ketones (Rowan et al., 1999). Apple flavour properties depend on the combi na tion of volatile compounds and odour thre-
174 MUREŞAN et al. shold concentration of each compound (Sanz et al., 1997). Volatile aldehydes are predominant in immature apples (Salazar et al., 2011), while ripe fruits contain greater amounts of alcohols and esters (Dixon et al., 2000). These compounds are qualitatively and quantitatively predominant in most apple crops. Several authors found that esters represented a large percentage of the total volatile compounds in apples (Lopez et al., 1998; Lavilla et al.,1999; Echeverria et al., 2004). As an example, in Granny Smith variety, esters represented 88%, in Golden Delicious 80% and in Fuji variety 90%. Only few volatile compounds (20-40) have a decisive impact on the sensory quality of apples. These compounds are called impact compounds (Salazar et al., 2011). Example of the impact compounds which contributes the most to the characteristic aroma of apple, are butyl acetate, 2-methyl butyl acetate and hexyl acetate (Fellman et al., 2000). However, all volatiles play a certain role in producing the characteristic apples aroma profile (Paillard, 1990). The relative contribution of each of these compounds is known as odourunit and it is determined by the ratio of the concentration of a compound and olfactory perception thresholds (Takeoka et al., 1992). MATERIALS AND METHODS Fruits from three apple varieties were analysed (Ionathan - I, Golden Delicious - GD and Starkrimson - S) at harvest time technological maturity (TM) and after 115 days of storage on controlled atmosphere when send to the market consumption maturity (CM). Apple samples were analysed according to the method described by Şerban et al. (2012) with some modifications. The analysis method was developed on a Shimadzu QP- 2010 GC-MS gas chromatograph equipped with an AOC - 5000 (CombiPAL ) autosampler. Tab. 1. Volatile compounds of apples from Ionathan variety Volatile compounds Varieties Ionathan RT (min) (%)TM ( %)CM Hexanal 8.89 17.74 12.04 Butyl acetate 9.57-19.94 2-Hexenal, (E)- 11.47-10.56 1-Hexanol 12.36 51.96 34.92 2-Methylbutyl acetate 12.88 1.03 8.52 Methyl heptenol 19.35-0.23 Butyl butanoate 19.5-2.13 Pentyl acetate 20.43-5.7 Methyl benzoate 24.97-0.5 Hexyl butanoate 30.22-2.15 Hexyl 2-methylbutyrate 32.47 7.19 - Hexyl hexanoate 39.7 1.06 0.45 1-Dodecanol 43.28 14.12 1.3 Heptadecane 43.709 3.41 - alpha.-farnesene 44.38-1.22 2,3,3-Trimethyloctane 47.47-0.16 Hexadecane 50.17 2.03 0.17 1,2-Benzenedicarboxylic acid 54.27 0.37 - butyl 2-ethylhexyl ester 56.44 0.37 - RT- retention time, TM- technological maturity, CM- consumption maturity
Volatile Compounds Profile during Storage of Ionathan, Starkrimson and Golden Delicious Apple Varieties 175 The volatiles from apple samples were extracted using the headspace (HS) technique. Thus, 2g of sample were weighted and placed together with 0.25 g NaCl in a sealed vial and incubated for 60 min. at 40 o C. An aliquot from the headspace phase was automatically injected in the GC injector. The column used to separate the volatiles constituents was a capillary column ZB-5ms with a 50 m length, 0.32 mm internal diameter and a film thickness of 0.25 μm. Method parameters are as follows: injector temperature 250 C; pressure 37.1 kpa; column flow 1.2 ml / min; carrier gas - helium; split ratio of 1:50; detector: MS; ion source temperature 250 C; interference temperature 250 C; MS mode - EI; scanning range: 40-400u. Chromatographic column temperature program was: 40 C for 5 minutes, then increasing with 3 C / min. to 142 C and then increasing with 5 C / min. to 225 C and maintained for 10 minutes. The data were acquired using the device software and the identification of the compounds was performed by comparing the obtained mass spectra with those from software libraries (NIST147 and NIST27). The concentrations of the identified compounds were expressed as percentages of the total peaks area. RESULTS AND DISCUSSIONS For Ionathan variety (Table 1), 10 aroma volatile compounds were identified in mature fruits harvested at TM (4 esters, 2 alcohols, 3 carbonyls, 1 acid) and 15 aroma volatile compounds for fruits ready to be marketed CM (7 esters, 2 alcohols, 5 carbonyls, 1 terpene). Tab. 2. Volatile compounds of apples from Starkrimson variety Volatile compounds Varieties Starkrimson RT (min) (%)TM ( %) CM Hexanal 8.89 39.6 16.46 Butyl acetate 9.57-26.29 Ethyl 2-methylbutyrate 10.96-0.19 Ethyl 2-methylbutanoate 11.33-0.19 2-Hexenal, (E)- 11.47 24.36 6.35 1-Hexanol 12.36 3.91 12.22 2-Methylbutyl acetate 12.88-17.3 Methyl heptenol 19.35-0.27 Butyl butanoate 19.5-2.07 Ethyl hexanoate 19.68-0.26 Pentyl acetate 20.43-8.83 Methyl benzoate 24.97-0.38 Hexyl butanoate 30.22 3.01 4.95 Hexyl 2-methylbutyrate 32.47-0.65 Nonane, 5-(2-methylpropyl)- 33.53-0.47 Hexyl hexanoate 39.7 2.26 0.02 1-Dodecanol 43.28 16.41 0.99 Heptadecane 43.709 4.68 alpha.-farnesene 44.38 4.31 0.3 1,2-Benzenedicarboxylic acid 54.27-0.74 Dibutyl phthalate 56.45-0.91 RT- retention time, TM- technological maturity, CM- consumption maturity
176 MUREŞAN et al. Tab. 3. Volatile compounds of apples from Golden Delicious variety Volatile compounds In fruits at technological maturity the predominant compounds were aldehydes and alcohols. 1-Hexanol had the highest concentration, giving the green floral flavour, followed by hexanal that gives the green grass flavour to the fruit. After storage we noticed a decrease in aldehydes concentration, while esters compounds were formed. Butyl acetate, 2-methylbutyl acetate, butyl butanoate and pentyl acetate are flavour compounds likely to contribute to the taste of apple fruit, giving the red apple, banana and fruit syrup taste. Fruit aroma is an important factor affecting the sensory quality of the products. Dixon et al. (2000) noticed also that the total number, identity and concentration of volatile compounds emitted by ripening apple fruit are cultivarspecific. The contribution of each compound to the specific aroma profile of each cultivar depends Varieties Golden Delicious RT (min) (%)TM ( %) CM Hexanal 8.89 28.4 21.54 Butyl acetate 9.57-11.43 2-Hexenal, (E)- 11.47 21.95 3.78 1-Hexanol 12.36 3.49 28.9 2-Methylbutyl acetate 12.88-2.22 Methyl heptenol 19.35-0.57 Butyl butanoate 19.5-2.75 Pentyl acetate 20.43-2.25 Methyl benzoate 24.97-0.51 Hexyl butanoate 30.22 5.71 6.18 Hexyl 2-methylbutyrate 32.47 11.26 1.32 3,8-Dimethylundecane 33.57 1.2 - Hexyl hexanoate 39.7 2.55 1.66 2,6,11-Trimethyldodecane 42.77 4.53-1-Dodecanol 43.28 13.25 6.2 Heptadecane 43.70 4.66 - alpha.-farnesene 44.38 2.21 7.06 Eicosane 50.28-0.82 1,2-Benzenedicarboxylic acid 54.27 0.38 0.31 butyl 2-ethylhexyl ester 56.44-0.42 Dibutyl phthalate 56.44-1.43 RT- retention time, TM- technological maturity, CM- consumption maturity on the activity and substrate specificity of the relevant enzymes in the biosynthetic pathway, the substrate availability, the odour threshold above which the compound can be detected by smell, and the presence of other compounds (Rizzolo et al., 2006). For Starkimson variety (Table 2), 8 aroma volatile compounds were identified in mature fruits harvested at TM (7 esters, 2 alcohols, 5 carbonyls, 1 acid, 1 terpene) and 20 volatile compounds for fruits ready to be marketed CM (13 esters, 1 alcohol, 4 carbonyls, 1 terpene, 1 acid). Predominant compounds in fruit at technological maturity are the same as for Ionathan variety. The compound with the highest concentration is hexanal followed by 2-hexenal (E) -, giving the fruit green grass and leafy flavour. After storage, the concentration of aldehydes decreases
Volatile Compounds Profile during Storage of Ionathan, Starkrimson and Golden Delicious Apple Varieties 177 and esters appeared. Butyl acetate, 2-methylbutyl acetate, butyl butanoate, pentyl acetate, 2-hexenal (E) and hexyl butanoate are the key compounds that give specific apple flavour for this variety. For Golden Delicious variety, 12 aroma volatile compounds were identified in mature fruits harvested at TM (3 esters, 2 alcohols, 5 carbonyls, 1 acid, 1 terpene ) and 18 volatile aromatic compounds for fruits ready to be marketed CM (10 esters, 2 alcohols, 3 carbonyls, 2 terpenes). For fruits at technological maturity, hexanal was the compound with the highest concentration followed by 2-hexenal (E) -, giving the green grass flavour to the fruits. For fruits ready to be marketed, the compounds that contribute to the specific aroma are esters, namely butyl acetate, 2-methylbutyl acetate, butyl butanoate and 2-Hexenal, (E)-, terpene, namely alpha.-farnesene. We can also observe a high concentration of 1-hexanol, an alcohol that is found in Golden Delicious apples, result confirmed also by Dixon et al. (2000). The simultaneous analysis of PCA scores and loadings (Figure 1) highlights a relative sample grouping depending on flavour compounds as changed by fruits maturity. Fruits at technological maturity have a high content of hexanal and 1-dodecanol in Golden Delicious and Starkrimson varieties (S_TM, G_TM), and a high content of 1-hexanol in Ionathan variety Fig. 1. Principal Component Analysis for volatile compounds of fruits from three apple varieties (Ionathan - I, Golden Delicious - G and Starkrimson - S) sampled at technological maturity (TM) and consumption maturity (CM)
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