Volatile Flavor Compounds of Peel and Pulp from Doum (Hyphaene thebaica L.) Fruit

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1 American Journal of Food Science and Nutrition Research 2017; 4(5): ISSN: X (Print); ISSN: (Online) Volatile Flavor Compounds of Peel and Pulp from Doum (Hyphaene thebaica L.) Fruit Waleed Aboshora 1, 3, 4, Sharaf E. Idriss 4, Khamis Ali Omar 1, Hinawi AM Hassanin 1, Jiahao Yu 1, 3, Mohammed Abdalla 4, Husnain Raza 1, 3 1, 2, 3, *, Lianfu Zhang 1 State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China 2 School of Food Science and Technology, Jiangnan University, Wuxi, China 3 National Engineering Research Center for Functional Food, Jiangnan University, Wuxi, China 4 Department of Food Processing, Faculty of Engineering, University of El Imam Elmahadi, Kosti, Sudan address lianfu@jiangnan.edu.cn (Lianfu Zhang), aboshora15@hotmail.com (W. Aboshora) * Corresponding author To cite this article Waleed Aboshora, Sharaf E. Idriss, Khamis Ali Omar, Hinawi AM Hassanin, Jiahao Yu, Mohammed Abdalla, Husnain Raza, Lianfu Zhang. Volatile Flavor Compounds of Peel and Pulp from Doum (Hyphaene thebaica L.) Fruit. American Journal of Food Science and Nutrition Research. Vol. 4, No. 5, 2017, pp Received: March 13, 2017; Accepted: April 27, 2017; Published: August 28, 2017 Abstract In this covenant of food additive, the world seeks for new natural food products through provision of natural flavors enriched foods. Peel and pulp of doum fruit (Hyphaene thebaica) were analyzed for volatile flavoring compounds by solid-phase microextraction gas chromatography/mass spectrometry (SPME-GC/MS). A total of 31 different volatile compounds were identified in pulp and peel of doum fruit. Acetic acid, propanoic acid, benzeneacetaldehyde, butanoic acid,2-methyl, hexanal and hexanoic acid were the major volatile compounds in pulp while the main volatile compounds of peel were acetic acid, propanoic acid, Butanoicacid,2-methyl, hexanal, 2-butanone,3-hydroxy, 3-methyl-3-oxetanemethanol and nonanal. The volatile compounds identified in doum fruit parts can be used by food industries to improve flavor and taste of food products. Keywords Doum Fruit (Hyphaene thebaica), Peel, Pulp, Volatile Compounds 1. Introduction Doum palm (Hyphaene thebaica) is an African palm tree. It is widespread in the Sahel and tends to grow in areas where groundwater is present and also found alongside the River Nile in Egypt and Sudan [1]. Various studies have revealed the fact that the doum fruit contain high levels of essential minerals such as potassium, sodium, calcium, magnesium, and phosphorus. As well as, Doum fruit contains B-complex vitamins, carbohydrates, and dietary fiber fiber, which is essential for good nutrition [2-5]. Numerous studies have emphasized that the doum fruit extracts contain high levels of phenols and flavonoids, and possess significant antioxidant and antimicrobial activities [6-8]. Fruit flavors make up of a fluffy blend of characterizing volatile compounds, organic acids and carbohydrates such as glucose, fructose, and sucrose; and generally, noncharacterizing volatile esters [9]. As well-known for other food matrices, the complex volatile fraction can be liberated to the headspace at different concentrations subjected to their solubility in the matrix, absolute amount, and volatility [9, 10]. Therefore, a single fruit may have more than hundred different volatile compounds, which also vary depending on the fruit s ripening stage. It is interesting to note that concentrations of fruit volatiles were the highest when compared with other foodstuffs, frequently over a 30 ppm. Previously, Monson [11] reported that the majority of volatile organic compounds (VOC) arise from plants; and one of the main indications of their presence is the strong odor emitted by them. In addition, the amount of organic acids in fruits has

2 American Journal of Food Science and Nutrition Research 2017; 4(5): been used as an index in identifying fruit maturity stages and it could possibly be one of the major analytical measurements on flavor quality [12-14]. To the best of our knowledge, this is the first study for detection and determination of volatile compounds in doum fruit parts. The aim of this work was to assess and compare the volatile organic compounds (VOC) of peel and pulp of doum (Hyphaene thebaica L.) fruit. 2. Materials and Methods Materials The collection and preparation of the raw material was carried out according to our previous study [2]. Peel and pulp of the doum fruit were dried separately for ten days at room temperature (23 25 C) under shade. Analytical reagents and HPLC-grade solvents were obtained from Sinopharm Chemical Reagent Co. Ltd., Shanghai, China Determination of flavor compounds in peel and pulp of doum fruit (Hyphaene thebaica) Isolation of the flavor compounds Flavor compounds in peel and pulp of doum fruit were extracted using headspace-solid phase micro extraction (HS- SPME) and analyzed via GC/MS according to Kataoka et al. [15] method with some modifications. Briefly, 3.0 g of sample was transferred to the SPME vial 15 cm 1 cm at temperature (12-15 C) within 3 min. The vial was fitted with a self-sealing septum. A SPME fiber (75 µm carboxen poly dimethyl siloxane) CAR/PDMS coating) was inserted through the septum and exposed to the headspace of the SPME vial. Extraction was carried out at 50 C for 40 min while stirring in a water bath. A SPME fiber (Supelco, Bellefonte, PA, USA) was then taken out and inserted into the GC injector for desorption at 250 C for 3 min while start the system for receiving the data. GC MS analysis Analyses were performed using Thermo Scientific ISQ GC-MS (Trace GC Ultra gas chromatograph combined with ISQ, Thermo Scientific, USA). The flavor compounds were separated using a Rtx-5Sil DB-5 MS capillary column 30 m 0.25 mm i.d µm film thickness (Restek, Bellefonte, PA, USA). The ionization voltage was 70 ev. The initial temperature of the column, 40 C, was held for 3 min and then increased at a rate of 5 C min 1 to a temperature 90 C. From this point, the temperature was increased at 10 C min 1 to a temperature 230 C which was held for 7 min. The carrier gas was ultra-purified helium at a constant flow rate of 0.9 ml/min. The spectrometer was operated in electronimpact (EI+) mode; emission current was 80 µa and detector voltage 1000 V. Ion source and GC MS transfer line temperatures were 200 and 250 C, respectively. A blank experiment was performed before analysis and each sample was analyzed in triplicate. Identification The peaks were identified by comparing mass spectrum and retention indices (RI) with the Wiley7n.l Database (Hewlett Packard, Palo Alto, CA) and Nist05a.l Database and previously reported RI. The results were expressed in terms of percentage of areas of identified peaks. 3. Results and Discussion The volatile compounds in peel and pulp of doum fruit were extracted by headspace -solid phase micro extraction (HS-SPME) and analyzed by gas chromatography mass spectrometry (GC MS). As shown in Table (1, 2) and Fig (1, 2) a total of 31 compounds were detected in doum fruit parts. Acids, aldehydes, alcohols, esters, hydrocarbons, ketones, furans, and other compounds have been identified. Hexanal, nonanal, ethane,1,2-bis[(4-amino-3-furazanyl)oxy, acetic acid, propanoic acid, benzeneacetaldehyde, butanoic acid,2- methyl, hexanoic acid, 6-oxa-bicyclo[3.1.0]hexan-3-ol, 1,2- benzenedicarboxylic acid, bis(2-meth) are the major volatile compounds in pulp while the main volatile compound of peel are hexanal, 2-butanone,3-hydroxy, nonanal, ethane,1,2- bis[(4-amino-3-furazanyl)oxy, acetic acid, furfural, propanoic acid, 5-methyl furfural, butanoic acid (CAS), butanoic acid,2-methyl, hexanoic acid. The ripening process of fruits involves many biochemical changes such as increase respiration, ethylene production, changes in fruit texture and color, and production of a vast array of compounds, ultimately leading to an acceptable quality fruit. Evidently the most rapidly growing area in the fruit flavor research is focused on understanding the biogenesis of flavor compounds and characterization of precursors [13]. In the present study, we found that organic acids are the major components of doum fruit and their amount is 44.5% for the fleshy part and 49.2% for peel; these organic acids play an important role in metabolic activity. Organic acids serve as useful index of authenticity in fruit products, since they have lower susceptibility to change during processing and storage than any other chemical component of fruit [12]. The organic acid composition of fruits is also of interest because of its important influence on the sensory properties of fruits and fruit juices. Even though they are minor components of fruits in combination with sugars, they are important attributes of the sensory quality of raw and processed fruits [14]. The unique and delicate flavor of pulp and peel in doum fruit is attributed to a number of volatile components. The presence of flavor compounds in these part of doum fruit is closely related to its sensory quality. Fruit cultivar, origin, maturity stage of fruit and storage conditions influence the flavor components of doum fruit and therefore its taste and aroma. In addition to the four basic flavors (sweet, sour, salty, and bitter) humans can recognize aroma in fruits and vegetables, which influence on the final consumer acceptance of the commodity. Our results indicated high amounts of furan derivatives present in doum fruit were generated from carbohydrates and fiber which are present in high proportions in doum fruit. Compounds such as furfural and 5-methyl furfural, which are generated in the thermal degradation of fiber, are present in high proportions in peel of doum fruit flavorings.

3 167 Waleed Aboshora et al.: Volatile Flavor Compounds of Peel and Pulp from Doum (Hyphaene thebaica L.) Fruit Fig. 1. Chromatograms of Flavor compounds of Pulp. Fig. 2. Chromatograms of Flavor compounds of Peel. Table 1. Pulp Flavor compounds. 1 2,3-Pentanedione (CAS) E Hexanal (CAS) E Heptanal E l-limonene E Cyclopropanecarboxylic acid, 2-ethylhexy E Butanone, 3-hydroxy- (CAS) E Octanal E Octen-3-one (CAS) E Heptenal, (E)- (CAS) E Methyl-5-hepten-2-one E Hexanol (CAS) E Nonanal E Ethane, 1,2-bis[(4-amino-3-furazanyl)oxy E

4 American Journal of Food Science and Nutrition Research 2017; 4(5): Octenal E Acetic acid E Octen 3 ol E Furancarboxaldehyde (CAS) E Propanone, 1-(acetyloxy)- (CAS) E Decanal (CAS) E Benzaldehyde (CAS) E Propanoic acid (CAS) E Nonenal, (E) E Furancarboxaldehyde, 5-methyl- (CAS) E Pentanoic acid (CAS) E Benzeneacetaldehyde E ,3,5-Cycloheptatriene, 7-ethyl- (CAS) E Butanoic acid, 2-methyl- (CAS) E Butenoic acid, (Z)- (CAS) E Hexanoic acid E Oxa-bicyclo[3.1.0]Hexan-3-ol E ,2-Benzenedicarboxylic acid, bis(2-meth E Others Table 2. Peel Flavor Compounds. 1 Hexanal (CAS) E Heptanal (CAS) E Cyclopentasiloxane, decamethyl- (CAS) E Furan, 2-pentyl E Pentanol (CAS) E Butanone, 3-hydroxy- (CAS) E Octanal E Octen-3-one (CAS) E Heptenal, (E)- (CAS) E Hepten-2-one, 6-methyl E Cyclohexasiloxane, dodecamethyl E Nonanal E Ethane, 1,2-bis[(4-amino-3-furazanyl)oxy E Acetic acid E Octen 3 ol E Furfural E Decanal (CAS) E Benzaldehyde (CAS) E Propanoic acid (CAS) E methyl furfural E Butanoic acid (CAS) E Benzeneacetaldehyde E Hexanone, 1-phenyl- (CAS) E Butanoic acid, 2-methyl- (CAS) E Pentanoic acid (CAS) E Butenoic acid, (Z)- (CAS) E Hexanoic acid E Octanoic acid E Methyl-3-oxetanemethanol E Phenol, 2-methoxy-4-(2-propenyl)- (CAS) E ,2-Benzenedicarboxylic acid, bis(2-methyl) E Others Conclusion In this study, volatile flavoring compounds in the peel and pulp of doum fruit were analyzed using SPME-GC/MS. According to our analysis, both peel and pulp samples contain a higher number of different volatiles compounds. The volatile compounds identified in peel and pulp of doum fruit can be used by food industries to improve flavor and taste of food products. Acknowledgements This work was supported by grants from the Natural Sciences Foundation of China ( ), the Fundamental Research Funds for the Central Universities (JUSRP51501) and the Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP ).

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