Impact of preharvest and postharvest factors on changes in volatile compounds of pomegranate fruit and minimally processed arils – Review

Scientia Horticulturae 188 (2015) 106–114

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Review

Impact of preharvest and postharvest factors on changes in volatile compounds of pomegranate fruit and minimally processed arils – Review Oluwafemi J. Caleb a,c , Olaniyi A. Fawole b , Rebogile R. Mphahlele b , Umezuruike Linus Opara a,b,∗ a Postharvest Technology Research Laboratory, South African Research Chair in Postharvest Technology, Department of Food Science, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa b Postharvest Technology Research Laboratory, South African Research Chair in Postharvest Technology, Department of Horticultural Science, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa c Department of Horticultural Engineering, Leibniz-Institute for Agricultural Engineering (ATB), D-14469 Potsdam, Germany

a r t i c l e

i n f o

Article history: Received 12 December 2014 Received in revised form 17 March 2015 Accepted 18 March 2015 Available online 10 April 2015 Keywords: Preharvest management Postharvest life Flavour life Aroma Volatile compounds Smart packaging

a b s t r a c t Composition, concentration and combination of volatile fractions in fresh and fresh-cut fruit and vegetables are essential in conferring the unique aroma characteristics of the product. The volatile organic compounds (VOCs) present are directly responsible for the taste and odour and, hence, the unique identities of fresh and fresh-cut produce. Flavour quality plays a crucial role in consumer preference and liking of pomegranate cultivars and products. This review discusses the volatile composition of pomegranate fruit, including a critical evaluation of the role played by various preharvest and postharvest factors on the flavour life of pomegranates. Future prospects and potential application of VOCs in smart/intelligent packaging and storage of horticultural crops are highlighted. This review provides some critical information for the entire role players along pomegranate value chain. © 2015 Elsevier B.V. All rights reserved.

Contents 1. 2.

3. 4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factors affecting volatile composition and concentration in pomegranate fruit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Preharvest factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1. Cultivar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Postharvest factors affecting volatile formation and content in pomegranates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1. Storage temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2. Storage atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.3. Chemical treatments and edible coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Influences of postharvest heat treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions and future prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

107 108 108 108 108 110 110 110 111 112 112 113 113

∗ Corresponding author at: Postharvest Technology Research Laboratory, South African Research Chair in Postharvest Technology, Department of Horticultural Science, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa. Tel.: +27 021 808 9242; fax: +27 021 808 3743. E-mail addresses: [email protected] (O.J. Caleb), [email protected] (U.L. Opara). http://dx.doi.org/10.1016/j.scienta.2015.03.025 0304-4238/© 2015 Elsevier B.V. All rights reserved.

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1. Introduction Pomegranate (Punica granatum L.) fruit has been reported to possess high antioxidant capacity and anti-mutagenic, antiinflammatory, anti-hypertension and anti-atherosclerotic activities (Fawole and Opara, 2013a; Opara et al., 2009; Viuda-Martos et al., 2010). Bioactive components reported in pomegranate arils in variable proportions are anthocyanins, ascorbic acid and ␤carotene (O’Grady et al., 2014). Additionally, pomegranate fruit is a good source of vitamin C, fatty acids, essential micro- and macronutrients and organic acids (Fawole and Opara, 2013a; Opara et al., 2009). While much is known about the micro- and macronutrients, antioxidant capacity and other quality attributes of the fruit, comparatively little is known about the volatile compounds in pomegranate. On the hand, more than 300 volatile organic compounds (VOCs) have been reported in fresh apples (Dixon and Hewett, 2000). Although the chemical group, total number and concentration VOCs identified is dependent on maturity of the apple and are cultivar specific (Holland et al., 2005; Villatoro et al., 2008). In pear fruit more than 300 VOCs have been characterized, with decadienoate methyl- and hexyl esters identified as the predominant impact-compounds (Rapparini and Predieri, 2003; Kahle et al., 2005). Mango’s VOCs have been extensively investigated over the past decades, due to its characteristic aroma. About 270 VOCs have been identified in different mango varieties (Pino and Mesa, 2006; Quijano et al., 2007). Strawberry flavour profile being a complex mixture of VOCs and non-volatiles, have been extensively examined and over 350 VOCs have been identified and described (Bood and Zabetakis, 2002; Wein et al., 2002; Lunkenbein et al., 2006; Klein et al., 2007). Although, a recent review by El Hadi et al. (2013) extensively reported on the advances in fruit aroma volatile research, no information was provided on pomegranate fruit. The composition and concentration of volatile compounds in fresh and fresh-cut fruit and vegetables (FFVs) is essential for the characteristic flavour of the produce and this has a direct influence on consumer perception of freshness and purchase decision (Kader, 2008; Belitz et al., 2009). In various types of FFVs, the class of volatiles representing characteristic flavour include alcohols, aldehydes, terpenes, esters and their derivatives (Bicas et al.,

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2011). Flavour quality is described based on the class of volatile compounds or combinations with the highest concentration/odour threshold that contributes to the global aroma of a given produce (Alonso et al., 2009; Belitz et al., 2009; Caleb et al., 2013a). In some type of produce, a single class of volatiles, often referred to as the “impact compound”, could reflect the global flavour of the product (Bicas et al., 2011). Hence, understanding the flavour life of each type of fruit or vegetable is essential towards maintaining or enhancing unique sensory quality attributes. Fig. 1 summarizes the different factors that could influence the flavour development and defect in fresh and fresh-cut (FC) produce. The flavour composition and volatile constituents of different exotic fruits have been described such as Brazilian cherry, acerola, jackfruit and starfruit (Bicas et al., 2011), and other tropical fruits (Maróstica and Pastore, 2007). During the last decade, there has been a drastic increase in global production and consumption of pomegranates, due mainly to the reported health benefits and enriched bioactive phytochemicals of this fruit (Caleb et al., 2012; Opara et al., 2009). Understanding the impacts of preharvest and postharvest management practices on flavour and consumer acceptability is important in future growth of this market. Research on aroma and flavour of pomegranate fruit has focused on the identification of unique volatiles produced by fully ripened whole fruit (Calín-Sánchez et al., 2011; Melgarejo et al., 2011; Mayuoni-Kirshinbaum et al., 2012; Fawole and Opara, 2013b). Using headspace solid-phase micro-extraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS) techniques CalínSánchez et al. (2011) and Melgarejo et al. (2011) identified 18 and 21 VOCs, respectively, in juice of nine different Spanish pomegranate cultivars. The effects of modified atmosphere packaging (MAP) and storage temperature on composition of VOCs in minimally processed pomegranate arils (cv. ‘Acco’ and ‘Herskawitz’) were investigated by Caleb et al. (2013a). The authors identified a total of 17 and 18 VOCs in the headspace of pomegranate juice of cv. ‘Acco’ and ‘Herskawitz’, respectively. Mayuoni-Kirshinbaum and Porat (2014) provided a detailed recent review on the sensory quality and biochemical compounds associated with flavour attributes of pomegranate arils; however, this article did not discuss the role of preharvest and postharvest factors on the development of flavour attributes in pomegranate fruit. Similarly, Mphahlele et al. (2014)

Fig. 1. Factors influencing the successful development/defect of flavour quality in fresh/fresh-cut fruit and vegetables.

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presented an extensive review on the pre-harvest and postharvest factors affecting bioactive compounds in pomegranate fruit, including phenolic compound, vitamin C and organic acids. Given the important role of volatile composition and concentration on quality and consumer acceptability of fruit and vegetables (Kader, 2008), there is a need for better understanding of the impacts of production and postharvest factors on the flavour quality and change in VOCs of fresh produce. The purpose of this review is to present the current status on the volatile composition of pomegranate fruit, including a critical evaluation of the impacts of various preharvest and postharvest factors on the development of flavour in pomegranate fruit. Where appropriate results on factors affecting VOCs and flavour quality of other fruit types are available, such will be used to highlight gaps in literature and demonstrate the potential applications on pomegranates. This review provides some critical information for the entire role players along pomegranate value chain.

2. Factors affecting volatile composition and concentration in pomegranate fruit 2.1. Preharvest factors 2.1.1. Cultivar Volatile organic compounds are responsible for the unique aroma of fresh fruit and vegetables (FFVs) and they also contribute to the flavour quality. Cultivar differences have been shown to play a crucial role on both the composition and concentration of VOCs in FFVs (Brat et al., 2004; Qin et al., 2012). Similarly, in pomegranate, which has numerous cultivars (Levin, 1994), the VOCs varied considerably qualitatively and in their quantitative ratio (Raisi et al., 2008; Caleb et al., 2013b; Fawole and Opara, 2014). The list of VOCs identified in various pomegranate cultivars investigated over the last five years is summarized in Table 1. Raisi et al. (2008) studied the volatile composition of pomegranate juice using multicomponent evaporation and identification using GC–MS approach. The authors detected a total of nine VOCs, comprising of 5 esters, 2 aldehydes, 1 terpenes and 1 alcohol in ‘Berit Kazeroon’ pomegranate. Similarly, eight pomegranate cultivars (Acco, Arakta, Bhagwa, Ganesh, Herskawitz, Molla de Elche, Ruby, Wonderful), grown in South Africa were examined by Fawole and Opara (2014). The authors identified a total of 15 VOCs, belonging to six chemical groups including aldehydes, alcohols, terpenes, and ketones. Furthermore, the authors observed consistent variation in VOCs amongst the cultivars investigated, and the alcohol chemical group, which was comprised, of isobutanol, 4-penten-1ol, 1-hexanol and 3-hexen-1-ol was the dominant group. Caleb et al. (2013a) reported a total of 17 and 18 volatiles in the headspace of pomegranate ‘Acco’ and ‘Herskawitz’ pomegranate juices, respectively. The groups included monoterpenes, monoterpene alcohols, aldehydes, ketones, alcohols, esters and sesquiterpenes. Furthermore, l-terpinen-4-ol and trans-␣-bergamotene were detected only in cv. ‘Herskawitz, while 2-octanone was only identified in ‘Acco’ cultivar. Andreu-Sevilla et al. (2013) reported 28 VOCs identified in pomegranate cvs. ‘Wonderful’ and ‘Mollar de Elche’, belonging to four chemical groups – aldehydes, alcohols, esters and terpenes. The authors showed that ‘Wonderful’ pomegranate had higher proportion of terpens (74.5%), aldehydes (16.1%), alcohols (5.2%) and esters (11.3%) than ‘Mollar de Elche’. Similarly, Melgarejo et al. (2011) identified 21 volatile compounds in pomegranate juice of Spanish cultivars. The chemical group of aldehydes was the predominant compound in the headspace, followed by monoterpenes, which was also highest in the juice extract from cultivar ‘ME1 . The authors also reported that alcohols played an important role

in the volatile profile of several pomegranate cultivars investigated (ME1, ME2, CRO2, PTO8, and BO1). However, Calín-Sánchez et al. (2011) reported that similar Spanish cultivars including ‘ME1’, ‘ME2’, ‘ME14’, ‘PTO7’, ‘PTO8’ and ‘BA1’ were dominated by monoterpenes, while aldehydes content was highest in the juice extract from ‘CRO2’ and ‘BO1’. However, both authors reported similar concentration of monoterpenes and aldehydes in ‘ADO4’ pomegranate juice. The differences in composition and concentration of VOCs reported for similar pomegranate cultivars could be attributed to differences in maturity stage of the fruit investigated, sample preparation methods as well as the extraction techniques applied. Table 2 presents a list of various analytical approaches that have been used to identify and characterize VOCs in pomegranate fruit. Mayuoni-Kirshinbaum et al. (2012) employed a series of identification methods, which detected a total of 15, 14 and 12 VOCs using (solvent-assisted flavour evaporation) SAFE coupled with GC–MS, HS-SPME coupled with GC–MS and GC–O coupled with GC–MS on SAFE and HS-SPME extracts, respectively, in ‘Wonderful’ pomegranate. The authors reported that hexenal (14.7%), limonene (23.1%), hexanol (22.8%), cis-3-hexenol (12.5%) and ␣terpineol (12.9%) dominated the HS-SPME juice extract. On the other hand, using the SAFE extraction method, the predominating VOCs found were hexanal (11.1%), hexanol (9.4%), ␣-bergamotene (18.7%) and ␣-terpineol (10.4%). Vázquez-Araújo et al. (2011) identified 23 aroma volatiles in ‘Wonderful’ pomegranate grown in the USA, with aldehydes, alcohols and terpenes dominating the aromatic profile. Furthermore, terpene derivatives (limonene, ␣terpineol, (Z,Z)-␣-farnesene and ␤-caryophillene) were the main volatile compounds. However, Koppel et al. (2014) detected only 15 aroma volatiles in cv. ‘Wonderful’ pomegranates grown in the USA. Tripathi et al. (2014) investigated free and bound aroma compounds of pomegranate ‘Ganesh’ using high vacuum distillation. Based on the findings, pomegranate juice was characterized by the presence of ethyl acetate, acetoin, trans-3-hexen-1-ol, 1-hexanol, 2-methyl pentanol, a-terpineol and 1-octen-3-yl acetate and heptadecanol. Jung (2014) analyzed VOCs in root, stem and fruit peels of pomegranate by thermal desorption gas chromatography combined with MS. A total of 62 compounds comprising of 18 alcohols, 17 esters, 10 hydrocarbons, 6 aldehydes, 4 ketones, 1 carboxylic acid and heterocyclic amongst others were identified in the fruit peels. These findings suggest that differences in cultivar and extraction technique were the major factors affecting the quantification and characterization of VOCs in pomegranates. Thus, there is need for further research focused on standardization of extraction methods in order to adequately characterize individual cultivars and thereby permit the traceability and inter-laboratory comparability of aroma profile data. 2.2. Maturity Aroma volatile synthesis is an integral part of the ripening process of pomegranate fruit and the volatile profiles change with advancing fruit maturation (Fawole and Opara, 2013b). Fawole and Opara (2013b) investigated aroma profile of ‘Bhagwa’ and ‘Ruby’ grown in South Africa at five different maturity stages (S1: immature (green skin); S2: unripe (light-red skin); S3: semi-ripe (red skin with pink arils); S4: ripened (first harvest); S5: fully-ripened (second harvest)), using the HS-SPME coupled with GC–MS method. During the first maturity stage (S1), the authors detected and identified two aroma volatile compounds (hexanol and limonene) in both cultivars with hexanol constituting 52.4% in ‘Bhagwa’ and 95.2% in ‘Ruby’, while limonene constituted 47.6% and 4.8% of the total aroma in ‘Bhagwa’ and ‘Ruby’, respectively. At maturity stage S2, the alcohol group had the highest relative proportion of the volatile composition, with an increase observed in ‘Bhagwa’ and decreased in ‘Ruby’, when compared to maturity stage S1.

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Table 1 List of volatile compounds extracted and characterized from various cultivars of pomegranate. Cultivar

Compounds

Berit Kazeroon

3-Methyl butanal, ethyl butyrate, isopentyl acetate, n-hexanol, amyl butyrate, diethyl allylmalonate, ethyl pelargonate, ␣-Ionone, aldehyde C-20 Limonene, benzeneacetaldehyde, L-terpinen-4-ol (Herskawitz), ␣-terpineol, trans-3-hexen-1-ol, 1-hexanol, 2-phenylethanol, 3-methyl-1-butanol acetate, cis-3-hexenyl acetate, acetic acid-hexyl ester, 2-octanone (Acco), 2-nonanone, trans-␣-bergamotene 1-Butanol, ethyl acetate, ethyl propanoate, isobutyl acetate, ethyl butyrate, 1-pentanol, ethyl-2-methylbutyrate, isoamyl acetate, amylpropionate, myrcene, ethyl hexanoate, octanal, hexyl acetate, limonene, isoamyl butyrate, nonanal, octanoic acid, diethyl butanedioate, terpinen-4-ol, ethyl octanoate, decanal, phenethyl alcohol, ethylphenethyl acetate, isoamyl hexanoate, phenethyl acetate, decanoic acid, ethyl decanoate Cis-3-hexenal, hexanal, trans-2-hexenal, cis-3-hexenol, hexanol, ␣-pinene, ␤-pinene, ␤-myrcene, 3-carene, ␣-terpinene, limonene, ␥-terpinene, fenchone, nonanal, camphor, terpinen-4-ol, ␣-terpineol, dodecane Cis-3-hexenal, hexanal, trans-2-hexenal, cis-3-hexenol, 1-hexanol, ␣-pinene, ␤-pinene, methyl-5-hepten-2-one, ␤-myrcene, 3-hexenyl acetate, hexyl acetate, p-cymene, limonene, ␥-terpinene, fenchone, nonanal, camphor, 3-hexenyl butyrate, ␣-terpineol, decanal, trans-caryophyllene Cis-3-hexenal, hexanal, trans-2-hexenal, cis-3-hexenol, hexanol, ␣-pinene, ␤-pinene, ␤-myrcene,3-carene, ␣-terpinene, limonene, ␣-terpinene, fenchone, nonanal, camphor, terpinen-4-ol, ␣-terpineol, dodecane Ethyl-2-methylbutanoate, limonene, ␤-cymene, octanal, 6-methyl-5-heptene-2-one, hexanol, cis-3-hexenol, nonanal, acetic acid, 2-ethylhexanol, 1-Nonanol, ␤-caryophyllene, ␣-terpineol, hexanal, cis-3-hexenal, ␣-bergamotene, 4-terpineol, ␤-farnesene, ␤-bisabolene, ␤-sesquiphellandrene, hexanoic acid, nonanoic acid, ␤-pinene, cis-3-hexenal, cis-2-heptenal, 2(5H)-furanone Hexanal, heptanal, octanal, nonanal, p-cumic aldehyde, Z-3-hexen-1-ol, 1-hexanol, 2-ethyl-1-hexanol, ␣-pinene, ␤-pinene, limonene, a-phellandrene, ␥-terpinene, menthol, 4-terpineol, ␣-terpineol, E-␣-bergamotene, E-␤-bergamotene, (Z,Z)-␣-farnesene, ␤-caryophyllene, cedrene, ␤-farnesene, bisabolene Pentanal, hexanal, decanal, propanol, isobutanol, ethanol, 4-Penten-1-ol, 1-hexanol, 3-hexen-1-ol, ␣-pinene, limonene, b-caryophyllene, octanone, carboxylic acid, acetic acid, ethyl acetate ␤-Pinene, B-myrecene, P-cymene, hexanal, nonanal, decanal, ␣-pinene, limonene, ␥-terpinene, fenchone, camphor, ␣-terpineol, 1-hexanol, hexyl acetate 3-Methyl butanol, hexanal, ethyl acetate, acetoin, trans-3-hexen-1-ol, 1-hexanol, 2-heptanol, 2-methyl pentanol, 2-nonanone, limonene dioxide, nonanol, alpha terpineol, farnesol isomer A, 3-octen-1-yl acetate, heptadecanol 2-Methylbutanoic acid methyl ester, 2-hexenal (E), hexanal, 3-hexen-1-ol (Z), 4-methyl-1-pentanol, R-␣-pinene, ␣-pinene, limonene, ␤-phellandrene, ␣-terpinene, cis-␤-terpineol, ␣-terpineol, trans-␣-bergamotene, caryophyllene, cedrene

Acco, Herskawitz

Wonderful, Mollar de Elche

Sweet (ME1, ME2, ME14, CRO2); sour-sweet (PTO7, PTO8, ADO4); sour (BA1, BO1)

Sweet (ME1, ME2, ME14, and CRO2), sour-sweet (PTO7, PTO8, and ADO4), sour (BA1 and BO1)

Mollar de Elche

Wonderful

Wonderful

Acco, Arakta, Bhagwa, Ganesh, Herskawitz, Molla de Elche, Ruby, Wonderful Asuity, Asuity beshoka, Asuity morkub, Manfalouty, Nab El-Gamal, Melasy, Sukkary, Maghal Ganesh

Wonderful

Furthermore, the authors showed that the ketone group comprising heptanone (7.8%) and 2-octanone (27.7%) were more prominent in ‘Bhagwa’ at maturity stage S3 while hexylacetate, 2-ethyl acetate and butyl acetate predominated in ‘Ruby’ and continued to dominate the rest of the maturity stages (S4 = 49%; S5 = 33.4%). On the other hand, when fruit were harvested at maturity stage S4, ‘Bhagwa’ was characterized by the dominance of esters while in S5 it was dominated by the ethanol group with the total proportion of

Descriptors

References Raisi et al. (2008)

Mild, citrus, sweet, orange, lemon, honey, flowery, must, turpentine, nutmeg, lilac, cheesy, green, fruity, dairy, buttery, apple, cherry, floral, pear

Caleb et al. (2013b)

Grape, oily, pear, banana, anise; ethereal, pineapple, jasmine, herbaceous, fruity, berry; lemon, woody, nutty, grape, wine-like, honey, green, waxy, floral, rose, apricot,

Andreu-Sevilla et al. (2013)

Sweet, vanilla, aromatic, woody, medicinal, fragrant, floral, lilac, berry, lemon, vegetable, woody, pepper, sharp, pine, mint, grass, balsamic, plastic Banana, green, vegetable, terpene odour, woody, spicy, fresh, green grass, mint, vanilla, wine-like, lilac, mild, citrus, sweet, orange, lemon, herbaceous, weak, citrus odour

Calín-Sánchez et al. (2011)

Berry, lemon, vegetable, woody, floral, citrus, orange, rose, fatty, mild, sweet, sharp, pine, green, grassy, powerful

Carbonell-Barrachina et al. (2012)

Mild, citrus, sweet, orange, lemon, fresh, green grass, mint, floral, rose, fatty, mushroom, soapy, terpene, almond, earthy, pine, herbal, fruity, apple, green, wood, warm, tea

Mayuoni-Kirshinbaum et al. (2012)

Gasoline, turpentine, pine, resin, turpentine, wood, warm, tea, balsamic, herbaceous, spice, oil, anise, mint, green,

Vázquez-Araújo et al. (2011)

Almond, malt, pungent, resin, green, flower, green, butter, pungent, pine, turpentine, sour, sweet, pineapple, orange, tallow, soap, Fatty, green, grassy, powerful Floral, citrus, orange, rose, fatty waxy, harp, pine, Mint, grass apple Fruity, buttery, creamy, grassy green, earthy, green-flower, sweet fruity green, floral, liliac, green-flower

Fawole and Opara (2014)

Fruity, sweet, apple, fruity, green, leafy, apple, vegetable, fragrant, floral, lilac, spicy, woody, pine, fresh, grass

Koppel et al. (2014)

Melgarejo et al. (2011)

Hamouda et al. (2014)

Tripathi et al. (2014)

36.4% and 44.5%, respectively. The influence of different maturity stages on VOCs in pomegranate cv. ‘Wonderful’ was investigated by Mphahlele et al. (2015). The authors found that 1-hexanol was predominant at the unripe and midripe stage, but was not detected in fully ripe fruit. Relative proportion of limonene ranged between 0.004% and 0.01% while ␣-terpineol ranged between 0.02% and 0.05% across the different maturity stages. Overall, the findings showed that the composition and relative proportions of the aroma

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Table 2 List of analytical techniques used and the number of volatile compounds (VOCs) detected/identified in pomegranate. Methods of analysis

Number of VOCs identified

References

Multicomponent pervaporation coupled with GC–MS HS-SPME coupled with GC–MS HS-SPME coupled with GC–MS and (GC-FID)

9 10 21 23 18 18 14 15 12 28 13 15 15 14 15 62a 69b

Raisi et al. (2008) Vázquez-Araújo et al. (2010) Melgarejo et al. (2011) Vázquez-Araújo et al. (2011) Calín-Sánchez et al. (2012) Carbonell-Barrachina et al. (2012) Mayuoni-Kirshinbaum et al. (2012)

Hydrodistillation (HD) coupled with GC–MS HS-SPME extracts coupled with GC–MS SAFE extracts coupled with GC–MS GC–O coupled with GC–MS on HS-SPME and SAFE extracts HS-SPME coupled with GC–MS

Dynamic headspace system coupled with GC–MS High vacuum distillation (HVD) coupled with GC–MS and GC-O Thermal desorption-GC combined with MS HS-SPME coupled with GC–MS

Andreu-Sevilla et al. (2013) Caleb et al. (2013b) Fawole and Opara (2014) Koppel et al. (2014) Hamouda et al. (2014) Tripathi et al. (2014) Jung (2014) Vázquez-Araújo et al. (2015)

Headspace solid-phase micro-extraction (HS-SPME); solvent-assisted flavour evaporation (SAFE); gas chromatography–olfactometry (GC–O, (‘sniffing’)); flame ionization detector (FID); gas chromatography–mass spectroscopy (GC–MS). a VOCs identified in fruit peels. b Arils blended with albedo.

volatiles were influenced by fruit maturity stages of the cultivar investigated. The limited information on volatile composition of other pomegranate cultivars, highlights the need for further research to characterize the volatiles responsible for the odour and flavour of individual pomegranate cultivar. Knowledge of the volatile profile of different pomegranate cultivars would provide unique guide. To the fruit processing industry, with potential application in juice blending and minimally processing of arils to meet the demand of different consumer markets. 2.3. Postharvest factors affecting volatile formation and content in pomegranates Changes in volatile composition continue after harvest through new synthesis as well as volatile loss, resulting in a continual change in the overall volatile profile of horticultural produce (Kader, 2008). The development of desired characteristic flavour in fresh and fresh-cut produce plays an important role in consumers perception of freshness quality (Caleb et al., 2013b; Arendse et al., 2014; Luca et al., 2014). Consistent flavour and postharvest quality of horticultural produce is required for sustained consumer acceptance. Hence, the need to maintain good flavour and fruit quality is crucial during postharvest handling and storage. There has been considerable research on the evolution and/or changes (including loss) in flavour and aroma of fresh produce during postharvest handling. Postharvest handling factors such as storage temperature (Marcilla et al., 2006; Obenland et al., 2013; Mayuoni-Kirshinbaum et al., 2013), controlled and modified atmosphere (Mattheis et al., 2005; Defilippi et al., 2006; Ortiz et al., 2009; Caleb et al., 2013b), as well as methods to control postharvest diseases (McDonald et al., 1996; Lurie, 1998; Dang et al., 2008b) have been reported to influence aroma volatiles in a range of fresh produce. Unfortunately, limited research has been conducted on the effects of these postharvest handling techniques on pomegranates volatile compounds. 2.3.1. Storage temperature Optimum storage temperature has been shown to be effective in extending the postharvest life of fresh and fresh-cut produce; however, it also influences the generation and changes in volatile composition over time (Table 3). For instance, high storage or holding temperature between 15 ◦ C and 25 ◦ C has been reported to reduce the orange-like flavour of ‘Valencia Late Frost’ orange and

‘W. Murcott Afourer’ mandarin and to accelerate the production of alcohols and ethyl esters, which are indicators of off-flavour (Marcilla et al., 2006; Obenland et al., 2013). In contrast, at low storage temperatures (2 ◦ C, 5 ◦ C and 8 ◦ C), the flavour quality of ‘Or’ mandarins was well maintained, while the composition and concentration of volatile compounds decreased in ‘Odem’ mandarins stored at the same storage temperatures (Tietel et al., 2012). Similar changes in VOCs due different storage temperatures was reported for nectarine (Cano-Salazara et al., 2013), peach (Zhang et al., 2011), tomatoes (León-Sánchez et al., 2009; Bai et al., 2011) and fresh-cut cantaloupe (Beaulieu, 2006). The effects of storage temperature on changes in volatile profile in pomegranates (cv. Wonderful) fruit stored at 7 ◦ C for 20 weeks was investigated by Mayuoni-Kirshinbaum et al. (2013). The authors reported the accumulation of six sesquiterpene volatiles, namely ␤-caryophyllene, ␣-curcumene, (E)-␣-bergamotene, (E)␤-farnesene, (Z)-␤-farnesene and ␤-sesquiphellandrene during storage. Similarly, Caleb et al. (2013b) studied the effects of storage temperature on changes in volatile profile of ‘Acco’ and ‘Herskawitz’ pomegranate arils. The authors observed an increase in the concentrations of ethyl esters organic volatiles with increasing off-flavour odour during storage, indicating that storage temperature can alter volatile composition and flavour. Thus, maintaining an optimal cold chain in postharvest handling of fresh and fresh-cut produce helps to maximize flavour and overall quality. This area needs to be explored for various commercial pomegranate cultivars.

2.3.2. Storage atmosphere Applications of controlled atmosphere (CA) storage and modified atmosphere packaging (MAP) technologies have been shown to be effective in prolonging the storage life and maintaining postharvest quality of fresh and fresh-cut produce. However, very few studies have considered the effects of atmosphere modifications (mostly controlled atmosphere) on volatiles of fruit crops including pomegranates (Table 4). The effects of CA storage on aroma production have been reported on ‘Rich Lady’ peach (Ortiz et al., 2009), ‘Tardibelle’ peach (Ortiz et al., 2010b), ‘Gala’ apple (Mattheis et al., 2005), and ‘Titania’ blackcurrant (Harb et al., 2008). Studies by Ortiz et al. (2009) suggested that CA storage has the potential to improve flavour perception and consumer acceptability of ‘Rich Lady’ peach stored under CA (3 kPa O2 : 10 kPa CO2 ) for 15 days. Improved sensory acceptance of CA-stored fruit was attributed to characteristic

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111

Table 3 Effects of storage temperature on volatile compounds in pomegranates and other types of fruit. Treatments

Produce

Effect of treatment on VOC

References

Storage at 7 ◦ C

Pomegranate ‘Wonderful’

Storage temperature at 5 ◦ C, 15 ◦ C, 20 ◦ C and 25 ◦ C Holding temperature at 20 ◦ C

Citrus ‘Valencia Late Frost’

Decrease in typical pomegranate flavour and increases in ‘overripe’ and ‘off-flavour’ odours were observed Higher temperatures reduced the orange-like flavour and increased the presence of off-flavours over storage Concentrations of alcohols and ethyl esters were enhanced suggesting off-flavour The flavour of ‘Or’ mandarins was not affected, whereas for ‘Odem’ severe flavour loss at low storage temperatures. Storage at 2 ◦ C caused accumulation of 13 volatiles, mainly terpenes and their derivates, whereas storage at 8 ◦ C resulted in decreases of six volatiles, comprising five terpenes and one terpene derivative Enhanced the accumulation of butyl propanoate, 2-methybutyl-2-methylpropanoate, and 2-methyl-1-butanol Enhanced the accumulation of propyl acetate, pentyl acetate, and 2-methyl-1-butanol Contents of total volatiles were reduced and declined gradually during storage at low temperature Refrigeration caused quantitative and qualitative modifications in the aroma volatiles Both chilling and heating reduced C6 aldehyde and alcohol aroma volatiles immediately after treatment

Mayuoni-Kirshinbaum et al. (2013) Marcilla et al. (2006)

Mandarin ‘W. Murcott Afourer’

Storage temperatures at 2 ◦ C, 5 ◦ C and 8 ◦C

Mandarins ‘Odem’ and ‘Or’

Pre-storage at 20 ◦ C followed by storage at −0.5 ◦ C

Nectarine ‘Big Top’

Pre-storage at 20 ◦ C followed by storage at −0.5 ◦ C Low temperature storage at 0 ◦ C, 5 ◦ C and 8 ◦ C Refrigeration at 10 ◦ C

Peach ‘Early Rich’

◦

Chilling at 5 C for 5 days or heating at 52 ◦ C water for 15 min, then cooled to 25 ◦ C with 23 ◦ C tap water Storage of fresh-cuts at 5 ◦ C

Peach ‘Hujingmilu’ Tomatoes ‘7705 Tomatoes ‘Tasti-Lee’

Cantaloupe ‘Sol Real’

The overall ester ratio increased between 2- and 3-fold

higher emissions of d-decalactone and g-dodecalactone which are believed to be responsible for improved sensory acceptance. Although CA treatments could effectively control scald and reduce the incidence and severity of decay in pomegranates, the treatments adversely affect the aroma volatiles composition of fruit. For instance, if O2 levels become too low under CA storage, the flavour of pomegranate can be altered due to the accumulation of fermentative metabolites such as ethanol, acetaldehyde and ethyl acetate (Defilippi et al., 2006). The authors observed that the fermentative metabolites were higher in pomegranate fruit stored in CA with about 1 kPa O2 than those with 5 kPa O2 . The effect of MAP and storage temperature on volatile profile of ‘Acco’ and ‘Herskawitz’ pomegranate arils was reported by Caleb et al. (2013b). The authors showed that MAP and abusive storage temperature had a significant impact on the change in volatile profile inside packaged ‘Acco’ and ‘Herskawitz’ pomegranate arils over time. For instance, volatiles belonging to classes such as ketones, aldehydes, alcohols and esters decreased during the storage period, while ethyl esters concentration increased during the same storage period. Increased concentration of ethyl esters had a positive correlation with temperature and microbial growth, suggesting fermentative metabolism. The volatile composition of pomegranate arils could be cultivar dependent and the aroma life of packaged pomegranate arils is shorter than the postharvest shelf life (Caleb et al., 2013b). The successes of MAP technology application for

Obenland et al. (2013) Tietel et al. (2012)

Cano-Salazara et al. (2013) Cano-Salazara et al. (2013) Zhang et al. (2011) León-Sánchez et al. (2009) Bai et al. (2011)

Beaulieu (2006)

minimally processed pomegranate arils have been established in literature (López-Rubira et al., 2005; Ayhan and Estürk, 2009; Caleb et al., 2013a). However, more work is needed to investigate the impacts of MAP technology in maintaining the desired volatile profile for different pomegranate cultivars during storage and shelf life. 2.3.3. Chemical treatments and edible coatings Effects of postharvest chemical treatments and edible coatings on aroma volatile compound have been reported for various horticultural produce such as apples (Saftner and Conway, 1999; Ortiz et al., 2010a), strawberry (Moreno et al., 2010a, 2010b), mangoes (Baldwin et al., 1999; Dang et al., 2008a), fresh-cut ‘Bhagwa’ pomegranate fruit fractions (Caleb et al., in press) and ready-toeat pomegranate arils (Martinez-Romero et al., 2013). Calcium treatment of apple fruit is a widely used practice to prevent the development of bitter pit (Ortiz et al., 2010a). The treatment has been shown to be a useful procedure to provide good quality apple fruit, and a suitable alternative to controlled atmosphere storage of ‘Golden Reinders’ apples. For instance, application of calcium notably increased the production of flavour-contributing volatile such as esters in ‘Golden Reinders’ apple stored after mid-term storage under air (Ortiz et al., 2010a). Edible calcium salt coating has a great potential as a postharvest shelf-life-extending treatment for apples. Findings reported by Saftner and Conway (1999) suggest

Table 4 Effects of storage atmosphere on volatile compounds in pomegranates and other types of fruit. Treatments

Produce

Effect of treatment on VOC

References

Modified atmosphere packaging of arils at 5 ◦ C, 10 ◦ C and 15 ◦ C Controlled atmosphere treatments at 7 ◦C Controlled atmosphere storage at 2 ◦ C

Pomegranates ‘Acco’ and ‘Herskawitz’ Pomegranate ‘Wonderful’

Development of off-flavour and increased levels of ethyl esters

Caleb et al. (2013b) Defilippi et al. (2006)

Controlled atmosphere storage and after exposure to 1-methylcyclopropene (1-MCP) at 1 ◦ C Controlled atmosphere storage at 1 ◦ C

Apple ‘Gala’

Resulted in accumulation of fermentative volatiles (acetaldehyde, ethanol, and ethyl acetate) Higher emissions of d-decalactone and g-dodecalactone were observed Ester production by fruit stored in CA decreased throughout the storage period regardless of previous 1-MCP treatment

Harb et al. (2008)

Controlled atmosphere at 1 ◦ C

Peach ‘Tardibelle’

Lowering of O2 and/or high CO2 levels decreased biosynthesis of alcohols Lead to significant changes in the emission of some volatile esters

Peach ‘Rich Lady’

Blackcurrant ‘Titania’

Ortiz et al. (2009) Mattheis et al. (2005)

Ortiz et al. (2010b)

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Table 5 Effects of chemical/edible coatings treatments on volatile compounds in other types of fruit. Treatments

Produce

Effect of treatment on VOC

References

Calcium infiltration alone and combined with surface coating treatments at 0 ◦ C

Apples ‘Golden Delicious’

Saftner and Conway (1999)

Methyl jasmonate vapour treatment followed by storage at 4 ◦ C Coated with cellulose-based polysaccharide, Nature Seal® 2020, carnauba wax and Tropical Fruit Coating 213 and stored at 21 ◦ C Heat-conditioning (8 h at 40 ◦ C and 83.5% RH), hot water dipping (52 ◦ C/10 min), dipping in cold or hot prochloraz and carbendazim Postharvest calcium treatment prior to storage at 1 ◦ C

Strawberry ‘Coral’

Pressure infiltration of water and increasing concentrations of CaCl2 resulted progressively in reduced total volatile levels after 2–4 months storage. Combined treatments had similar but stronger and more persistent effects on volatile levels Most of the investigated volatile compounds increased significantly Mango carnauba coating increased the levels of aroma volatiles while Semperfresh and A. vera gel reduced fruit aroma volatile development Hot prochloraz or carbendazim at ambient and high temperatures showed enhanced concentrations of volatiles, while heat conditioning and hot water dipping did not significantly affect the volatile development Enhanced the emission of flavour-contributing volatile esters

Dang et al. (2008b)

Mango

Mangoes ‘Kensington Pride’

Apples ‘Golden Reinders’

that although infiltration of ‘Golden Delicious’ apples with CaCl2 solutions transiently inhibited synthesis of volatiles. This treatment does not adversely affect flavour-associated volatiles when used in conjunction with optimum storage conditions for over 4 months and additional shelf life period of about three weeks. Mango fruit coated with Nature Seal® 2020, a cellulose-based polysaccharide coating, exhibited improved levels volatiles, with 66-fold higher ethanol and 7-fold higher acetaldehyde compared to uncoated fruit (Dang et al., 2008a), as shown in Table 5. Similarly, Dang et al. (2008a) reported that carnauba wax was effective in improving levels of aroma volatiles, while Semperfresh and Aloe vera gel (1:1 or 100%) slightly delayed fruit ripening and reduced fruit aroma volatile development. Dang et al. (2008b) reported that ripe pulp of mango fruit treated with hot prochloraz or carbendazim at ambient and high temperatures showed enhanced concentrations of aroma volatiles. Treatment of pomegranate fruit with aqueous Topsin-M (0.1%) and Bavistin (0.05–0.1%) was reported to inhibit the growth of Aspergillus niger (Padule and Keskar, 1988). About 8% reduction in the incidence of decay was reported in pomegranate fruit treated with fludioxonil and stored at 10 ◦ C for 2–5 months (Adaskaveg and Förster, 2003). Although chemical treatments and coatings have shown to be effective in prolonging the storage and maintaining postharvest quality of pomegranate fruit (Caleb et al., 2012), no research has been reported on how these treatments affect the volatile composition and concentration. Thus, the need to examine the effects of such treatments on VOC profile a whole pomegranate fruit is essential towards maintaining the flavour quality and consumer acceptance, as new treatments are being investigated.

3. Influences of postharvest heat treatments Studies have shown that postharvest heat treatments of fruit and vegetables can control incidence of diseases, extend storage life and influence flavour life. Hence, it is important to select treatments that adequately extended storage life with the least negative alterations in volatile profiles and concentrations (McDonald et al., 1996). Applicable postharvest techniques include hot water dipping, hot air and vapour treatments, intermittent warming (Lurie, 1998; Artés et al., 2000a,b; Mirdehghan et al., 2007a,b; Dang et al., ˜ 2008b; Pena-Estévez et al., 2014). Hot water dipping at 45 ◦ C was used to reduce chilling injury disorder and to increase the ratio of saturated/unsaturated fatty acids (Mirdehghan et al., 2007a,b). Similarly, intermittent warming of pomegranate fruit at high temperature prior to cold storage has been reported to prevent chilling injury symptoms and reduce the incidence of fruit decay (Artés et al., 2000a,b).

Moreno et al. (2010b) Dang et al. (2008a)

Ortiz et al. (2010a)

Dang et al. (2008b) reported that hot water dipping did not significantly affect the aroma volatiles development in the ripe pulp of mango fruit. This observation is similar to that of McDonald et al. (1996), who reported decreased volatile compounds in ‘Agriset’ tomatoes subjected to pre-storage hot water treatments (42 ◦ C for 60 min), hot air treatment (38 ◦ C air for 48 h) or ethylene treatment. Mild heat treatments have the potential to reduce microbial growth and to inactivate enzymes associated with browning in ˜ et al., 2014). It is imporfresh-cut pomegranate arils (Pena-Estévez tant to evaluate the capability of the treatment to maintain flavour, textural and colour attributes, as well as nutritional and microbial quality.

4. Conclusions and future prospects Comprehensive review of literature showed that both preharvest and postharvest treatments play a major role in the concentration and composition of VOCs and flavour quality in fresh whole fruit and minimally processed pomegranate arils. The impact of cultivar differences and maturity stages on the volatile compounds was reported, which highlighted the need for future research focused on characterization of the VOCs and flavour profile for new and commercially viable cultivars, as the global market for pomegranate fruit continues to grow. This would provide valuable knowledge for the pomegranate industry and information for consumers. Evidence from the literature review showed that major VOCs and flavour descriptors in pomegranate such as the terpenes (limonene, ␣-terpineol, ␤-pinene and ␤-caryophyllene), the alcohol group (trans-3-hexen-1-ol, 1-hexanol, 3-hexanol-1-ol and hexanol) and ketones (2-octanone and 2-nonanone) decrease significantly due to prolonged storage or minimal processing. Additionally, prolonged storage and MA-packaging has been shown to enhance the synthesis and accumulation of ethyl esters (octanoic acid- and decanoic acid-ethyl ester, 2-phenylethyl acetate, and ethyl hexanoate) associated with off-odour development. Therefore, the ability to maintain the desired volatile profile during storage or MA-packaging would require further research. These include investigating the role postharvest treatments can play preserving sensory quality and the need to optimize existing postharvest storage conditions in order to reduce accumulation of off-flavour/secondary volatiles. Literature evidence also showed that high correlations have been established between the developments and accumulation of secondary fermentative VOCs (off-flavours) and microbial growth during pomegranate fruit storage. This highlights the potential role that VOCs could play as discriminators or indicators of fruit

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quality, microbial safety and shelf life. Better understanding of VOCs biosynthesis and the effects of pre- and postharvest factors on change in VOC profiles can be use to identify secondary VOCs associated microbial spoilage and senescence. The identification of secondary VOCs would be useful in making crucial postharvest management decisions such as optimum storage conditions and duration for whole fruit and minimally processed pomegranate fruit. Additionally, changes in VOCs reported in literature further emphasized the need for a shift from the traditional assessment of chemical attributes (total soluble solids (TSS), titratable acidity (TA) and pH) and physical attributes (colour, firmness, juiciness and presence/absence of decay), to a holistic assessment, which include the change in VOC as a component of fresh and fresh-cut fruit quality. This is particularly important given that research evidence has shown that the flavour life of fresh and fresh-cut produce is often shorter than the postharvest storage life based on chemical and physical quality attributes. Furthermore, the application of real time freshness monitoring systems via the synergy of information transmission and nanotechnology hold much promise in optimizing fresh produce packaging and storage conditions. The integration of nano-sensors (via nanoencapsulation of desired volatile precursor compounds in particles) into packaging materials could serve as an active shelf life labelling indicator based on possible links between produce quality status and changes in colour of the encapsulated nano-particle. This offers the possibility to track spoilage and detect changes in VOCs in the headspace of packaged horticultural crops. Acknowledgments This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation. The NRF Free-Standing Postdoctoral Fellowship (Grant No.: 85243) awarded to Dr. O.J. Caleb and the Claude Leon Foundation Postdoctoral Fellowship awarded to Dr. O.A. Fawoleare appreciated. References Adaskaveg, J.E., Förster, H., 2003. Management of gray mold of pomegranate caused by Botrytis cinerea using two reduced-risk fungicides, fludioxonil and fenhexamid. Phytopathology 93, 127. Alonso, A., Vázquez-Araujo, L., García-Martínez, S., Ruiz, J.J., Carbonell-Barrachina, A.A., 2009. Volatile compounds of traditional and virus-resistant breeding lines of Muchamiel tomatoes. Eur. Food Res. Technol. 230, 315–323. Andreu-Sevilla, A.J., Mena, P., Martí, N., Viguera, C.G., Carbonell-Barrachina, Á., 2013. Volatile composition and descriptive sensory analysis of pomegranate juice and wine. Food Res. Int. 54, 246–254. Arendse, E., Fawole, O.A., Opara, U.L., 2014. Discrimination of pomegranate fruit quality by instrumental and sensory measurements during storage at three temperature regimes. J. Food Process. Preserv., http://dx.doi.org/10.1111/jfpp. 12424. Artés, F., Tudela, J.A., Villaescusa, R., 2000a. Thermal postharvest treatment for improving pomegranate quality and shelf life. Postharvest Biol. Technol. 18, 245–251. Artés, F., Villaescusa, R., Tudela, J.A., 2000b. Modified atmosphere packaging of pomegranate. J. Food Sci. 65, 1112–1116. Ayhan, Z., Estürk, O., 2009. Overall quality and shelf life of minimally processed and modified atmosphere packaged ready-to-eat pomegranate arils. J. Food Sci. 74, C399–C405. Bai, J., Baldwin, E.A., Imahori, Y., Kostenyuk, I., Burns, J., Brecht, J.K., 2011. Chilling and heating may regulate C6 volatile aroma production by different mechanisms in tomato (Solanum lycopersicum) fruit. Postharvest Biol. Technol. 60, 111–120. Baldwin, E.A., Burns, J.K., Kazokas, W., Brecht, J.K., Hagenmaier, R.D., Bender, R.J., Pesis, E., 1999. Effect of two edible coatings with different permeability characteristics on mango (Mangifera indica L.) ripening during storage. Postharvest Biol. Technol. 17, 215–226. Beaulieu, J.C., 2006. Volatile changes in cantaloupe during growth, maturation, and in stored fresh-cuts prepared from fruit harvested at various maturities. J. Am. Soc. Hortic. Sci. 131, 127–139. Belitz, H.D., Grosch, W., Schieberle, P., 2009. Aroma compounds. In: Belitz, H.D., Grosch, W., Schieberle, P. (Eds.), Food Chemistry. Springer, Berlin, pp. 340–343.

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