Physical, Chemical and Sensory Properties of Nine Thai Mango Cultivars and Evaluation of their Technological and Nutritional Potential

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1 International Symposium Sustaining Food Security and Managing Natural Resources in Southeast Asia - Challenges for the 21st Century - January 8-11, 22 at Chiang Mai, Thailand Physical, Chemical and Sensory Properties of Nine Thai Mango Cultivars and Evaluation of their Technological and Nutritional Potential A.L. Vásquez-Caicedo 1, S. Neidhart 1, P. Pathomrungsiyounggul 2, P. Wiriyacharee 2, A. Chattrakul 3, P. Sruamsiri 3, P. Manochai 4, F. Bangerth 5, R. Carle 1 1 University of Hohenheim, Institute of Food Technology, Plant Foodstuff Technology, 7593 Stuttgart, Germany 2 Chiang Mai University, Faculty of Agroindustry, Chiang Mai 51, Thailand 3 Chiang Mai University, Faculty of Agriculture, Chiang Mai 51, Thailand 4 Maejo University, Department of Horticulture (Pomology), Chiang Mai 529, Thailand 5 Hohenheim University, Institute of Fruit Science, Vegetable Science and Viticulture, Growth Regulators in Plant Production, 7593 Stuttgart, Germany Keywords: Mango, Thai cultivars, quality profile, sensory, processing Abstract Nine Thai mango cultivars (,,,,,, and ) were evaluated in terms of their physical properties (size, mass, mesocarp yield, peel thickness, firmness and color of peel and flesh), chemical composition (TSS, TA, TSS/TA, ph, pectin, fiber, sugars, organic acids, total phenols and β-carotene) and sensory attributes at full maturity. Each variety showed unique characteristics, greatly differing among each other in terms of mesocarp yield and nutritive value. is a promising cultivar, due to its high β-carotene content (9.6 ±.7 mg/1 g dry mater) and high flesh yield (7.5%), as opposed to, which presented extremely low β-carotene content (.41 mg/1 g dry mater) and flesh yield (52.8%). This study is an approach to give a quality profile of Thai mango cultivars as well as their potential for technological and nutritional utilization. 1 Introduction Mango (Mangifera indica L., Anacardiaceae) is one of the most preferred and broadly distributed tropical fruits around the world. However, Thai mangoes have not yet reached the popularity of some mango cultivars coming e.g. from India or Florida, due to their

2 2 Physical, Chemical & Sensory Properties of Nine Thai Mango Cultivars special characteristics and the lack of studies on their technological, nutritional and market potential. This fact, together with the elevated prices of some native varieties, reduces the chances of taking advantage of the local biodiversity, and may affect in the long term the local farmers as well. Even though the consumption of fresh and processed fully ripe mango in Thailand is reduced to some varieties, it is necessary to be aware of the potential of alternative native mango cultivars, which can open new perspectives to the farmers and to the local industry, benefiting the consumer by offering a great source of vitamin A as well. This study focused on the physical, chemical, nutritional, and sensory quality attributes of 9 mango cultivars, coming from the main harvesting season (May 21) in Northern Thailand, in order to evaluate their nutritional and technological potential, since these mango cultivars have been hardly described in the international literature so far. 2 Materials and Methods 2.1 Fruit Lots Investigated Mangoes of the cultivars,,,,,,, and were obtained from Maejo University and a local farm (Chiang Mai, Thailand). Fruits were harvested at their mature ripe stage and ripened using calcium carbide at 29 ± 2 C and 9-95% RH. The fully ripe stage of mango fruits was objectively defined based on their color of peel and flesh (L*, a*, b*, chroma and hue angle), firmness, soluble solids (TSS), titratable acidity (TA), TSS/TA ratio and ph, as a result of preliminary studies on the behavior of each variety during postharvest ripening. 2.2 Physical Characterization of the Fruits T max Wmax L Tmin Wmin Figure 1 Definition of mango size parameters (mm) All physical properties were evaluated at the same day for each variety, once full ripeness was reached. These analyses were performed at the Food Product Development Department laboratories of the Agroindustry Faculty, Chiang Mai University.

3 Vásquez-Caicedo et al. 3 2 fully ripe mangoes from each cultivar were first evaluated in terms of size (Fig. 1): length (L), maximum width (W max ) and thickness (T max ), minimum width (W min ) and thickness (T min ), and fruit mass. Then the same fruits were peeled using a hand peeler, and flesh, peel and seeds were weighed and expressed as percentage of total fruit weight. The peel was collected and set up randomly over a white surface to measure the average color of the peel with a colorimeter CR31 (Minolta) according to the CIELAB color system L* a* b*. Peel thickness was evaluated without the flesh sticked to it after manual peeling. Mesocarp firmness was measured using an Instron Universal Texture Analyzer type 5565 equipped with a Warner-Bratzler shear cell and expressed as maximum shear force needed to cut a fruit cube over an area of 1 x 1 cm. For determination of flesh color, a purée was obtained from flesh and homogeneously distributed on a Petri-plate over a white background. 2.3 Chemical Characterization of the Edible Part (Mesocarp) Soluble solids (TSS in Brix) of a purée were measured using a hand refractometer (N1, Atago, 1-32 Brix), correcting values for temperature (2 C) and acidity. Titratable acidity (TA expressed as g citric acid/1 g) was determined by titration with.1n NaOH to ph 8.1 [1]. Using Folin Ciocalteau and sulfuric acid-vanillin reagents, summary indices of total phenol content and flavonol content, respectively, were determined [2], both related to catechol. Sucrose, glucose and fructose were subsequently determined using an enzymatic method [3]. For further analyses at Hohenheim University, mesocarp pieces were deep-frozen with liquid nitrogen, packed into aluminum bags, and sealed under vacuum. Total pectin and its water soluble (WSP), oxalate soluble (OXP) and alkaline (OHP) fractions [4], selected organic acids, i.e. citric, malic and succinic acid [5], fiber content [6] and ß-carotene [7] were evaluated at the Institute of Food Technology. 2.4 Sensory Evaluation The sensory test was carried out with nine volunteers recruited from the Faculty of Agroindustry at Chiang Mai University. Panelists were trained on descriptive analysis, using the Spectrum method [8]. Introductory sessions to discuss flavor and aroma concepts, as well as training sessions to test their ability to detect the basic tastes and to describe and discriminate aromas, were performed during April and May 21. A vocabulary for basic tastes, texture, aroma, aromatics, chemical feeling factors, and aftertaste attributes for mangoes was developed. An intensity scale from (lowest) to 15 (highest) was used, following the universal intensity scale for common aromatics [8].

4 4 Physical, Chemical & Sensory Properties of Nine Thai Mango Cultivars 2.5 Statistical analysis Data were subjected to analysis of variance using the General Linear Model (GLM) procedure [9] and the least significant difference test (LSD) for comparing the means (α =.5). JMP [1] software was also used as a complementary tool for correlation analysis. 3 Results 3.1 Physical Characteristics of the Fruits Table 1 shows size, mass, and yield for the cultivars studied. Significant differences (α =.5) were found between cultivars in terms of fruit mass, yield of flesh and seeds. Moreover, all fruits significantly differed in their dimensions (length, width, and thickness). Altogether, mango cv. presented the highest fruit size, mass, and flesh yield, as well as the lowest portion of seeds. However, flesh yield of Maha Chanok was not significantly different from those of the cultivars, and. The smallest fruits were those of cv., which also had the lowest flesh yield. Mango cv. had the thickest peel (1.23 mm), followed by (1.15 mm), whereas, and had the thinnest peel (.63,.79 and.68 mm, resp.). Peel thickness provides a protection and may reduce postharvest losses, however this fact could increase the difficulty of removing the peel before processing, e.g. by steam peeling techniques. Fruit maturity did not correlate with peel color in all cultivars. Color saturation (chroma) and yellowness (b*) showed the highest correlation coefficients (r=.79 and r=.78) between color of peel and flesh, respectively. Only the peel of,, and showed visible color changes that could indicate full ripeness as well. Peel of cv. showed red spots over a green-yellowish background at its harvest time, and developed up to a bright yellow peel color with red chicks. Peel color of cv. completely turned to yellow-orange at full maturity. Also peel of cv. and cv. turned to a dark yellow color, but still showed some greenish parts that did not vanish during ripening. However, flesh color of had one of the most intensive and bright yellow-orange flesh color (a*=14.3) together with (a*=14.7) and Maha Chanok (a*=18.3), contrasting with and which rather showed pale yellow-greenish mesocarp color (a*= -2.9) (Fig. 2).

5 Vásquez-Caicedo et al. 5 Table 1 Physical characteristics of Thai mango cultivars Cultivar Mass [g] ± 16.3 Flesh [%] 7.54 ± 1.95 Seed [%] ±.34 Peel [%] ± 2.29 Length [mm] ± 1.78 Width max Width min Thick max [mm] [mm] [mm] ± 1.8 ±.4 ±.45 Thick min [mm] ± 1.38 Nam Dokmai # ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±.6 Texture was found to be quite similar in all fruits, however cv. significantly differed from other mangoes (Fig. 3), being 26% firmer than the average of the other cultivars. This may be related to both the higher fiber content (2.34%, dry weight basis) and total pectin content (5732 mg/kg fresh mesocarp) as compared to other cultivars (Fig. 3). a* or b* b* (yellow) a* (red-green) L* chroma hue angle fiber 1 firmness (force) total pectin chroma, hue angle or L* fiber [% dry weight] or shear force [N/cm 2 ] pectin content [mg/kg] -1 1 Figure 2 Flesh color of mango cultivars Figure 3 Texture, fiber and pectin of mesocarp

6 6 Physical, Chemical & Sensory Properties of Nine Thai Mango Cultivars 3.2 Chemical Characteristics of the Mesocarp and Nutritive Value Fully ripe mango fruits differed in their soluble solids (TSS) and titratable acid content (TA). Therefore, these parameters or even the TSS/TA ratio alone are not sufficient to evaluate full ripeness of mangoes in general, but dependent on cultivar. and cultivars had the highest TSS content (18.7 Brix and 18.2 Brix, resp.), contrasting with and (15. Brix and 15.3 Brix, resp.). It is interesting to notice that the varieties commonly consumed as mature green ripe fruits by the local people were at the same time those with the lowest titratable acidity of fully ripe mesocarp (e.g. ). On the other hand, cultivars usually consumed at their fully ripe stage showed the highest titratable acidity values (i.e.,, and ) and therefore the lowest TSS/TA ratio (Fig. 4), which ranged from 47.6 to among the nine cultivars. 2 TSS TA [CA, ph 8.1] TSS / TA ratio 12 2 TSS sucrose fructose glucose 2 TSS [ Brix] or TA [g/kg] sugar / acid ratio total soluble solids [ Brix] sugar content [g/1g] Figure 4 Soluble solids, acidity and TSS/TA ratio Figure 5 Sugar composition of mango cultivars Main sugar composition of the mesocarp (glucose, sucrose, and fructose) was also very variable among the mango cultivars. In spite of the differences in TSS/TA ratio (Fig. 4), cv., and possessed the highest sucrose content as nonreducing sugar (Fig. 5). However, compared to the portion of reducing sugars, sucrose was most in flesh of cv. and, indicating lowest tendency to nonenzymatic browning reactions during processing. On the other hand, high fructose contents may increase the sweetness sensation in samples of similar TSS/TA ratios, due to its high sweetness potency [11] (Fig. 5). Among organic acids, citric, malic and succinic acid were evaluated (Fig. 6), since the balance of the organic acid composition may modulate the palatability of the fruits largely resulting from TSS/TA ratio. Low acidity of

7 Vásquez-Caicedo et al. 7 mesocarp in cultivars for green eating, such as,, and Okrong Thong, is reflected by small amounts of citric acid (1.1, 1.7 and 2.2 g/kg, resp.) and elevated ph values (4.8, 4.8 and 5.1, resp.), meaning that processing of such cultivars would require acidification to ph < 4.5 prior to thermal preservation at temperatures below 1 C. titratable acidity [g/kg] or ph ph TA [CA, ph 8,1] citric malic succinic succinic, malic or citric acid [g/kg] index of total phenol or flavonol, resp. [mg catechol /1 g] total phenol index (FC) V/FC ratio flavonol index (V) V/FC ratio [%] Figure 6 Titratable acidity, ph and organic acids Figure 7 Indices of total phenols and flavonols Summary indices of total phenols (FC) varied in a range from 35. to mg/1g edible fruit (cv. and, resp.) and those of total flavonols (V) from 2.3 to 9.4 mg/1g (cv. and, resp.), both expressed as catechol (Fig. 7). Since total phenol indices of cv. were significantly higher than of other cultivars, the highest browning potential due to polyphenol oxidation and a slightly astringent taste may be expected for this cultivar. However, compared to other fruit species, the total phenol indices were altogether as low as those found for dessert apples [2] known to be poor in polyphenols [12]. Therefore, tendency to mesocarp browning appears to be rather poor for all mango cultivars studied, and possibly also due to low polyphenol oxidase activity in the mesocarp [13]. The polyphenol pattern of commercially available mango purée concentrate was described in [14], showing that gallic acid is the predominant phenolic acid, which may be the primary substance taking part in browning reactions during mango processing. According to [2], low V/FC ratios shown in Fig. 7 for all cultivars may be related to the occurrence of condensed polyphenols. Hydrolizable gallotannins are reported to be present in mangoes [13]. However, the gallotannin isolated from mango purée concentrate [14] consisted of only four gallic acid units attached to a hexose, possibly due to hydrolysis during processing.

8 8 Physical, Chemical & Sensory Properties of Nine Thai Mango Cultivars The technological potential for mango purée production also depends on the native pectin content of the mesocarp and the distribution of the pectin fractions (Fig. 8), determining purée viscosity and mouth feeling. cultivar showed far the highest amount of total pectin (6484 mg/kg), followed by (5732 mg/kg) and (5512 mg/kg). However, with pectin contents above 2 mg/kg, mango flesh of all cultivars is typically rich in pectin. On an average, approximately 65% of total pectin was water soluble (WSP in Fig. 8), being decisive for the viscosity of purées and juices. 7 total pectin WSP OXP OHP 1 11 a* beta-carotene b* chroma 1 pectin content [mg/kg] portion of pectin fraction [%] β-carotene [mg/kg DW] or a* b* or chroma 1-1 DW: dry weight Figure 8 Total pectin and its fractions (in mg / kg fresh mesocarp) Figure 9 β-carotene content and color of flesh Mangoes have a high nutritional potential due to their relatively high β-carotene content (provitamin A). However, marked differences between the varieties under study suggested that only the cultivars, and (9.6, 9.4 and 8.3 mg/1g dry weight, resp.) could be really considered as interesting sources of provitamin A, contrasting noticeably with (.4 mg/1g dry weight) which possessed the smallest amount of β-carotene and the palest color (yellow-green) at the same time (Fig. 9). The intense yellow-orange color of the fruit pulp may be a good indicator of β- carotene, whereby the a*-value plays the most important role on predicting it, with a correlation coefficient r= Sensory Evaluation All mango cultivars differently performed in terms of their sensory attributes. Basic tastes, aromas, aromatics, texture, and aftertaste parameters were evaluated. However, only basic taste and texture data gave more information about the performance of the cultivars studied. was found to be the sweetest, in accordance with the extremely

9 Vásquez-Caicedo et al. 9 high TSS/TA ratio (Fig. 4), its high sucrose content and low citric acid concentration (Fig. 5 and 6). provided the firmest and chewiest fruit, which is reflected by the high shear force values measured for this cultivar (Fig. 3). Performance of each cultivar and their most important attributes are summarized in Fig. 1. sweet astringent aftertaste 1 8 sour basic tastes bitter aftertaste 6 bitter aftertaste 4 sour aftertaste 2 firmness * * sweet aftertaste juicyness feeling factor astringent fibrous texture aroma mango impact chewy (*) cultivars not evaluated Figure 1 Main sensory attributes of selected mango cultivars at the fully ripe stage (scale see 2.4) Table 2 Significant correlations (α=.5) between chemical and sensory attributes on mangoes ph TA TSS/TA Citric acid Malic acid L* a* Chroma Hue angle Sucrose Basic tastes Sweet n.s* n.s n.s n.s n.s n.s n.s Sour n.s n.s n.s n.s n.s n.s Bitter n.s n.s n.s n.s n.s n.s Feeling factor Astringent n.s n.s n.s n.s n.s n.s.79 n.s Aftertaste Sour n.s n.s n.s.82 n.s n.s n.s n.s n.s n.s Sweet n.s n.s n.s n.s n.s n.s n.s Astringent n.s n.s n.s n.s -.79 n.s n.s Bitter n.s n.s n.s n.s n.s n.s n.s n.s n.s.79 Texture %Fiber OHP OXP Firm.82 n.s.75 Juicy n.s Chewy n.s n.s.75 * n.s = non-significant correlations were found

10 1 Physical, Chemical & Sensory Properties of Nine Thai Mango Cultivars Some interesting correlations between texture-sensory data and pectin and fiber content were found as well (Table 2). Firmness and juiciness may also be related to the fiber content (r =.82 and r = -.87, respectively) and, as expected, TSS/TA ratio is a better indicator for sweetness (positive) and sourness (negative), than sugar content or titratable acidity alone. Citric acid may not be only responsible for sourness, but also for bitterness (r=.82). 4 Discussion Thai mangoes showed great variability among the cultivars studied in terms of their chemical composition, physical properties (Table 1, Fig. 11) as well as of their sensory attributes (Fig. 1). For this reason, not all mango cultivars could be used for similar purposes. Conversely, the group of green-eating mangoes has little β-carotene content in their ripe mesocarp, being of no great interest as fully ripe fruits. colour of flesh chroma hue angle 25 firmness texture of flesh * peel thickness fiber size and yield portion of peel 2 15 OHP portion of seed 1 OXP pectins portion of flesh 5 WSP mass total Pectin beta-carotene suc / (gluc+fruc) nutritive value polyphenols glucose citric acid / malic acid fructose * citric acid sourness TA TSS / TA TSS sucrose sweetness ( * ) firmness was not evaluated Figure 11 Characteristic profiles of Thai mango cultivars. Scaling as percentage of the respective mean of all nine cultivars for each parameter (see table 3) Due to their high ph value, green eating varieties such as cv. or may need further acidification on processing, thus altering the original taste of these fruits. On the whole, Thai mangoes investigated in this study are comparable to mangoes generally

11 Vásquez-Caicedo et al. 11 offered on the world market (Table 3). They did not greatly differ from the average range of other mangoes in terms soluble solids, acidity, main sugars (glucose, sucrose and fructose), and organic acid (citric and malic) content. The β-carotene contents of Thai mangoes are also falling into the range of values cited in the literature, but tend to be below the average of all other mangoes, cited to be 16.3 and mg β-carotene / kg fresh weight, respectively [13, 15]. Table 3 Comparison between Thai mangoes and mangoes from diverse origin Thai mangoes [13] [15] Attribute Average Min. Max. Range Range Mass [g] Flesh [%] Seed [%] Peel [%] Peel thickness [mm] Total phenol index (a) [mg / 1g] β-carotene [mg / kg FW (b) ] Chroma [ ] Hue angle [ ] Firmness [N/cm 2 ] Fiber [%DW (c) ] Total pectin [mg GA / Kg] WSP [mg GA / Kg] OXP [mg GA / Kg] OHP [mg GA / Kg] Glucose [g / 1g] Fructose [g / 1g] Sucrose [g / 1g] TSS [ Brix] TSS / TA (w/w) TA [g citric acid / 1g] ph Citric acid [g / 1g] Malic acid [g / 1g] (a) Expressed as catechol equivalents, (b) FW= fresh weight, (c) DW= dry weight This study of Thai mango cultivars offers new perspectives to the local industry, in consideration of their unique fruit characteristics. Even though short-season cv. was one of the smallest fruits and presented medium flesh yields, it remains being preferred for processing, e.g. for canning and juices. This is not only due to its low price, but also to its specific chemical properties. This cultivar showed the highest total pectin content, a good TSS/TA balance, low portion of reducing sugars, and an optimum acidity level for mild thermal preservation. The high ß-carotene and total phenol content in cv. also reveals its high nutritional and antioxidant potential. appears

12 12 Physical, Chemical & Sensory Properties of Nine Thai Mango Cultivars to be a promising cultivar for fresh consumption, due to its size, peel and flesh color, and high ß-carotene content. However, given reasonable price levels, utilization of cv. Maha Chanok for purée and drinks may be also a good option, because of its high flesh yield, small seeds, thin peel, high total pectin, adequate TSS/TA ratio and acidity level. Utilization of cv. for purée blends is also interesting, because of its high yield, thin peel, bright yellow-orange color, high ß-carotene content and good taste. A lower total pectin content of cv. may contribute to modulate viscosity of purée blends. has become interesting for canning and freezing due to its high yield, firmness and fiber content, even though ß-carotene content is only modest. Other mango cultivars consumed at their mature green stage may not be a potential source of provitamin A. In this case, vitamin C content, not yet considered in this study, would play a more important role. The information provided may also open the international market to Thai mangoes, which are not sufficiently known outside the country. Therefore, this interdisciplinary study is continued, considering also characteristics such as vitamin C, availability, seasonal variability of quality as well as ripening behavior. Acknowledgements This research is funded by DFG (Deutsche Forschungsgemeinschaft), Bonn, Germany: Project no. SFB 564-E2. The project is part of the collaborative research program Sustainable Land Use and Rural Development in Mountainous Regions of Southeast Asia of Hohenheim University (Germany) in cooperation with Chiang Mai University and Kasetsart University in Thailand and various universities and institutions in Vietnam, funded by DFG and cofunded by National Research Council of Thailand and Ministry of Science, Technology and Environment of Vietnam. The authors would like to thank to Berit Jöns, Nattaya Konsue, Suparat Sirisakulwat and the sensory panel for their participation in this project during the analysis of the samples. References 1. IFU (1962) IFU-Analyses No.3 and No.11, International Federation of Fruit Juice Producers 2. Poffet, J.R. (1997) Polyphenole im Apfel- und Birnensaft. Flüss. Obst 64(7): Boehringer (1998) Enzymatical analysis of sucrose / D-glucose /D-Fructose, No , Boehringer Mannheim, Roche Diagnostics 4. IFU (1995) IFU-Analyses No. 26, International Federation of Fruit Juice Producers

13 Vásquez-Caicedo et al Boehringer (21) Enzymatical analysis of citric acid (No ), L-malic acid (No ) and succinic acid (No ), Boehringer Mannheim, Roche Diagnostics 6. AOAC (1996) AOAC Official Method Fiber (crude) in animal feed and pet food. AOAC Official Methods of Analysis, Chapter 4, p Marx, M., Schieber, A., and Carle, R. (2) Quantitative determination of carotene stereoisomers in carrot juices and vitamin supplemented (ATBC) drinks. Food Chem. 7: Meilgaard, D., Civille, B.S., and Carr, M.S. (1991) Sensory Evaluation techniques. 2 nd Ed., CRC Press, Boca Raton, FL. 9. SAS (2) SAS Companion for the Microsoft Windows Environment. Version 8e, SAS Institute Inc., SAS Corpus Drive, Cary NC 1. Sall, J., and Lehman, A. (1996) JMP Start Statistics, version 3.2.1, JMP IN Edition, SAS Institute Inc., Duxbury Press, Belmont, CA 11. Belitz, H.D., and Grosch, W. (1992) Lehrbuch der Lebensmittelchemie. 3 rd Ed. Springer Verlag. 12. Keller, P., Strecker P., Arnold, G., Schieber, A., Carle, R. (21) Bestimmung phenolischer Verbindungen in Tafel- und Mostäpfeln mittels HPLC. Flüss. Obst 68, Herrmann, K.(1994) Über die Inhaltstoffe und die Verwendung wichtiger exotischer Obstarten. I. Grundsätzliche Angaben zu den Inhaltstoffen sowie über Mango. Ind. Obst- Gemueseverwert. 79(1): Schieber, A., Wieland, U., and Carle, R. (2) Characterization of polyphenols in mango purée concentrate by HPLC with diode array and mass spectrometric detection. Innovative Food Science & Emerging Technologies 1: Souci, S.W., Fachmann, W., and Kraut, H. (1994) Food Composition and Nutrition Tables. 5 th Ed. Medpharm GmbH Scientific Publishers, Germany.