2020 Volume 26 Issue 1 Pages 59-64
Sensory descriptors of mango ‘Ataulfo’ treated with dose of γ-rad (Cobalt 60) of 0, 0.15, 0.30, and 0.45 kGys were evaluated. Eight trained panelists evaluated eleven sensory descriptors, three on taste, four on texture and four on odor. Judges found significant differences (P < 0.05) for sweetness, sourness, astringency, juiciness, firmness, mango odor and honey odor in at least one treatment. The principal component analysis revealed a positively association between juiciness, mango odor, and honey odor with the irradiation dose of 0.30 kGy, besides the positively association between creaminess and the irradiation dose of 0.15 kGy. Any descriptors were influenced clearly by the radiation with dose at 0.45 kGy. Dose of 0.15 kGy of radiation can be used as phytosanitary treatment without substantially affecting the sensory properties of mango ‘Ataulfo’.
The first selection criterion used by food consumers is the sensory properties, and in fresh fruits, such characteristics are keys for acceptance (Guimarães et al., 2013). The mango (Mangifera indica L.) ‘Ataulfo’ is very attractive due to their intense yellow color, thin skin, small seed, high sugar content and sweet taste and odor, besides longer shelf life compared to other varieties. In México, this cultivar is highly produced, hence is vulnerable to agricultural pests like the Mexican fruit fly Anastrepha ludens Loew (Bustos et al., 2004). Therefore, the procedures used to eliminate the presence of larvae of this insect that should not affect the sensorial properties and the quality of the fruit. Phytosanitary treatments include fumigation with methyl bromide, hydrothermal treatment, using hot steam treatment at high pressures and gamma irradiation (γ-rad) (Bustos et al., 2004). The established dose for A. ludens and A. obliqua is 70 Gy and 100 Gy for Ceratitis capitata (Gómez-Simuta et al., 2017). A generic dose of 150 Gy was established worldwide against various species of fruit fly pests of the family Tephritidae as a minimum absorbed dose to prevent the emergence of adults (Hallman, 2012).
The γ-rad is adequate and secure to eliminate pests and even to increase fruits shelf life (Yadav et al., 2014). Irradiation at doses less or equal to 1 000 Gy aside from a phytosanitary treatment, can also extend shelf life (Gómez-Simuta et al., 2017). Some studies showed that 0.15 kGy dose killed the fruit fly larvae (Bustos et al., 2004) and that less than 1 kGy dose do not damage fruit physiology (Yadav et al., 2014). However, the effect of γ-rad is not similar with all food matrices, because in some of them there are not changes but, in some others could alter the composition or even structure in fruit, i.e. the antioxidant activity and the total polyphenols and anthocyanins contents decreased in fresh Granada when the fruits are irradiated with doses of 1 kGy (Shahbaz et al., 2014), even though consumers acceptance was improved. Similarly, doses up to 14 kGy in lycium fruit did not produce changes in the sensory characteristics but a decrease in the vitamin C content (Wen et al., 2006).
In contrast, a dose of 2 kGy resulted in firmness loss in raspberries (Guimarães et al., 2013). In persimmon fruit, irradiation caused softening of flesh and decrease of the astringency when doses of 10 kGy were applied (Kim et al., 2015). Although there are reports that γ-rad at doses up to 1 kGy do not produce changes in the physicochemical and physiological properties in ‘Ataulfo’ mangoes, only a few studies report the sensory changes (Gómez-Simuta et al., 2017), however, these results were obtained through untrained judges, so that when conducting the study with trained judges, more strictly results can be obtained. Furthermore, the world market for mango ‘Ataulfo’ is booming (Ledesma and Campbell, 2019), which leads to higher requirements for assessing the effect of quarantine methods; especially the sensory changes (with trained panels) derived from irradiation (Bustos-Griffin et al., 2015). Thus, the aim of this study was to evaluate the effect of doses lower than 1 kGy of gamma radiation on texture, odor, and taste properties of Ataulfo mango fruit.
(1) Fruits, irradiation, and storage Two hundred mangoes variety Ataulfo were provided by Santa Cecilia SPR orchard from Tapachula, Chiapas, Mexico, which were cut at the mature green stage and without visual damages. Fruits were selected for caliber 12 (weight ranged between 378–436 g; NOM, 2012). All fruits were washed with tap water and disinfected with NaClO solution (200 ppm) for 5 min. Then the fruits were randomised into four groups (treatments) of 50 fruits each. Fruits were irradiated with Co60γ-rays at the MOSCAFRUT facility (IICA-SAGARPA, Mexico) in Chiapas, Mexico following the procedure described by Gómez-Simuta et al. (2017). The irradiation process was carried out in a Cobalt −60 dry storage gamma irradiator (Model GB-127), with an activity of 59 956 Ci (Calibration date: sept. 2006). The dose rate at the moment of the test was 2.14 Gy/minutes, approximately. The time of exposure was calibrated previously to achieve doses of 0 (control), 0.15 (70 min), 0.30 (140 min) and 0.45 kGy (210 min). After this, irradiated fruits were stored at 25 °C and non-irradiated (control) at 20 °C, both with 80% RH. Storage at different temperatures was to synchronise the arrival of full ripening (11 d of storage).
(2) Panel recruitment and training Prior to the study, the consent of the institutional bioethics committee was obtained to carry out consumption tests with human subjects. The sensory panel was recruited from undergraduate students (age ranged 18–23). Based on procedures of descriptive analysis (QDA method) a questionnaire was used to screen prospective panelists, based on healthy, eating and non-smoking habits (Lawless and Heymann, 2010). Further selection was based on good health (self-report), interest and ability to describe and express the perceived stimuli when eating mangoes or derivative products. Then 15 pre-selected candidates performed detection tests in triplicate with characteristic descriptors like using solutions of 16 g/L sucrose (sweetness), 1 g/L tartaric acid (sourness), 5 g/L sodium chloride (salty) and 1 g/L tannic acid (astringent) (Lawless and Heymann, 2010). A candidate was accepted as panelists once they accomplished with 100% of sensory tests. After this, training was performed during the 30 following weeks, each one lasting 3–4 h. In the first session, the panelists were presented with samples of mango to generate appropriate descriptors about odor and texture. After this session, they were considered four descriptors for odor and four for texture (Table 1). During the following sessions, panelists were trained using ranking tests for basic tastes and triangular discriminative tests following the same procedure as Vázquez-Ovando et al. (2015). For taste ranking tests they were used standard solutions of sucrose (1.5, 2.5, 3.0, 4.0 g/L), tartaric acid (0.025, 0.037, 0.055, 0.085 g/L) and tannic acid (0.085, 0.150, 0.175, 0.200 g/L), and subsequently were replaced subsequently by mango pulp. Similarly, panelists were trained by unstructured scales tests for texture and odor descriptors so that all panelists agreed on the same sensory language. For odor test, mango samples were mashed and keep for 60 min before the session in sealed polyethene vessels to hold volatiles. The data generated by panelist and attribute were subjected to ANOVA and eight panelists (7 women and 1 men) were chosen on the basis of their discriminative capacity (P < 0.30) and repeatability (P > 0.05) (Melo et al., 2009).
| Taste | ||
| Sweetness | Characteristic taste of a sucrose solution | |
| Sourness | Characteristic taste of a tartaric acid solution | |
| Astringency | Characteristic taste of a tannic acid solution | |
| Texture | ||
| Juiciness | Amount of juice released with the first bite | |
| Creaminess | Thick (viscosity), softness (smoothness) and greasy | |
| Fibrousness | Fibrous /granules fragments during chewing | |
| Firmness | Initial force required when biting the sample with the front teeth | |
| Odor | ||
| Pineapple | Pineapple fruit aroma | |
| Apple | Apple fruit aroma volatiles | |
| Mango | A sweet fruity aroma, associated with mangoes | |
| Honey | Honey volatiles aroma | |
(3) Sensory evaluation The final evaluation was conducted in a single session in a spacious enclosed area with adequate lighting and a temperature of 25 °C. Cubes of 2 cm3 cubes of pulp fruit obtained away from the seed were used. By odor test, 72 polyethene containers (110 cm3) were employed and two cubes of pulp mango placed in. Then fruit was smashed and the containers were sealed and left for 1h at 25 °C. For the taste test, ten pieces of fruit were used, that were placed in a 10 cm diameter plate (n=72 plates) prepared at the moment. Both containers and plates were coded with three digits. For taste tests, panelists were asked to evaluate the samples for sweetness, sourness, and astringent attribute, rinse their mouth with water between samples. Odor testing was performed with a series of four containers arranged in front the panelists. Then each of the panelists was asked to remove the lid of the sealed container, inhale the volatiles and cast their judgement. Unstructured line scales of 150 mm were used to ask the stimulus perceived for each of the attributes (one line per attribute). This procedure was carried out thrice using codes of three different digits for each sample and replicates; 21 different combinations. When required, the panelists used tea bags to desaturate their olfactory system or flavourless biscuits to desaturate taste. Panelists also take 10 min breaks between sessions.
(4) Instrumental measurements Using pulp of ripe fruit, soluble solids content was quantified based on the 932.12 method of AOAC (2010). The result was expressed in °Brix. Titratable acidity (TA) was determined by the method 942.15 of AOAC (2010) and the results were expressed as g citric acid/100 g pulp. The total polyphenols content was measured according to the procedures described by Shahbaz et al. (2014). Gallic acid was used as standard and the results are reported as gallic acid equivalent (µg GAE/g pulp).
(5) Data analysis The data were analyzed by ANOVA and the means were classed by the Newman-Keuls test at 5% limit. A Pearson analysis and a principal component analysis (PCA, Yamamoto et al., 2013) to stablish the relation between the variables analyzed and treatments were performed using the XLSTAT software v. 2012.
The results of descriptors proposed and used for panelists for ‘Ataulfo’ mangoes are shown in Figures 1–3. For taste attributes, a significant difference was found (P < 0.05) in at least one treatment (Figure 1). The non-irradiated mangoes were the fruits with the highest sweetness value (6.59), which was significantly different (P < 0.05) with the irradiated treatments, which among themselves were statistically equal. This difference contradicts the content of soluble solids contents which was significantly equal (P > 0.05) between treatments (Table 2). Therefore, the sweetness difference detected by panelists may be due to a higher proportion of sugars with greater sweetening power (such as sucrose = 1 and fructose = 1.733) and a lower proportion of glucose (less sweetening power = 0.743) in the non-irradiated fruits. It has been reported that in samples of mango juice, the glucose content increased when doses of 0.5, 1 and 3 kGy were applied, but the sucrose and fructose content increased only when 3 kGy doses were used (Naresh et al., 2015). There are no reports of adverse effects of radiation on fruits when are irradiated with doses up to 0.7 kGy on sugar content once maturity is reached (Mahto et al., 2013). Shahbaz et al. (2014) observed that in pomegranate fruits the sugar content (sweetness) did not change regardless of the radiation dose applied (0 to 2 kGy). Kim and Yook (2009) reported that irradiation at a dose up 3 kGy in kiwifruit do not cause any change sweetness. In contrast, it was reported that irradiation induces amylolytic enzymes activity, where glucose is the main product (Surendranathan, 2005). Postharvest, although these results are contrary with the reported in potato, where irradiation reduces amylolytic activity (Mahboob et al., 2004). It was observed that panelists give them a lower rating for sourness to irradiated fruits (0.15 and 0.30 kGy) with differences between treatments (P < 0.05), and only in doses up 0.45 kGy results were no significantly different (P > 0.05) with control. The acid content in mango (mainly citric and malic acid; Lobit et al., 2006) does not explain the sourness perception given by panelists because the titratable acidity content did not report any differences (P > 0.05) between treatments (Table 2). It has been reported that doses less than 1 kGy have no effect on organic acid content in fruits or mango juice (Naresh et al., 2015). The judges perceived less sourness in the irradiated fruits with doses of 0.15 and 0.30 kGy probably due to a higher malic acid content, which could increase the sweetness perception due to sucrose; meanwhile in fruits irradiated with 0.45 kGy the organic acid content could be primarily citric acid which masks the perception of the sweetest sugars as sucrose and fructose (Green et al., 2010). The mangoes treated with 0.45 kGy registered the highest astringency and was significantly different (P < 0.05) to other three treatments (Figure 1). This corresponded with the phenolic content because this dose showed the highest content (Table 2), and these molecules are mainly responsible for astringent taste. When fruits reached maturity polyphenols content does not exceed 300 µg GAE/g pulp. Even when the radiation doses do not have a clear effect on the polyphenol content in Ataulfo mango (Table 2), until evaluated doses (0.5 kGy), the panelists detected astringent taste in treatments with the highest dose (Figure 1). The astringency can be easily confused with sourness, which in high acidity fruits (such as oranges) both stimuli can overcome. Even if there was no a significant correlation (P = 0.801) between sourness and astringent descriptors, the tendencies of values were similar for the same treatments.
Sensory evaluation of taste descriptors in 'Ataulfo' mango at different doses of gamma radiation. In the graphic, bars showed the average values of eight trained panelists, lines showed the standard deviation. Means followed by the same letter by descriptor, do not differ by Newman-Keuls test (P > 0.05).
Sensory evaluation of texture descriptors in ‘Ataulfo’ mango at different doses of gamma radiation. In the graphic, bars showed the average values of eight trained panelists, lines showed the standard deviation. Means followed by the same letter by descriptor, do not differ by Newman-Keuls test (P > 0.05).
Sensory evaluation of odor descriptors in ‘Ataulfo’ mango at different doses of gamma radiation. In the graphic, bars showed the average values of eight trained panelists, lines showed the standard deviation. Means followed by the same letter by descriptor, do not differ by Newman-Keuls test (P > 0.05).
| Irradiation dose (kGy) |
Soluble solids (TSS) (°Brix) |
Titratable acidity (TA) (g citric acid/100 g pulp) |
TSS /TA ratio | Total polyphenols (µg GAE/g pulp) |
|---|---|---|---|---|
| 0 | 22.15±0.78a | 0.11±0.01a | 201.36 | 227.08±11.07a |
| 0.15 | 20.10±0.26a | 0.09±0.02a | 223.33 | 204.13±11.07b |
| 0.3 | 21.35±3.65a | 0.11±0.01a | 194.09 | 182.25±1.90b |
| 0.45 | 22.05±0.49a | 0.12±0.20a | 183.75 | 233.29±1.52a |
Values correspond to the average of the three determinations ± standard deviation. Means followed by the same letter, in the same column, do not differ by Newman-Keuls test (P > 0.05).
Regarding texture descriptors, the panelists gave the highest values to juiciness, creaminess, and fibrousness; in contrast, firmness registered the lowest values (Figure 2). There were no significant differences in the juiciness descriptors, between control and treatment with 0.45 kGy, but these treatments were different with other two treatments (0.15 and 0.30 kGy dose). McDonald et al. (2012) reported that the irradiation produced juicier peaches when doses of 0.69 and 0.9 kGy are applied. This is similar to our results only for doses of 0.15 and 0.30 kGy, but higher doses do not influence the juiciness of Ataulfo mango. The juiciness of mangoes is apparently inversely associated with firmness because the juiciest treatments were detected as the less firm. At the same time, the firmness was inversely related to fibrousness since irradiated fruits registered the highest fibrous values. Some studies mentioned that doses less than 1 kGy do not affect firmness when is evaluated both instrumental (Gomes et al., 2008) and sensory (McDonald et al., 2013) perspective. However, our results showed a perception of less firmness in all irradiated fruits (Figure 2). Some studies report the effect of different doses of radiation on peach (McDonald et al., 2012), apple (Jung et al., 2016), and mango (Yadav et al., 2014) softening. Probably, irradiation modifies the synthesis or activity of enzymes that degrades polymers responsible for maintaining the structure, such as polygalacturonase and pectin methylesterases (Kim et al., 2015).
There were no significant differences in creaminess between treatments perceived by panelists (Figure 2), which demonstrates that irradiation had no effect on this descriptor. Creaminess is a sensory complex descriptor because it related to multiple food properties including texture viscous (flow resistance in the mouth or melting describe for Valente et al., 2011), smoothness, thickness and greasy sensation which is associated with fatty acid composition (Jellema et al., 2013). Even mango fruit lipid content does not exceed 1% (Ali et al., 1985), it is probably that gamma doses radiation up to 0.50 kGy in Ataulfo mango does not increase the level of peroxidation lipids when they reach maturity. Thus, there was no effect on this descriptor.
No significant differences were found between treatments (P > 0.05) for both apples' odor and pineapples odor (Figure 3). These odors are associated with ethyl esters of fatty acids, such as methyl/ethyl butyrate, which give the pineapple odor (Fellman et al., 2000) and butanoate for the apple odor (Wang et al., 2005). Despite this result, the apple odor was inversely correlated with the sweet taste (Figure 4). In contrast, there were differences (P < 0.05) with honey and mango odor descriptors at doses of 0.30 kGy and other treatments (for both descriptors). At this dose, panelists gave the highest scores for mango odor (4.75) and honey (2.26). This was also verified by a multivariate analysis because Pearson correlation showed a significant value (P = 0.02; R2 = 0.9820) between honey and mango odors (Figure 4).
Pearson correlation analysis of trained panelist's scores to descriptors (top) and Principal Component Analysis of relationships between sensory descriptors and gamma irradiation treatments in Ataulfo mangoes (bottom).
Also, the PCA analysis showed graphically an association between the doses of 0.30 kGy and odor honey, odor mango, and juiciness (Figure 4). This could indicate that gamma radiation could stimulate volatiles production as 3-carene, D-germacrene, α-pinene, β-selinene, terpinolene associated with mango Ataulfo odor (Salazar et al., 2007).
The gamma irradiation of ‘Ataulfo’ mango fruits produces slight changes in odor, taste and texture characteristics at doses up to 0.45 kGy. The irradiated fruits were perceived as less sweet (0.15, 0.30 and 0.45 kGy), more astringent (0.45 kGy), juicier (0.15 and 0.30 kGy) but with a greater smell of mango and honey (0.30 kGy). The irradiation of fruits with 0.15 kGy impacted little on the sensorial descriptors evaluated and can therefore be suggested as a method of post-harvest treatment of mango ‘Ataulfo’.
Acknowledgments The authors thank to Roberto Bustamante who kindly provided the mango fruits.
