Introduction
Pineapples are farmed largely in the subtropical region of Okinawa, the southernmost prefecture of Japan, and are one of the most popular fruits in this prefecture (Sugawara et al., 2019)i). The average annual commercial production of pineapple in Okinawa was approximately 7 536 t from 2017 to 2021i). The major cultivars in Okinawa include “N67-10” (Hawaiian smooth cayenne), “Yugafu,” and “Yonekura,” and they vary in physical traits and chemical composition, especially volatile components that emit distinct aroma characteristics and contribute to their flavor qualities (Asikin et al., 2022). Various new pineapple breeding lines suitable for the climate and soil conditions in Okinawa have been developed in recent years, and efforts have also emphasized producing fruits in higher quantities and creating a better quality of fruits with unique flavor properties (Shoda et al., 2012; Sugawara et al., 2019).
Physicochemical and flavor qualities are crucial for evaluating and assessing the quality of fruits, including pineapple (Asikin et al., 2022; Fan et al., 2021; Zhao et al., 2023). These traits play important roles in determining the overall quality, consumer acceptance, and marketability of various horticultural products (Du et al., 2022; Fan et al., 2021). By monitoring physicochemical characteristics, such as size, weight, color, soluble solid content, and acidity, farmers and agribusiness industries can assess fruit quality, determine maturity stages, optimize harvesting times, and improve storage conditions (Gomez et al., 2022; Park et al., 2018; Pontesegger et al., 2023; Zhao et al., 2023). Moreover, the appearance of the edible part of the pineapple is greatly influenced by the presence of yellow carotenoids (Gomez et al., 2022; Sugawara et al., 2019). The intensity and distribution of carotenoids throughout the fruit contribute to its visual appeal, attracting consumers and influencing their acceptance (Romli et al., 2021; Steingass et al., 2020; Sugawara et al., 2019).
The pineapple has a rich and characteristic aroma, primarily attributed to the diverse array of volatile compounds in the fruit (Ito et al., 2006; Tokitomo et al., 2005). These volatile compounds include esters, terpenes, aldehydes, ketones, and alcohols (Asikin et al., 2022; Montero-Calderón et al., 2010). Volatile compounds, especially those with high odor activity values (OAVs), contribute to the overall aroma profile and create a unique and recognizable scent in fruits (Montero-Calderón et al., 2010; Tokitomo et al., 2005). On the other hand, the orthonasal aroma of fruits, which is the perceived aroma detected through the nose when inhaled, is an integral part of the overall sensory experience and greatly influences the perception and enjoyment of fruits, including pineapples (Feldmeyer et al., 2021; Iobbi et al., 2023). Understanding the volatile compounds and orthonasal olfaction qualities of pineapples is crucial for quality assessment, flavor characterization, and product development (Asikin et al., 2022; Spence, 2023). This allows researchers and producers to identify key aroma contributors, optimize cultivation and postharvest practices, and develop pineapple-based products with enhanced and desirable aroma qualities.
To the best of our knowledge, this is the first report on the physicochemical and flavor qualities of newly bred Okinawan pineapple lines. The present study thus aimed to characterize the physicochemical and flavor qualities of edible fruit parts of five new pineapple breeding lines from Okinawa, Japan, compared to those of a known cultivar (“N67-10”). Their physicochemical traits (i.e., fruit weight, total soluble solids, titratable acidity, and L*a*b* color spaces), total carotenoid content, volatile component content, and orthonasal aroma profiles were compared. The aroma-active compounds of fruits with OAVs greater than 1 (OAV > 1) were also presented.
Materials and Methods
Sample preparation Pineapple fruits of the “N67-10” cultivar (control cultivar) and five breeding lines, namely “Okinawa No. 22,” “Okinawa No. 25,” “Okinawa No. 26,” “Okinawa No. 27,” and “Okinawa No. 28” were harvested at the ripe stage from a farm at the Okinawa Prefectural Agricultural Research Center, Nago, Okinawa, Japan from June to August 2020. The parentage of the breeding lines was as follows: “A882” × “Soft Touch,” “Julio Star” × “A882,” “Julio Star” × “MD2,” “Summer Gold” × “MD2,” and “Okinawa P17” × “Bogor,” respectively. Ten fruits of the “N67-10” cultivar or the new breeding lines were collected from the farm, and three representative fruits of each cultivar or line were then randomly selected for further analysis. Upon arrival at the laboratory, the fruits were immediately peeled and cut longitudinally into eight equal pieces. The edible fruit flesh cuts were used as follows: two pieces for physicochemical properties; two pieces were homogenized for carotenoids and volatile components analyses; and the remaining pieces were used for orthonasal aroma profile evaluation. The edible portion of the fruits after peeling and core removal ranged from 42.67 % to 45.68 % of the total fruit weight. The CIE L*a*b* color traits of edible fruit flesh were measured using an NF333 colorimeter (Nippon Denshoku, Tokyo, Japan). The fruit flesh was squashed using a hand-press juicer, and the total soluble solids and titratable acidity of the juice were measured using an NH-2000 Brix/acidity content analyzer (Horiba Advanced Techno, Tokyo, Japan). The fruit flesh was cryopulverized using a multi-bead shocker (Yasui Kikai, Osaka, Japan), and the homogenized puree was lyophilized for 48 h using an EYELA FDU-2000 freeze dryer (Tokyo Rikakikai, Tokyo, Japan). The fruit flesh, puree, and lyophilized tissue were stored in sealed vials at −30 °C before analysis.
Standards and reagents Acetone was purchased from the Fujifilm Wako Pure Chemical Corporation (Osaka, Japan). NaCl was obtained from Merck (Darmstadt, Germany), and 2-methyl-1-pentanol was obtained from Tokyo Chemical Industry (Tokyo, Japan). The standards for identifying volatile components were obtained from Sigma-Aldrich (St. Louis, MO, USA) and Tokyo Chemical Industry. All other reagents were of analytical grade.
Total carotenoids analysis Carotenoids were extracted using an organic solvent, and the optical densities of the extracts, which represented their total content, were measured using a microplate spectrophotometer (Aono et al., 2021). Briefly, 20 mg lyophilized tissue and 0.35 mL acetone were placed in a 2-mL tube, and then homogenized at 15 Hz for 10 min (TissueLyser LT; Qiagen, Hilden, Germany). The mixture was centrifuged (15 000 rpm, 5 min, 20 °C), and the supernatant was collected and placed on ice. The extraction process was repeated twice, resulting in approximately 0.4 mL of extracts. Subsequently, 300 μL of the extract was transferred into a 96-well glass microplate (Nikkei Products, Osaka, Japan). The optical density of the extract was measured at 662, 645, 470, and 750 nm using a PowerWave XS2 microplate reader (BioTek, VT, USA), and the wavelengths were corrected using the optical path length of the microplate well with optical density at 750 nm. Total carotenoids were calculated using the following equations:
where Ca is the chlorophyll a; Cb is the chlorophyll b; Ax is the absorbance at x nm; v is the volume of the solvent (mL); and w is the weight of the sample (mg). The total carotenoid content of the fruits was expressed as mg/kg fresh weight. All analyses were performed in triplicate.
Volatile components analysis The volatile components were extracted using a solid-phase microextraction (SPME)-Arrow and analyzed using gas chromatography-flame ionization detection/mass spectrometry (GC-FID/MS) (Asikin et al., 2022). Briefly, homogenized puree (2 g), internal standard 2-methyl-1-pentanol (3 μg/mL, 20 μL), and NaCl (0.2 g) were placed into a 10-mL glass vial. The sealed vials were subsequently sonicated at 25 °C for 10 min and heated at 40 °C for 7.5 min. The volatile components were then absorbed onto an SPME-Arrow fiber containing 120 μm divinylbenzene/polydimethylsiloxane (Restek, PA, USA) and heated for 30 min. For the analysis of the composition of volatile compounds, an Agilent 7890B GC-FID system equipped with a DB-Wax column (60 m × 0.25 mm, 0.25 μm, Agilent Technologies) was used to analyze the composition of the volatile compounds. Volatile compounds were desorbed from the column at a split ratio of 10:1 for 1 min. The injection and FID temperatures were both set to 250 °C. Helium was used as the carrier gas, and the flow rate was programmed to 32 cm/s. The column temperature was maintained at 40 °C for 2 min and then increased to 200 °C at a rate of 2 °C/min without any hold time at the final temperature.
For MS identification, GC-MS analysis was performed using an Agilent 7890A GC-5975C MS system (Agilent Technologies). The volatile extraction and chromatography conditions were the same as those described above. The ion source and interface were both set at 250 °C. The ionization energy was programmed to 70 eV, and the mass acquisition scan range was m/z 33–450 amu. Volatile compounds were identified based on linear RIs, which were determined from the retention times of n-alkanes (C7–C30) followed by a comparison of the MS patterns with the NIST MS Library Version 2008 and the MS data of co-injected authentic standards. The weight intensity of the peak was calibrated to the FID response of the internal standard, and the volatiles were expressed as relative percentages (%) and μg/kg. The OAV was determined by dividing the concentration of a compound by its odor threshold value. Aroma-active volatiles were assigned to compounds with an OAV greater than 1. All analyses were performed in triplicate.
Orthonasal aroma profile evaluation The frozen fruit flesh was acclimated to room temperature (25 °C) for 1 h before sensory evaluation. The fruit flesh was cut into slices of approximately 3 × 5 × 20 mm, and the flesh cuts were mixed. Afterward, the slices (10 g) were randomly placed in 50-mL amber glass vials (78 × 35 od. mm; Nichiden-Rika Glass, Hyogo, Japan). The aroma profiles of the fruit slices were evaluated by 15 trained assessors (10 males and five females, aged between 22 and 61 years). An assessor was asked to sniff the presence of fruity, sweet, coconut, peach, and green-grassy odors from the fruit slices in an opened vial for approximately 15 s. A 15–20 s-break interval between sample testing for nasal passage resetting was allowed. The perceived orthonasal aromas of the odors were aggregated from several assessors, and the odor detection frequency was presented from “0” (no assessor identified the odor) to “15” (all assessors identified the odor).
Statistical analysis Each result is expressed as the mean value and standard deviation. Statistical differences in physicochemical traits (including fruit total soluble solid/titratable acidity ratio and color space) and volatile components among the groups were examined using the Tukey-Kramer honestly significant difference test (JMP Version 13, SAS Institute, NC, USA). Pearson’s correlations between the parameters and multivariate plots were calculated using GraphPad Prism Version 9 (GraphPad Software, CA, USA).
Results and Discussion
Physicochemical traits and total carotenoids of Okinawan pineapple breeding lines The fruit weight of the “N67-10” cultivar and five new breeding lines could reach approximately 1 275 g when they were in the fully ripened stage for harvest (Table 1). The heaviest fruits were recorded in the “Okinawa No. 26” line, and the lightest one was “Okinawa No. 22” (1 574.3 vs. 1 104.7 g); however, there was no significant difference between the “N67-10” cultivar and newly bred lines (p < 0.05). The fruits also had similar total soluble solids (TSS), which ranged from 15.87 to 20.33° Brix but varied in their titratable acidity (TA) values. Accordingly, there was variability in their TSS to TA ratios, and the “Okinawa No. 26” and “Okinawa No. 28” had the greatest TSS/TA values at 46.99 and 45.19, respectively. In contrast, the TSS/TA values of the other three breeding lines were lower (30.19–39.70). However, compared with the “N67-10” cultivar and other commercial Okinawan pineapple cultivars such as “Yugafu” and “Yonekura” of the previously reported study (Asikin et al., 2022), the newly bred lines had greater TSS/TA ratios. Farmers have used these basic physicochemical traits to monitor the degree of fruit maturity and may indicate their overall flavor quality (Pontesegger et al., 2023; Romli et al., 2021). Although TSS and TA do not represent sugar and organic acid contents exactly, these values have also been associated with the sensory characteristics of fruits and their organoleptic acceptance properties (Du et al., 2022; Park et al., 2018; Romli et al., 2021).
Table 1. Physicochemical traits of the “N67-10” cultivar and Okinawan pineapple breeding lines.
| Traits |
‘N67-10’ |
‘Okinawa No. 22’ |
‘Okinawa No. 25’ |
‘Okinawa No. 26’ |
‘Okinawa No. 27’ |
‘Okinawa No. 28’ |
| Fruit weight (g) |
1 195.0 ± 37.8 a |
1 104.7 ± 80.1 a |
1 344.3 ± 208.4 a |
1 574.3 ± 96.9 a |
1 163.7 ± 102.0 a |
1 266.0 ± 385.9 a |
| Total soluble solid (°Brix) |
17.17 ± 3.35 a |
15.87 ± 0.32 a |
16.20 ± 0.87 a |
17.70 ± 0.52 a |
17.73 ± 0.51 a |
20.33 ± 2.07 a |
| Titratable acidity (%) |
0.60 ± 0.05 a |
0.50 ± 0.04 abc |
0.54 ± 0.02 ab |
0.38 ± 0.03 c |
0.45 ± 0.05 bc |
0.45 ± 0.09 bc |
| Total soluble |
28.61 ± 3.91 b |
31.52 ± 1.75 ab |
30.19 ± 0.37 b |
46.99 ± 4.34 a |
39.70 ± 3.81 ab |
45.19 ± 12.96 a |
| solid/titratable acidity ratio |
|
|
|
|
|
|
| Color space L* |
76.14 ± 18.30 a |
64.58 ± 0.95 a |
67.52 ± 1.23 a |
62.45 ± 4.06 a |
70.20 ± 1.23 a |
67.62 ± 1.25 a |
| Color space a* |
−2.67 ± 0.03 ab |
−1.57 ± 0.97 a |
−4.16 ± 0.73 b |
−1.01 ± 0.93 a |
−2.28 ± 0.08 ab |
−3.01 ± 1.24 ab |
| Color space b* |
19.56 ± 2.39 c |
35.13 ± 1.77 a |
25.28 ± 0.92 b |
34.84 ± 2.91 a |
25.14 ± 0.69 b |
28.11 ± 2.10 b |
Each value is expressed as the mean ± standard deviation of three replicates. Means in the same row followed by the same letter are not significantly different at p < 0.05.
The brightness index (color space L*) of the edible fruit flesh of these breeding lines was comparable at 62.45 to 70.20, while the “N67-10” cultivar had a higher average value at 76.14; however, its high variation (±18.30) caused no statistical differences on flesh lightness among all evaluated fruits (p < 0.05) (Table 1). There were also variations in the green color index (a*) of these lines, from −4.16 to −1.01. However, since the values were close to zero, they might have a limited impact on the overall appearance of the pineapple flesh. In contrast, the “Okinawa No. 22” and “Okinawa No. 26” lines had greater yellow color index (b*), 35.13 and 34.84, respectively, followed by other three lines that ranged from 25.14 to 28.11, whereas the “N67-10” was recorded at a considerably lower value. The color space b* of these fruits was significantly positively associated with their total carotenoid content (Pearson’s correlation coefficient, r = 0.9424; p = 0.0049) (Fig. 1), and the “Okinawa No. 26” breeding line contained the highest carotenoids at 8.74 mg/kg, while the “N67-10” cultivar only had 1.62 mg/kg. Carotenoid contents of the other newly bred lines were 6.82, 5.24, and 4.59 mg/kg in the “Okinawa No. 22,” “Okinawa No. 28,” and “Okinawa No. 27” lines, respectively. These phytopigments may be composed of violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, α-carotene, and β-carotene (Steingass et al., 2020; Sugawara et al., 2019), could contribute to the appearance of yellow and golden colors in pineapples. Moreover, the presence of carotenoids in pineapple, which have antioxidant and antiproliferative properties, could enhance its nutritional value and contribute to its positive perception as a healthy and beneficial fruit (Antunes et al., 2022; Gomez et al., 2022).
Volatile components of Okinawan pineapple breeding lines The volatile components of the “N67-10” cultivar and the five new breeding lines comprised 36 esters, 11 terpenes, 10 ketones, 6 alcohols, 4 aldehydes, 3 carboxylic acids, and 1 hydrocarbon (Table 2). The order of the cultivar or breeding line with the most to the least content of volatile components was as follows: “Okinawa No. 28” > “Okinawa No. 22” > “Okinawa No. 26” > “Okinawa No. 27” > “N67-10” > “Okinawa No. 25”; ranged from 87.51 to 668.93 μg/kg. For esters, the “Okinawa No. 28” breeding line contained the highest amount and relative percentage, 516.48 μg/kg and 68.79 %, respectively, followed by the “Okinawa No. 22” and “Okinawa No. 26” lines. Conversely, the “N67-10” cultivar and “Okinawa No. 25” line contained much lower amounts and number of identified compounds. The most predominant ester in these fruits was methyl hexanoate, in which the “Okinawa No. 22” line contained a significantly higher amount, 234.07 μg/kg (p < 0.05). The other major esters in the “Okinawa No. 22” line were methyl 3-(methylthio)propanoate and methyl octanoate (91.77 and 26.49 μg/kg, respectively). Moreover, line 28 contained high levels of methyl 3-(methylthio)propanoate, methyl 2-methylbutanoate, ethyl 3-(methylthio)propanoate, and methyl butanoate (172.79, 74.44, 57.81, and 38.42 μg/kg, respectively). In contrast, the major esters in the “Okinawa No. 26” line were methyl 2-methylbutanoate, ethyl 3-(methylthio)propanoate, and ethyl 2-methylbutanoate.
Table 2. Volatile components of the “N67-10” cultivar and Okinawan pineapple breeding lines (μg/kg)
a.
| No |
RI |
Compoundb |
‘N67-10’ |
‘Okinawa No. 22’ |
‘Okinawa No. 25’ |
‘Okinawa No. 26’ |
‘Okinawa No. 27’ |
‘Okinawa No. 28’ |
| 1 |
886 |
Ethyl acetate |
9.66 ± 9.65 a |
1.80 ± 0.80 a |
1.76 ± 0.41 a |
25.50 ± 31.57 a |
5.25 ± 2.56 a |
15.02 ± 12.68 a |
| 2 |
902 |
Methyl propanoate |
3.64 ± 1.68 a |
4.36 ± 1.41 a |
3.49 ± 0.53 a |
2.60 ± 0.77 a |
3.83 ± 0.36 a |
3.66 ± 0.41 a |
| 3 |
983 |
Methyl butanoate |
1.94 ± 0.32 b |
5.82 ± 3.35 b |
1.42 ± 0.53 b |
2.86 ± 2.80 b |
13.91 ± 13.14 b |
38.42 ± 6.11 a |
| 4 |
1008 |
Methyl 2-methylbutanoate |
1.23 ± 0.18 a |
2.05 ± 0.66 a |
1.10 ± 0.15 a |
40.26 ± 27.25 a |
17.77 ± 19.26 a |
74.44 ± 57.54 a |
| 5 |
1011 |
Isobutyl acetate |
tr |
nd |
nd |
1.29 ± 0.55 a |
1.30 ± 0.36 a |
1.05 ± 0.24 a |
| 6 |
1016 |
Methyl 3-methylbutanoate |
1.86 ± 0.12 b |
1.93 ± 0.60 b |
1.64 ± 0.83 b |
3.69 ± 1.20 ab |
3.21 ± 2.54 ab |
6.77 ± 1.69 a |
| 7 |
1033 |
Ethyl butanoate |
2.01 ± 1.59 b |
2.19 ± 1.15 b |
2.17 ± 0.34 b |
5.72 ± 3.92 ab |
2.62 ± 1.49 b |
9.25 ± 2.90 a |
| 8 |
1048 |
Ethyl 2-methylbutanoate |
tr |
nd |
1.51 ± 1.00 b |
33.53 ±21.13 a |
2.98 ± 2.30 b |
9.22 ± 2.60 ab |
| 9 |
1081 |
Methyl pentanoate |
nd |
2.13 ± 0.74 a |
nd |
nd |
tr |
2.46 ± 0.78 a |
| 10 |
1115 |
2-Methylbutyl acetate |
nd |
nd |
nd |
tr |
7.20 ± 3.38 a |
2.72 ± 0.54 a |
| 11 |
1116 |
3-Methylbutyl acetate |
3.61 ± 2.65 a |
2.54 ± 1.55 a |
1.23 ± 0.33 a |
6.02 ± 3.08 a |
nd |
2.13 ± 0.25 a |
| 12 |
1181 |
Methyl hexanoate |
9.96 ± 5.13 b |
234.07 ± 140.63 a |
4.74 ± 3.32 b |
4.04 ± 3.58 b |
28.33 ± 16.57 b |
62.80 ±21.51 b |
| 13 |
1229 |
Ethyl hexanoate |
8.17 ± 6.46 a |
8.87 ± 0.90 a |
4.95 ± 3.80 a |
12.59 ± 14.91 a |
11.27 ± 3.97 a |
3.64 ± 0.36 a |
| 14 |
1249 |
Prenyl acetate |
tr |
1.00 ± 0.29 a |
nd |
nd |
1.05 ± 0.20 a |
1.42 ± 0.23 a |
| 15 |
1253 |
Methyl (Z)-3-hexanoate |
nd |
1.42 ± 0.30 |
nd |
nd |
nd |
nd |
| 16 |
1259 |
Methyl (E)-3-hexanoate |
tr |
2.62 ± 1.47 a |
nd |
1.38 ± 0.36 a |
tr |
2.56 ± 0.16 a |
| 17 |
1283 |
Methyl heptanoate |
nd |
nd |
nd |
15.00 ± 8.93 a |
tr |
4.20 ± 1.90 a |
| 18 |
1371 |
Methyl 3-hydroxy-3-methylbutanoate |
nd |
nd |
0.87 ± 0.07 a |
1.73 ± 0.33 a |
nd |
1.14 ± 0.10 a |
| 19 |
1384 |
Methyl octanoate |
4.01 ± 1.08 b |
26.49 ± 5.19 a |
tr |
4.50 ± 0.81 b |
2.98 ± 1.12 b |
2.30 ± 1.18 b |
| 20 |
1425 |
Methyl (Z)-5-octenoate |
nd |
2.11 ± 0.39 |
nd |
nd |
nd |
nd |
| 21 |
1431 |
Ethyl octanoate |
5.08 ± 4.82 a |
tr |
tr |
3.93 ± 4.19 a |
tr |
2.50 ± 0.57 a |
| 22 |
1451 |
Methyl (E)-3-octenoate |
2.64 ± 0.35 a |
2.78 ± 0.40 a |
1.82 ± 0.42 a |
1.89 ± 0.18 a |
nd |
2.24 ± 0.62 a |
| 23 |
1507 |
Dimethyl propanedioate |
0.92 ± 0.10 b |
2.98 ± 1.46 ab |
nd |
nd |
tr |
7.54 ± 3.29 a |
| 24 |
1518 |
Methyl 3-(methylthio)propanoate |
5.91 ± 0.41 b |
91.77 ± 53.88 ab |
4.81 ± 1.08 b |
11.54 ± 10.26 b |
17.10 ± 15.65 b |
172.79 ± 91.67 a |
| 25 |
1537 |
Methyl 2-acetoxybutanoate |
tr |
3.60 ± 1.90 b |
4.03 ± 1.16 b |
16.15 ± 3.64 a |
tr |
15.45 ± 1.74 a |
| 26 |
1555 |
Methyl 3-acetoxy-2-methylbutanoate |
nd |
1.61 ± 0.27 b |
tr |
15.76 ± 4.99 a |
1.69 ± 0.15 b |
3.79 ± 0.87 b |
| 27 |
1563 |
Ethyl 3-(methylthio)propanoate |
3.79 ± 3.25 b |
2.14 ± 0.29 b |
3.98 ± 1.00 b |
34.90 ± 24.07 ab |
5.09 ± 3.61 b |
57.81 ± 26.67 a |
| 28 |
1567 |
Tetrahydrofuranyl acetate |
tr |
nd |
nd |
tr |
nd |
1.67 ± 0.12 |
| 29 |
1626 |
3-(Methylthio)propyl acetate |
nd |
2.83 ± 1.84 a |
1.70 ± 0.52 a |
l.ll ± 0.12 a |
2.97 ± 0.97 a |
1.93 ± 0.73 a |
| 30 |
1638 |
Methyl 4-(methylthio)butanoate |
nd |
nd |
nd |
3.96 ± 2.51 a |
nd |
2.67 ± 0.02 a |
| 31 |
1647 |
Methyl 3-hydroxyhexanoate |
tr |
1.64 ± 0.34 a |
nd |
4.51 ± 2.66 a |
nd |
nd |
| 32 |
1725 |
Phenylmethyl acetate |
8.38 ± 11.79 a |
tr |
nd |
5.47 ± 2.16 a |
7.35 ± 2.52 a |
2.67 ± 0.88 a |
| 33 |
1732 |
Methyl 4-acetoxyhexanoate |
tr |
3.65 ± 1.21 a |
nd |
3.59 ± 3.19 a |
nd |
nd |
| 34 |
1756 |
Methyl phenylacetate |
nd |
3.91 ± 1.50 a |
nd |
nd |
nd |
2.22 ± 0.80 a |
| 35 |
1772 |
Methyl 5-acetoxyhexanoate |
1.23 ± 0.16 b |
11.67 ± 5.22 a |
nd |
10.46 ± 5.82 ab |
1.19 ± 0.14 b |
tr |
| 36 |
1921 |
Methyl 5-acetoxyoctanoate |
nd |
nd |
nd |
8.51 ± 10.70 |
tr |
nd |
|
|
Total esters (relative percentage, %) |
74.04 (26.04%) |
427.98 (65.41%) |
41.22 (31.73%) |
282.49 (40.81%) |
137.09 (29.43%) |
516.48 (68.79%) |
| 37 |
935 |
Ethanol |
73.32 ± 74.25 a |
5.08 ± 1.49 a |
7.45 ± 0.60 a |
120.57 ± 96.09 a |
39.16 ± 26.76 a |
28.23 ± 18.12 a |
| 38 |
1040 |
2-Methyl-3-buten-2-ol |
1.98 ± 0.59 |
nd |
nd |
nd |
nd |
nd |
| 39 |
1456 |
1-Heptanol |
1.65 ± 0.70 a |
1.95 ± 0.19 a |
1.54 ± 0.51 a |
tr |
1.16 ± 0.05 a |
2.14 ± 1.11 a |
| 40 |
1491 |
2-Ethyl-1 -hexanol |
7.43 ± 4.64 a |
8.57 ± 1.13 a |
6.81 ± 0.70 a |
5.69 ± 1.86 a |
8.66 ± 1.14 a |
7.16 ± 1.85 a |
| 41 |
1560 |
1-Octanol |
4.86 ± 2.30 a |
3.82 ± 0.44 a |
2.67 ± 0.55 a |
2.01 ± 0.31 a |
2.82 ± 0.65 a |
3.26 ± 0.53 a |
| 42 |
1657 |
2-Furanmethanol |
2.63 ± 0.65 b |
4.59 ± 0.52 a |
2.63 ± 0.37 b |
2.55 ± 1.08 b |
2.90 ± 0.32 ab |
3.85 ± 0.97 ab |
|
|
Total alcohols (relative percentage, %) |
91.87 (32.31%) |
24.01 (3.67%) |
21.10 (16.24%) |
130.82 (18.90%) |
54.70 (11.74%) |
44.64 (5.95%) |
| 43 |
1076 |
Hexanal |
7.83 ± 3.02 ab |
14.36 ± 4.56 a |
8.04 ± 4.28 ab |
6.20 ± 1.42 ab |
6.49 ± 3.09 ab |
4.95 ± 2.28 b |
| 44 |
1212 |
2-Hexanal |
tr |
1.61 ± 0.41 a |
1.56 ± 0.15 a |
2.61 ± 1.11 a |
nd |
1.24 ± 0.09 a |
| 45 |
1387 |
Nonanal |
8.71 ± 3.82 a |
6.13 ± 0.41 a |
5.53 ± 0.82 a |
4.65 ± 0.26 a |
6.40 ± 0.69 a |
6.45 ± 1.07 a |
| 46 |
1639 |
trans-2-Decenal |
1.74 ± 0.42 a |
1.76 ± 0.21 a |
1.35 ± 0.32 a |
nd |
tr |
nd |
|
|
Total aldehydes (relative percentage, %) |
18.28 (6.43%) |
23.86 (3.65%) |
16.48 (12.69%) |
13.46 (1.94%) |
12.89 (2.77%) |
12.64 (1.68%) |
| 47 |
1227 |
cis-β-Ocimene |
nd |
2.26 ± 0.90 b |
nd |
nd |
7.07 ± 3.48 b |
39.12 ± 16.54 a |
| 48 |
1243 |
trans-β-Ocimene |
nd |
9.86 ± 1.74 b |
nd |
tr |
65.31 ± 33.15 a |
nd |
| 49 |
1414 |
Isodurene |
nd |
1.37 ± 0.08 a |
nd |
nd |
1.48 ± 0.29 a |
nd |
| 50 |
1481 |
Copaene |
7.64 ± 7.61 |
nd |
nd |
nd |
nd |
nd |
| 51 |
1548 |
Linalool |
2.59 ± 0.97 ab |
4.71 ± 0.71 a |
1.12 ± 0.14 b |
2.21 ± 0.48 ab |
2.96 ± 0.15 ab |
2.63 ± 1.05 ab |
| 52 |
1581 |
β-Elemene |
4.10 ± 1.96 a |
nd |
nd |
2.01 ± 0.56 a |
nd |
nd |
| 53 |
1600 |
4-Terpineol |
tr |
2.16 ± 0.56 a |
nd |
nd |
1.32 ± 0.05 a |
nd |
| 54 |
1641 |
Menthol |
tr |
1.02 ± 0.16 b |
1.20 ± 0.28 ab |
tr |
1.61 ± 0.19 ab |
2.61 ± 0.58 a |
| 55 |
1681 |
γ-Muurolene |
5.20 ± 2.79 a |
nd |
nd |
3.66 ± 1.63 a |
nd |
1.96 ± 0.41 a |
| 56 |
1717 |
α-Muurolene |
7.67 ± 6.15 |
nd |
nd |
nd |
nd |
nd |
| 57 |
1751 |
δ-Cadinene |
4.65 ± 3.17 |
nd |
nd |
nd |
nd |
nd |
|
|
Total terpenes (relative percentage, %) |
31.85 (11.20%) |
21.38 (3.27%) |
2.32 (1.79%) |
7.88 (1.14%) |
79.75 (17.12%) |
46.32 (6.17%) |
| 58 |
1332 |
Methyl heptenone |
1.06 ± 0.14 a |
1.26 ± 0.04 a |
tr |
1.08 ± 0.04 a |
nd |
nd |
| 59 |
1590 |
4-Methoxy-2,5-dimethyl-3(2H)-furanone |
1.89 ± 0.10 a |
5.54 ± 2.44 a |
nd |
18.33 ± 15.45 a |
29.85 ± 20.11 a |
17.74 ± 6.09 a |
| 60 |
1695 |
γ-Hexalactone |
tr |
23.58 ± 5.37 a |
nd |
16.16 ± 8.59 ab |
7.88 ± 3.27 b |
5.33 ± 2.32 b |
| 61 |
1787 |
δ-Hexalactone |
nd |
3.79 ± 1.20 a |
nd |
2.29 ± 0.84 a |
nd |
nd |
| 62 |
1798 |
γ-Heptalactone |
nd |
1.47 ± 0.55 |
nd |
tr |
nd |
nd |
| 63 |
1912 |
γ-Octalactone |
nd |
18.57 ± 6.18a |
nd |
3.39 ± 3.09 b |
2.38 ± 0.49 b |
1.90 ± 0.23 b |
| 64 |
1964 |
δ-Octalactone |
nd |
8.68 ± 2.60 |
nd |
tr |
tr |
nd |
| 65 |
2039 |
4-Hydroxy-2,5-dimethyl-3(2H)-furanone |
4.06 ± 0.30 bc |
5.39 ± 2.16 bc |
3.03 ± 0.92 c |
3.27± 1.17 c |
9.06 ± 1.84 ab |
13.89 ± 3.20 a |
| 66 |
2142 |
γ-Decalactone |
nd |
5.19 ± 0.92 |
nd |
nd |
nd |
nd |
| 67 |
2193 |
δ-Decalactone |
nd |
3.86 ± 0.48 |
nd |
nd |
nd |
nd |
|
|
Total ketones (relative percentage, %) |
7.01 (2.47%) |
77.33 (11.82%) |
3.03 (2.33%) |
44.52 (6.43%) |
49.17 (10.56%) |
38.86 (5.18%) |
| 68 |
1851 |
Hexanoic acid |
2.46 ± 0.98 a |
4.91 ± 3.87 a |
3.36 ± 1.65 a |
4.85 ± 1.74 a |
3.92 ± 0.51 a |
7.91 ± 4.29 a |
| 69 |
2068 |
Octanoic acid |
nd |
tr |
nd |
2.08 ± 1.10 |
nd |
tr |
| 70 |
2178 |
Nonanoic acid |
3.06 ± 1.19 a |
1.67 ± 0.34 a |
nd |
nd |
tr |
nd |
|
|
Total carboxylic acids (relative percentage, %) |
5.52 (1.94%) |
6.58 (1.01%) |
3.36 (2.59%) |
6.93 (1.00%) |
3.92 (0.84%) |
7.91 (1.05%) |
| 71 |
1445 |
1,3,5,8-Undecatetraene |
nd |
3.12 ± 1.16 a |
nd |
nd |
nd |
2.08 ± 0.51 a |
|
|
Total hydrocarbons (relative percentage, %) |
nd |
3.12 (0.48%) |
nd |
nd |
nd |
2.08 (0.28%) |
|
|
Total identified (%) |
80.40% |
89.29% |
67.37% |
70.22% |
72.46% |
89.09% |
|
|
Total volatile components |
228.57 |
584.26 |
87.51 |
486.10 |
337.52 |
668.93 |
a Each value is expressed as the mean ± standard deviation of three replicates; nd. not detected; tr. trace (<0.01 μg/kg). Means in the same row followed by the same letter are not significantly different at
p< 0.05.
b Compound was identified by comparing MS fragmentation patterns from GC-MS analysis with the NIST MS Spectral Library and RI on a DB-WAX column.
The amount and ratio of volatile compounds in Okinawan pineapple fruits can vary depending on differences in their genetic parents. Accordingly, “Okinawa No. 22” and “Okinawa No. 28” breeding lines had 2.56- and 2.93-folds higher volatile concentrations compared with that of the control cultivar N67-10, respectively (Table 2), indicating that these newly bred lines had promising capacities to release greater volatile substances from their fruits. Numerous studies have shown that the total number of volatile components may not always positively affect the sensory attributes of fruits and their products (Li et al., 2021; Spaho et al., 2021). Hence, the volatile composition could distinguish the aroma characteristics of each breeding line, wherein esters, as the predominant volatile group, provided strong typical fruity and pineapple aromas. For instance, the major ester components of the “Okinawa No. 22” line can impart the following odors to its fruit: fruity and ethereal (methyl hexanoate), sweet-fruity and vegetable (methyl 3-(methylthio)propanoate), and fruity and green (methyl octanoate) (Ito et al., 2006)ii). Likewise, besides the strong sweet-vegetable aroma from methyl 3-(methylthio)propanoate, “Okinawa No. 28” fruits might also be complemented by green-fruity, sulfuric-fruity odor, and sweet-fruity scents from methyl 2-methylbutanoate, ethyl 3-(methylthio)propanoate, and methyl butanoate, respectively (Ito et al., 2006; Tokitomo et al., 2005)ii).
Moderate amounts of alcohols, terpenes, aldehydes, and ketones were found in the Okinawan pineapple fruit (Table 2). The relative concentrations of these volatile compounds ranged from 3.67–32.31, 1.79–17.12, 1.68–12.69, and 2.33–11.82 %, respectively. The volatiles in the alcohol group were composed of ethanol, 2-ethyl-1-hexanol, 1-octanol, 2-furanmethanol, and 1-heptanol, whereas 2-methyl-3-buten-2-ol was only available in the “N67-10” cultivar. The “Okinawa No. 27” breeding line contained greater amounts of terpenes, especially trans-β-ocimene (65.31 μg/kg), whereas the “Okinawa No. 28” line contained significantly higher cis-β-ocimene (39.12 μg/kg). Moreover, the “N67-10” cultivar exclusively contained copaene, α-muurolene, and δ-cadinene. In addition, the “N67-10” cultivar and the new breeding lines contained two predominant aldehydes, hexanal and nonanal (4.95–14.36 and 4.65–8.71 μg/kg, respectively), and small amounts of 2-hexanal and trans-2-decenal. Furthermore, the ketones in the pineapple fruits were composed of seven lactones, two furanones, and one methyl alkyl ketone. The “Okinawa No. 22” breeding line had greater amounts of lactones than the “N67-10” cultivar and other lines, including γ-hexalactone, γ-octalactone, δ-octalactone, γ-decalactone, and δ-decalactone, whereas most of the lactones were absent in the “N67-10” cultivar and “Okinawa No. 25” line. Moreover, the fruits contained 4-methoxy-2,5-dimethyl-3(2H)-furanone and 4-hydroxy-2,5-dimethyl-3(2H)-furanone in the range of 1.89–29.85 and 3.03–13.89 μg/kg, respectively. Additionally, all newly bred lines contained carboxylic acids at concentrations of 3.36–7.91 μg/kg (0.84–2.59 %), but a hydrocarbon compound, 1,3,5,8-undecatetraene, was only found in the “Okinawa No. 22” and “Okinawa No. 28” (0.48 and 0.28 %, respectively).
The moderately volatile components, including alcohols, terpenes, aldehydes, and ketones, might impart various characteristic aroma properties to Okinawan fruits of different breeding lines. For the alcohol group, 2-ethyl-1-hexanol, 1-octanol, and 2-furanmethanol in those fruits have potent capabilities to emit fresh-floral, waxy-green, and sweet roasted-caramel aromas, respectively (Asikin et al., 2016; ii). Furthermore, trans-β-ocimene could promote greater sweet and herbal odors in the “Okinawa No. 27” line than in fruits from other lines, whereas its stereoisomer, cis-β-ocimene, might complement the “Okinawa No. 28” line with stronger green and floral scentsii). Aldehyde components might enrich fruits with various green-grassy and floral aromas, which might be necessary for constructing a well-balanced pineapple flavor (Asikin et al., 2018)ii). In the ketone group, furanones might be the responsible compounds for enhancing sweet and caramel aromas in all fruits, whereas lactones could provide a sensation of tropical fruits, such as coconut-like and peach-like aromas, particularly to “Okinawa No. 22” (Asikin et al., 2016; Tokitomo et al., 2005; ii). The above-mentioned volatile components (predominant esters and moderate compounds) displayed a proportion of potent aroma characteristics in fruits of the “N67-10” cultivar and five new breeding lines, showing differences in flavor qualities. However, every volatile component has a different odor threshold level, the minimum concentration at which an odor can be detected by human senses (van Gemert, 2011). Hence, the OAV of these compounds was compared among the breeding lines by considering their unique odor threshold concentrations, and the aroma-active compounds of the fruits were determined.
Fourteen compounds had OAVs greater than 1, including nine esters: methyl butanoate, methyl 2-methylbutanoate, methyl 3-methylbutanoate, ethyl butanoate, 3-methylbutyl acetate, methyl hexanoate, ethyl hexanoate, ethyl octanoate, and methyl 3-(methylthio)propanoate (Table 3). The “Okinawa No. 28,” “Okinawa No. 26,” and “Okinawa No. 27” breeding lines had methyl 2-methylbutanoate with superior OAVs, 297.78, 161.04, and 71.08, respectively. Moreover, ethyl octanoate was found with high OAVs in the “N67-10” cultivar as well as “Okinawa No. 26” and “Okinawa No. 28” lines (50.81, 39.26, and 24.96, respectively); however, this ester was only available in trace amounts in the other breeding lines. Distinguished OAVs were also detected in the “Okinawa No. 26” and “Okinawa No. 27” lines for ethyl hexanoate (25.17 and 22.53, respectively). However, several esters were only considered aroma-active compounds in N67-10 cultivar or particular breeding lines, but not in others because their OAVs were less than 1. For instance, OAV higher than 1 of methyl butanoate was only found in “Okinawa No. 22,” “Okinawa No. 27”,” and “Okinawa No. 28” lines, 3-methylbutyl acetate in “N67-10” cultivar and “Okinawa No. 26” line, methyl hexanoate in “Okinawa No. 22” line, and methyl 3-(methylthio)propanoate in “Okinawa No. 28” line. In addition to these esters, other aroma-active compounds were nonanal, linalool, furanones, and δ-decalactone. The OAVs of nonanal ranged from 1.33 to 2.49, while except for the “Okinawa No. 25” line, the values varied from 1.47 to 3.14 for linalool. Additionally, OAVs greater than 1 for 4-methoxy-2,5-dimethyl-3(2H)-furanone, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, and δ-decalactone were limited to “Okinawa No. 27,” “Okinawa No. 28,” and “Okinawa No. 22” lines, respectively.
Table 3. Odor activity values (OAVs) of aroma-active compounds of the “N67-10” cultivar and Okinawan pineapple breeding lines.
| Compound |
Odor threshold (μg/kg)a |
‘N67-10’ |
‘Okinawa No. 22’ |
‘Okinawa No. 25’ |
‘Okinawa No. 26’ |
‘Okinawa No. 27’ |
‘Okinawa No. 28’ |
| Methyl butanoate |
5 |
0.39 |
1.16 |
0.28 |
0.57 |
2.78 |
7.68 |
| Methyl 2-methylbutanoate |
0.25 |
5.10 |
8.18 |
4.42 |
161.04 |
71.08 |
297.78 |
| Methyl 3-methylbutanoate |
0.4 |
4.65 |
4.82 |
4.11 |
9.22 |
8.03 |
16.92 |
| Ethyl butanoate |
1 |
2.01 |
2.19 |
2.17 |
5.72 |
2.62 |
9.25 |
| 3-Methylbutyl acetate |
3 |
1.20 |
0.85 |
0.41 |
2.01 |
nd |
0.71 |
| Methyl hexanoate |
75 |
0.13 |
3.12 |
0.06 |
0.05 |
0.38 |
0.84 |
| Ethyl hexanoate |
0.5 |
16.35 |
17.74 |
9.90 |
25.17 |
22.53 |
7.28 |
| Ethyl octanoate |
0.1 |
50.81 |
tr |
tr |
39.26 |
tr |
24.96 |
| Methyl 3-(methylthio)propanoate |
150 |
0.04 |
0.61 |
0.03 |
0.08 |
0.11 |
1.15 |
| Nonanal |
3.5 |
2.49 |
1.75 |
1.58 |
1.33 |
1.83 |
1.84 |
| Linalool |
1.5 |
1.72 |
3.14 |
0.75 |
1.47 |
1.98 |
1.76 |
| 4-Methoxy-2,5-dimethyl-3(2H)-furanone |
25 |
0.08 |
0.22 |
nd |
0.73 |
1.19 |
0.71 |
| 4-Hydroxy-2,5-dimethyl-3(2H)-furanone |
10 |
0.41 |
0.54 |
0.30 |
0.33 |
0.91 |
1.39 |
| δ-Decalactone |
1 |
nd |
3.86 |
nd |
nd |
nd |
nd |
The OAV was calculated by dividing the compound concentration by its odor threshold; nd. not detected; tr. the compounds were present in trace concentration (< 0.01 μg/kg).
A high OAV suggests that the concentration of a particular compound is above its odor threshold and is thus likely to contribute significantly to the aroma profile of fruits (Kuroki et al., 2021; Tokitomo et al., 2005; Yilmaztekin, 2014). Methyl 2-methylbutanoate was the most active aromatic substance in the three breeding lines (“Okinawa No. 28,” “Okinawa No. 26,” and “Okinawa No. 27”) (Table 3), indicating its potent contribution to the overall aroma characteristics of the fruits contributing to sweet and fruity odors (Ito et al., 2006; Tokitomo et al., 2005). The higher concentration of the compound in those lines (17.77–74.44 μg/kg) was augmented in the OAV calculation due to its lower odor threshold value, 0.25 μg/kg (Tables 2 and 3). However, although “Okinawa No. 22” contained higher methyl hexanoate (234.07 μg/kg), higher odor threshold concentration (75 μg/kg) caused its OAV to become much lower than that of methyl 2-methylbutanoate, thus lowering its aroma activity prominence. The OAV calculation also emphasized the importance of esters (ethyl hexanoate, methyl 2-methylbutanoate, and ethyl butanoate) and linalool in pineapple fruits to provide pleasant fruity and floral aromas, respectively (Asikin et al., 2018; Ito et al., 2006). Overall, the results provide insights into the key aroma-active compounds that contribute the most to the overall aroma of the new pineapple breeding lines.
Orthonasal aroma profiles of Okinawan pineapple breeding lines The fruits of the “N67-10” cultivar and five breeding lines had different orthonasal aroma characteristics. They emitted eight aroma traits (fruity, sweet, coconut, peach, green-grassy, woody peel, metallic, and sulfuric) at different intensities. Differences in the orthonasal aroma profiles of the fruits were visualized in a principal component analysis (PCA) score and loading biplot, which accounted for 74.87 and 11.38 % of the first two factors, respectively (Fig. 2). Principal component (PC) scores of “Okinawa No. 22,” “Okinawa No. 26,” “Okinawa No. 27,” and “Okinawa No. 28” lines were plotted in a positive direction to factor 1 where pleasant-desirable orthonasal traits such as fruity, sweet, coconut, and peach aromas were outlined as their loadings. In contrast, the PC scores of the “Okinawa No. 25” breeding line and the “N67-10” cultivar were outlined in the opposite direction. Moreover, the fruits were distinguished by factor 2, creating a unique distribution of newly bred lines toward specific loading plots of aroma traits. The “Okinawa No. 22” and “Okinawa No. 28” lines were associated with fruity, coconut, and peach aromas in the positive directions of factors 1 and 2. However, the perceived sweet odor might influence the distinction between “Okinawa No. 26” and “Okinawa No. 27” fruits from other lines. The plot of the “Okinawa No. 25” breeding line might be influenced by green-grassy, peel-woody, and metallic odors.
Volatile compounds in Okinawan pineapples influenced the orthonasal aroma profiles (Fig. 3). The aggregated volatile components had a positive and significant Pearson’s correlation with fruity aroma detection frequency at r = 0.8530 (p = 0.0308), whereas the total ester concentration was associated with this pleasant scent at r = 0.8266 (p = 0.0425) (Fig. 3a and Fig. 3b). This indicates that the higher the total volatiles or esters in a fruit, the higher the perceived fruity aroma. In this respect, the “Okinawa No. 28” fruit with the highest total contents of volatiles and esters could be distinguished from fruits of other lines owing to its high fruity aroma detection frequency, that is, 11 out of 15 panelists perceived the aroma (Table 2; Fig. 3b). This outcome agrees with previously reported studies on the typical fruity odor characteristics of esters in fruits; however, the fruity sensation from esters can vary depending on ester composition as well as fruit materials (Ito et al., 2006; Tokitomo et al., 2005). Among the aroma-active compounds of newly bred lines, eight ester compounds, methyl butanoate, methyl 2-methylbutanoate, methyl 3-methylbutanoate, ethyl butanoate, 3-methylbutyl acetate, methyl hexanoate, ethyl hexanoate, and ethyl octanoate, potently emit different types of fruity odors to fruits (Ito et al., 2006; Tokitomo et al., 2005)ii).
The sweet aroma detection frequency in Okinawan pineapple fruits was positively associated with furanone content (Fig. 3c). Both 4-methoxy-2,5-dimethyl-3(2H)-furanone and 4-hydroxy-2,5-dimethyl-3(2H)-furanone were accounted as aroma-active compounds in “Okinawa No. 27” and “Okinawa No. 28” lines, respectively, and the Pearson’s correlation coefficient between the total furanones and sweet aroma detection frequency was r = 0.7466 (Table 3; Fig. 3c). However, there was a delay in the development of the detection frequency of sweet aroma against furanone concentrations from approximately 10 to 40 μg/kg, indicating that the presence of other substances might also be involved in providing the sweet aroma to fruit. Nonetheless, the furanone-sweet aroma correlation confirmed the role of these sweet odor-producing compounds as influencing components for the distinct separation of the “Okinawa No. 27” line in the PCA biplot (Fig. 2). Furanones are one of the key odorants in various fruits, providing a likable sweet aroma with additional caramel, cotton candy, and creamy scents, indicating their strong influence on the overall flavor quality and sensory acceptance of the fruits (Ito et al., 2006; Kuroki et al., 2021).
Furthermore, γ-octalactone was significantly associated with the emitted coconut-like aroma of pineapple fruits (r = 0.9400; p = 0.0053) (Fig. 3d). This lactone is one of the most potent aroma compounds in mango and cape gooseberry, and thus it contributes to the overall aroma of these fruits (Kuroki et al., 2021; Yilmaztekin, 2014). However, there was a pseudo-effect correlation between δ-decalactone concentration against peach aroma detection frequency. Although only the “Okinawa No. 22” line possessed the compound, the peach odor sensation was also perceived from fruits of the “N67-10” cultivar and other breeding lines (Fig. 3e). Similar statistical association could also be found with γ-decalactone, which was only available in the “Okinawa No. 22” fruit (Table 2). Although δ-decalactone or γ-decalactone can emit a sweet-peach odor (Kuroki et al., 2021; Tokitomo et al., 2005)ii), these correlation data indicated that the peach-like aroma in pineapples could not be determined by only one compound; thus, more studies are required to comprehend the volatile components responsible for peach-like aroma sensation in pineapples. In addition, there was a low correlation between aldehyde content and the perceived green-grassy aroma (r = 0.3429) (Fig. 3f), and similar outcomes were observed for each aldehyde constituent against the orthonasal olfaction of this odor. This result indicated that besides aldehydes, other chemical groups could also influence green-grassy odor detection frequency in fruits. Thus, complex combinations of chemicals might elaborate the release mechanisms of freshly cut leaves or grass odors (Shao et al., 2022; Wu et al., 2022).
Collectively, these data provide an important basis for the practical use of new breeding lines by farmers and the agribusiness industry. For example, the “Okinawa No. 22” fruit with a high yellow color index, carotenoids, and superior peach-coconut-fruity orthonasal aroma could be used for pineapple juice production. Moreover, “Okinawa No. 26” and “Okinawa No. 27” lines could be proposed for raw fresh consumption or processed into canned pineapple products for having a high TSS/TA ratio and rich in aroma-active compounds with pleasant fruity and sweet aromas. Similarly, with enhanced distinct coconut-like and peach-like orthonasal aromas, the “Okinawa No. 28” line may be suitable for fresh fruit consumption and processed food production.
