Influence of genetic variability on the quality of strawberry cultivars: sensorial, physical-chemical and nutritional characterization

Strawberries are berry-type fruits that are very popular and widely consumed all over the world. The sensorial, physical-chemical and nutritional characteristics of strawberries are parameters of quality that influence the choices of consumers. However, these characteristics may be influenced by intrinsic and extrinsic factors that alter the fruit quality. The concentrations of nutrients and other chemical compounds in strawberries may increase and/or decrease according to the cropping system, maturation stage, climatic conditions, and preservation and storage methods. Factors characteristic of the cultivar, such as the genetic profile, may also influence the composition of strawberries. In this context, the objective of this research was to evaluate the sensorial, physical-chemical and nutritional characteristics of different strawberry cultivars to identify the genotype(s) with the best characteristics for commercialization and human consumption. The day-neutral strawberry cultivar "Aromas" and short-day strawberry cultivars "Camarosa, Camino Real, Dover, Sweet Charlie, and Tudla" were cultivated in the Olericultura Sector of the State University of the Midwest (UNICENTRO), Paraná State, Brazil. The fruits were characterized in relation to their physical-chemical, nutritional and sensorial aspects. According to the sensorial profiles, the Camarosa, Camino Real, Dover, and Tudla genotypes showed greater acceptability among consumers. Camarosa, Sweet Charlie, and Tudla presented better physical-chemical characteristics for human consumption, while the cultivars Camarosa, Dover, and Tudla had the best nutritional contents. In general, it is concluded that the genotypes Camarosa and Tudla are the most favourable for human consumption, according to their sensorial, physical-chemical and nutritional characteristics.


Introduction
The fruits of the strawberry plant (Fragaria x ananassa Duch.) are very popular and widely consumed berries (Paparozzi et al., 2018). World strawberry production has increased by more than 80% in recent decades, reaching more than 9 million tons in 2016. China and the United States stand out among the largest strawberry producers, at 3,801,865 tonnes year -1 (141,498 ha) and 1,420,570 tonnes year -1 (21,242 ha), respectively. These countries also have the highest gross income relative to strawberry production, varying between US$ 7 billion and US$ 2 billion annually (FAOSTAT, 2016). In Brazil, strawberry productivity was approximately 150,000 tons for an area of 4,200 ha in the period of 2017. The states of Minas Gerais (74,000 tons 2,000 ha -1 ), Paraná (21,450 tons 650 ha -1 ), and Rio Grande do Sul (20,350 tons 550 ha -1 ) are the largest producers of the fruit . In 2015, Brazilian sales from strawberry exports totalled US$ 272 million (Antunes, Fagherazzi, & Vignolo, 2017). Fresh strawberries account for 80% of the world production, while the remainder is destined for industrial processing for the preparation of yogurts, jams, jellies and wine (Paparozzi et al., 2018). Considering this aspect, strawberry is one of the most studied genomic and agronomic berries due to its commercial, industrial and economic impacts (Giampieri, Alvarez-Suarez, & Battino, 2014).
The main quality parameters that influence the acceptability of strawberries are the intense red colour, sweet taste and juicy texture of the fruit (Zeliou, Papasotiropoulos, Manoussopoulos, & Lamari, 2018). The

Plant material and cultivation technique
The day-neutral strawberry cultivar (Fragaria x ananassa Duch.) "Aromas" and short-day cultivars "Camarosa, Camino Real, Dover, Sweet Charlie, and Tudla" (Figure 1) were cultivated in the Olericultura Sector of the State University of the Midwest (UNICENTRO) of the municipality of Guarapuava (25°23'28.9"S 51°27'42.5" W, with an altitude of 1,116.5 m), Paraná State, Brazil. Seed germination was carried out in a chapel-type agricultural stove (276 m 2 with a right foot of 3.5 m) with a clear plastic cover 150 microns in thickness. The seedlings were transplanted to an open field with a low tunnel system. The planting depth of the seedlings was sufficient to leave the crown exposed superficially. The experimental design was a randomized block with 3 replicates. The strawberries were harvested in November 2017 at the end of the ripening period (> 75% of the red surface). The berries were separated to remove damaged, withered and green fruits. Three hours after harvesting, approximately 1 kg of each cultivar was placed in storage at -20°C and stored for 30 days for further analysis of the quality parameters. For sensory evaluation, approximately 70 whole fruits of each cultivar were stored at 4°C and evaluated the day after harvest.

Sampling and processing
The strawberries were thawed in a refrigerator (Electrolux ® , DC35A, Brazil) at 4°C for 24 hours. The pulp was then homogenized in a household grinder (Britânia ® , Black Plus, Brazil) for approximately 1 minute. For the analyses, approximately 300 g of pulp was used from each cultivar.

Sensory evaluation
Sensory evaluation was performed with 60 untrained adult consumers (18 to 59 years) of both genders, recruited from academics and UNICENTRO employees in Guarapuava, Paraná State, Brazil. The attributes of appearance, aroma, flavour, texture and colour were evaluated, in addition to global acceptance, through a structured hedonic scale of 9 points, varying from "very disagreeable" (note 1) to "liked very much" (note 9). An intention of purchase test was also applied, using a 5-point scale ranging from "certainly buy" (note 5) and "certainly would not buy" (note 1) (Meilgaard, Civille, & Carr, 2015). The judges received two samples of each cultivar (approximately 15 g) in white plastic cups encoded with 3-digit numbers in a balanced and randomized manner (Macfie & Bratchell, 1989); the judges were provided with water for cleansing the palate. Samples were offered to the judges in sequential monadic form (Macfie & Bratchell, 1989). The acceptability index (IA) was calculated according to the following equation: IA (%) = A x 100/B (A = average score obtained for the sample; B = maximum grade given to the sample) (Guimarães, Vendramini, Santos, Leite, & Miguel, 2013).

Physical-chemical composition
The following physical-chemical parameters were measured in fresh strawberries in triplicate and expressed on a wet basis: pH, obtained by direct reading with a bench pH meter (Tecnopon ® , Mpa-210, Brazil); water activity (Aw), measured by direct measurement with an Aw analyser (Novasina ® , Labswift, Switzerland) at 13°C; soluble solids (SS) (°Brix), determined by direct reading with a calibrated optical refractometer (Optech ® , RMT, Canada); titratable acidity (TA), titrated using a standard 0.1 M NaOH solution to a pH of 8.2 (IAL, 2005). The results were expressed as % citric acid per 100 g fresh weight (%); SS/TA ratio, obtained by dividing the SS readings and TA results; total sugar (TS) and reducing sugar (RS) contents, determined by the Lane-Eynon method (Association of Official Analitical Chemists [AOAC], 2000); non-reducing sugar (NRS) content, calculated as the difference between the TS and RS; colour, measured directly from the surface of the fresh fruits. The system of the Commission Internatinale de E'clairage (CIE) L*, a*, b* was used for the colorimetry readings by means of a previously calibrated colorimeter (Konica Minolta ® , Chroma Meter CR 4400, Japan) with illuminant D65 and an angle of 10°. The parameters analysed were L* (luminosity), a* (red-green) and b* (yellow-blue) in addition to the values for chroma (vivacity-opacity) and hue (hue); and antioxidant capacity (µmol Trolox 100 g -1 ), which includes hydrophilic and lipophilic antioxidants, determined using 2.20-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) (Miller & Rice-Evans, 1997). The samples were analysed at 734 nm in a spectrophotometer (Agilent Technologies ® , Cary 60 UV, Malaysia).

Ethical issues
The research was approved by the Research Ethics Committee of UNICENTRO, opinion No. 2,201,325/2017. To participate in the sensory analysis, the individuals signed the Free and Informed Consent Form and participated voluntarily through an invitation from the researchers in which all the steps and objectives were explained to the participants.
The inclusion criteria required adult individuals aged 18 years or older and 59 years or younger. Individuals younger than 18 or older than 59 years, pregnant individuals and individuals with strawberry allergies or who did not routinely consume the fruit were excluded.

Statistical analysis
The results were subjected to one-way ANOVA, using Tukey's test to compare the means. All the tests were analysed at a 5% level of significance using the IBM SPSS Statistics ® version 17 software.

Sensory evaluation
The sensory profile of the strawberry cultivars is described in Table 1. Higher scores for appearance and colour (p < 0.05) were attributed to the cultivars Camarosa, Dover, and Tudla, while Aromas and Sweet Charlie presented lower scores. There were no differences (p > 0.05) in the acceptability of the strawberries in the aroma and texture attributes, the overall acceptance or the purchase intent. The cultivar Camino Real was awarded a significantly higher flavour score than Aromas and Camarosa. The remaining fruits did not differ in flavour score (p > 0.05). Similar results have been reported in other studies evaluating genotypes from Brazil (Antunes, Cuquel, Zawadneak, Mogor, & Resende, 2014) and from Greece (Zeliou et al., 2018). Regarding the purchase of strawberries, attributes such as colour and appearance have greater consumer impact than other attributes because they are the first attributes to be evaluated (Fernández-Lara et al., 2015). Research has already demonstrated that the appearance/colour of strawberries positively influences the fruit flavour (Maksimović et al., 2015;Tahir et al., 2018). Maksimović et al. (2015) evaluated the sensory characteristics of 8 strawberry genotypes (Daroyal, Honeoye, Elsanta, Figaro, Sonata, Salsa, Florence, and Symphony) cultivated in Serbia. The highest notes for flavour were attributed to cultivars with better appearance. In strawberries treated with an edible coating based on gum arabic, the acceptability was higher (p < 0.05) than that for uncoated fruit (Tahir et al., 2018). This process was able to highlight the colour and brightness of strawberries, increasing scores for appearance and flavour, although the coated and uncoated fruits had similar physical-chemical and nutritional characteristics. In the present research, the positive effect of appearance on acceptability was confirmed for the cultivars Dover and Tudla and did not occur for Camarosa, Camino Real or Sweet Charlie. The cultivars presented AI ≥ 70% for all sensory parameters (Corradini et al., 2014). These results demonstrate that strawberries have good sensory acceptance (Šamec et al., 2016), regardless of the type of cultivar. However, considering the sensory profile of strawberries, it can be observed that, in general, the Camarosa, Camino Real, Dover, and Tudla genotypes are more acceptable to consumers.

Physical-chemical composition
The physical-chemical compositions of the strawberry cultivars are described in Table 2. The genetic profile was associated with changes (p < 0.05) in the pH value of the fruits. The highest pH value was observed in the Tudla cultivar, in contrast to those found for Aromas and Camarosa, which were the lowest with no difference between them (p > 0.05). The A w values did not differ significantly between cultivars. Dermesonlouoglou et al. (2017) observed similar results for pH (3.49) and A w (0.95) in the Camarosa cultivar from Greece. Strawberry is a naturally acidic fruit (pH < 6) due to the presence of organic acids, which may vary according to the type of cultivar . Strawberries with less acidic pH (> 3) are sensorially better accepted because they have low acidity (Oliveira et al., 2015), as verified in this research. Despite the variation in the pH and TA values, all the cultivars had good global acceptance (Table 1). From the genetic point of view, the type of cultivar has little or no influence on A w (Dermesonlouoglou et al., 2017), since strawberries are composed of 95% water (Bovi et al., 2018).
The levels of SS and TA varied (p < 0.05) between cultivars. The cultivar Tudla had the highest SS content, while Aromas and Dover had the lowest concentrations, not differing from each other (p > 0.05). The highest TA content (p < 0.05) was found in Camarosa (1.42 g AC 100 g -1 ) and the lowest in Camino Real (0.97 g AC 100 g -1 ). The Camino Real genotype was distinguished by a higher SS/TA ratio, while Aromas and Camarosa had the lowest proportions. Results similar to these evaluations were observed by Šamec et al. (2016) in Albion, Capri, Murano, and Monterey genotypes grown in Croatia. In strawberries, the SS content indicates the amount of solids such as sugars, vitamins, amino acids and pectin dissolved in the fruit pulp, while TA represents the acid concentration (Akhatou & Fernándes-Recamales, 2013). The balance between SS/TA is associated with fruit flavour , as verified in the present study. The cultivar Camino Real presented the highest SS/TA ratio and consequently a more palatable taste (Table 1). Lower scores for this attribute were attributed to the cultivars Aromas and Camarosa due to their low SS/TA ratios. The concentrations of SS and TA in strawberries are related to the reactions of the cultivar with external factors. Some genotypes, for example, are more sensitive to elevated temperatures (> 25°C) during cultivation. This factor can increase the respiratory rate of the fruit, which reduces the SS content and increases TA .
The strawberry cultivars differed (p < 0.05) in relation to the sugar concentration ( Table 2). The highest TS content was observed in the Tudla cultivar, with no difference (p > 0.05) between Aromas and Camarosa, which presented the lowest percentages. The Tudla cultivar also presented a higher concentration of RS (p < 0.05), while those of Camino Real and Sweet Charlie were lower (p > 0.05). The NRS content was higher in Camino Real, while those of Aromas and Camarosa were lower and did not differ from each other (p > 0.05). Similar results were reported for the cultivar Chandler at different irrigation intervals (4 to 14 days) (Akhtar & Rab, 2015). In contrast, the same cultivar produced in India presented levels of TS and RS (Muzzaffar et al., 2016), which were lower than those observed in the present study. In strawberries, the sugars are synthesized during the photosynthetic process (Akhtar & Rab, 2015). In stress conditions or in the postharvest period, these substances are used as energy sources for the metabolic and respiratory processes of the fruit (Muzzaffar et al., 2016). Thus, the sugar content in the fruit, as well as the levels of SS and TA, varies according to the response of each cultivar to the macro or microenvironmental conditions during maturation and ripening (Perla et al., 2016). Sugars can also be used as a parameter of sensory quality in strawberries because sugars are converted to aromatic compounds such as esters, terpenoids and furanones (Akhatou & Fernández-Recamales, 2014). Despite this fact, the differences in the sugar contents of the cultivars did not interfere with the affective scores for the aroma (Table 1).
The colour parameters L*, a*, b*, chroma and hue differed significantly among the genotypes ( Table 2). The cultivars Tudla and Camarosa showed high luminosity (L*), while the lowest percentage was found in Dover. The cultivars Dover, Sweet Charlie and Tudla had a higher red content (a*) (p < 0.05) than Camino Real. Higher yellow (b*) content was observed for Camarosa, Sweet Charlie and Tudla. The value of chroma was higher for the Sweet Charlie cultivar than for Aromas and Camino Real, while Camarosa and Sweet Charlie showed higher values for hue than the Dover genotype. Other cultivars produced in Mexico (Fernández-Lara et al., 2015) obtained results for instrumental colour very close to those of the present research. In general, strawberries can be considered to be dark in colour, since all the values for L* were lower than 50%, with shades of red (a*) and subtones of yellow (b*) (Peretto et al., 2014). In addition, the strawberries stand out for their brightness (values of chroma closer to 60) and red hues (hue values closer to 0) (Fadda et al., 2015). According to Boonyakiat et al. (2016), an increase in the concentration of anthocyanins reduces the luminosity at the surface of the fruits and increases the values of chroma, which was suggested in this research. 3.44 ± 0.01 c 3.40 ± 0.00 c 3.57 ± 0.06 b 3.57 ± 0.01 b 3.52 ± 0.01 b 3.72 ± 0.11 a Water activity 0.98 ± 0.00 a 0.98 ± 0.00 a 0.98 ± 0.00 a 0.98 ± 0.00 a 0.98 ± 0.00 a 0.97 ± 0.00 a Soluble Solids (°Brix) 6.42 ± 0.14 d 7.58 ± 0.14 c 7.50 ± 0.00 c 6.50 ± 0.00 d 8.25 ± 0.00 b 8.92 ± 0.14 a Titratable Acidity (g AC 100 g -1 ) 1 The antioxidant capacity presented little variability among the genotypes (Figure 2). The antioxidant potential of the hydrophilic fraction was higher (p < 0.05) in Dover and lower in Camarosa. Conversely, Dover showed the lowest antioxidant capacity through the lipophilic fraction, while Sweet Charlie demonstrated the highest potential. Lower results were observed for Magic and Premial cultivars produced in Romania (Nour, Trandafir, & Cosmulescu, 2017) and for Camarosa, Sabrina, and Fortuna cultivated in Greece (Zeliou et al., 2018). In strawberries, the main hydrophilic antioxidant substances are vitamin C and phenolic compounds. Carotenoids and vitamin E are classified as lipophilic antioxidants (Hernández et al., 2017). Thus, it was observed that cultivars with higher concentrations of vitamin C and phenolic compounds (Table 3) also had higher hydrophilic antioxidant capacities (Figure 2). This result proves that the genetic profile is a factor that directly influences the synthesis of bioactive compounds and the antioxidant capacity. Strawberry is considered a functional food because of its potential health benefits (Skrovankova, Sumczynski, Mlcek, Jurikova, & Sochor, 2015), especially since it has high antioxidant capacity (Souza et al., 2014). In this context, the cultivars Camarosa, Sweet Charlie, and Tudla presented better physical-chemical characteristics for human consumption, while the reverse was observed in Aromas, Camino Real, and Dover.  Table 3 shows the evaluation of the nutritional composition of the strawberry cultivars, which showed little variation. The fruits presented high moisture content, with higher percentages for Aromas, Camino Real and Sweet Charlie. Camarosa, Dover, and Tudla had lower moisture contents (p < 0.05). High moisture content in strawberries is associated with the fruit's capacity to expand, which increases water absorption during the irrigation process (Akhtar & Rab 2015), a fact that reduces the shelf-life of the strawberry (Okut et al., 2018). The ash values of the cultivars ranged from 0.32 g 100 g -1 (Camino Real) to 0.46 g 100 g -1 Acta Scientiarum. Agronomy, v. 43, e46862, 2021 (Tudla). All the cultivars presented low levels of proteins (0.49 g 100 g -1 to 0.74 g 100 g -1 ), lipids (0.16 g 100 g -1 to 0.23 g 100 g -1 ), carbohydrates (7.13 g 100 g -1 to 8.93 g 100 g -1 ) and calories (30.81 kcal 100 g -1 at 38.62 kcal 100 g -1 ). However, higher concentrations of proteins, lipids, carbohydrates and calories were observed for Camarosa and Dover. These results are similar to those for other strawberry genotypes (FA 01, FA 02, FA 03, and FA 06) cultivated in Bangladesh (Hossain et al., 2016). The concentrations of ascorbic acid, phenolic compounds and anthocyanins were different among the cultivars (Table 3). The ascorbic acid content ranged from 19.91 mg 100 g -1 (Camarosa) to 37.64 mg 100 g -1 (Camino Real). These results corroborate those of Maksimović et al. (2015), who studied strawberry genotypes (Daroyal, Honeoye, Elsanta, Sonata, Figaro, Salsa, Florence, and Symphony) grown in Serbia. The content of phenolic compounds was higher in the cultivar Tudla (230.15 mg GAE 100 g -1 ) than in Dover (112.84 mg GAE 100 g -1 ). The cultivar Dover (24.90 mg CGE 100 g -1 ) had the highest concentration of anthocyanins, while Aromas (18.36 mg CGE 100 g -1 ) presented the lowest value. These findings are in agreement with other studies that evaluated strawberries (Magic and Premial) cultivated in Romania (Nour et al., 2017) and in Croatia (Albion, Capri, Murano and Monterey) (Šamec et al., 2016). In strawberries, phytochemicals act as protective agents against the action of pathogens (Nour et al., 2017). The morphological characteristics of strawberry leaves may also influence the phytochemical contents. Cultivars with more developed leaves may block the incidence of sunlight in some parts of the fruit, which reduces the synthesis of bioactive substances in strawberries (Pátkai, 2012). Compounds such as ascorbic acid are synthesized in the fruit from reducing sugars such as glucose and galactose. Thus, strawberries with high levels of ascorbic acid tend to present low levels of RS (Perla et al., 2016), which was indicated in this study (Table 2). In the human body, phytochemicals act as antioxidants, protecting cells from the action of free radicals . These substances perform anticarcinogenic , anti-inflammatory , anti ageing (Rendeiro, Rhodes, & Spencer, 2015) and antihypertensive (Lajous et al., 2016) functions. According to the nutritional characteristics, the cultivars Camarosa, Dover, and Tudla presented more favourable profiles for human consumption, while Aromas, Camino Real, and Sweet Charlie were less favourable cultivars in this respect.

Conclusion
It is concluded that the cultivars Camarosa and Tudla present the most favourable sensorial, physicochemical and nutritional characteristics for human consumption and are more suitable for commercialization.