IJFS#1877_bozza Ital. J. Food Sci., vol. 32, 2020 - 912 PAPER INFLUENCE OF DIFFERENT PRETREATMENTS AND CHAPTALIZATION TYPES ON THE PHYSIOLOGICAL CHARACTERISTICS AND ANTIOXIDANT ACTIVITY OF APRICOT (PRUNUS ARMENIACA L.) WINE K.-T. CHOI1, S.-B. LEE1, J.-S. CHOI1 and H.-D. PARK*1,2 1School of Food Science and Biotechnology, Kyungpook National University, 80 Daehakro, Daegu 41566, South Korea 2Institute of Fermentation Biotechnology, Kyungpook National University, 80 Daehakro, Daegu 41566, South Korea *Corresponding author: hpark@knu.ac.kr ABSTRACT The effects of pretreatment (pectinase and CaCO3) and chaptalization (sugar and puree concentrate) on the quality of apricot wine were investigated. Pectinase-treated apricot wines had increased amounts of total phenolics, flavonoid compounds, as well as antioxidant activities. The apricot wine chaptalized with puree concentrate and treated with pectinase (PCP) showed the highest total acidity and some organic acid contents, which resulted in the strongest sourness. In contrast, the apricot wine treated with pectinase and CaCO3 (SCPC and PCPC) showed the lowest total acidity and least sourness. Antioxidant activities of PCP and PCPC wines were higher than other wines, and other pectinase-treated wines were also higher than the control wine. Volatile higher alcohols and terpenes increased in all the pectinase-treated wines, whereas volatile ester compounds were decreased. Sensory evaluation showed that SCPC, PCP, and PCPC wines obtained significantly high flavor scores, and SCPC and PCPC wines obtained the highest overall preference scores. Keywords antioxidant, apricot wine, aroma profile, fruit wine, pretreatment Ital. J. Food Sci., vol. 32, 2020 - 913 1. INTRODUCTION Apricot (Prunus armeniaca L.) is a stone fruit mainly grown in China, the Mediterranean European countries, Turkey, and the USA (SOLIMAN, 2013). Consumption of apricot has shown human health benefits because of its antioxidant, anti-inflammatory, and immune- stimulating properties, which might be attributed to the presence of various phytochemicals, such as carotenoids, polyphenols, vitamins, and fiber (DRAGOVIC- UZELAC et al., 2007; HEGEDŰS et al., 2010; MADRAU et al., 2009). Due to the various advantages of apricot, the development of apricot wine has good potential for commercialization. Despite the excellent functionality, the strong sourness of apricot, associated with its notably high acidity, has still not been acceptable, which prevents the development of apricot wine. Pretreatment of high-acid wines by deacidification offers a suitable resolution to this issue, and it is commonly carried out by physicochemical methods, such as carbonic amelioration, blending, chemical neutralization, and precipitation, and by biological methods, such as malolactic fermentation (LOIRA et al., 2018; VOLSCHENK et al., 2006). Among these methods, chemical neutralization by the addition of salts (CaCO3) to deacidify fruit wines is usually preferred because it reduces the risk of increasing the pH levels and, additionally, prevents microbial problems (COSME et al., 2018; MATTICK et al., 1980). Pectinases are enzymes that are generally added to maximize juice yield and act by degrading the pectins that interfere with extraction and clarification of most fruit juices (SHARMA et al., 2017). In addition, treatment of fruit juice with pectinase has been reported to increase the amounts of phenolics and anthocyanins, facilitate filtration, and contribute to the release of the molecules responsible for aroma and color, two of the major components that characterize a wine (PARDO et al., 1999; PINELO et al., 2006; WATSON et al., 1999). Some fruits with low sugar content must be chaptalized to obtain sufficient sugar content for making wine (JARVIS, 1996; MIYAWAKI et al., 2016). Several researchers have used various technologies, such as freeze-concentration and nanofiltration, to decrease the levels of available water in fruits deficient in sugar content, thereby concentrating the sugar content (BANVOLGYI et al., 2006; CLARY et al., 2006; MIYAWAKI et al., 2016). Puree concentrate can also be a suitable alternative instead of chaptalization because of its concentrated sugar content and using the apricot puree concentrate could reduce labors and enhance productivity by skipping the process of washing the fruit and removing the seed for the industrial mass production of apricot wine. This study aimed to improve the quality of apricot wine. Apricot wines were prepared following different types of pretreatments, including pectinase and CaCO3, and chaptalization, by the addition of sugar and puree concentrate, and their physicochemical parameters, volatile aromatic profiles, antioxidant activities, and sensory characteristics were investigated. 2. MATERIALS AND METHODS 2.1. Chemicals and reagents 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), Trolox, Folin–Ciocalteu reagent, methanol (HPLC grade), potassium Ital. J. Food Sci., vol. 32, 2020 - 914 metabisulfite (K2S2O5), organic acids, and all other standards were obtained from Sigma– Aldrich (St Louis, MO, USA). White table sugar (CJ Co., Seoul, South Korea), used to adjust the sugar content of the must, was bought from the local market. Apricot puree concentrate (30.7°Bx, pH 4.1, and acidity 1.31%) was procured from Aftun Gida Ltd. (Yenisehir, Mersin, Turkey). Rapidase® X-Press L (pectinase+hemicellulase, 180,000 AVJP/g) was purchased from DSM Food Specialties (Delft, Netherlands). The fermentation agent Saccharomyces cerevisiae var. bayanus EC-1118 yeast was purchased from Lallemand Inc. (Montreal, Canada). CaCO3 was acquired from Daejung Co. (Siheung, South Korea). 2.2. Apricot fruit samples Fully-ripened apricot fruit (P. armeniaca L.) were bought from local farms in Yeongcheon (Gyeongsangbuk-do, South Korea) during the 2017 harvest season. ”Harcot” apricot fruit was selected for uniformity of size, color, and absence of decay or rot. Fruit was stored at –18℃ until further use. 2.3. Apricot fruit must preparation and pretreatment conditions Apricot fruit was washed with tap water, the seeds removed manually. The deseeded fruit was blended using a household juicer (NJ-9300A, NUC Juicer, Daegu, South Korea) and then combined immediately with 0.02% (w/v) K2S2O5 to prevent bacterial contamination and oxidation. To determine the most suitable amount of enzyme and CaCO3 (for deacidification), a part of the apricot fruit pulp was divided into four portions of 300 mL each. The first portion was used as the control while the three remaining portions were treated with pectinase (Rapidase® X-Press L) at 0.05%, 0.1% and 0.2% (v/w), respectively. For the deacidification process, CaCO3 was added at 0.1%, 0.2%, and 0.3% (w/w), respectively. Pectinase treatment or deacidification occurred for 2 h under constant agitation using a shaking incubator (30℃, 200 rpm). The pulp samples were centrifuged at 3,578 × g for 10 min, and the obtained juices were analyzed and compared for pH level, total acidity, total soluble solids, and reducing sugars. 2.4. Apricot wine-making Apricot fruit pulp was divided into five wine-making trial batches (5 kg), from which wines were prepared in triplicate and, subsequently, treated before fermentation. The chaptalization and pretreatment conditions are listed in Table 1. In the first batch, namely, the control batch (SC), the apricot pulps were chaptalized with white sugar to obtain 22°Bx. In the second batch (SCP), the apricot pulps were chaptalized to 22°Bx with white sugar and then treated with 0.1% (v/w) pectinase. In the third batch (SCPC), the apricot pulps were chaptalized to 22°Bx with white sugar, treated with 0.1% (v/w) pectinase, and then deacidified with 0.3% CaCO3. In the fourth batch (PCP), the apricot pulps were chaptalized to 22°Bx with apricot puree concentrate and then treated with 0.1% (v/w) pectinase. In the fifth batch (PCPC), the apricot pulps were chaptalized to 22°Bx with apricot puree concentrate, treated with 0.1% (v/w) pectinase, and then deacidified with 0.3% (w/w) CaCO3. Each treatment process lasted for 2 h under constant agitation (30℃, 200 rpm), 200 mg/L of K2S2O5 was added to prevent bacterial contamination, and then the batches were centrifuged at 3,578 × g for 10 min. The apricot wine was fermented with 1–2 × 106 CFU mL−1 S. cerevisiae var. bayanus EC-1118 that was rehydrated by sterile distilled Ital. J. Food Sci., vol. 32, 2020 - 915 water at 40℃ for 30 minutes, according to the manufacturer’s instruction. Each sample was fermented without shaking at 20℃ for 7 days until complete fermentation. The final wine samples were filter-sterilized, poured into wine bottles with 50 mg/L of K2S2O5, and stored at 4℃ for further analysis and sensory assessment. Table 1. List of ingredients used in apricot wine-making. Ingredients (g) Chaptalization and pretreatment conditions SC SCP SCPC PCP PCPC Apricot pulp 4,472.5 4,472.5 4,472.5 2,430 2,430 Sugar 527.5 527.5 527.5 Apricot puree concentrate 2,570 2,570 Pectinase 1 1 1 1 CaCO3 15 15 SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3 2.5. Physicochemical parameters The physicochemical analysis was undertaken on the supernatant obtained from centrifugation of the wine samples at 3,578 × g for 10 min. The pH was measured using a pH meter (MP225K, Mettler-Toledo CH, Seoul, South Korea). Soluble solids (°Bx) were determined using a refractometer (RA250, Atago, Tokyo, Japan). A vinometer was used to evaluate the alcohol content at 15°C. Titratable acidity was assayed using NaOH solution (0.1 N) until neutralization of the organic acids to pH 8.2-8.3, and the results were expressed as a percentage of citric acid/100 g. 2.6. Total phenolic compounds The total phenolic compounds in the apricot wine samples were estimated, as detailed by OUGH and AMERINE (1988), with some modifications. Wine samples (2 mL) were mixed with 2 mL of 1:1 (v/v) Folin–Ciocalteu reagent and incubated at room temperature for 3 min. Afterward, each tube was added with 2 mL of 10% Na2CO3, vortexed, and allowed to stand at room temperature for 1 h. The absorbance was measured at 700 nm. The results were expressed as gallic acid equivalents in mg/mL of apricot wine. 2.7. Total flavonoid content The total flavonoid contents of the apricot wines were determined, as described by ZHISHEN et al. (1999) with minor modifications. The wine samples were examined spectrophotometrically at 510 nm against a blank solution containing all reagents and 200 μL of distilled water instead of wine samples using a spectrophotometer (UV-1601, Shimadzu Co.). First, 430 μL of 50% ethanol, 70 μL of wine sample, and 50 μL of 5% NaNO2 were combined in a test tube. After 30 min of incubation, samples were combined with 50 μL of 10% Al(NO₃)₃·9H2O. Six minutes later, 500 μL of NaOH (1 N) was added, Ital. J. Food Sci., vol. 32, 2020 - 916 and the solutions vortexed. The results were expressed as rutin equivalents in mg/mL of apricot wine. 2.8. DPPH radical scavenging activity DPPH radical scavenging activity was measured according to the method previously described by OSZMIAŃSKI et al. (2011). Here, 100 μM of DPPH was dissolved in pure ethanol (96%). The radical stock solution was prepared just before experimentation. Then, 1 mL of DPPH was added to 1 mL of apricot wine sample and 3 mL of 96% ethanol. The mixture was thoroughly shaken and placed at room temperature in the dark for 10 min. The decrease in absorbance of the resulting solution was observed at 517 nm at 10 min. The results were corrected for dilution and expressed in μM of Trolox/mL of apricot wine. Absorbance was measured using a spectrophotometer (UV-1601, Shimadzu Co.). 2.9. ABTS radical scavenging activity ABTS radical scavenging activity was measured based on the method previously reported by OSZMIAŃSKI et al. (2011). ABTS was dissolved in water to make a 7 μM concentration. ABTS radical cation (ABTS+) was produced by reacting the ABTS stock solution with 2.45 of μM potassium persulfate (final concentration) and kept in the dark at room temperature for 12–16 h before use. The radical was stable in this form for more than 2 days when stored in the dark at room temperature. The samples containing ABTS+ solution were diluted with redistilled water to an absorbance of 0.700±0.02 at 734 nm and equilibrated at 30℃. After adding 3.0 mL of diluted ABTS+ solution (A734 nm = 0.700±0.02) to 30 μL of apricot wine sample, the absorbance was read at exactly 6 min after initial mixing. The results were corrected for dilution and expressed in μM Trolox/1 mL of apricot wine. Absorbance was measured using a spectrophotometer (UV-1601, Shimadzu Co.). 2.10. FRAP assay Ferric ion reducing antioxidant power was measured according to the method previously described by OSZMIAŃSKI et al. (2011). The assay was based on the reducing power of a compound (antioxidant). A potential antioxidant will reduce ferric ions (Fe3+) to ferrous ions (Fe2+), with the latter forming a blue complex (Fe2+/TPTZ) that increases absorbance at 593 nm. Moreover, FRAP reagent was prepared by mixing with an acetate buffer (300 μM, pH 3.6), a solution of 10 μM of TPTZ in 40 μM of HCl and 20 μM of FeCl3 at a ratio of 10:1:1 (v/v/v). The reagent (300 μL) and apricot wine sample solutions (10 μL) were added to each well and thoroughly mixed. The absorbance was measured at 593 nm after 10 min. A standard curve was plotted using different Trolox concentrations. All solutions were prepared on the same day of experimentation. The results were corrected for dilution and expressed in μM of Trolox/1 mL of apricot wine. Absorbance was measured using a spectrophotometer (UV-1601, Shimadzu Co.). 2.11. Free sugar and organic acid analyses The free sugar and organic acid contents in the wine samples were identified and quantified using a Prominence HPLC instrument (Shimadzu Co.) with a refractive index detector (RID-10A, Shimadzu Co.), as described by KIM et al. (2018). The wine samples were centrifuged at 3,578 × g for 10 min, and the resultant supernatants were filtered Ital. J. Food Sci., vol. 32, 2020 - 917 through a Millex-HV 0.45-μm membrane filter (Millipore Co., Bedford, MA, USA) to obtain analytical samples. Free sugar content was determined using a Sugar-Pak I column (6.5 mm × 300 mm, 10 μm; Waters, Milford, MA, USA). The mobile phase was Ca–EDTA buffer (50 mg/L) at a flow rate of 0.5 mL/min at 90°C. Organic acids were quantified using a Shodex RSpak KC-811 column (8.0 mm × 300 mm, 6 μm; Showa Denko KK, Kawasaki, Japan), and a mobile phase of 0.1% H3PO4 at a flow rate of 1 mL/min at 65°C. Standard curves were plotted using different concentrations of each compound. The results were expressed as each compound’s equivalents in g/L of apricot wine. 2.12. Analysis of volatile compounds Volatile compounds were analyzed as described by LEE et al. (2016) with minor modifications, using a 7890A GC–MS system (Agilent, Santa Clara, CA, USA). Volatile compounds were separated using a DB-WAX column (60 m × 0.25 mm i.d., 0.25 μm film thickness, Agilent, Santa Clara, CA, USA) and detected using an Agilent 5975C TAD inert XL MSD. Helium was used as the carrier gas at a constant flow rate of 1 mL/min. The temperature of the GC oven was initially held at 40°C for 2 min, increased at a rate of 2°C/min until 220°C, and then increased at 20°C/min to 240°C, and maintained at 240°C for 5 min. Volatile compounds were collected using a headspace (HS) solid-phase microextraction (SPME) fiber (10 mm length, 50/30 μm DVB/CAR/PDMS; Supelco, Bellefonte, PA, USA) with magnetic stirring. Five milliliters of each sample was placed in a HS vial (20 mL, 23 × 75 mm, PTFE/silicone septum, magnetic cap, Agilent, Santa Clara, CA, USA) and then 1.25 g NaCl was added to increase the efficiency of salting-out of volatile aromatic compounds in the HS. Prior to extraction, the sample was shaken in a water bath at 35°C for 20 min to achieve equilibrium. Afterward, the SPME fiber was inserted into the vial and incubated at 35°C for 40 min. The chemical standards for volatile ester compounds were customized by Chem Service Inc. (West Chester, PA, USA). Other volatile compound standards were purchased from Sigma-Aldrich (St Louis, MO, USA). Volatile compounds were identified by comparing their retention times and mass spectra against the Wiley 9 spectral library (John Wiley and Sons, Hoboken, NJ, USA) using NIST 0.8 (version 5.0; NIST, Gaithersburg, MD, USA). For the quantitative analysis of each compound in the wine, a calibration curve was established by plotting the peak area against the concentration of the chemical standards. Some chemicals that were commercially unavailable were quantified using standard curves of volatile compounds that had similar molecular properties. The results were expressed as each volatile alcohol compound’s equivalents in mg/L of apricot wine and each volatile ester and terpene compound’s equivalents in μg/L of apricot wine, respectively. 2.13. Sensory evaluation A seven-point hedonic scale was used for sensory evaluation. Each apricot wine was placed in a sample bottle and left undisturbed at room temperature for 1 h, with the bottle lid still closed before being subjected to sensory evaluation. After opening the lid, each wine was poured into wine glasses to evaluate color, sweetness, sourness, and overall preference. Clarity and turbidity levels were considered as part of the parameters for color evaluation. The well-trained panel was composed of 20 students (13 males and 7 females aged 20–29 years old) from the School of Food Science and Biotechnology, Kyungpook National University, Korea. Each panelist evaluated the apricot wines with at least a 3-min Ital. J. Food Sci., vol. 32, 2020 - 918 interval between samples, and water was provided to cleanse their palate. Sensory scores ranged from 1 (very poor) to 7 (excellent). 2.14. Statistical analysis All experiments were conducted at least three times or more. Statistical significance was determined by the Student’s t-test for independent means using Microsoft Excel (Microsoft, Redmond, WA, USA). One-way analysis of variance and Duncan's multiple range test were used to determine significant differences between means. Statistical significance was set at p<0.05. 3. RESULTS AND DISCUSSION 3.1. Effect of different pretreatment conditions on the physicochemical parameters of apricot juice The effects of different pretreatments on the physicochemical parameters of apricot juice are listed in Table 2. The yield of apricot juices subjected to pectinase treatment were higher by 5.66%, 10.02%, and 10.38% in apricot pulp containing 0.05%, 0.1%, and 0.2% pectinase, respectively, compared with the control juice, but the yields of juices treated with 0.1% and 0.2% pectinase enzyme were not considerably different. In addition, juices treated with pectinase enzyme had a statistically lower pH and higher total acid contents relative to the control juice. The reducing sugar contents of apricot juices also increased with increasing pectinase enzyme concentrations, but no significant differences were found between pectinase-treated juices. Apricot juices treated with 0.05%, 0.1%, and 0.2% pectinase had reducing sugar contents of 15.65%, 15.83%, and 15.90%, respectively. The pH and total acid contents of apricot juices by deacidification significantly increased and decreased, respectively, with increasing CaCO3 concentration compared with those of non- treated apricot juice. Table 2. Effects of pectinase enzyme and CaCO3 concentrations on the physicochemical properties of apricot juices. Treatment Pectinase enzyme Non-treated 0.05% 0.1% 0.2% Juice yield (%) 67.20±0.12d 72.86±0.03c 77.22±0.05b 77.58±0.05a pH 3.16±0.02a 3.11±0.01b 3.10±0.04b 3.10±0.07b Total acidity (%) 2.56±0.02b 2.62±0.03a 2.63±0.04a 2.64±0.3a Soluble solids (°Bx) 16.2±0.05b 16.4±0.08a 16.4±0.05a 16.4±0.09a Reducing sugars (%) 14.5±0.04b 15.65±0.10a 15.83±0.08a 15.90±0.12a Treatment Deacidification (CaCO3) Non-treated 0.1% 0.2% 0.3% pH 3.14±0.06d 3.22±0.01c 3.33±0.02b 3.42±0.01a Total acidity (%) 2.56±0.10a 2.48±0.03a 2.30±0.05b 2.17±0.04c All data are expressed as mean±standard deviation (n = 3). Different letters in the same row indicate significant differences at p<0.05. Ital. J. Food Sci., vol. 32, 2020 - 919 Fruits other than grape, such as apricot, have high acidity, which needs to be controlled before, during, or after fermentation, for producing a suitable final wine (VELIĆ et al., 2018). In this study, each 0.1% pectinase treatment and 0.3% CaCO3 treatment improved the juice yield and appropriate physicochemical changes in apricot juice, so we further investigated the appropriate combination of these pretreatment conditions for apricot wine. 3.2. Effects of different chaptalization types and the combination of pretreatments on the fermentation and physicochemical properties of apricot wine The influences of the various chaptalization techniques and the combination of pretreatments on the changes in fermentation characteristics during alcohol fermentation and physicochemical properties of fully fermented apricot wine are provided in Fig. 1 and Table 3. The soluble solid and alcohol contents of all the apricot wines similarly decreased and increased, respectively, for the first 3 days of fermentation. After then, all the pectinase-treated apricot wines showed higher soluble solid and alcohol contents, compared with the control wine because of increased juice yield and reducing sugar caused by 0.1% pectinase treatment. The pH and total acidity of all the apricot wines decreased and increased, respectively, for first or second days of fermentation, then steadily increased and slightly decreased, respectively, until complete fermentation. The pH and total acidity of apricot wines treated with CaCO3 (SCP and PCP wines) were significantly lower and higher, respectively, than those of other apricot wines from beginning to end of the fermentation process. The total phenolic and total flavonoid contents of all the apricot wines were significantly superior to those of the control wine because pectinase released phenols and polyphenols from the plant cell wall (CHANG et al., 1995). In addition, PCP and PCPC wines that were chaptalized with puree concentrate presented higher total acidity, as well as total phenolic and flavonoid contents, compared with those of SCP and SCPC wines that were chaptalized with sugar, because all of these compounds were concentrated in the added apricot puree concentrate. Although the total phenolic and total flavonoid contents of pectinase-treated apricot wines were relatively higher than those of other groups, the lower pH and higher total acid content of PCP wine may be negatively associated with the sensory properties. On the contrary, PCPC wine contained similar contents of functional compounds but better palatability compared to PCP wine because of deacidification. Figure 1. Changes in the soluble solid, alcohol, pH, and total acidity of apricot wines during fermentation. SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3 Ital. J. Food Sci., vol. 32, 2020 - 920 Table 3. Effects of different chaptalization types and pretreatment conditions on the physicochemical parameters of apricot wines. Parameter Wine SC SCP SCPC PCP PCPC Soluble solids (°Bx) 9.80±0.20b 10.75±0.10a 10.75±0.10a 10.80±0.20a 10.70±0.10a Alcohol (%) 10.9±0.10b 11.74±0.20a 11.72±0.10a 11.70±0.10a 11.64±0.10a pH 3.53±0.10ab 3.42±0.09b 3.65±0.05a 3.36±0.03c 3.58±0.05a Total acidity (%) 1.78±0.04c 2.02±0.01b 1.35±0.01e 2.20±0.03a 1.43±0.04d Total phenolic compounds (mg/mL) 11.41±0.37c 16.95±3.11b 17.15±2.03b 21.87±0.96a 21.43±1.21a Total flavonoids (mg/mL) 0.39±0.00b 0.41±0.01a 0.42±0.01a 0.43±0.01a 0.43±0.01a All data are expressed as mean±standard deviation (n = 3). Different letters in the same row indicate significant differences at p<0.05. SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3 3.3. Free sugar and organic acid contents of apricot wines The impacts of different chaptalization types and the combination of pretreatments on the free sugar and organic acid contents in apricot wines are evident in Table 4. After alcoholic fermentation, sucrose, glucose, galactose, and fructose were identified in the apricot wines. Fructose was the most abundant reducing sugar (0.599±0.014–4.662±0.019 g/L) in all the apricot wines. Marked differences in the organic acids were observed between each apricot wine. Citric acid and quinic acid of SCP and SCPC wines were significantly decreased and increased compared with SC wine, respectively, whereas tartaric acid and malic acid of SCPC wine were the lowest among all the apricot wines. Citric acid and quinic acid contents of PCP and PCPC wines were significantly higher than other wines because various components of apricot were concentrated during puree concentrate preparation, whereas tartaric acid of PCPC wine was significantly lower than PCP wine due to deacidification. Succinic acid levels were comparable among all the apricot wines, and acetic acid of pectinase-treated apricot wines was slightly increased compared with control apricot wine. According to AMERINE et al. (1965), the decreasing order of sourness intensity of organic acids is malic acid, tartaric acid, citric acid, and lactic acid. CaCO3 treatment was reported to reduce wine acidity by inducing the precipitation of tartrate and malate (MATTICK et al., 1980). Thus, the combination of pectinase and CaCO3 treatments increased the yield of apricot juice and reduced the acidity in apricot wine. 3.4. Antioxidant activity of apricot wines The various antioxidant activities, such as DPPH radical scavenging activity, ABTS radical scavenging activity, and FRAP of apricot wines are shown in Fig. 2. All of the antioxidant activities were highest in PCP and PCPC wines, followed by SCP and SCPC wines, and then SC wine, which might be attributed to the release of pigment compounds, such as flavonoids, by pectinase (all the pectinase-treated apricot wines) and the concentration of those compounds in the added puree concentrate (PCP and PCPC wines). Ital. J. Food Sci., vol. 32, 2020 - 921 Table 4. Composition of free sugar and organic acid contents (g/L) of apricot wines depending on different chaptalization types and pretreatment conditions. Parameter Wine SC SCP SCPC PCP PCPC Free sugars Sucrose 0.08±0.01a ND ND ND ND Glucose 0.16±0.06c 0.28±0.03b 0.25±0.01b 0.70±0.02a 0.67±0.03a Galactose 0.23±0.04c 0.86±0.01b 0.82±0.04b 1.58±0.02a 1.50±0.06a Fructose 0.60±0.01c 2.66±0.01b 2.64±0.01b 4.56±0.02a 4.66±0.02a Organic acid Citric acid 11.58±0.35b 9.89±0.25c 9.61±0.34c 14.40±0.51a 14.25±0.48a Tartaric acid 2.83±0.08b 2.84±0.11b 0.42±0.04d 3.11±0.12a 0.73±0.06c Malic acid 5.61±0.12a 4.39±0.12b 3.20±0.09c 4.29±0.09b 2.96±0.10d Quinic acid 7.37±0.16c 11.48±0.34b 11.34±0.33b 34.17±1.03a 32.87±1.17a Succinic acid 0.50±0.02a 0.54±0.04a 0.52±0.04a 0.45±0.02b 0.44±0.02b Acetic acid 0.18±0.01c 0.31±0.04b 0.29±0.01b 0.42±0.02a 0.40±0.02a All data are expressed as mean±standard deviation (n = 3). Different letters in the same row indicate significant differences at p<0.05. SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3, ND not detected Figure 2. Effects of different chaptalization types and pretreatment conditions on the DPPH radical scavenging activity (A), ABTS radical scavenging activity (B), and ferric ion reducing power (C) antioxidant activities of apricot wines. Different letters indicate significant differences at p<0.05. L-AA L-ascorbic acid, TE Trolox equivalents, SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3 Ital. J. Food Sci., vol. 32, 2020 - 922 Apricot contains numerous phenolic compounds, including catechin, epicatechin, p- coumaric acid, caffeic acid, and ferulic acid, that contribute to the antioxidant activity and nutritional benefits (CAMPBELL and PADILLA-ZAKOUR, 2013; SOCHOR et al., 2010). ARNOUS et al., (2002) mentioned that total polyphenol and total flavonol compounds could significantly contribute to the overall antioxidant activity of wine. As such, in the present study, the high antioxidant activities displayed by the apricot wines depended on the increased total phenolic and flavonoid compounds released by pectinase pretreatment and concentrated by puree concentrate chaptalization. 3.5. Volatile aromatic compounds of apricot wines The volatile aromatic compounds of apricot wines are given in Table 5. The volatile higher alcohol compounds were more abundant in pectinase-treated apricot wines than control apricot wine. In PCP and PCPC wines, most of the volatile higher alcohols, except for 1- propanol, were detected at levels lower than in SCP and SCPC wines, respectively. Moreover, SCPC wine showed the highest amount of 1-propanol, isobutanol, isoamyl alcohol, 1-hexanol, 3-ethoxypropanol, 1-decanol, and benzyl alcohol, among all the apricot wines. A higher amount of 2,3-butanediol, which is an unattractive compound in wine because of its buttery aroma (BARTOWSKY and HENSCHKE, 2004), was detected in greater quantities in SC and SCP wines than in the other apricot wines examined. Total volatile ester compounds were the highest in SC wine, as those of pectinase-treated apricot wines were evaporated during pectinase treatment at 30℃ for 2 h. Furthermore, PCP and PCPC wines presented significantly lower total volatile ester compounds than those of the other wines, which is considered to be due to the loss of their corresponding precursors during heat treatment of the puree concentrate production process. SC wine contained the highest amounts of isoamyl acetate, ethyl hexanoate, ethyl octanoate, and ethyl-9- decanoate, as well as ethyl decanoate. These compounds primarily influenced the changes in the amount of total volatile ester compounds. Volatile terpenes were higher in all the pectinase-treated apricot wines than control apricot wine. In particular, linalool and α- terpineol of PCP and PCPC wines were significantly higher than those of the other wines. The group of higher alcohols is well known as one of the dominant chemical constituents in wine, in which they play a major role as ester precursors (LAMBRECHTS and PRETORIUS, 2000). Esters are well recognized as the most abundant aromatic compounds in wine (ROJAS et al., 2001) and are produced by yeasts during alcoholic fermentation, whereas terpenes are only present in small amounts in some fruits, such as grape (especially in aromatic cultivars), apricot, and peach. However, terpenes can mostly affect the floral properties of wines with low odor thresholds (100-400 ppb) (MAICAS and MATEO, 2005). In the present study, significantly decreased contents of volatile ester compounds were detected in the pretreated apricot wines compared with non-treated apricot wine, but the levels of volatile higher alcohols and terpenes were greater, which might have assisted in improving the sensory properties of apricot wine. Ital. J. Food Sci., vol. 32, 2020 - 923 Table 5. The concentration of volatile aromatic compounds in apricot wines depending on different chaptalization types and pretreatment conditions. Compound Odor description Threshold (mg/L) Amount of volatile aromatic compound SC SCP SCPC PCP PCPC 1-Propanol Alcohol, ripe fruity[1] 306[1] 85.48±6.55b 97.17±9.45b 169.76±14.11a 103.27±10.11b 178.63±13.28a Isobutanol Alcohol, solvent, green, bitter[1] 75 [1] 159.27±12.09b 176.03±16.23ab 199.71±20.56a 141.00±12.24b 162.13±15.06b Isoamyl alcohol Solvent, sweet, nail polish[2] 60[2] 2605.68±233.17a 2863.76±256.18a 3024.25±306.50a 2729.15±250.06a 2896.57±269.77a 1-Hexanol Herbaceous, grass, woody[1] 1.1[1] 20.10±1.94c 30.68±3.31b 37.41±3.42a 23.85±2.65c 32.64±3.04ab 3-Ethoxypropanol Fruity[1] 0.1[1] 10.04±1.11a 10.27±0.98a 10.73±0.94a 6.82±0.61b 6.77±0.64b 1-Octanol Jasmine, lemon[1] 0.8[1] 13.62±1.26b 89.27±7.24a 10.10±0.88b 8.83±0.77b 5.04±0.62c 2,3-Butanediol Floral, fruity, herbal, buttery[2,3] 150 [2] 14.70±1.32a 14.24±1.52a 11.21±1.05b 9.52±0.89b 8.16±0.72b 1-Decanol Floral, fruity, bitter, winey[2] 0.4[2] 5.13±0.44b 6.21±0.56a 6.51±0.52a 4.44±0.41b 4.50±0.39b Benzyl alcohol Roasted, sweet, fruity[1] 200[1] 20.07±2.12c 52.63±5.10a 60.63±6.12a 35.17±3.41b 41.17±4.41b Phenylethyl alcohol Rose, honey[1] 14[1] 201.16±19.43a 242.63±22.73a 245.14±26.18a 249.67±24.07a 243.81±23.58a ∑Alcohols 3135.25±279.43a 3582.89±323.30a 3775.46±380.28a 3311.73±305.22a 3579.42±331.51a Methyl acetate ND 13.93±1.30b 15.67±1.51b 23.25±2.16a 25.17±2.32a Ethyl acetate Pineapple, fruity, balsamic[2] 12[2] 729.35±74.28a 668.56±64.86a 760.26±71.34a 726.78±70.86a 810.59±78.50a Ethyl propionate Fruity[4] 1.8[4] 18.65±1.56a 17.24±1.55a 19.18±1.68a 15.43±1.62a 16.22±1.55a Ethyl isobutyrate Sweet, rubber[4] 0.015[4] 11.51±1.05a 9.51±0.92ab 11.11±1.06a 7.77±0.74b 8.95±0.78b Propyl acetate Sweet, fruity[4] 4.7[4] 24.83±2.62a 18.04±1.77b 21.16±2.04ab 19.21±1.78b 22.04±2.04ab Isobutyl acetate Fruity, apple, banana[4] 1.6[4] 42.19±3.84a 30.40±3.13b 34.23±2.99b 23.79±2.24c 25.64±2.82bc Ethyl butanoate Banana, pineapple, strawberry[1] 0.4 [1] 43.24±4.13a 28.37±2.47b 29.59±3.41b 22.59±2.01b 23.10±1.98b Butyl acetate Fruity[5] 4.88±0.43a 3.96±0.35ab 4.37±0.56a 3.35±0.36b 3.84±0.33ab Isoamyl acetate Banana[1] 0.16[1] 2472.35±242.56a 1403.56±142.53b 1541.19±136.04b 871.05±82.60c 972.42±88.09c Ethyl pentanoate Yeast, fruity[4] 0.094[4] 4.24±0.36a 2.89±0.27b 3.62±0.35a 4.19±0.40a 4.63±0.51a Ethyl hexanoate Banana, green apple[1] 0.08[1] 749.92±72.65a 515.85±49.06b 535.92±55.50b 388.25±36.12c 442.16±43.69bc Hexyl acetate Apple, cherry, pear, floral[1] 1.5[1] 60.09±7.32a 47.19±4.53b 58.32±5.36a 18.63±1.92c 22.85±2.12c Ethyl heptanoate Fruit[4] 0.22[4] 9.26±0.87a 6.41±0.67b 5.27±0.61bc 4.04±0.38c 4.36±0.41c Ital. J. Food Sci., vol. 32, 2020 - 924 Methyl octanoate Orange[4] 34.89±3.57a 40.63±3.88a 43.31±4.10a 35.28±3.11a 41.49±3.89a Ethyl octanoate Fruity, sweet, banana, pear[1,2] 0.24-0.58 [1,2] 2552.69±226.39a 1521.94±126.93b 1668.65±171.03b 890.86±82.62d 1114.51±103.43c Geranyl acetate Floral, rose[6] 96.95±9.32b 120.62±11.05a 102.99±10.23ab 67.65±6.59c 62.78±6.32c Ethyl nonanoate 44.32±4.34a 32.19±3.36b 33.67±3.42b 36.19±3.54b 35.20±3.17b Methyl decanoate Wine[4] 1.2[4] 14.46±1.28a 12.63±1.01a 13.90±1.21a 9.91±0.79b 10.33±0.92b Ethyl decanoate Fatty acids, fruity, soap[1,2] 0.2[1,2] 1840.95±156.98a 878.86±90.09b 957.66±92.06b 464.04±42.22c 504.38±48.56c Ethyl benzoate Heavy, floral, fruity[4] 5.75[4] 315.49±33.65b 577.75±46.60a 589.05±54.98a 606.73±61.17a 631.40±56.77a Ethyl 9-decenoate Fruity[4] 0.1[4] 231.95±24.25a 32.81±3.14b 27.38±2.67b 7.50±0.73c 5.53±0.50c Methyl salicylate Pepper, mint[4] 11.38±1.14b 15.12±1.87a 16.64±1.52a 12.13±1.10b 12.44±1.39b Ethyl phenylacetate Fruity, sweet[4] 2.03±0.15b 1.88±0.23b 2.08±0.19b 3.26±0.33a 3.41±0.31a 2-Phenylethyl acetate Fruity, rose[1] 1.8[1] 41.38±3.36a 34.34±3.18a 35.77±3.48a 24.39±2.31b 26.72±2.43b Ethyl dodecanoate Oily, fatty, fruity[1] 1.5[1] 175.20±18.21b 178.56±15.56b 223.61±21.13a 120.02±10.65d 154.12±12.98c ∑Esters 9532.22±894.31a 6213.25±580.31b 6754.61±648.47b 4406.30±418.35c 4984.28±465.81c Linalool Flowery, muscat[1] 0.025[1] 731.91±71.03c 1007.80±96.32b 897.27±90.43bc 1424.51±153.07a 1369.53±128.25a α-Terpineol Lilac, floral, sweet[1] 0.25[1] 135.46±12.63c 184.23±16.70b 159.49±14.17bc 302.61±28.65a 288.09±26.72a Citronellol Rose[1] 0.1[1] 18.48±1.72c 28.88±2.64b 27.68±2.60b 58.05±5.57a 60.98±5.78a Geraniol Citric, geranium[1] 0.02[1] 40.89±4.65b 53.12±5.35a 49.27±4.55ab 56.91±5.43a 51.64±5.33a ∑Terpenes 926.75±90.03c 1274.03±121.01b 1133.72±111.75bc 1842.09±192.72a 1770.24±166.08a All data are expressed as mean±SD (n = 3). Different letters in the same row indicate statistically significant differences at p<0.05. SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3, ND not detected [1] CAI et al., 2014; [2] BUTKHUP et al., 2011; [3] BARTOWSKY and HENSCHKE, 2004; [4] ZHANG et al., 2015; [5] NATTAPORN and PRANEE, 2011; [6] NISHIMURA, 1995 Ital. J. Food Sci., vol. 32, 2020 - 925 3.6. Sensory evaluation of apricot wines The sensory evaluation results of apricot wines are shown in Fig. 3. All the pectinase- treated apricot wines obtained higher color scores compared with control apricot wine, due to clarification by pectinase enzyme. The flavor scores of SCPC wine, containing the highest amount of total volatile higher alcohols, and PCP and PCPC wines, which recorded the greatest abundance of total volatile terpenes, were significantly higher relative to the other apricot wines. The sweetness scores of pectinase-treated apricot wines were slightly higher than control apricot wine because of some remaining free sugars. The sourness of PCP wine was the strongest, whereas that of SCPC wine was the weakest because these wines contained, respectively, the highest and lowest presence of tartaric acid and malic acid, which are the two strongest organic acids. PCPC wine also obtained low sourness score because of its low tartaric acid and malic acid levels. In the overall preference, SCPC and PCPC wines, having the most reduced sourness, obtained the highest scores among all the apricot wines. SCP and PCP wines also obtained higher scores when compared with SC wine. Figure 3. Sensory evaluation of apricot wines depending on different chaptalization types and pretreatment conditions. SC sugar chaptalization, SCP sugar chaptalization treated with 0.1% pectinase, SCPC sugar chaptalization treated with 0.1% pectinase and 0.3% CaCO3, PCP puree concentrate chaptalization treated with 0.1% pectinase, PCPC puree concentrate chaptalization treated with 0.1% pectinase and 0.3% CaCO3 In this study, we investigated the effects of puree concentrate chaptalization and various pretreatments on the quality of apricot wine. The results demonstrated that apricot wines chaptalized with puree concentrate have shown not only higher antioxidant activity and total volatile terpene compounds than sugar-chaptalized apricot wines but also higher acidity that negatively affects the sensory properties of wine. 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Paper Received April 20, 2020 Accepted September 9, 2020