Physicochemical , antioxidant , and sensorial properties of peach snacks prepared from different cultivars

High potentiality of medicinal benefits of peach have increased its demand, however, supply of fresh fruit to meet the demand is challenging as it grows in specific climatic regions and in particular season. Preparation of varieties of processed peach products could be a good option to supply in lean season. Objective of the study was to assess the quality characteristics of peach snacks prepared from 11 different cultivars. We investigated the physicochemical (soluble solid, titratable acidity, hardness and dry yield), antioxidant (DPPH radical scavenging capacity and total phenolics content) and sensorial properties (color, flavor, texture, sweetness and overall acceptance) of peach snacks prepared from 11 peach cultivars. Peach snacks of different cultivars evaluated in this study showed substantial variations in antioxidant capacity, physicochemical and sensorial properties. Some of the samples showed higher physicochemical properties while the others contained better antioxidant capacity or sensory properties. Results of this study reveal that quality peach snacks having different properties could be prepared by drying thin slices of fresh fruits of different cultivars. However, supplementary studies on cost effective techniques of peach snacks preparation and variation in nutritive and medicinal properties of processed products could increase the application of the findings of this experiment.


INTRODUCTION
Peach (Prunus persica L. Batsch) is a cool season fruit that could be cultivated in different parts of the world.It is regarded as an important economic crop and also recommended for its various health benefits (Yang et al., 2011).Peach contains caffeoylquinic acid, one of the bioactive polyphenols with significant antioxidant activity and important beneficial effect in human health (Luo et al., 2008).Antioxidants present in peach scavenge the reactive oxygen species in human blood plasma and thus provide a potential protection against various chronic diseases with dietary consumption of peach (Tsantili et al., 2010).*Corresponding author.E-mail: dhshin@knu.ac.kr.Tel: +82-53-950-5707.Fax: +82-53-958-6880.
Author(s) agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License As the fruit is grown only in a particular season and specific climatic regions, supply of fresh fruit to a large extent is challenging in spite of its big demand from across the world.On the other hand, some consumers decline to buy fresh fruits as they find the internal quality poor when fruit is consumed fresh (Byrne, 2002).In such a scenario, high quality dried fruits could be a good option to replenish the supply of health benefits of peach during off-season and in those areas where peach is not produced.
High potentiality of medicinal benefit (Manzoor et al., 2012) of some fruits including peach has increased their demand; however, some of the processing related problems have raised concerns among large number of consumers.In order to maintain the quality in some dried fruits, sulfur fumigation is often applied to prevent quality deterioration and fungal attacks (Miller, 1984).However, the hazardous nature of sulfur raises a health risk and food safety concerns (Islam and Hoque, 2013) as the traces of sulfur dioxide remained in food causes asthma or allergic reaction to some people.
Different cultivars of peach have different fruit quality and nutritional composition.Various preferences of consumers have raised the interest in breeding programs worldwide to focus on fruit quality and nutritional composition (Wolfe et al., 2008).Some of them are devoted to produce cultivars with excellent taste, high sugar levels, and balanced sugar/acid ratios (Esti et al., 1997).Other breeding programs are focused to the identification and quantification of phenolic compounds (Cantin et al., 2009).High quality dried fruits could be a good option to replenish the supply of health benefits of peach during off-season and in those areas where peach is not produced.
Very limited studies regarding the potential use of dried peach snacks have been reported.In the context of big scope of dried fruits of peach as fresh fruits are not available year round in the all parts of the world and different quality and nutritional composition of the cultivars, the objective of this study was to evaluate the physicochemical, antioxidant, and organoleptic properties of peach snacks prepared from 11 peach cultivars.This work will benefit the preparation of good quality processed dry peach snacks.

Sample and chemicals
Fruits of 11 peach cultivars namely; Hikawa Hakuho, Yume Fuji, Kunika, Jinmi, Kawanakajima Hakutou, Baekhyang, Changhowon Hwangdo, Wolbongjosaeng, Daemyung, Red Start and Shuho, grown at Cheongdo Peach Experiment Station of Cheongdo-city in Korea, were manually harvested 80-85 days after flowering and transported to the laboratory.Fruits were thoroughly washed with tap water and kept for surface drying at room temperature.Seed was separated from flesh and 5 mm thick slices of flesh were prepared manually using knife.The slices were delivered to quick freezing (−40°C) for 12 h then kept for freeze drying to prepare peach snacks.The freeze-dried snacks were packed into air-tight plastic bags until further analysis.All the chemicals and reagents used in the study were of analytical grade.

Rheological measurement of hardness and weight
Hardness of peach snacks was measured using a rheometer (COMPAC-100, Sun scientific Co., Japan) under the following operational conditions: test type, mastication; probe, 25 mm aluminium cylinder probe; load cell, 2.0 kg and table speed, 60 mm/min.Fresh and dry weight of peach slices were measured to observe the dry yield of peach snacks of different cultivars.

Standard chemical analysis
Titratable acidity (TA) and soluble solid (SS) content of peach snacks of 11 cultivars were analyzed to determine their chemical properties.Peach snacks were ground into flour (60-mesh).Measurement of titratable acidity was carried out by titrating 10 mg of ground peach snack to 100 mL of deionized water and expressed as percentage citric acid.Soluble solid content was determined using a refractometer (RX-5000α, Atago, Tokyo, Japan) and expressed as °Brix.

Determination of total phenolic compounds
Total phenolic compounds in ground peach snacks were analyzed following Folin-Ciocalteu method (Singleton, 1999).The reagents were allowed to react for 60 min at room temperature and absorbance was measured at 750 nm using ELISA microplate reader (Infinite F50, Tecan, Switzerland).Standard calibration curve was drawn using gallic acid and results were expressed as μg/g on a dry weight basis of sample.The values are presented as means of triplicate experiments.

Determination of DPPH radical scavenging activity
Antioxidant capacity of ground peach snack was quantified by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method as described by Blois (1958).The DPPH solution was prepared at the concentration of 4×10 -4 mol/L in methanol.Ground sample (1 g) was extracted in 10 mL of absolute methanol and hot water (100°C) at room temperature for 12 h.The supernatant was centrifuged (1660×g) at room temperature for 10 min and filtered through 2-µm syringe filter.A 0.1-mL of sample extract was mixed with 2.9 mL of freshly prepared DPPH solution.The mixture was incubated in the dark at room temperature for 30 min and absorbance (Abs) was measured at 517 nm by ELISA microplate reader (Sunrise basic, Tecan, Austria).The control was prepared without mixing any sample extract, and methanol was used for the baseline correction.
Values are presented as means of three replications.The radical scavenging activity was calculated using the following equation: DPPH radical scavenging activity (%) = (Control Abs − Sample Abs)/Control Abs × 100

Sensory properties evaluation
Sensory properties of peach snacks were evaluated for color, taste (sweetness, astringency), texture, and overall acceptance on 5-scale basis: 1 = very bad, 2 = bad, 3 = moderate, 4 = good, 5 = very good.All the sensory properties were evaluated by 20 volunteer panelists (10 women and 10 men) selected in Kyungpook National University, Daegu, Korea.The values are the average of 10 evaluations for each sensory property.

Statistical analysis
Data were analyzed using the statistic version 4.0 package (Analytical Software, AZ, USA) to generate one-way or two-way analysis of variance (ANOVA) when needed and the significant differences between means were identified using the Tukey's mean test (p<0.05).

RESULTS
Peach snacks of different cultivars evaluated in this study showed substantial variations in antioxidant capacity, physicochemical, and sensorial properties as mentioned by other authors (Byrne et al., 1991;Cantín et al., 2009a;2009b).

Antioxidant capacity
Total phenolic compounds and DPPH radical scavenging activity were considered to evaluate the antioxidant capacity of peach snacks of different cultivars.Peach snacks of some of the cultivars showed variability in their antioxidant capacity in hot water extract and methanol extract (

Sensory characteristics
Sensorial characteristics of peach snacks varied slightly among cultivars (Table 3).The highest and lowest values

DISCUSSION
Significant differences in SS content were found in the dried peach snacks made of different cultivars.These variations enrich the scope of preparing varieties of snacks from them since SS content is a key quality trait in peaches and nectarines as it is reported that consumer acceptance and satisfaction are related to these traits.However, this relationship varies with cultivar as no standard SS content satisfies consumer, moreover, is affected by other quality traits, such as TA (Crisosto and Crisosto, 2005).
A large number of reports showed a beneficial effect of phenol antioxidants on heart disease and cancer.Phenolic content found in these peach snacks are higher than those previously reported (Gil et al., 2002;Celia et al., 2009) which might be due to the difference in the nature of sample: dry fruit sample was used in the present study instead of fresh one as did in previous studies.However, the proportion of variation in antioxidant capacities between hot water and methanol among different cultivars were not clearly understood.
Differences in overall acceptance of peach snacks in the present study could be considered to prepare highly acceptable product as statistics showed that many food products, even when developed from a sound scientific point of view, encounter poor market acceptance (Hilliam, 1998).Approximately 75% of newly launched food products suffer from poor liking and are withdrawn from the food market during their first two years (Menrad, 2003).
The variation in physicochemical, antioxidative, and sensorial traits of different peach snacks might be due to the genotypic variation among cultivars as pomological characteristics of fruits are strongly affected by the genotypes and environments (Moghaddama et al., 2013;Mratinic et al., 2011).
In conclusion, high potentiality of medicinal benefits of peach have increased its demand, however, supply of fresh fruit to meet the demand is challenging as it grows in specific climatic regions and in particular season.Preparation of varieties of processed peach products could be a good option to supply in lean season.This study, portrayed that peach snacks having different physicochemical, sensorial, and antioxidant properties could be prepared by drying thin slices of fresh fruits of different cultivars.However, further study on cost effective techniques of peach snacks preparation could increase the application of the findings of this experiment.

Table 2 .
Total phenolic content and DPPH radical scavenging activity of 11 peach snacks in hot water and methanol extracts.Shuho.GAE = Gallic acid equivalent; HWE = hot water extract; ME = methanol extract.Values are means±SD of three replications.The values followed by different superscript within a column indicate significant difference (p<0.05).