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Abstract [Objectives] This study was conducted to provide basic information for the utilization， quality control and deep processing of ‘Xintai Tianhong’ hawthorn fruit resources.
[Methods] The contents of sugar and acid components in ‘Xintai Tianhong’ hawthorn fruit were determined by high performance liquid chromatography （HPLC）.
[Results] ‘Xintai Tianhong’ hawthorn fruit contained such four kinds of sugar components as fructose， sorbitol， glucose and sucrose， and such six kinds of organic acid components as oxalic acid， tartaric acid， malic acid， acetic acid， citric acid and succinic acid. The fruit had the highest sucrose content， accounting for 70.53% of the total sugar content， followed by fructose， glucose and sorbitol. For the organic acid components， the content of succinic acid was the highest， accounting for 47.32% of the total acid content， followed by citric acid， malic acid， oxalic acid and tartaric acid， and acetic acid had the lowest content.
[Conclusions] ‘Xintai Tianhong’ hawthorn should be a succinic acidtype hawthorn variety， which can be used as a parent in genetic research and breeding practice.
Key words High performance liquid chromatography; Hawthorn; Sugar; Organic acid
‘Xintai Tianhong’ hawthorn （also known as Tianhongzi） is a wild variant of the wild hawthorn in Nanliuquan Village， Liudu Town， Xintai City[1]. ‘Xintai Tianhong’ hawthorn fruit is flat round， with pink flesh and fine texture. It tastes sweet and sour and is suitable for fresh eating， so it is very popular among consumers. In this study， high performance liquid chromatography （HPLC） was applied to analyze the sugar and acid components of ‘Xintai Tianhong’ hawthorn fruit， so as to provide basic information for the utilization， quality control and deep processing of this variety.
Materials and Methods
Test materials and sample treatment
The hawthorn variety used in this experiment was ‘Xintai Tianhong’ hawthorn， which was planted in the Jinniushan Experimental Base of Shandong Institute of Pomology. The orchard is hilly land with sandy loam soil. The plant spacing is 3 m×4 m， and the trees have a sparse layer shape with a small crown. The treeswere 6 years old， and the fruit yield was about 22 500 kg/hm2. The management level is medium.
In September 2018， 5 representative trees were selected， and 30 mature hawthorns were collected from the north， south， and north of the trees in total， and immediately taken to Shandong Institute of Pomology for treatment. At room temperature， the fruit was cut to remove the cores， and the flesh was chopped and mixed （30 hawthorns of each variety were chopped and mixed）， and frozen at -80 ℃. Determination methods
The contents of sugar and acid components in the fruit were determined referring to the method of Chen et al.[2]， with slight modifications.
Extraction and determination of sugar and acid components in fruits
At first， 5 g of flesh was accurately weighed， ground with 15 ml of 80% ethanol， and heated in a water bath （75 ℃） for 30 min. The mixture was then centrifuged at 4 000 g/min for 5 min， obtaining the supernatant which was transferred to a 25 ml volumetric flask. Into the precipitate， 10 ml of 80% ethanol was added， and the obtained mixture was heated in a water bath （75 ℃）for 30 min， followed by centrifugation at 4 000 g/min for 5 min. The supernatant was added into the above 25 ml volumetric flask， in which the liquid was diluted to constant volume and then evaporated at 60 ℃ to dryness. The residue was dissolved in 5 ml of distilled water for testing.
Chromatographic conditions： an Agilent 1100 HPLC equippedwith a Kromasil C18 reversed phase column （250 mm×4.6 mm， 5 μm） was employed for flow measurement. Preparation of the mobile phase： 1.56 g of sodium dihydrogen phosphate was weighed and dissolved in 800 ml of water， and added with 16 ml of methanol， and the obtained solution was adjusted to the pH of 2.8 with phosphoric acid. During determination， the computer， detector and pump were turned on first， and the column was installed. The software was open to set method group including the injection volume of 10 μl， the flow rate at 0.8 ml/min， the column temperature at 25 ℃， the sample detection time of 20 min， and the UV wavelength of 214 nm which were saved in the HPLC. The mobile phase was introduced to the column until the base line was stable， and the sample was then loaded. The contents of the sugar and acid components were calculated using an N2000 chromatography workstation （Ver. 3.30）.
Results and Analysis
Analysis of sugar components in fruit
Fig. 1 shows that four sugar components were detected in ‘Xintai Tianhong’hawthorn fruit. Table 1 shows that for the sugar components of ‘Xintai Tianhong’ hawthorn fruit， the sucrose content was the highest at 0.34 mg/g， accounting for 29.98%of total sugar， followed by glucose， fructose and sorbitol， accounting for 25.87%， 23.14% and 21.00% of the total sugar， respectively.
Discussion and Conclusions
Sugar and acid components in fruit are important indicators to determine fruit quality. Since the 1960s， with the development of liquid chromatography technology， great progress has been made in the determination of fruit sugar acid at home and abroad. The sugar and acid compositions of different tree species are different. In apple fruit[3]， fructose， glucose and sucrose are the main sugar components， and the main organic acids are malic acid， citric acid， succinic acid and oxalic acid. The sugar components of pear[4]are mainly fructose， followed by glucose and sucrose; and the organic acids are mainly malic acid， quinic acid， shikimic acid and citric acid， and the contents of tartaric acid and succinic acid are less. The sugar components of peach[5]are mainly sucrose， followed by glucose and fructose， and sorbitol had the lowest content; and the organic acids are mainly citric acid and malic acid， and quinic acid and succinic acid are less. There are few studies on the sugar and acid components of hawthorn fruit[6-7]. This study showed that for the sugar components of ‘Xintai Tianhong’ hawthorn fruit， the sucrose content was the highest， followed by glucose， fructose and sorbitol; and among the organic acid components of ‘Xintai Tianhong’ hawthorn fruit， succinic acid had the highest content， sequentially followed by citric acid， malic acid， oxalic acid and tartaric acid， and the acetic acid content was the lowest. Divided by types， ‘Xintai Tianhong’ hawthorn should be a succinic acidtype hawthorn variety， which can be used as a parent in genetic research and breeding practice.
References
[1] CAO YC， XU Y， SONG YP， et al. Traits and cultivation techniques of new hawthorn variety Tianhongzi[J]. Deciduous Fruits， 2019（1）： 40-42. （in Chinese）
[2] CHEN MX， CHEN XX， CI ZJ， et al. Changes of Sugar and Acid Constituents in Apricot during Fruit Development[J]. Acta Horticulturae Sinica， 2006， 33（4）： 805-808. （in Chinese）
[3] YAN ZY， YI K， LIU Z， et al. Genetic Analysis of sugar and acid components in the ‘Hongyu’ × ‘Golden Crown’ hybrid of apple[J]. Journal of Fruit Science， 2017， 34（2）： 129-136. （in Chinese）
[4] CHEN JL， WANG ZF， WU JH， et al. Chemical compositional characterization of eight pear cultivars grown in China[J]. Food Chemistry， 2007（104）： 268-275.
[5] VERSARI A， CASTELLARI M， PARPINELLO GP， et al. Characterisation of peach juices obtained from cultivars Redhaven， Suncrest and Maria Marta grown in Italy[J]. Food Chemistry， 2002（76）： 181-185.
[6] wANG SZ， XIN L， YAN Y， et al. Effects of dehydration and drying on sugar and acid contents in apple and hawthorn[J]. Food Science， 1993（4）： 3-6. （in Chinese）
[7] QI XJ， LI ZY， XU SK. Relationship between Soluble Sugars and Peel Pigments in Hawthorn Fruit[J]. Journal of Fruit Science， 2005（1）： 81-83.（in Chinese）
Editor： Yingzhi GUANG Proofreader： Xinxiu ZHU
[Methods] The contents of sugar and acid components in ‘Xintai Tianhong’ hawthorn fruit were determined by high performance liquid chromatography （HPLC）.
[Results] ‘Xintai Tianhong’ hawthorn fruit contained such four kinds of sugar components as fructose， sorbitol， glucose and sucrose， and such six kinds of organic acid components as oxalic acid， tartaric acid， malic acid， acetic acid， citric acid and succinic acid. The fruit had the highest sucrose content， accounting for 70.53% of the total sugar content， followed by fructose， glucose and sorbitol. For the organic acid components， the content of succinic acid was the highest， accounting for 47.32% of the total acid content， followed by citric acid， malic acid， oxalic acid and tartaric acid， and acetic acid had the lowest content.
[Conclusions] ‘Xintai Tianhong’ hawthorn should be a succinic acidtype hawthorn variety， which can be used as a parent in genetic research and breeding practice.
Key words High performance liquid chromatography; Hawthorn; Sugar; Organic acid
‘Xintai Tianhong’ hawthorn （also known as Tianhongzi） is a wild variant of the wild hawthorn in Nanliuquan Village， Liudu Town， Xintai City[1]. ‘Xintai Tianhong’ hawthorn fruit is flat round， with pink flesh and fine texture. It tastes sweet and sour and is suitable for fresh eating， so it is very popular among consumers. In this study， high performance liquid chromatography （HPLC） was applied to analyze the sugar and acid components of ‘Xintai Tianhong’ hawthorn fruit， so as to provide basic information for the utilization， quality control and deep processing of this variety.
Materials and Methods
Test materials and sample treatment
The hawthorn variety used in this experiment was ‘Xintai Tianhong’ hawthorn， which was planted in the Jinniushan Experimental Base of Shandong Institute of Pomology. The orchard is hilly land with sandy loam soil. The plant spacing is 3 m×4 m， and the trees have a sparse layer shape with a small crown. The treeswere 6 years old， and the fruit yield was about 22 500 kg/hm2. The management level is medium.
In September 2018， 5 representative trees were selected， and 30 mature hawthorns were collected from the north， south， and north of the trees in total， and immediately taken to Shandong Institute of Pomology for treatment. At room temperature， the fruit was cut to remove the cores， and the flesh was chopped and mixed （30 hawthorns of each variety were chopped and mixed）， and frozen at -80 ℃. Determination methods
The contents of sugar and acid components in the fruit were determined referring to the method of Chen et al.[2]， with slight modifications.
Extraction and determination of sugar and acid components in fruits
At first， 5 g of flesh was accurately weighed， ground with 15 ml of 80% ethanol， and heated in a water bath （75 ℃） for 30 min. The mixture was then centrifuged at 4 000 g/min for 5 min， obtaining the supernatant which was transferred to a 25 ml volumetric flask. Into the precipitate， 10 ml of 80% ethanol was added， and the obtained mixture was heated in a water bath （75 ℃）for 30 min， followed by centrifugation at 4 000 g/min for 5 min. The supernatant was added into the above 25 ml volumetric flask， in which the liquid was diluted to constant volume and then evaporated at 60 ℃ to dryness. The residue was dissolved in 5 ml of distilled water for testing.
Chromatographic conditions： an Agilent 1100 HPLC equippedwith a Kromasil C18 reversed phase column （250 mm×4.6 mm， 5 μm） was employed for flow measurement. Preparation of the mobile phase： 1.56 g of sodium dihydrogen phosphate was weighed and dissolved in 800 ml of water， and added with 16 ml of methanol， and the obtained solution was adjusted to the pH of 2.8 with phosphoric acid. During determination， the computer， detector and pump were turned on first， and the column was installed. The software was open to set method group including the injection volume of 10 μl， the flow rate at 0.8 ml/min， the column temperature at 25 ℃， the sample detection time of 20 min， and the UV wavelength of 214 nm which were saved in the HPLC. The mobile phase was introduced to the column until the base line was stable， and the sample was then loaded. The contents of the sugar and acid components were calculated using an N2000 chromatography workstation （Ver. 3.30）.
Results and Analysis
Analysis of sugar components in fruit
Fig. 1 shows that four sugar components were detected in ‘Xintai Tianhong’hawthorn fruit. Table 1 shows that for the sugar components of ‘Xintai Tianhong’ hawthorn fruit， the sucrose content was the highest at 0.34 mg/g， accounting for 29.98%of total sugar， followed by glucose， fructose and sorbitol， accounting for 25.87%， 23.14% and 21.00% of the total sugar， respectively.
Discussion and Conclusions
Sugar and acid components in fruit are important indicators to determine fruit quality. Since the 1960s， with the development of liquid chromatography technology， great progress has been made in the determination of fruit sugar acid at home and abroad. The sugar and acid compositions of different tree species are different. In apple fruit[3]， fructose， glucose and sucrose are the main sugar components， and the main organic acids are malic acid， citric acid， succinic acid and oxalic acid. The sugar components of pear[4]are mainly fructose， followed by glucose and sucrose; and the organic acids are mainly malic acid， quinic acid， shikimic acid and citric acid， and the contents of tartaric acid and succinic acid are less. The sugar components of peach[5]are mainly sucrose， followed by glucose and fructose， and sorbitol had the lowest content; and the organic acids are mainly citric acid and malic acid， and quinic acid and succinic acid are less. There are few studies on the sugar and acid components of hawthorn fruit[6-7]. This study showed that for the sugar components of ‘Xintai Tianhong’ hawthorn fruit， the sucrose content was the highest， followed by glucose， fructose and sorbitol; and among the organic acid components of ‘Xintai Tianhong’ hawthorn fruit， succinic acid had the highest content， sequentially followed by citric acid， malic acid， oxalic acid and tartaric acid， and the acetic acid content was the lowest. Divided by types， ‘Xintai Tianhong’ hawthorn should be a succinic acidtype hawthorn variety， which can be used as a parent in genetic research and breeding practice.
References
[1] CAO YC， XU Y， SONG YP， et al. Traits and cultivation techniques of new hawthorn variety Tianhongzi[J]. Deciduous Fruits， 2019（1）： 40-42. （in Chinese）
[2] CHEN MX， CHEN XX， CI ZJ， et al. Changes of Sugar and Acid Constituents in Apricot during Fruit Development[J]. Acta Horticulturae Sinica， 2006， 33（4）： 805-808. （in Chinese）
[3] YAN ZY， YI K， LIU Z， et al. Genetic Analysis of sugar and acid components in the ‘Hongyu’ × ‘Golden Crown’ hybrid of apple[J]. Journal of Fruit Science， 2017， 34（2）： 129-136. （in Chinese）
[4] CHEN JL， WANG ZF， WU JH， et al. Chemical compositional characterization of eight pear cultivars grown in China[J]. Food Chemistry， 2007（104）： 268-275.
[5] VERSARI A， CASTELLARI M， PARPINELLO GP， et al. Characterisation of peach juices obtained from cultivars Redhaven， Suncrest and Maria Marta grown in Italy[J]. Food Chemistry， 2002（76）： 181-185.
[6] wANG SZ， XIN L， YAN Y， et al. Effects of dehydration and drying on sugar and acid contents in apple and hawthorn[J]. Food Science， 1993（4）： 3-6. （in Chinese）
[7] QI XJ， LI ZY， XU SK. Relationship between Soluble Sugars and Peel Pigments in Hawthorn Fruit[J]. Journal of Fruit Science， 2005（1）： 81-83.（in Chinese）
Editor： Yingzhi GUANG Proofreader： Xinxiu ZHU