[ Original Article ]

Journal of Apiculture - Vol. 33, No. 4, pp.297-301

ISSN: 1225-0252 (Print)

Print publication date 30 Nov 2018

Received 09 Nov 2018 Revised 28 Nov 2018 Accepted 28 Nov 2018

DOI: https://doi.org/10.17519/apiculture.2018.11.33.4.297

Free Sugar and Organic Acid in the Fruit of Hawthorn (Crataegus pinnatifida Bunge) Selected Clones as Honey Plant in Korea

Youngki Park^* ; Jae-Hee Kim

Department of Forest Genetic Resources, National Institute of Forest Science, Suwon 16631, Korea

Correspondence to: ^* E-mail: woodpark@korea.kr

Abstract

Hawthorn is widely distributed in Korea and has been used as herbal medicine for treating various cardiovascular disease, arteriosclerosis and hypertension in Korea. In order to select superior honey tree plant from Korea, the free sugar and organic acid in hawthorn fruits, including five Korean clones and four Chinese cultivars, were evaluated. We also compared these hawthorn fruits of five clones (selected from different area of Korea) with Chinese hawthorn cultivars. Glucose, galactose, fructose and sucrose were the major sugar components of hawthorn. In this study, we observed that sucrose, glucose and fructose content. The highest sucrose content of hawthorn fruit was 188.12g/100g in Daegeumseong cultivar. The sweetness index, which plays important role of taste, was also calculated from the content of sucrose, glucose and fructose. The contribution of each carbohydrate was calculated, based on the fact that fructose is 2.30 and sucrose 1.35 times sweeter than glucose. The highest sweetness of hawthorn fruit was 579.52 in Pocheon clone. Main organic acid detected in hawthorn fruit were citric acid, malic acid and shikimic acid. The highest citric acid and malic acid content in hawthorn fruit were 157.50g/100g (Pocheon 3) and 34.12g/100g (Daegeumseong), respectively. The results of this study would be helpful for using food and functional food products, due to the beneficial effects of free sugar and organic acid for human health such as antioxidants and anticarcinogenic properties.

Keywords:

Citric acid, Hawthorn fruit, Malic acid, Sucrose, Sweetness index

INTRODUCTION

The fruits of Hawthorn (Crataegus pinnaitifida Bunge, Rosaceae) have been used traditionally as a peptic agent in oriental medicine and recently as a local soft drink material (Kao et al., 2007). It is believed that preparations of fruits of C. pinnatifida improve the heart function when there are indications of declining cardiac performance, deficiency in coronary blood supply, and mild forms of arrhythmia. The pharmacological effects of C. pinnatifida have mainly been attributed to their polyphenolic contents, and oligomeric procyanidins (OPCs) are abundant in hawthorn. The active constituents and the antioxidant effects of the extracts of the fruit of C. pinnatifida have been widely studied (Kao et al., 2005).

Hawthorn is widely distributed in Korea and has been used as herbal medicine for treating various cardiovascular disease, arteriosclerosis and hypertension in Korea (Chang et al., 2002). It is also used to improve digestion, remove retention of food, promote blood circulation and resolve blood stasis both in traditional and folk medicine (Ammon and Handel, 1981).

Phenolics, mainly flavonoids and proanthocyanidins, are known as active ingredients of hawthorn (Zhang et al., 2001). Previously, we reported the contents of five major phenolic compounds such as (-)-epicatechin (EC), procyanidin B₂ (PC-B₂), hyperoside (HP), isoquercitrin (IQ) and chlorogenic acid (ChA) (Park et al., 2010).

Even though, there are some data on the biologically active chemical constituents such as total phenol, flavonoid and vitamin C of hawthorn fruit (Zhang et al., 2001), there are no studies of the free sugar and organic acid content of five clones and four Chinese hawthorn cultivars. Thus, in this study, we report the overall free sugar and organic acid content of hawthorn fruit of five clones selected from different area of Korea with Chinese four hawthorn cultivars grown in the National Institute of Forest Science, Suwon. The aim of this study was to evaluate nutrition values of hawthorn fruit, which may be useful for using fruit as food and functional food products.

MATERIALS AND METHODS

Plant materials and sample collection

The fruits of C. pinnatifida used in this study were Chuncheon 1, Chuncheon 8, Chuncheon 15, Jungsun and Poechun which were selected from Korea and Maban, Changgu, Keumsung and Daekeumsung which were Chinese cultivar. C. pinnatifida fruits grown in the National Institute of Forest Science (Suwon, Korea) were collected in October after mature.

Free sugar content analysis

The sugars content levels (sucrose, glucose, and fructose) in the samples were analyzed by a reported LC method with some modification (Godin et al., 2011). A total of 2g of freeze-dried hawthorn powders was extracted with 100mL of water in a cooled ultrasonic bath (40kHz) for 60 min. Then the extract was centrifuged (15,000 rpm, 4°C, 10 min) and the supernatant was separated with membrane filter (0.45 um) and transferred to vials. Samples were analyzed on a Dionex Ultimate 300 HPLC system. A Sugar-pak (waters, 300×6.5mm) column with deionized water as the mobile phase was used for separation of the sugars. The flow rate were optimized as 0.5mL/min and a Shodex RI-101 detector was used for identification. Quantification was performed on the basis of linear calibration plots of the logarithm of peak areas versus the logarithm of concentrations. The concentrations were expressed in grams per 100g of distilled water (DW). The summary of HPLC conditions used for free sugar analysis in this study were shown in Table 1.

Table 1.

The operating conditions of HPLC for analysis of free sugars

Organic acid analysis

The freeze-dried hawthorn powders of 3g were transferred to Eppendorf tube with 5 ml of distilled water. Then the extract was centrifuged (15,000 rpm, 4°C, 10 min) and the supernatant was separated with membrane filter (0.45 um) and transferred to vials. Organic acids in hawthorn fruit were analyzed by a Dionex Ultimate 300 HPLC system. The chromatographic separation used for organic acid detection employed 0.01 N H₂SO₄ as the mobile phase, Aminex 87H (300×10mm) column (Bio-Rad, USA) with a flow rate of 0.5ml/min, samples organic acids were detected with a RI detector (ERC, RefractoMax, Japan).

Estimation of hawthorn taste parameters

Sweetness index in this study was calculated based on the amount and sweetness properties of individual carbohydrate in fruit (Keutgen and Pawelzik, 2007). The contribution of each carbohydrate was calculated, based on the fact that fructose is 2.30 and sucrose 1.35 times sweeter than glucose. Accordingly, sweetness index=1.0 (glucose) + 2.30 (fructose) +1.35 (sucrose).

Statistical analysis

All experiments were performed at least three times and the results were reported as mean±SD. Data were statistically evaluated by one-way ANOVA analysis and Duncan’s multiple range test. Results of tables and figure were presented as mean±standard deviation.

RESULTS AND DISCUSSION

Free sugars analysis of hawthorn fruit

Generally, the sugar composition is one of the most important parameters for food energy level. In Table 2, we listed the HPLC quantitative analytical data of the free sugars in the hawthorn fruit. The fruits of five different hawthorn clones selected from Korea and four Chinese cultivars were used in this study. Glucose, sorbitol and sucrose were the major sugar components of the hawthorn fruit.

Table 2.

Free sugar content of the fruit of hawthorn clones and Chinese cultivars

Glucose contents are between 48.90 and 179.34g/100g, and sucrose contents are between 188.12 and 0.00g/100g, respectively. The highest sucrose content of hawthorn fruit was 188.12g/100g in Daekeumsung cultivar.

Because the relationship between fructose and glucose content was about 1:1, which is typical for berry fruit, (Keutgen and Pawelzik, 2007) and the same results were observed in this study. It is well known that fruit sweetness depends not only on the content of each sugar, but also on the ratios of the main individual sugars (Zheng et al., 2016). It is also found that the sweetness index, which plays important role of taste in hawthorn fruit (Fig. 1).

Fig. 1.

Sweetness index of the fruit of hawthorn selected clones and Chinese cultivars. (CH1: Chuncheon 1, CH8: Chuncheon 8, CH15: Chuncheon 15, JS: Jungsun, PC: Poechun, MB: Maban, CG: Changgu, KS: Keumsung, DKS: Daekeumsung).

The highest sweetness of hawthorn fruit was 579.52 in Poecheon clone while the lowest sweetness of hawthorn fruit was 285.59 in Chuncheon 8 clone.

Organic acids analysis of hawthorn fruit

Hawthorn fruits have long been used in traditional Korean, Chinese and European medicine, and are widely consumed as food, in the form of juice, drink, jam and canned fruit. Due to the significant amounts of various organic acids, including caffeic acid, malic acid and tartaric acid, contained in the hawthorn fruits (Gao et al., 1995), the components in hawthorn preparations, such as hawthorn drink, might exist in acidic condition.

Organic acids represent further compounds contributing to taste and flavour of hawthorn fruit. Three major organic acids in hawthorn fruit, citric acid, malic acid, and shikimic acid, were detected by HPLC. The organic acids of the fruit of hawthorn clones and Chinese cultivars are shown in Table 3. The results showed that citric acid showed was the main organic acid in hawthorn fruit and followed by malic acid and shikimic acid. While, Albertini et al. (2006) reported that citric acid dominated in lemons, limes and orange, the malic acid was the main organic acid in hawthorn fruit. Citric acid content in Poechun clone fruit was the highest as 157.50g/100g. Citric acid can be used for proper mineral supplementation of food and as a flavoring ingredient. It is also reported that citric acid ensures proper functioning of the kidneys and prevents the formation of kidney stones. Recently, it is found that organic acids have been used in food preservation and as a new generation of growth promotors instead of antibiotics (Kim and Rhee, 2015). Shikimic acid was the third-most common organic acid, and occupied 0.67~0.22g/100g according to clones and cultivars. A similar trend was reported for strawberry and jujube fruit (Keutgen and Pawelzik, 2007; Park and Kim, 2016). Malic acid contents in Daekeumsung cultivar was the highest as 34.12g/100g.

Table 3.

Organic acid content of the fruit of hawthorn clones and Chinese cultivars

In this study, we analyzed the free sugars and organic acid using HPLC. To our knowledge, this is the first study investigating the content of free sugars and organic acids in the fruit of five different hawthorn clones selected from Korea and four Chinese hawthorn cultivars. From the results of this study we found that the glucose sorbitol and sucrose were the major sugar components of the hawthorn fruit. The sweetness index was also calculated from the content of free sugars. The highest sweetness of hawthorn fruit was 579.52 in Pocheon clone while the lowest sweetness of hawthorn fruit was 285.59 in Chuncheon 8 clone.

Three major organic acids in hawthorn fruit were citric acid, malic acid, and shikimic acid. The highest citric acid and malic acid content in hawthorn fruit were 157.50g/100g (Poechun clone) and 34.12g/100g (Daekeumsung cultivar), respectively. The results of this study would be helpful for using food and functional food products, due to the beneficial effects of free sugar and organic acid for human health such as antioxidants and anticarcinogenic properties.

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