Elsevier

Food Chemistry

Volume 297, 1 November 2019, 124993
Food Chemistry

Optimization model for ultrasonic-assisted and scale-up extraction of anthocyanins from Pyrus communis ‘Starkrimson’ fruit peel

https://doi.org/10.1016/j.foodchem.2019.124993Get rights and content

Highlights

  • UAE of cyanidin-3-galactoside was successfully optimized.

  • Lower ultrasonic power and sonication time were found best for Cy3-gal extraction.

  • Cy3-gal concentration was found significantly higher under UAE compared to CE.

  • Viscosity of the extract had a negative impact on Cy3-gal extraction yield.

  • Batch scale-up UAE of Cy3-gal was found significantly better than continuous process.

Abstract

Ultrasonic effect on extraction of cyanidin-3-galactoside (Cy3-gal) from pear fruit peel was investigated and compared with conventional extraction (CE) method. Different process factors were tested to determine the optimum conditions for ultrasonic-assisted extraction (UAE). Results revealed that under optimized UAE conditions (ultrasonic power = 162 W, temperature = 71 °C, trifluoroacetic acid = 3%, ethanol = 57%, ultrasonication time = 11 min, and sample to solvent ratio = 1:30 g/ml), Cy3-gal yield was significantly higher (0.34 3± 0.005 mg/g) than from CE (0.266 ± 0.004 mg/g), whereas the extract viscosity during UAE showed a negative impact. UPLC-Triple-TOF/MS analysis detected a total number of 13 anthocyanin compounds, out of which 8 were identified and that mainly consisted of cyanidin, delphinidin and petunidin compounds. Higher yield of Cy3-gal under UAE compared to CE was also justified by higher deformations in the cell structure. The possible mechanism of ultrasonication effect during the extraction process is also proposed in the present study. During scale-up UAE process, the extraction yield of Cy3-gal was recorded higher under batch scale-up compared to continuous operation. The present study is an attempt to optimize UAE of valuable anthocyanins from Pyrus communis ‘Starkrimson’ fruit peel and further scaled-up for higher volume extraction which can be utilized for industrial applications.

Introduction

The need and applications of plant-derived bioactive compounds and extracts are increasing over the past several years mainly as nutraceuticals for promoting human health. Among several plant-derived bioactive compounds, anthocyanins are one of the special classes of flavonoid compounds which has been recognized for its multi-functional and multi-industrial applications (Khoo, Azlan, Tang, & Lim, 2017). From transparency market research report (TMR, 2019), the anthocyanin market in the year 2018 was over US$ 500 million, which was expected to increase with a compound annual growth rate (CAGR) of 4.6% from 2019 to 2026. Among other anthocyanin compounds, cyanidin-3-O-galactoside (Cy3-gal) contain 3-O-beta-d-galactoside group esterified to the 3rd position of the C ring of cyanidin. The natural occurrence of Cy3-gal is limited to some fruit and berry species such as Aronia melanocarpa (Chocke berries), Vaccinium macrocarpon (Cranberries), Vaccinium vitis-idaea (Lingon berries), Amelan chieralnifolia (Saskatoon berries), Empetrum nigrum (Crow berries), Pyrus pyrifolia and Pyrus communis (Lin and Harnly, 2008, Zhang et al., 2012, Fang, 2015). Anthocyanins were well tested for their health effects and found effective against a variety of disease conditions (Li et al., 2017, Belwal et al., 2017). Specifically, Cy3-gal was found to improve spatial memory (Tan et al., 2014), and showed strong antioxidant and cytoprotective activity (Bellocco et al., 2016). Moreover, anthocyanins are also gaining pace as a natural colorant in food, bevrages, pharmaceutical and cosmetic products (Khoo et al., 2017). Also, it has been reported that among different anthocyanin compounds, cyanidin market share was found to be the highest (~30%) compared to other common anthocyanins (TMR, 2019).

Extraction is an important and crucial step in plant and food processing in terms of extracting desired bioactive compounds in their optimum yield without affecting their functional qualities (Chemat et al., 2017, Chemat et al., 2017, Belwal et al., 2018). Ultrasonic-assisted extraction (UAE) is one of the advanced forms of classical extraction techniques and uses ultrasonic waves to generate cavitation bubbles which on collision generate a hot spot/micro-jet with higher temperature and pressure, thus resulting in faster and efficient extraction of components from the plant matrix (Chemat, Rombaut, Sicaire et al., 2017). The extract quality and yield are significantly affected by various UAE factors, such as ultrasonic power/intensity, reaction vessel type, extraction temperature and time, solvent pH, concentration and volume (Pandey et al., 2018, Huang et al., 2019). More specifically, UAE has been widely used and optimized for the extraction of anthocyanins from plant samples (Zou et al., 2011, Celli et al., 2015) and also in our previous work (Huang et al., 2019). Thus, determination of significant process factors and optimization of their levels for getting superior quality of extract are prerequisite.

Pyrus communis fruits are cultivated and consumed in larger quantities especially in China (Silva, Souza, Barbieri, & De Oliveira, 2014). From the available report, in the year 2017–18 the global production of Pears is recorded as 24.17 million metric tons, led by China with approximately 80% of the total production (Report on ‘Major pear producing countries worldwide 2017/2018). The Starkrimson cultivar of Pyrus communis, also known as ‘Hongpi’ in Chinese, is known for its attractive crimson red color. Pyrus is consumed as raw fruit and also used in the preparation of various food products such as pies, cakes, cheese, carpaccio, risotto, jams, and ice creams, due to its pleasant taste and low calorie value (Silva et al., 2014). The food processing of Pyrus fruits mainly requires removal of its peel and core, which are considered as a waste (Featherstone, 2016). However, the peel contains valuable bioactive compounds and has studied for its chemical profiling and bioactivity. For instance, among ten different pear varieties, the peel contained a higher concentration of bioactive compounds especially polyphenols as compared to its flesh (Li et al., 2014). The peel of red cultivars of Pyrus fruit is also a rich source of anthocyanins, among which concentration of Cy3-gal was reported the highest (∼93%) (Huang, Zhang, Qin, Wenquan, & Wu, 2012). Moreover, studies (Wu et al., 2019) revealed that Starkrimson has highest anthocyanin content as compared to other red Asian and European pear cultivars (i.e., 5 Hao, Red Zaosu, Red Sichou, Palacer, and Red Bartlett).

A number of studies have been conducted on UAE optimization of anthocyanins from various plant sources. Nevertheless, very few studies were conducted on utilizing food waste for bioactive compound recovery under optimized advanced extraction conditions. No such studies have been proposed for UAE optimization of anthocyanins (especially Cy3-gal) from fruit peel waste and further tested for its higher volume extraction. Thus, keeping in mind the high anthocyanin contents in fruit peel of Pyrus communis ‘Starkrimson’, the present study was designed to test the ultrasonic effect on extraction of Cy3-gal and further testing for its batch and continuous scale-up extraction process. The UAE was also compared with the conventional extraction (CE) method.

Section snippets

Chemicals and reagents

Cyanidin-3-O-galactoside (Idaein chloride, ≥90%) and cyanidin-3-O-glucoside (Kuromanin chloride, ≥95%) standards were procured from Sigma Chemicals (Sigma-Aldrich, USA). 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,4,6-tri(2-pryridyl)1,3,5-triazine (TPTZ), ascorbic acid, analytical grade ethanol, methanol, acetone, trifluoroacetic acid, hydrochloric acid, formic acid and LC-MS grade acetonitrile were purchased from Aladdin Industrial Corporation (Shanghai, China). For solvent dilution and mobile

Selection of factors and their levels

With increasing ultrasonic power from 60 to 200 W, a significant higher extraction yield (0.29 mg/g) of Cy3-gal was recorded (Fig. 1A). However, it was interesting to note that a significant (p < 0.05) decreased in Cy3-gal extraction yield was recorded when applied lower (60 W) and higher (400 and 600 W) ultrasonic power (Fig. 1A). Ultrasonic power played an important role in the extraction of compounds due to cavitation effect. As seen from the single factor study, moderate ultrasonication

Conclusions

The present study is an attempt to determine the ultrasonication factors, mechanism and especially their relation with viscosity for optimizing cyanidin-3-O-galactoside extraction yield from Pyrus communis ‘Starkrimson’ fruit peel. And further project a scale-up model for higher volume extraction. The results revealed a significant role of ultrasonication during extraction of anthocyanins, which was justified by higher Cy3-gal extraction yield and deformations of the cell surface compared to

Declaration of Competing Interest

None.

Acknowledgments

The research was financially supported by the Key Research and Development Program of Zhejiang Province (2018C02049), China; Special Fund for Science and Technology Base and Talent of Guangxi (GKAD17195088), China; Technology Innovation Programme of Zhejiang Province (ZJWR0102001), China; Hangzhou Science and Technology Development Program (20180432B31), China and China Postdoctoral Science Foundation (2018M642443), China.

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