1. bookVolume 32 (2020): Issue 2 (December 2020)
Journal Details
License
Format
Journal
eISSN
2083-5965
First Published
01 Jan 1989
Publication timeframe
2 times per year
Languages
English
access type Open Access

Comparison of physico-chemical characteristics of myrtle at different ripening stages

Published Online: 06 Aug 2020
Volume & Issue: Volume 32 (2020) - Issue 2 (December 2020)
Page range: 125 - 133
Received: 09 Apr 2020
Accepted: 13 Jul 2020
Journal Details
License
Format
Journal
eISSN
2083-5965
First Published
01 Jan 1989
Publication timeframe
2 times per year
Languages
English
Abstract

The fruits of myrtle at different stages of development, namely green (G), colour break (C) and mature (M), were used to investigate the changes of fruit quality and anthocyanin composition during its development. Five anthocyanin components, such as delphinidin (Dp), cyanidin (Cy), pelargonidin (Pg), peonidin (Pn) and malvidin (Mv), were detected. Among them, the content of Dp glucoside was the highest (2.12 μg · g−1) and the content of Pn glucoside was the lowest (0.17 μg · g−1) at the green stage. The content of Cy glucoside was the highest (120.94 and 1,200.03 μg · g−1), and the content of Mv glucoside was the lowest (19.50 and 62.72 μg · g−1) at the colour break and mature stages. The single fruit weight, vertical diameter and transverse diameter at the mature stage were significantly higher than those at the colour break and the green stages by 0.87 g, 1.27 mm, 1.53 mm and 1.54 g, 3.4 mm, 3.55 mm, respectively. Fruit quality, the contents of soluble sugar and carotenoids, gradually increased with the development of fruit; and the contents were the highest at the mature stage (17.68% and 16.90 μg · L−1). The contents of titratable acidity, total phenol, flavonoids, chlorophyll a and total chlorophyll gradually decreased with the development of fruit, the content was the lowest at the mature stage (2.71 mmol · 100 g−1, 9.29 μg · g−1, 0.1%, 0.37 μg · L−1, 0.9 μg · L−1) and the content was the highest at the green stage (5.25 mmol · 100 g−1, 21.07 μg · g−1, 0.17%, 8.86 μg · L−1, 15.47 μg · L−1). The difference between the green period and the colour break period was significant.

Keywords

INTRODUCTION

Myrtle (Rhodomyrtus tomentosa) is a kind of shrub originating from South-East Asia and belongs to the Myrtaceae family. It is wildly developed in many countries such as Vietnam, Philippines, Malaysia and including China. Myrtle is a nourishing drug in traditional Chinese medicine (Lai et al., 2015). Its fruits and seeds can be used to treat the menopausal syndrome, irregular menstruation, insomnia, urinary tract infection, anaemia and so on (Zou et al., 2017). Also, its fruit is rich in polysaccharides, anthocyanin and other useful compounds (Zhao and Chen, 2016). Anthocyanin is a flavonoid compound which is a water-soluble natural pigment widely found in plants (Peng et al., 2018). There are more than 20 kinds of anthocyanins known in nature, mainly including pelargonidin (Pg), cyanidin (Cy), delphinidin (Dp), peonidin (Pn), petunidin (Pt) and malvidin (Mv) (Li et al., 2018).

The chemical composition of myrtle varies greatly depending on the location, origin and maturity (Xiao et al., 2014; Gu et al., 2018). Exploring the changes in chemical composition and antioxidant activity of fruits at different growth stages is of great significance for further study of the mechanism of action of myrtle. The study found that the contents of phenolic, flavonoids and anthocyanin, as well as antioxidant enzyme activities, varied depending on the developmental stages (Sun et al., 2018). The main reason was that the enzyme activity was different, and the temperature and moisture were also different at different periods. Zhao et al. (2018) studied the nutritional quality and aroma changes of strawberries at different developmental stages and found that contents of anthocyanins, soluble sugars and vitamin C increased with fruit development. Sugar is an important raw material for anthocyanin synthesis. When the sugar content of the fruit reaches a certain concentration, the fruit can have colour. Other studies pointed out that the content of C6-alcohols gradually decreased and the content of esters increased rapidly as the fruit matures, mainly due to the increase in ethyl acetate content (Luo et al., 2012). At present, there is less research on myrtle, focusing on its chemical composition and other nutritional qualities (Ye et al., 2019). Also, it is unclear how the stage of fruit development affects the chemical composition and antioxidant activity of myrtle. In this experiment, the changes in fruit quality and anthocyanin composition at different developmental stages of myrtle fruits were studied to provide a theoretical reference for the selection of high-quality fruit.

MATERIALS AND METHODS
Plant materials

Myrtle fruits at different stages of development, namely green (G), colour break (C) and the mature (M), were collected in the orchard located at 150 m above sea level in Yanping Village, Fengshan Town, Huaan County, Zhangzhou City, Fujian Province. The average annual rainfall in the orchard was about 1,700 mm. The climate was characterized by mild and rainy. The plants were grown with 2.0 m spacing within rows and 3.0 m spacing between rows. The colour of all fruits in the green period was green, in the colour break period it was purple-red and in the mature period it was purple-black. Three replicates were set up for each period, with three experimental trees each, for a total of 27 myrtle trees. Each time a sample was collected, fruits with the same maturity, no insect pests and no mechanical damages. Fruits were collected homogeneously from the east, west, south and north of the experimental tree, and 90 fruits were collected at each stage. The collected samples were quickly taken to the laboratory, of which 15 were used for the determination of development indicators and the rest were immediately frozen in liquid nitrogen and stored at −80°C for the determination of the intrinsic quality of the fruit.

Vertical and transverse diameters and weight of fruit

Data were collected on the vertical and transverse diameters of 15 fruits in each period, they were measured using a vernier calliper and the average value was calculated. Fruit shape index was obtained by proportioning the fruit length to the fruit width (Eskimez et al., 2019). The average fruit weight of 15 fruits in each period was determined by an electronic scale. Soluble solids content (SSC) was measured using a digital refractometer (mark and model information) and the results were given in percentages (Okatan, 2018).

Determination of the intrinsic quality of fruits
Soluble sugar

The determination of the soluble sugar content was carried out in accordance with the method described by Zhu et al. (2019). Of note, 0.2 g of the sample was ground in liquid nitrogen, and the powdered sample was homogenized in 10 mL of water, then activated carbon was added and the sample was placed in a boiling water bath for 30 min (repeated twice). After cooling, the cells were centrifuged, and the supernatant was collected and made up to a volume of 25 mL with distilled water for further analysis. Of note, 0.5 mL of the supernatant was added to a 10 mL tube containing 2 mL of distilled water, and 0.5 mL of enthrone and ethyl acetate were added to the mixture. Five millilitres of concentrated sulphuric acid was slowly added to the mixture. The mixture was boiled in a water bath for 1 min, and after cooling to room temperature the absorbance was measured at 630 nm using a UV–VIS spectrophotometer.

Titratable acidity

The determination of the titratable acidity content was carried out in accordance with the method described by Wang and Huang (2015). 0.2 g of the sample was ground in liquid nitrogen, and 10 mL of water was added to the powdered sample, then an appropriate amount of activated carbon was added and the sample was boiled in a water bath for 30 min. After cooling, centrifugation was carried out, the supernatant was collected in another test tube and the process was repeated. The supernatant was aspirated and made up to 25 mL with distilled water for further analysis. The supernatant (10 mL) was placed in a 50 mL Erlenmeyer flask and 3–5 drops of phenolphthalein indicator were added. The mixture was then titrated with a 0.1 N NaOH solution until a pink colour that did not fade within 30 s appeared. The initial and final volumes were recorded to calculate the titratable acidity.

Extraction and estimation of total phenolic, flavonoid and anthocyanin contents

The sample was first ground in liquid nitrogen with the aid of a mortar and pestle, and 0.2 g of the powder was homogenised in 5 mL of 80% chilled ethanol. The extract was centrifuged at 11,000 rpm for 10 min at 4°C, and the supernatant was aspirated, collected and used for calculation of total phenol and flavonoids.

A simple modification of the method of Huang et al. (2009) was performed using a Folin–Ciocalteu colorimetric method to determine the total phenolic content of the sample. Of note, 0.5 mL of sample and different concentrations (20, 40, 60, 80 and 100 μg · mL−1) of standard gallic acid were added to a 5 mL tube containing 2 mL of distilled water and 0.25 mL of Folin–Ciocalteu’s previously added reagent (FCR) (Sigma Chemical, St. Louis, Missouri, USA) and shaken well. After about 5 min, 1 mL of 7% sodium carbonate (Na2CO3) was added to the mixture. The mixture was kept at 25°C for 120 min in the dark. The blank absorbance was then measured at 765 nm using a UV–vis spectrophotometer (TU-1810; Beijing Beifen Ruili Analytical Instruments (Group) Co., Ltd., China). Measurements were made in triplicate. The total phenol content data are expressed in milligrams of gallon acid equivalent (GAE) 100 g−1 berry skin fresh weight (FW). The equation obtained for the calibration curve of gallic acid was y = 17.771x + 0.016 (R2 = 0.9974).

The total flavonoid content was determined by colorimetry according to Huang et al. (2009). Of note, 0.5 mL of sample solution and 0.5 mL of quercetin standard solution (100, 200, 400, 600, 800 and 1,000 mg · mL−1) were added to a 10 mL tube containing 4 mL of water, and 0.3 mL of 5% NaNO2 was added to it. Then, the mixture was allowed to stand at room temperature for 5 min. Of note, 0.3 mL of 10% AlCl3 was added to the mixture. After 5 min, 2 mL of 1 M NaOH was added. The distilled water to a volume of 10 mL was added and mixed well. The absorbance was measured spectrophotometrically at 510 nm against a blank. The equation obtained for the calibration curve of quercetin curve was y = 1.6225x + 0.0442 (R2 = 0.9854).

Anthocyanin extractions were performed with a protocol similar to that of Fuleki and Francis (1968) with slight modifications. After grinding the sample with liquid nitrogen, 0.5 g of powder was taken, placed in a 50 mL centrifuge tube, added 10 mL of 2% hydrochloric acid methanol solution, ultrasonically extracted for 60 min, centrifuged at 4°C, 12,000 rpm for 10 min and collected the supernatant for extraction.

The method of determining anthocyanin is as follows: 2 mL of anthocyanin extract was drawn, diluted to 4 mL with water and shaken thoroughly. Using 2% methanolic hydrochloric acid as a control, the absorbance was measured at 520nm. To use spectrophotometry, the switch was first turned on and preheated for 20 min in advance. The appropriate wavelength according to the experimental requirements was chosen. The sample to be measured was put into the cuvette and measure.

The chromatographic analysis of individual anthocyanin, delphinidin-3-O-glucoside (DP-3-G), cyanidin-3-O-glucoside (CG-3-G), petunidin-3-O-glucoside (PT-3-G), peonidin-3-O-glucoside (PN-3-G) and malvidin-3-O-glucoside (MV-3-G) was measured using a high-performance liquid chromatography (HPLC) system (LC-100; Wufeng Series, Shanghai, China) equipped with LC-P100 pump and operated by LC-WS100 software with modification. Skin extractvs were filtrated by a membrane filter (0.45 mm, MillexHV; Millipore, Bedford, MA, USA) and a volume of 20 mL of solution was injected directly into the HPLC system. The samples were analysed using a BRISA LC2 C18 column (5 mm particle size, 250 × 4.6 mm). The gradients profile consisted of two eluents: A: water/acetonitrile/formic acid = 40/50/10 (v/v/v), mobile phase and B: water/acetonitrile/formic acid = 87/3/10 (v/v/v), column temperature 45°C. The injection volume was 20 μL, and the detection wavelength was 520 nm. Gradient elution conditions were (1) 0–15 min, 6% A → 30% A; (2) 15–30 min, 30% A → 50% A; (3) 30–35 min, 50% A → 60% A and (4) 35–40 min, 60% A → 6% A, and constant for 5 min before the mobile phase returned to the initial conditions. The flow rate was 1.0 mL · min−1 at 30°C and detection was at 520 nm. Peaks were identified according to each peak of UV–vis spectra corresponding to the spectra of standard and comparing with their retention times. Anthocyanin content was quantified using peak areas of external standards. Standard curves were constructed using peak area vs. concentration. The resultant individual anthocyanin was expressed as milligram per kilogram berry FW.

Vitamin C

The determination of vitamin C content is carried out according to the method by Qiu et al. (2018). Of note, 0.2 g sample was weighed, placed in a 250 mL volumetric flask, added water 100 mL and dilute acetic acid 10 mL to dissolve, added 1 mL of starch indicator solution, immediately titrated with iodine standard titration solution, until the solution is in blue colour that does not fade within 30 s. Each 1 mL of iodine titration solution (0.05 mol · L−1) is equivalent to 8.806 μg of vitamin C.

Carotenoid

Carotenoid content in the sample was determined according to the method by Liang et al. (2019). Of note, 0.2 g of the sample was accurately weighed, ground with liquid nitrogen, placed in 5 m of absolute ethanol containing 0.1% ascorbic acid (m/V) and allowed to stand at 4°C in the dark. Three hundred microlitres of an 80% potassium hydroxide solution (m/V) was added to the extract, shaken and then heated in a constant temperature water bath at 95°C for 45 min. The solution was then added to 5 mL of precooled deionised water and immediately cooled in an ice bath. Five millilitres of petroleum ether was added, and the solution was shaken, extracted and centrifuged at 4°C and 12,000 rpm for 10 min. After 30 min, the supernatant was aspirated. The extraction was repeated three times and the supernatant was combined. The petroleum ether in the supernatant was volatilised by blowing nitrogen gas in a 35°C water bath environment. Then, 3 mL of dichloromethane and methanol in a volume ratio of 1:1 were added and redissolved. The solution was slowly filtered through a 0.22-mm organic filter for HPLC analysis.

Chlorophyll

Chlorophyll content in the sample was determined according to the method by Liu et al. (2020). Of note, 0.2 g of the sample was ground by an acetone method, extracted with an 80% acetone solution, filtered to a constant volume and then measured by a UV–VIS spectrophotometer.

Statistical analysis

HPLC mapping was performed using LC-WS100 chromatography workstation software. Results were expressed as mean ± standard deviation (SD). Each value was the average of three replications. The Pearson correlation analysis was subjected to two-tailed analysis of variance using the SPSS 19. A difference between the developmental stages of fruit was considered statistically significant (p < 0.05) by Tukey’s test.

RESULTS
Growth data at different developmental stages of fruit

Vertical diameter, transverse diameter and single fruit weight are important indicators reflecting the quality of fruit growth. Vertical diameter, transverse diameter, single fruit weight and soluble solids of myrtle fruits from green to colour break and to mature increased significantly (p < 0.05) (Table 1). The single fruit weight at the mature stage was 2.74 g, which was a significant increase of 1.54 g compared with the green stage (p < 0.05). The vertical and transverse diameters of the green stage were 14.68 and 11.52 mm, respectively, which were significantly different from the colour break and the mature stages (p < 0.05). The soluble solids gradually increased as the fruit matures. The content of soluble solids was 12.17 at the mature stage, which was significantly higher than the green and the colour break stages (p < 0.05). However, the fruit shape index decreased with the development of the fruit and there was no significant difference in the three periods.

Physical properties of myrtle fruit at different developmental stages

Growth stagesFruit weight (g ± SD)Vertical diameter (mm ± SD)Transverse diameter (mm ± SD)Fruit shape indexSoluble solid content (% ± SD)
G1.20 ± 0.03 c14.68 ± 1.49 c11.52 ± 0.84 c1.27 ± 0.10 ns3.40 ± 0.26 c
C1.87 ± 0.04 b16.81 ± 0.81 b13.54 ± 0.67 b1.24 ± 0.05 ns7.23 ± 0.25 b
M2.74 ± 0.05 a18.08 ± 0.66 a15.07 ± 0.83 a1.20 ± 0.08 ns12.17 ± 0.40 a

Means followed by different letters indicate significant differences at 0.05 level of probability.

SD, standard deviation; G, green; C, colour break; M, mature.

Fruit quality at different developmental stages

The contents of soluble sugars and titratable acidity showed a different trend during the development of myrtle fruits (Figure 1). Soluble sugar contents of fruits significantly increased (14.30%–17.68%) from green stage to mature stage, while titratable acidity contents decreased significantly at different stages of development from 5.25 to 2.71 mmol/100 g from green stage to mature stage.

Figure 1

Influence of different developmental stages of fruit on soluble sugars and titratable acidity. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

The contents of total flavonoids and total phenolic in myrtle fruit (Figure 2) showed the same patterns of change during development. The content of flavonoids at the green stage was the highest (0.17%), and the colour break and the mature stages were significantly reduced by 0.04% and 0.07% (p < 0.05). The content of total phenolic at the green stage was 21.07 μg · g−1, and at the colour break period and mature stages it was 16.71 and 9.29 μg · g−1, and the difference between the three stages was significant (p < 0.05).

Figure 2

Influence of different developmental stages of fruit on total phenolic and total flavonoids. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

Total anthocyanin content and qualitative identification by HPLC

With the development of myrtle fruit, the fruit colour gradually changed from green to purple-black (Figure 3). For HPLC analysis, according to the standard samples and references, five anthocyanins were detected in the three developmental stages of myrtle fruits. The type of anthocyanin was determined based on the peak time of the standard sample, followed by Dp, Cy, Pg, Pn and Mv. The contents of Dp, Cy, Pg, Pn and Mv were 2.12, 0.47, 0.45, 0.17, 0.55 μg · g−1, respectively, at the green stage in sequence, 113.79, 120.94, 33.66, 37.26 and 19.50 μg · g−1, respectively, at the colour break stage and 398.76, 1,200.03, 149.00, 371.46, 62.72 μg · g−1, respectively, at the mature stage.

Figure 3

High-performance liquid chromatographic results of anthocyanins at different developmental stages of myrtle fruit. G, Green; C, colour break; M, mature.

The anthocyanin contents of myrtle at different stages were shown in Table 2. It was observed that during the development of myrtle fruit, the anthocyanin content increased significantly at different periods (p < 0.05) of fruit development from the green stage to the mature stage. The same trend was observed across all other studied compounds. The content of Dp was the highest in the green fruit period (2.12 μg · g−1) and that of Pn was the lowest (0.17 μg · g−1). The total anthocyanin content (TAC) at the green stage was 3.76 μg · g−1. The content of Cy glucoside was the highest at the colour break and mature stages (120.94 and 1,200.03 μg · g−1), and the content of Mv glucoside was the lowest (19.50 and 62.72 μg · g−1). The contents of total anthocyanins were 325.15 and 2,181.97 μg · g−1, respectively, at the colour break and mature stages.

Content of anthocyanins (μg · g−1) in myrtle fruit at different developmental stages

Growth stagesTAC (μg · g−1 ± SD)Dp (μg · g−1 ± SD)Cy (μg · g−1 ± SD)Pg (μg · g−1 ± SD)Pn (μg · g−1 ± SD)Mv (μg · g−1 ± SD)
G3.76 ± 0.26 c2.12 ± 0.18 c0.47 ± 0.02 c0.45 ± 0.07 c0.17 ± 0.04 c0.55 ± 0.04 c
C325.15 ± 20.02 b113.79 ± 7.56 b120.94 ± 8.99 b33.66 ± 1.67 b37.26 ± 2.22 b19.50 ± 1.60 b
M2,181.97 ± 70.50 a398.76 ± 17.81 a1,200.03 ± 34.85 a149 ± 4.34 a371.46 ± 10.26 a62.72 ± 5.33 a

Means followed by different letters indicate significant differences at 0.05 level of probability.

SD, standard deviation; G, green; C, colour break; M, mature; TAC, total anthocyanin content.

Correlation analysis of vertical diameter (VD), transverse diameter (TD), soluble sugar content (SSC), titratable acidity content (TaC), total phenol content (TPC), total flavonoids content (TFC), chlorophyll a content (CaC), chlorophyll b content (CbC), total chlorophyll content (TCC), vitamin C content (Vit.C), total anthocyanin content (TAC) and carotenoids content (CC)

VDTDSSCTaCTPCTFCCaCCbCTCCVit.CTACCC
VD1
TD0.953**1
SSC0.884**0.830**1
TaC−0.875**−0.811**−0.968**1
TPC−0.884**−0.827**−0.966**0.896*1
TFC−0.873**−0.822**−0.989**0.967**0.966**1
CaC−0.749*−0.711*−0.905**0.950**0.769*0.880**1
CbC−0.726*−0.706*−0.879**0.919**0.732*0.840**0.992**1
TCC−0.740*−0.710*−0.895**0.939**0.755**0.865**0.999**0.997**1
Vit.C−0.562−0.605−0.726*0.798**0.6250.770*0.832**0.800**0.820**1
TAC0.873**0.811**0.893**−0.788*−0.964**−0.887**−0.621−0.588−0.609−0.4201
CC0.694*0.767*0.812**−0.842**−0.718*−0.823**−0.880**−0.872**−0.878**−0.938**0.5541

Correlation is significant at the 0.05 level.

Correlation is significant at the 0.01 level (two-tailed).

It was observed from Figure 4 that the contents of total chlorophyll, chlorophyll a and chlorophyll b decreased significantly from the green stage to the mature stage (p < 0.05). The total chlorophyll, chlorophyll a and chlorophyll b were the highest at the green stage (15.47, 8.86 and 6.61 μg · L−1, respectively). The contents of chlorophyll a and total chlorophyll were the lowest at the mature period (0.37 and 0.90 μg · L−1), while the content of chlorophyll b was the lowest at the colour break stage (0.44 μg · L−1). Also, the difference of chlorophyll a, chlorophyll b and total chlorophyll from the colour break stage to the mature stage was not significant.

Figure 4

Influence of different developmental stages of fruit on chlorophyll a, chlorophyll b and total chlorophyll. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

The contents of carotenoids and vitamin C at the different developmental stages of myrtle fruits were determined (Figure 5). In the green fruits development period, no carotenoid component was detected and it reached the highest at the mature stage (16.90 μg · L−1) of the fruit development. The content of vitamin C reached the highest (7.5 μg · 100 g−1) at the green stage and the lowest (3 μg 100 g−1) at the colour break stage. The difference from the green stage to the colour break stage was significant (p < 0.05).

Figure 5

Influence of different developmental stages of fruit on carotenoids and vitamin C. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

Fruit size is an important indicator of fruit appearance quality and is closely related to the development of fruit vertical and transverse diameters. After fruit setting, the fruit showed a certain growth dynamic after continuous cell division and cell expansion. So, the growth progress of vertical and transverse diameters is parallel (r = 0.953). With the increase of the fruit’s vertical and transverse diameters, anthocyanins combine with glucose or other sugars in cells to form other components of various anthocyanins (Wang et al., 2015). The soluble sugar was positively correlated with the formation of anthocyanins. The correlation coefficients of the vertical diameter of the fruit with soluble sugar and anthocyanin were 0.884 and 0.873, respectively. The correlation coefficient of soluble sugar and anthocyanin was 0.893. The genes that regulate carotenoids were abundantly expressed during the development of myrtle, so the diameter and carotenoid were positively correlated. The correlation coefficients of fruit vertical and transverse diameters with carotenoids were 0.694 and 0.767. This is consistent with Cheng et al. (2007) research on tomatoes. The organic acidity in the fruit is converted into sugar with the increase of the vertical and transverse diameters under the action of enzymes. At the same time, the chlorophyll in the fruit is continuously degraded (Wang et al., 2013). The correlation coefficients of fruit vertical diameter with total chlorophyll and titratable acidity were −0.740 and −0.875, respectively. The titratable acidity content was significantly negatively correlated with soluble sugar (r = −0.968). Soluble sugar was significantly negatively correlated with chlorophyll (r = −0.895). Fruit vertical and transverse diameters were significantly negatively correlated with total phenols and flavonoids, indicating that the enzyme activity regulating phenols decreased during fruit development. This is consistent with Zhu et al.’s (2018) research on Myrica rubra. The correlation coefficients of the vertical and transverse diameters with total phenols were −0.884 and −0.827, and the correlation coefficients with flavonoids were −0.873 and −0.822. Soluble sugar was significantly negatively correlated with total phenol (r = −0.966), flavonoids (r = −0.989) and vitamin C (r = −0.726). It can keep the fruit in a dynamic balance. Titratable acidity was significantly positively correlated with flavonoids, chlorophyll, vitamin C and total phenols, indicating that titratable acidity was closely related to phenols, chlorophyll and vitamin C in plant metabolism. Titratable acidity was significantly negatively correlated with anthocyanins (r = −0.788) and carotenoids (r = −0.842), indicating that the reduction of titratable acidity content promoted the synthesis of anthocyanins and carotenoids. Total phenols were significantly positively correlated with flavonoids (r = 0.966) and chlorophyll (r = 0.755) and negatively correlated with anthocyanins. It showed that the reduction of total phenol content promotes the degradation of chlorophyll and the accumulation of anthocyanins.

DISCUSSION

Fruit colour is an important indicator of fruit quality. Anthocyanin is the main pigment that determines fruit colour and is also the main symbol of fruit ripeness (Qi et al., 2018). The changes in fruit colour are closely related to the type and content of anthocyanins. The colour of Pg usually is brick red, Dp, Pt and Mv exhibit blue-violet and Cy and Pn exhibit a purplish red colour (Zhang et al., 2011). In this experiment, five anthocyanins were detected, which were Dp, Cy, Pg, Pn and Mv. In this study, it was observed that the main anthocyanin component in myrtle was cyanidin after the colour change. Cui et al. (2013) found six anthocyanins in the fruits of myrtle, among which the main component was cyanidin. This was basically consistent with the results of this study. The only difference was that no petunia was detected in this study. This may be attributed to differences in the growth conditions and cultivar. Yang et al. (2017) also found five anthocyanins in their work and the content of anthocyanin increased significantly with the development of ripening, which was consistent with the results of this experiment.

Organic acids are an important part of fruits quality and together with sugar they form fruit flavour. Most fruits have gradually increasing contents of soluble sugar during fruit development, and when matured the organic acid content decreases (Wen et al., 2001; Shaw and Wilson 1981; Zhou et al., 2015). Su et al. (2019) reported that as grapefruit mature, the soluble sugar content gradually increased, and the titratable acidity content decreases gradually which is an agreement with our findings.

Flavonoids and polyphenols were widely found in plants. They not only have important physiological functions on plants but also have strong anti-oxidation, anti-mutation, anti-arteriosclerosis, antitumour and antiviral effects (Guo et al., 2008; Song et al., 2000). Xia et al. (2016) found that the contents of total phenols and flavonoids in the development of apricot were the lowest in the early developmental stage which gradually increased to maximum and decreased with the increase of fruit ripening. Su et al. (2018) showed that the flavonoids and total phenols showed a downward trend with fruit development through the changes of physiological indices during pear fruit development. This is consistent with the results of this study. On the one hand, the contents of flavonoids and total phenols were closely related to the rapid growth period of fruit development. As the fruit gradually approaches maturity, the fruit surface began to appear red, reaching a lower maturity. Due to the rapid growth of the fruit, the supply absorption capacity was weak. On the other hand, fruit trees provided energy during fruit ripening, and the content of soluble sugar and soluble solids increased sharply. Phenolic substances were required to induce the differentiation of related cells, so the content of flavonoids and total phenol gradually decreased to maintain the nutritional balance of the tree.

Vitamin C is a water-soluble substance with antioxidant and anti-free radical effects. It was found in many fruits and vegetables but cannot be synthesised by the human body (Mo et al., 2018). Zhu and Du (2019) measured the content of vitamin C in the development of persimmon and found that the vitamin C content in persimmon gradually increased as the fruit develops and reached the highest level at maturity. This is in contrast with the results obtained in this experiment. In this study, vitamin C content reached the highest in young fruits. The reason may be due to differences in the varieties. Also, in our study carotenoids were not detected in the green fruit stage and slowly formed after the turning period. This is basically consistent with the findings of Li et al. (2006). The only difference is that carotenoids were detected at an early stage of wolfberry development in Li’s research.

CONCLUSIONS

Our research showed that the physicochemical properties of myrtle varied greatly at different developmental stages. Five anthocyanin components were detected, and each component gradually increased during the three stages of myrtle development. The contents of soluble sugar, soluble solids and carotenoids decreased as the fruit matures. The content of titratable acidity, phenols and chlorophyll decreased with the developmental stage. This study will help us to better understand the effect of myrtle development stage on physicochemical characteristics.

Figure 1

Influence of different developmental stages of fruit on soluble sugars and titratable acidity. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.
Influence of different developmental stages of fruit on soluble sugars and titratable acidity. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

Figure 2

Influence of different developmental stages of fruit on total phenolic and total flavonoids. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.
Influence of different developmental stages of fruit on total phenolic and total flavonoids. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

Figure 3

High-performance liquid chromatographic results of anthocyanins at different developmental stages of myrtle fruit. G, Green; C, colour break; M, mature.
High-performance liquid chromatographic results of anthocyanins at different developmental stages of myrtle fruit. G, Green; C, colour break; M, mature.

Figure 4

Influence of different developmental stages of fruit on chlorophyll a, chlorophyll b and total chlorophyll. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.
Influence of different developmental stages of fruit on chlorophyll a, chlorophyll b and total chlorophyll. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

Figure 5

Influence of different developmental stages of fruit on carotenoids and vitamin C. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.
Influence of different developmental stages of fruit on carotenoids and vitamin C. Bars with different letters differ significantly (p < 0.05). G, green; C, colour break; M, mature.

Correlation analysis of vertical diameter (VD), transverse diameter (TD), soluble sugar content (SSC), titratable acidity content (TaC), total phenol content (TPC), total flavonoids content (TFC), chlorophyll a content (CaC), chlorophyll b content (CbC), total chlorophyll content (TCC), vitamin C content (Vit.C), total anthocyanin content (TAC) and carotenoids content (CC)

VDTDSSCTaCTPCTFCCaCCbCTCCVit.CTACCC
VD1
TD0.953**1
SSC0.884**0.830**1
TaC−0.875**−0.811**−0.968**1
TPC−0.884**−0.827**−0.966**0.896*1
TFC−0.873**−0.822**−0.989**0.967**0.966**1
CaC−0.749*−0.711*−0.905**0.950**0.769*0.880**1
CbC−0.726*−0.706*−0.879**0.919**0.732*0.840**0.992**1
TCC−0.740*−0.710*−0.895**0.939**0.755**0.865**0.999**0.997**1
Vit.C−0.562−0.605−0.726*0.798**0.6250.770*0.832**0.800**0.820**1
TAC0.873**0.811**0.893**−0.788*−0.964**−0.887**−0.621−0.588−0.609−0.4201
CC0.694*0.767*0.812**−0.842**−0.718*−0.823**−0.880**−0.872**−0.878**−0.938**0.5541

Content of anthocyanins (μg · g−1) in myrtle fruit at different developmental stages

Growth stagesTAC (μg · g−1 ± SD)Dp (μg · g−1 ± SD)Cy (μg · g−1 ± SD)Pg (μg · g−1 ± SD)Pn (μg · g−1 ± SD)Mv (μg · g−1 ± SD)
G3.76 ± 0.26 c2.12 ± 0.18 c0.47 ± 0.02 c0.45 ± 0.07 c0.17 ± 0.04 c0.55 ± 0.04 c
C325.15 ± 20.02 b113.79 ± 7.56 b120.94 ± 8.99 b33.66 ± 1.67 b37.26 ± 2.22 b19.50 ± 1.60 b
M2,181.97 ± 70.50 a398.76 ± 17.81 a1,200.03 ± 34.85 a149 ± 4.34 a371.46 ± 10.26 a62.72 ± 5.33 a

Physical properties of myrtle fruit at different developmental stages

Growth stagesFruit weight (g ± SD)Vertical diameter (mm ± SD)Transverse diameter (mm ± SD)Fruit shape indexSoluble solid content (% ± SD)
G1.20 ± 0.03 c14.68 ± 1.49 c11.52 ± 0.84 c1.27 ± 0.10 ns3.40 ± 0.26 c
C1.87 ± 0.04 b16.81 ± 0.81 b13.54 ± 0.67 b1.24 ± 0.05 ns7.23 ± 0.25 b
M2.74 ± 0.05 a18.08 ± 0.66 a15.07 ± 0.83 a1.20 ± 0.08 ns12.17 ± 0.40 a

Cheng, X. J., Wang, J., Huang, X. P., Li, C., Tian, L. P., Xue, L., and Zhao, J. R. (2007). Study on the effect of combined application of nitrogen, phosphorus and potassium fertilizers on processing tomato under drip irrigation under mulch. Journal of Anhui Agricultural Sciences, 35, 11509–11511.ChengX. J.WangJ.HuangX. P.LiC.TianL. P.XueL.ZhaoJ. R.2007Study on the effect of combined application of nitrogen, phosphorus and potassium fertilizers on processing tomato under drip irrigation under mulchJournal of Anhui Agricultural Sciences351150911511Search in Google Scholar

Cui, C., Zhang, S., You, L., Ren, J., Luo, W., Chen, W., and Zhao, M. (2013). Antioxidant capacity of anthocyanins from Rhodomyrtus tomentosa (Ait.) and identification of the major anthocyanins. Food Chemistry, 139, 1–8.CuiC.ZhangS.YouL.RenJ.LuoW.ChenW.ZhaoM.2013Antioxidant capacity of anthocyanins from Rhodomyrtus tomentosa (Ait.) and identification of the major anthocyaninsFood Chemistry.1391810.1016/j.foodchem.2013.01.10723561070Search in Google Scholar

Eskimez, İ., Polat, M., Korkmaz, N., and Mertoğlu, K. (2019). Investigation of some blackberry cultivars in terms of phenological, yield and fruit characteristics. International Journal of Agriculture Forestry and Life Sciences, 3(2), 233–238.Eskimezİ.PolatM.KorkmazN.MertoğluK.2019Investigation of some blackberry cultivars in terms of phenological, yield and fruit characteristicsInternational Journal of Agriculture Forestry and Life Sciences.32233238Search in Google Scholar

Fuleki, T., and Francis, F. J. (1968). Quantitative methods for anthocyanins extraction and determination of total anthocyanin in cranberries. Journal of Food Science, 3(1)3, 78–83.FulekiT.FrancisF. J.1968Quantitative methods for anthocyanins extraction and determination of total anthocyanin in cranberriesJournal of Food Science313,788310.1111/j.1365-2621.1968.tb00888.xSearch in Google Scholar

Gu, R. H., Li, P., Wang, Y. Z., Wu, S. B., Kennelly, E. J., and Long, C. L. (2018). Analysis of constituents from different parts of Rhodomyrtus HPLC-TOFMS. Chinese Herbal Medicines, 49, 554–560.GuR. H.LiP.WangY. Z.WuS. B.KennellyE. J.LongC. L.2018Analysis of constituents from different parts of Rhodomyrtus HPLC-TOFMSChinese Herbal Medicines.49554560Search in Google Scholar

Guo, C. J., Xu, J., Wei, J. Y., Yang, J. J., and Wu, J. J. (2008). The flavonoid content of common fruits in China. Acta Nutrimenta Sinica, 30, 130–135.GuoC. J.XuJ.WeiJ. Y.YangJ. J.WuJ. J.2008The flavonoid content of common fruits in ChinaActa Nutrimenta Sinica.30130135Search in Google Scholar

Huang, C., Yu, B., Teng, Y., Su, J., Shu, Q., Cheng, Z., and Zeng, L. (2009). Effects of fruit bagging on coloring and related physiology, and qualities of red Chinese sand pears during fruit maturation. Scientia Horticulturae, 121, 158.HuangC.YuB.TengY.SuJ.ShuQ.ChengZ.ZengL.2009Effects of fruit bagging on coloring and related physiology, and qualities of red Chinese sand pears during fruit maturationScientia Horticulturae12115810.1016/j.scienta.2009.01.031Search in Google Scholar

Lai, T. N. H., André, C., Rogez, H., Mignolet, E., Nguyen, T. B. T., and Larondelle, Y. (2015). Nutritional composition and antioxidant properties of the sim fruit (Rhodomyrtus tomentosa). Food Chemistry, 168, 410–416.LaiT. N. H.AndréC.RogezH.MignoletE.NguyenT. B. T.LarondelleY.2015Nutritional composition and antioxidant properties of the sim fruit (Rhodomyrtus tomentosa)Food Chemistry.16841041610.1016/j.foodchem.2014.07.08125172728Search in Google Scholar

Li, H., Chen, M., Ma, W. P., and Wang, J. Y. (2006). Law of changes of carotenoids contents in cructus lycii of Chinese wolfberry (Lycium barbarum L.) at different mature periods. Chinese Agricultural Science Journal, 39(3), 599–605.LiH.ChenM.MaW. P.WangJ. Y.2006Law of changes of carotenoids contents in cructus lycii of Chinese wolfberry (Lycium barbarum L.) at different mature periodsChinese Agricultural Science Journal.393599605Search in Google Scholar

Li, M., Luo, Y. T., Lu, X. C., Sun, Y. T., and Qiu, D. L. (2018). Changes in composition of anthocyanins in Brunfelsia acuminata flowers. Journal of Tropical and Subtropical Botany, 26, 627–632.LiM.LuoY. T.LuX. C.SunY. T.QiuD. L.2018Changes in composition of anthocyanins in Brunfelsia acuminata flowersJournal of Tropical and Subtropical Botany.26627632Search in Google Scholar

Liang, M. H., Yang, Z. F., Su, X. G., and Song, C. B. (2019). Effect of blue light treatment on soluble sugar and carotenoid synthesis in postharvest peaches. Preservation and Processing Journal, 19, 10–15.LiangM. H.YangZ. F.SuX. G.SongC. B.2019Effect of blue light treatment on soluble sugar and carotenoid synthesis in postharvest peachesPreservation and Processing Journal.191015Search in Google Scholar

Liu, H. B., Bai, Y. G., Zhang, J. H., and Ding, P. (2020). Effect of water spray on SPAD and chlorophyll content of grape leaves. Chinese Agricultural Science Bulletin, 57(5), 822–829.LiuH. B.BaiY. G.ZhangJ. H.DingP.2020Effect of water spray on SPAD and chlorophyll content of grape leavesChinese Agricultural Science Bulletin.575822829Search in Google Scholar

Luo, H., Li, M., Feng, Z. W., Song, H. R., and Zhang, L. Z. (2012). Aroma components and their changes in Feicheng peach fruits at different developmental stages. Journal of Hunan Agricultural University (Natural Science Edition), 38(3), 276–281.LuoH.LiM.FengZ. W.SongH. R.ZhangL. Z.2012Aroma components and their changes in Feicheng peach fruits at different developmental stagesJournal of Hunan Agricultural University (Natural Science Edition).38327628110.3724/SP.J.1238.2012.00276Search in Google Scholar

Mo, Y., Zhang, Y., and Chen, L. Y. (2018). Factors affecting vitamin C content in citrus fruits. Modern Horticulture, 40(2), 1–5.MoY.ZhangY.ChenL. Y.2018Factors affecting vitamin C content in citrus fruitsModern Horticulture.40215Search in Google Scholar

Okatan, V. (2018). Phenolic compounds and phytochemicals in fruits of black mulberry (Morus nigra L.) genotypes from the Aegean region in Turkey. Folia Horticulturae, 30(1), 93–101.OkatanV.2018Phenolic compounds and phytochemicals in fruits of black mulberry (Morus nigra L.) genotypes from the Aegean region in TurkeyFolia Horticulturae.3019310110.2478/fhort-2018-0010Search in Google Scholar

Peng, Z. M., Deng, M. Y., Yan, Y. Y., Zhu, L., and Zhang, X. G. (2018). Study on the determination of anthocyanin content and its species distribution in plants. Food Research and Development, 39, 100–104.PengZ. M.DengM. Y.YanY. Y.ZhuL.ZhangX. G.2018Study on the determination of anthocyanin content and its species distribution in plantsFood Research and Development.39100104Search in Google Scholar

Qi, Y. Y., Deng, L., Hao, G. J., and Zhu, C. Y. (2018). Comparison and analysis on contents of black and white berries from Lycium ruthenicum Murr. Acta Botanica Boreali-Occidentalia Sinica, 38, 2053–2059.QiY. Y.DengL.HaoG. J.ZhuC. Y.2018Comparison and analysis on contents of black and white berries from Lycium ruthenicum MurrActa Botanica Boreali-Occidentalia Sinica.3820532059Search in Google Scholar

Qiu, Q. L., Wu, S. Y., Liu, G. L., Cai, W. J., Dai, D. D., and Zhu, Y. W. (2018). Determination of vitamin C in grape seed extraction. Journal of Food Safety Quality, 9, 39–44.QiuQ. L.WuS. Y.LiuG. L.CaiW. J.DaiD. D.ZhuY. W.2018Determination of vitamin C in grape seed extractionJournal of Food Safety Quality.93944Search in Google Scholar

Shaw, P. E., and Wilson, C. W. (1981). Determination of organic acids and sugars in loquat (Eriobotrya japonica Lindl.) by high-pressure liquid chromatography. Journal of the Science of Food & Agriculture, 32, 1242–1246.ShawP. E.WilsonC. W.1981Determination of organic acids and sugars in loquat (Eriobotrya japonica Lindl.) by high-pressure liquid chromatographyJournal of the Science of Food & Agriculture.321242124610.1002/jsfa.27403212177321534Search in Google Scholar

Song, L. J., Di, Y., and Shi, B. (2000). The significance and development trend in research of plant polyphenols. Progress in Chemistry, 12, 161–170.SongL. J.DiY.ShiB.2000The significance and development trend in research of plant polyphenolsProgress in Chemistry.12161170Search in Google Scholar

Su, X., Shan, S. M., Xu, Y. L., Liu, C. M., and Li, Y. L. (2019). Effect comparison of leaf-berry ratio of ‘cabernet franc’ berry quality. Northern Horticulture, 8, 53–58.SuX.ShanS. M.XuY. L.LiuC. M.LiY. L.2019Effect comparison of leaf-berry ratio of ‘cabernet franc’ berry qualityNorthern Horticulture.85358Search in Google Scholar

Su, Y. L., Yang, J., Tian, Y. Z., Wan, L., Wang, S. K., Xue, H. B., and Li, X. G. (2018). Study on the changes of physiological indexes related to browning during fruit development in pears. Journal of Fruit Science, 35, 118–124.SuY. L.YangJ.TianY. Z.WanL.WangS. K.XueH. B.LiX. G.2018Study on the changes of physiological indexes related to browning during fruit development in pearsJournal of Fruit Science.35118124Search in Google Scholar

Sun, Y. T., Li, M., Mitra, S., Muhammad, R. H., Debnath, B., Lu, X. C., Jian, H.X., and Qiu, D.L. (2018). Comparative phytochemical profiles and antioxidant enzyme activity analyses of the southern highbush blueberry (Vaccinium corymbosum) at different developmental stages. Molecular Diversity Preservation International. 23(9), 2209.SunY. T.LiM.MitraS.MuhammadR. H.DebnathB.LuX. C.JianH.X.QiuD.L.2018Comparative phytochemical profiles and antioxidant enzyme activity analyses of the southern highbush blueberry (Vaccinium corymbosum) at different developmental stagesMolecular Diversity Preservation International239220910.3390/molecules23092209622512730200335Search in Google Scholar

Wang, H., Li, M. F., Yang, Y., and Jin, W. M. (2015). Research progress on molecular mechanism of anthocyanin biosynthesis in fruits. Journal of Plant Physiology, 51(1), 29–43.WangH.LiM. F.YangY.JinW. M.2015Research progress on molecular mechanism of anthocyanin biosynthesis in fruitsJournal of Plant Physiology.5112943Search in Google Scholar

Wang, X., and Huang, J. (2015). Experimental principle and technology of plant physiology and biochemistry. Beijing, China: Higher Education Press.WangX.HuangJ.2015Experimental principle and technology of plant physiology and biochemistryBeijing, ChinaHigher Education PressSearch in Google Scholar

Wang, Z. C., Meng, X. Y., Feng, J. R., Pan, L. Z., and Liu, H. F. (2013). The effect of different color covering on the pigment accumulation of red globe grape (Vitis vinifera L.) mallow. Journal of Shihezi University (Natural Science Edition), 31(3), 276–282.WangZ. C.MengX. Y.FengJ. R.PanL. Z.LiuH. F.2013The effect of different color covering on the pigment accumulation of red globe grape (Vitis vinifera L.) mallowJournal of Shihezi University (Natural Science Edition)313276282Search in Google Scholar

Wen, T. X., Zeng, W. G., and Liu, Y. P. (2001). Study on the change of organic acid synthetase activity during fruit development of navel orange (Citrus sinesis Osbeck). Journal of Sichuan Agricultural University, 19, 27–30.WenT. X.ZengW. G.LiuY. P.2001Study on the change of organic acid synthetase activity during fruit development of navel orange (Citrus sinesis Osbeck)Journal of Sichuan Agricultural University.192730Search in Google Scholar

Xia, L. K., Chen, Y. L., Feng, Y. B., Jiao, Z. G., Liu, H., and Wang, Q. H. (2016). Changes in flavonoids, total phenolics, triterpenoidic acids and antioxidant capacity during fruit development of different cultivars of apricot. Journal of Fruit Science, 33, 425–435.XiaL. K.ChenY. L.FengY. B.JiaoZ. G.LiuH.WangQ. H.2016Changes in flavonoids, total phenolics, triterpenoidic acids and antioxidant capacity during fruit development of different cultivars of apricotJournal of Fruit Science.33425435Search in Google Scholar

Xiao, T., Cui, J. M., Guo, Z. H., and Zhao, Y. T. (2014). Determination of five phenolic compounds from fruits of Rhodomyrtus tomentosa in different regions and its antioxidant effect. Chinese Herbal Medicines, 45, 2703–2706.XiaoT.CuiJ. M.GuoZ. H.ZhaoY. T.2014Determination of five phenolic compounds from fruits of Rhodomyrtus tomentosa in different regions and its antioxidant effectChinese Herbal Medicines.4527032706Search in Google Scholar

Yang, R., Chen, W., Lu, X. C., Li, M., and Qiu, D. L. (2017). Contrastive analysis of the composition of anthocyanins in mulberry from different varieties and growing periods. Journal of Fujian Forestry Science & Technology, 44, 48–51, 78.YangR.ChenW.LuX. C.LiM.QiuD. L.2017Contrastive analysis of the composition of anthocyanins in mulberry from different varieties and growing periodsJournal of Fujian Forestry Science & Technology44485178Search in Google Scholar

Ye, C. H., Chen, D., Zheng, X. T., Chen, H. H., Chen, T. H., and Wu, Y. (2019). Study on the anatomical structure of Rhodomyrtus tomentosa leaf blade and its ecological adaptability. Anhui Agricultural Sciences, 47, 1–3.YeC. H.ChenD.ZhengX. T.ChenH. H.ChenT. H.WuY.2019Study on the anatomical structure of Rhodomyrtus tomentosa leaf blade and its ecological adaptabilityAnhui Agricultural Sciences.4713Search in Google Scholar

Zhang, J., Wang, L. S., Gao, J. M., Li, S. B., Xu, Y. J., Li, C. H., and Yang, R. Z. (2011). Identification of anthocyanins involving in petal coloration in Chaenomeles speciosa cultivars. Horticultural Plant Journal, 38, 527–534.ZhangJ.WangL. S.GaoJ. M.LiS. B.XuY. J.LiC. H.YangR. Z.2011Identification of anthocyanins involving in petal coloration in Chaenomeles speciosa cultivarsHorticultural Plant Journal.38527534Search in Google Scholar

Zhao, G. F., Wang, J. A., and Xie, T. H. (2018). Nutritional quality and aroma change of Hongyan strawberry in different developmental periods. Zhejiang Journal of Agricultural Sciences, 30(12), 2044–2048.ZhaoG. F.WangJ. A.XieT. H.2018Nutritional quality and aroma change of Hongyan strawberry in different developmental periodsZhejiang Journal of Agricultural Sciences.301220442048Search in Google Scholar

Zhao, G. H., and Chen, Z. L. (2016). Study on extraction of crude polysaccharides and antioxidant activity of Rhodomyrtus tomentosa. Food Research and Development, 37, 78–80.ZhaoG. H.ChenZ. L.2016Study on extraction of crude polysaccharides and antioxidant activity of Rhodomyrtus tomentosaFood Research and Development377880Search in Google Scholar

Zhou, X. Y., Zhu, C. H., Li, J. X., Gao, J. Y., Gong, Q., Shen, Z. S., and Yue, J. J. (2015). Advances in the study of fruit organic acid metabolism. South China Fruits, 44, 120–125.ZhouX. Y.ZhuC. H.LiJ. X.GaoJ. Y.GongQ.ShenZ. S.YueJ. J.2015Advances in the study of fruit organic acid metabolismSouth China Fruits.44120125Search in Google Scholar

Zhu, J., Peng, W. Q., Shen, R. Y., Li, W. J., Zhou, G. L., and Huang, X. X. (2019). Effects of waterlogging stress on the growth and physiological characteristics of pakchoi seedlings. Hubei Agricultural Sciences, 58(23), 63–71.ZhuJ.PengW. Q.ShenR. Y.LiW. J.ZhouG. L.HuangX. X.2019Effects of waterlogging stress on the growth and physiological characteristics of pakchoi seedlingsHubei Agricultural Sciences.58236371Search in Google Scholar

Zhu, T. T., Liang, S. M., Zhang, S. W., Zhen, X. L., Ren, H. Y., and Qi, H. J. (2018). Study on the regularity of fruit development and quality formation of early fresh Myrica rubra. Zhejiang Agricultural Journal, 30(5), 764–770.ZhuT. T.LiangS. M.ZhangS. W.ZhenX. L.RenH. Y.QiH. J.2018Study on the regularity of fruit development and quality formation of early fresh Myrica rubraZhejiang Agricultural Journal.305764770Search in Google Scholar

Zhu, X. M., and Du, J. X. (2019). Determination of vitamin C content in different parts of development process of ersimmon in Xingtai area. Heilongjiang Agricultural Sciences, 113–116.ZhuX. M.DuJ. X.2019Determination of vitamin C content in different parts of development process of ersimmon in Xingtai areaHeilongjiang Agricultural Sciences113116Search in Google Scholar

Zou, Y. C., Luo, S. Y., Duan, H. Y., Liu, L., Luo, Y. X., and Wang, C. (2017). Effect of pre-soaking on the antioxidant compounds and antioxidant activity of Hill Gooseberry (R. tomentosa) juice. Science & Technology of Food Industry, 38(1), 75–80, 86.ZouY. C.LuoS. Y.DuanH. Y.LiuL.LuoY. X.WangC.2017Effect of pre-soaking on the antioxidant compounds and antioxidant activity of Hill Gooseberry (R. tomentosa) juiceScience & Technology of Food Industry381758086Search in Google Scholar

Recommended articles from Trend MD

Plan your remote conference with Sciendo