influence of edible coatings in plum

8/10/2019 Influence of Edible Coatings in Plum

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O RI G I N A L P A P E R

Influence of edible coating on quality of plum(Prunus salicina Lindl. cv. Sapphire)

Hyang Lan Eum

Dae Keun Hwang

Manfred Linke

Seung Koo Lee

Manuela Zude

Received: 26 December 2008 / Revised: 6 March 2009 / Accepted: 9 March 2009 / Published online: 8 April 2009

Springer-Verlag 2009

Abstract Edible coating may enhance the boundary layer

resistance resulting in enhanced shelf life of fruits. Plums(Prunus salicina Lindl. cv. Sapphire) were treated with

coating material based on carbohydrate (Versasheen) with

sorbitol as plasticizer and stored at 20 C and 85% RH. The

influence of coating on the gas transmission rates was esti-

mated using a carrier of 100% cellulose paper. Coating

treatment reduced the transmission rate of CO2, O2, and

H2O. Changes in fruit weight, fruit flesh firmness, color

parameters (L*, a*, and hue angle), soluble solids content,

pH, titratable acidity, ethylene, CO2, malondialdehyde

(MDA), and VIS/NIR fruit reflectance spectrum were

recorded in 2-day interval. Edible coating was effective in

delaying the increase of pH and the loss of firmness, titrat-

able acidity, L*, hue angle, and MDA. The incorporation of

sorbitol showed beneficial effects on decreasing the weight

loss, CO2, and ethylene exchange. In the room temperature

storage period, not only fruit ripening was measurable in the

VIS (350750 nm) and NIR (7501,400 nm) wavelength

ranges due to the decrease in the fruit chlorophyll absorptionbut also water loss, respectively. After 5-day room temper-

ature storage the chlorophyll absorption peak in the spectra

was already beyond the detection limit in all treatments,

while after 3-day storage, the coating effect on the spectral

intensities was feasible to separate control from coated

plums.

Keywords Edible coatingFirmnessMalondialdehydePlum Shelf life

Introduction

Plum is a highly perishable product and has a short shelf

life. Furthermore, cold storage (010 C) may lead to the

development of chilling injury symptoms occurring when

the plums have been moved from cold storage to room

temperature [14]. Based on their ripening properties,

plums have been classified into climacteric and suppressed

climacteric types [1]. Climacteric ripening is characterized

by enhanced respiration rate accompanying an autocata-

lytic ethylene production during fruit development. In

contrast, suppressed climacteric ripening arises if the eth-

ylene production increases only during the later period of

ripening with still lower rates compared to climacteric

plum cultivars [5, 6]. Particularly climacteric plums have

high market value, thus the shelf life needs to be extended.

In order to increase the sensory quality and acceptability of

consumer, Crisosto et al. [7] suggested that plums should

be harvested at early maturity stage.

Edible coatings are used to enhance the quality of fresh

crops and extend the shelf life, through provide the boundary

layer resistance, which may regulate oxygen, carbon

H. L. Eum (&)

Fruit Research Division, National Institute of Horticultural

and Herbal Science, RDA, 475 Imok-dong, Jangan-gu, Suwon,

South Korea

e-mail: [email protected]

D. K. HwangCheolwon Agricultural Technology Center, 761 Jangheung-ri,

Dongsong-eup, Cheorwon, South Korea

M. Linke M. ZudeLeibniz Institute for Agricultural Engineering Potsdam-Bornim

e.V. (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany

S. K. Lee

Department of Plant Science, College of Agriculture

and Life Sciences, Research Institute for Agriculture

and Life Sciences, Seoul National University, San 56-1,

Sillim-dong, Seoul 151-921, South Korea

1 3

Eur Food Res Technol (2009) 229:427434

DOI 10.1007/s00217-009-1054-8


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dioxide, and water vapour around the commodities. The

influence of edible coating on the fruit ripening can, there-

fore, appear similarly such as modified atmosphere storage

through the change of gas composition in coated products

[8,9]. Ethylene stimulates ripening and senescence, thereby

shortening shelf life. The ethylene production of fruits

requires O2. Internal atmosphere of low-oxygen partial

pressure (pO2) and high pCO2 through edible coatingtreatment is expected to slow down respiration and retard

ethylene production and therefore ripening [1012].

Various coatingmaterials havebeen widely studied to keep

fruit quality in a range of horticultural products. Polysaccha-

ride or protein-based coating materials have good gas barrier

properties but show marginal effects on the moisture barrier

properties. In contrast, the lipid-based coating compounds

show good moisture barrier properties but exhibit poor gas

permeability [13]. Edible coatings incorporatedwith additives

such as volatile precursors, firming compounds, and plasti-

cizers could improve the properties through physical and

chemical interaction [11,14]. The plasticizer as additive mayimprove the fruit quality by means of modifying the

mechanical characteristics of base compounds that can result

in better application properties of coating materials and

changes in its barrier properties as well [8].

Versasheen (National Starch & Chemical Ltd, Hamburg,

Germany) is a carbohydrate-based polymer from waxy

maize starch obtained from varieties of maize consisting

largely (99%) of amylopectin, compared to common maize

starch with 26% amylose and 74% amylopectin. The coating

material dissolves easily in water and has a low viscosity at

high solids concentrations [15, 16]. Versasheen has been

used in the food industry as versatile glazing agent on dry

products, but no application on fresh crops has been repor-

ted. The aim of the present work was to study the effects of

Versasheen with and without sorbitol as a plasticizer on

physico-chemical fruit properties of Sapphire plums

during short-term storage. The cultivar selected shows

climacteric ripening property [5,6].

Materials and methods

Plant material

Plums were purchased from the wholesale agricultural

market at Berlin, Germany. The fruits were carefully

selected to be uniform in appearance and free from

mechanical damage and deterioration.

Coating solution preparation

The Versasheen solutions were prepared by dissolving 5%

(w/v) Versasheen in distilled water. Sorbitol was added as a

plasticizer at a concentration of 0.2% (w/v). These con-

centrations were derived from preliminary experiments on

various fruits. The coating solutions were mixed for 35 min

by stirring at 95 C and subsequently stored at room tem-

perature. The coating treatments were applied by dipping

plums into the solutions for 60 s, then drained and air-dried

for 2 h at room temperature. Control fruit was subjected to

distilled water treatment. Following the coating process,plums were placed on open plastic grids and stored at

20 C and 85% RH for 8 days.

Gas transmission rate

CO2 and O2 transmission rate

CO2 and O2 transmission rates (mg/cm2 h) were measured

in a closed system in two polyethylene boxes (outer box U

19.5 cm 9 29.9 cm), the inner box (19.7 cm9 13.4 cm

9 10.5 cm) on one side was equipped with a frame

(16.3 cm 9 9.6 cm) for adjusting the carrier (100%cellulose paper) for the coating material or treatment with

distilled water serving as the control. Papers were mounted

on the box and 3% CO2 and 3% O2 concentrations were

continuously streamed through the inlet of the inner box.

CO2 sensors (FY A600 CO2, Ahlborn Mess- und

Regelungstechnik GmbH, Germany) and O2sensors (KE-25,

GS YUASA Corp., Japan) were placed in outer and inner

box. CO2 and O2 transmission rates were monitored by

measuring the concentration in outer and inner boxes in 15-s

interval. Slopes of the CO2increase in outer box and the O2increase in inner box as a function of time were analyzed

by linear regression in the linear section of the curve.

Water transmission rate and water gain capacity

Water vapor transmission rate (WVTR) and water gain

capacity were measured using edible coated 100% cellu-

lose paper. For WVTR, cellulose papers cut into

16.3 cm 9 9.6 cm were mounted on the polypropylene

box (19.7 cm 9 13.4 cm 9 10.5 cm) to expose the coated

face to the outside of the box filled with 200 ml of distilled

water. The boxes were placed in a climatised room at

25 C and 35% RH. Weight of polypropylene boxes was

monitored by weighing every hour for 8 h. Slopes of the

steady-state portion of weight loss versus times curves

were determined by linear regression to estimate WVTR.

The WVTR through a film is expressed as unit of mg H2O/

cm2 h [17]. Water uptake capacity was estimated by

weighing of coated papers in 30-min intervals during 24 h

at climatised room at 22 C and 55% RH. The cellulose

papers were located on a wire grid for free convection

conditions. The weight change of paper was measured

(repetition rate n = 3).

428 Eur Food Res Technol (2009) 229:427434

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Fruit quality parameters

Weight of individual plums was recorded following treat-

ment (day 0) and after the different sampling dates. Weight

loss was calculated for each fruit as percentage loss of

initial weight (n = 10).

Skin color was measured on the opposite sides of the

fruit along the equatorial axis using a colorimeter(CM-2600d, Minolta Camera Co., Osaka, Japan). The L*,

a* and b* parameters as well as hue angle were monitored

(n = 10).

Fruit flesh firmness was analyzed by means of stress

strain curves using a universal testing machine (Zwicki

1120, Zwick Materialprufung Co. Ltd., Germany). A

cylindrical probe of 4-mm diameter was applied at a drive

forward speed of 200 mm min-1. Previous to the test, the

skin of the fruit was removed about 1-cm diameter and

1-mm depth. Two readings were carried out per fruit on

opposite sides (n = 7). The results were expressed in

Newton (N).Soluble solids content (SSC) was measured with a digital

refractometer (PR-1, Atago Co. Ltd., Japan) at 20 C and

results expressed as oBrix (n = 7). The pH was recorded

with pH meter (inoLab, Wissenschaftlich Technische Wer-

kstatten, Weilheim, Germany), and subsequently titratable

acidity was analysed by titration with 0.1 N NaOH up to pH

8.1 and expressed as percentage of citric acid equivalent per

100 g fresh weight.

Gas exchange

Ethylene and CO2 production

CO2and ethylene exchange rates were measured by placing

a batch of three fruits in a 0.75-l jar sealed with a rubber

stopper for 2 h in an ambient atmosphere at room temper-

ature (n = 4). Gas samples were taken from each jar and

CO2 and ethylene, respectively, were measured in closed

system by electrochemical CO2 sensor (FY A600 CO2,

Ahlborn Mess und Regelungstechnik GmbH, Germany) and

a gas chromatograph (GC-17A, Shimazu Corp., Kyoto,

Japan) equipped with a flame ionization detector and a

packed stainless steel column.

Determination of lipid peroxidation

Lipid peroxidation was measured using thiobarbituric acid

as reactive reagent (TBARMs) in which TBARMs react

with malondialdehyde (MDA) [18,19]. Approximately 2 g

of each sample was homogenized in ice-cold 0.2 M phos-

phate buffer [1:5 (w/v), pH 6.5, 1% Triton X-100]. The

homogenates were centrifuged at 5,000g for 15 min at

4 C, and the supernatants collected. A 1-ml aliquot of

plum was mixed with 4 ml of 20% trichloroacetic acid and

0.5% thiobarbituric acid and heated at 95 C for 25 min.

The tubes were cooled immediately in an ice bath and

centrifuged at 5,000g for 10 min at 4 C. Following cen-

trifugation, the resulting supernatants were used for MDA

determination. Absorbance at 440, 532, and 600 nm was

recorded using a UVVis-NIR spectrophotometer (Lambda

950, PerkinElmer Corp., Massachusetts, USA). MDAequivalent (lmol g-1) was calculated using an extinction

coefficient (E) of 157 mM-1 cm-1 by the following

equation [20]:

A532 A600 A440 A600E352=E440

157103;

whereA is absorbance in 1.0 cm cuvette and E532and E440are the molar extinction coefficients addressing the sucrose

by the coefficients 8.4 and 147, respectively.

Non-invasive spectroscopy

Before and after coating treatment in a 2-day interval, thediffuse reflectance of plums (n = 10) was measured non-

invasively using the UVVis-NIR spectrophotometer

(Lambda 950, PerkinElmer Corp., Massachusetts, USA)

equipped with an integrating sphere and referenced every

day with 100% white standard (Spectralon, Labsphere Ltd.,

North Sutton, USA). The spectral plum reflectance was

scanned from 350 to 1,400 nm.

Data analysis

All experiments were prepared using completely random-

ized designs. SAS statistical software (SAS Institute, Cary,

NC, USA) was used to conduct variation analyses (ANOVA)

on the treatment results. Least significant difference (LSD)

atP B 0.05 was calculated to compare differences between

means.

The normalized difference vegetation index (NDVI)

parameter was estimated using spectral recorder by the

equation: NDVI = (I780 - I680)/(I780 ? I680). Principle

component analysis was carried out in Matlab (R2008a,

MathWorks, USA) environment using the PLS Toolbox

(Eigenvector Inc., USA).

Results and discussion

Transmission rate and water gain capacity

Transmission rate is considered appropriate for describing

the permeability of films when they are tested for instance

regarding the RH gradient [21]. The effect of coating with

Versasheen was shown in gas and water vapour transmission

rates (Table1). Versasheen coating treatment provided a

Eur Food Res Technol (2009) 229:427434 429

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barrier against oxygen, carbon dioxide and water vaporproving the similar effect on the fruits such as in modified

atmosphere storage [9]. During 8 h, the weight of cellulose

paper increased (Fig.1). Versasheen coating treatment

increased the weight in comparison to untreated paper. No

difference was found by adding sorbitol as plasticizer.

Although fresh fruit and paper have different physical and

physiological properties, use of edible coating material with

additive could result in CO2 increase and O2 decrease in

internal atmosphere of fresh fruit.

Gas composition

Ethylene production

Ethylene production of uncoated and Versasheen-coated

plums increased during room temperature storage (Fig. 2).

The coating of Versasheen without sorbitol showed a higher

ethylene production than uncoated and Versasheen withsorbitol since 3-day room temperature storage. Using Ver-

sasheen without sorbitol, coating application did not affect

ethylene efflux of the fruit, while Versasheen with sorbitol-

coated plums delayed the ethylene production. Although

Versasheen without sorbitol coating showed higher ethylene

levels than other treatment, ripening indicators such as color

development and firmness changes were delayed (Tables 2,

4). Similarly in other cultivar of plums, the changes in acidity

and color were at least ethylene-dependent while SSC

changes appeared to be ethylene-independent [26]. Some

previous studies showedthat the effect of coating application

on ethylene production depended on the commodity andcoating materials [11]. Ethylene production of apple coated

with polysaccharide-based compound was reduced, whereas

those of plum coated with hydroxypropyl methylcellulose

was not affected [11].

CO2 production and the ratio of CO2 increase

CO2 production rate in uncoated plums significantly

increased during room temperature storage, whereas

maintenance was found in Versasheen-coated plums

(Fig.2). After 3-day room temperature storage, the per-

centage CO2 increase was 45.90, 28.53 and 31.96% for

uncoated and Versasheen with and without sorbitol-

coated plums, respectively. Especially Versasheen with

sorbitol treatment significantly reduce CO2 production.

This effect of Versasheen coating could be explained by

formation of a barrier to gas diffusion between plums

and atmosphere as shown for other edible coating

materials [22]. This result was confirmed by low CO2and high O2 transmission rate using cellulose paper as a

more reproducible carrier.

Table 1 Transmission rate of cellulose paper treated with distilled

water (control), and coated with Versasheen, and Versasheen with

sorbitol (?S)

Transmission rate (mg/cm2 h)

CO2 O2 H2O

Control 6.82 0.23 a 16.81 1.52 a 2.74 0.04 a

Versasheen 6.29 0.25 ab 12.34 0.75 b 2.02 0.07 bVersasheen? S 5.99 0.13 b 13.62 0.68 b 1.93 0.04 b

Mean separation within a column (a and b) indicates significant dif-

ferences among coating treatments at p B 0.05; values are given as

mean SE

Time (min)

0 50 100 150 200 250 300

Sheetweight[mg]

0

10

20

30

40

50

ControlVersasheenVersasheen + S

Fig. 1 Changes of sheet weight of cellulose 100% paper coated with

Versasheen and Versasheen with sorbitol (?S) as a function of time at

22 C and 55% RH

Days of storage

0 1 3 6

Ethyleneproduction

[gg

-1

h

r-1]

0.00

0.02

0.04

0.06

0.08

0.10

Control

Versasheen

Versasheen + S

a

Days of storage

0 1 3 6

CO

2production[gg

-1h

r-1]

20

30

40

50

60

70

Control

Versasheen

Versasheen + S

b

Fig. 2 Effect of Versasheen

and Versasheen with sorbitol(?S) coating ona ethylene and

b CO2 production of Sapphire

plums on fresh weight basis

during storage at 20 C. Bars

indicate the standard errors of

the means. Thearrow indicates

the point of coating treatment


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Fruit quality parameters

Weight loss

Plums are naturally covered by a wax layer that protects the

fruit against environmental stresses and works as a barrier to

gas diffusion and moisture loss. Weight loss increased in

uncoated and Versasheen-coated plums during room tem-

perature storage, but it was accelerated in control and

Versasheen without sorbitol treatment compared to

Versasheen with sorbitol-coated plums (Table 2). No dif-

ferences in weight loss were observed between control and

Versasheen without sorbitol-treated plum. At the end of

room temperature storage, control and Versasheen without

sorbitol treatment lost 4.60% 0.20 and 4.52% 0.33,

respectively, whereas the loss of its initial weight in Ver-

sasheen with sorbitol-treated plums was 3.77% 0.23.

However, the use of sorbitol as additive in Versasheen-

coated plums had no or marginal effect on WVTR (Table1).

The enhanced weight loss could be additionally caused by

the higher respiration rate [23]. During storage, the tendency

of higher water loss of uncoated plums was consistent with

the increase of respiration rate (Table 2; Fig. 2).

Firmness determination

Fruit firmness is a major factor determining the quality of

the fruit and affecting the acceptability by the consumers.

Application of coating materials reduces or delays the

texture loss during storage due to water loss and pectin

solubilization, as has been reported in strawberry, table

grape and cherry treated with yam starch, Aloe vera and

Semperfresh, respectively [24, 25]. In the present experi-

ment, fruit flesh firmness in all treatments decreased during

room temperature storage, but its rate was influenced by

the coating treatment. In uncoated plums, lower firmness

values were recorded in comparison to fruits with Ver-

sasheen coating (Table2). According to previous study, the

decrease of firmness coincided with high production of

ethylene, suggesting that plum ripening was triggered by

already low ethylene concentration in plum [26]. However,

our results showed that the decrease of flesh firmness

depended on coating, while no clear influence on the eth-

ylene production was found (Table 2; Fig. 2).

SSC, pH and titratable acidity

The SSC and titratable acidity are good indicators for

acceptance of plums by consumers [4,7]. The SSC did not

change significantly during room temperature storage and

was not affected by coating application with and without

sorbitol (Table3). The pH was increased after 4-day room

temperature storage. The Versasheen coatings slowed the

pH and titratable acidity changes, resulting in lower pH and

increased titratable acidity at the end of the room temper-

ature storage period in comparison to uncoated plums

(p B 0.05). Martnez-Romero et al. [27] suggested that the

reduced ripening by edible coating was explained by the

maintenance of titratable acidity.

Color change

Surface color of Sapphire plums changed from green to red

and dark black during room temperature storage (Table4).

The main color changes of plum were identified by hue angle

and correlated to the anthocyanin as well as chlorophyll

alterations [1, 4]. L* value was not different in all treatments.

Table 2 Effect of Versasheen and Versasheen with sorbitol (?S)

coating on weight loss and firmness of Sapphire plums during

storage at 20 C

Days Control Versasheen Versasheen? S

Weight loss (%)

1 0.90 0.04 a, z 0 .72 0.06 b, z 0.600.04 b, z

3 2.23

0.10 a, y 2 .14

0.16 ab, y 1.76

0.11 b, y5 3.43 0.15 a, x 3 .36 0.24 ab, x 2.820.17 b, x

7 4.59 0.19 a, w 4.52 0.33 ab, w 3.770.23 b, w

Firmness (N)

0 8.44 0.17 a, z 8.44 0.17 a, z 8.440.17 a, z

2 2.67 0.14 b, y 3.37 0.32 a, y 3.160.32 ab, y

4 1.08 0 .07 b, x 1.29 0.06 a, x 1.370.08 a, x

Mean separation within a row (a and b) and a column (w, x, y, and z)

indicate significant differences among coating treatments atp B 0.05;

values are given as mean SE


coating on SSC, pH and titratable acidity (TA) of Sapphire plums

during storage at 20 C


SSC (o

Brix)

2 12.270.34 a, x 12.66 0.23 a, x 12.60 0.37 a, c

4 13.26

0.34 a, x 12.23

0.20 ab, x 11.56

0.48 b, xy8 11.00 0.33 ab, y 10.99 0.30 ab, y 10.70 0.34 b, y

pH

2 4.61 0.04 b, z 4.76 0.06 ab, y 4.76 0.01 ab, x

4 5.08 0.09 a, y 4.74 0.07 b, y 4.47 0.08 bc, y

8 5.30 0.06 a, x 5.20 0.00 ab, x 5.05 0.10 c, x

TA (%)

2 0.38 0.01 a, x 0.37 0.01 a, x 0.35 0.01 a, x

4 0.32 0.02 a, x 0.33 0.02 a, xy 0.35 0.01 a, x

8 0.24 0.01 b, y 0.2 9 0.01 ab, y 0.33 0.02 a, x

Mean separation within a row (a, b and c) and a column (x, y and z)




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However, throughout the storage period, the value was

diminished as shown in previous results (p B 0.05) [7].

Also, a* value and hue angle was decreased (p B 0.05). The

decrease of a* value and hue angle indicates that plums

became redder and darker during ripening and senescence

[28]. In the present study, the a* value was less sensitive. For

more specific impression on the pigment changes spectros-

copy in the visible wavelength range was carried out.

Lipid peroxidation

After 4-day room temperature storage, differences in MDA

value of plums were detected between uncoated and Ver-

sasheen with and without sorbitol (Table 5). After 8-day

room temperature storage, the production of MDA in

Versasheen-coated plums reached the same level of

uncoated plum after 4-day storage. The treatment with and

without sorbitol did not influence the MDA value. Lipid

degradation and peroxidation can provide early responses

in many tissues of horticultural crops undergoing ripening

and senescence [29]. Hydrogen ion can easily be removed

from double bond of unsaturated fatty acid and lipid radical

formed through this reaction. Many lipid hydroxyl radical

and active oxygen species might be proliferated as chain

reaction and resulted in oxidative stress leading to perox-

idative damage in the chloroplast and thylakoide

membrane [18, 30, 31]. Finally it could enhance chloro-

phyll degradation. The increment of MDA, which is adecomposition production of the oxidation of polyunsatu-

rated fatty acids, is a measure for large production of active

oxygen species that results in oxidative stress leading to

peroxidative damage in the membranes [32].

Spectral fruit reflectance analysis

An assessment of non-destructive reflectance spectrum can

serve as an indicator of fruit development in many fruits

[3335]. During the room temperature storage period, the

decrease in chlorophyll content and increase in anthocya-

nin can be seen in the visible wavelength range (350

750 nm), while water loss as well as carbohydrate changes

appear in the near-infrared (7501400 nm) region [3639].

Consistently, during the room temperature storage period

the reflectance spectrum from 560 to 610 nm was

decreased during storage, indicating plums were getting

redder and darker (Fig. 3). Also increased reflectance

intensities appeared from 660 to 700 nm due to ripening-

related decrease in fruit chlorophyll content. Spectral

responses to the room temperature storage periods and

coating treatment were investigated. No differences were

found in the NIR wavelength range. In the visible intensity

values of the wavelength range from 350 to 699 nm from

150 samples, resulting in a matrix of 350 9 150, were

subjected to a principle component analysis (PCA).

Regarding the entire storage time, clusters of the storage

periods were recognized regarding the first principle

component (PC#1) capturing 67.63% variance and PC#2

capturing 14.26% variance (Fig.4a). After 5-day room

temperature storage, the chlorophyll absorption was

already beyond the detection limit in all treatments, as this

is indicated by the disappearance of chlorophyll absorption


coating on L*, a*, hue angle, and NDVI of Sapphire plums during

storage at 20 C


L*

0 32.49 0.77 a, x 33.39 0.82 a, x 34.95 0.98 a, x

1 30.23

0.43 b, y 30.76

0.85 ab, y 33.29

1.31 a, x3 24.90 0.36 b, z 24.81 0.42 b, z 26.72 0.68 a, y

5 24.79 0.17 a, z 24.81 0.18 a, z 25.13 0.58 a, y

7 24.24 0.19 a, z 24.50 0.22 a, z 24.19 0.41 a, y

a*

0 29.77 0.55 a, w 27.96 0.81 a, w 27.92 0.79 a, w

1 31.35 0.77 a, w 29.87 1.08 a, w 30.66 1.03 a, w

3 22.38 0.84 a, x 22.10 1.02 a, x 23.76 1.59 a, x

5 12.34 0.64 b, y 13.51 0.75 ab, y 16.22 1.39 a, y

7 9.43 0.52 a, z 9.24 0.65 a, z 11.01 0.98 a, z

Hue angle ()

0 0.42 0.01 b, w 0.48 0.02 ab, w 0.50 0.03 a, w

1 0.39 0 .01 b, x 0.45 0.01 ab, w 0.49 0.03 a, w

3 0.31 0.00 b, y 0.33 0.00 b, x 0.36 0.01 a, x

5 0.22 0.00 b, z 0.24 0.01 ab, y 0.26 0.01 a, y

7 0.20 0.00 a, z 0.22 0.01 a, y 0.23 0.01 a, y

NDVI

0 0.46 0.01 a, x 0.49 0.02 a, w 0.49 0.02 a, x

1 0.38 0.01 a, y 0.40 0.02 a, x 0.40 0.02 a, y

3 0.31 0.01 a, z 0.33 0.01 a, y 0.35 0.02 a, yz

5 0.28 0.01 a, z 0.29 0.01 a, yz 0.31 0.01 a, z

7 0.27 0.01 a, z 0.27 0.01 a, z 0.29 0.01 a, z

Mean separation within a row (a and b) and a column (w, x, y and z)




coating on MDA of Sapphire plums during storage at 20 C

Days MDA production (lmol g-1

fresh wt)

Control Versasheen Versasheen? S

0 0.91 0.50 a, z 0.91 0.50 a, z 0.91 0.50 a, z

4 26.59 3.86 a, y 17.29 1.76 b, y 16.78 2.13 b, y

8 46.61 3.58 a, x 30.44 1.14 b, x 30.11 3.27 b, x

Mean separation within a row (a and b) and a column (x, y, and z)




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peak (Fig. 3). Consistently, the coating treatment affected

the spectral intensities after 3-day room temperature stor-

age (Fig.4b). The loadings of PCA pointed to changes in

the anthocyanin and chlorophyll absorption bands. Thecontrol plums were separated from the coated fruits, while

on day 7 the chlorophyll was no longer detectable and no

clustering appeared (Fig. 4c).

The normalized difference vegetation index (NDVI)

calculated from the spectra has a high correlation with

chlorophylla[35] and resulting the NDVI might be used as

an indicator of chlorophyll degradation. The NDVI value

gradually decreased in all plums with and without edible

coating (Table4). However, NDVI value of Versasheen

with and without sorbitol-coated plums was slightly

delayed compared to uncoated plum. Such as in the prin-

ciple component analysis, the hue angle address both the

anthocyanins and chlorophyll resulting in more pronouncedchanges during fruit development.

Conclusion

The gas and water vapour transmission rate using cellulose

paper as coating carrier was reduced in the Versasheen

coating treatment. The Versasheen-based coating creating a

modified atmosphere in the plums extended the shelf life of

Wavelength [nm]

450 600 750 900 1050 1200 1350

Intensit

yofdiffusereflectance[%]

0

10

20

30

40

50

60

70

0 day7 day

a

Wavelength [nm]

350 400 450 500 550 600 650 700

Intensityofdiffusereflectance[%]

0

10

20

30

40

50

600 day1 day3 day5 day7 day

b

Fig. 3 Spectral changes of

diffuse reflectance intensities of

Sapphire plums during storage

at 20 C. a Mean VIS/NIR

spectra of fruits coated with

Versasheen,b mean spectra in

the visible wavelength range of

Versasheen-coated fruits

-40 -20 0 20 40 60 80-15

-10

-5

0

5

10

15

20

Scores on PC# 1

Scores

onPC#2

Scores for PC# 1 versus PC# 2

-350 -300 -250 -200 -150-30

-20

-10

0

10

20

30

40

Scores on PC# 1

ScoresonPC#2

-400 -350 -300 -250 -200-25

-20

-15

-10

-5

0

5

10

15

Scores on PC# 1

ScoresonP

C#2

b c

a

Fig. 4 Scores plot for the first

two principle components of

fruit spectra (350700 nm) of

Sapphire plums during storage

at 20 C: a development during

storage (times0 day,plus

1 day,asterisk3 days;open

circle 5 days;open triangle

7 days);b after 3 days storage;and c after 7 day storage (times

control;plusVersasheen;

asteriskVersasheen with

sorbitol)


1 3


8/8

plums by decreasing the weight loss and delaying changes

in firmness, color, pH, and titratable acidity during room

temperature storage. The coatings also significantly

reduced the MDA production pointing to diminished lipid

peroxidation. In particular, Versasheen with sorbitol coat-

ing was useful to improve moisture and gas barrier as

shown by weight loss and CO2 production. The measure-

ment of CO2 and ethylene needs specific facilities andmight be rare to decide on the quality of fresh crops. MDA

and flesh firmness provided sensitive, but destructive

methods. As a non-destructively measured parameter, the

fruit reflectance spectra in the visible wavelength range

appeared feasible to monitor the fruit development.

According to these results, the application of Versasheen-

based edible coatings could enhance the shelf life of plums.

Acknowledgments The project was carried out with the financial

support provided by the DFG-Project HESPERIDES (Germany).

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influence of edible coatings in plum

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