research article effect of sodium alginate in combination

Research ArticleEffect of SodiumAlginate inCombinationwithZatariamultifloraBoiss on Phenolic Compounds Antioxidant Activity andBrowning Enzymes of Fresh In-Hull Pistachio (Pistacia vera L)

Maryam Hashemi 12 Ahmad Shakerardekani 2 Abdolmajid Mirzaalian Dastjerdi 1

and SeyedHossein Mirdehghan 3

1Departmentof Horticultural Sciences University of Hormozgan Bandar Abbas Iran2Pistachio Research Center Horticultural Sciences Research Institute Agricultural ResearchEducation and Extension Organization (AREEO) Rafsanjan Iran3Departmentof Horticultural Sciences Vali-e-Asr University of Rafsanjan Iran

Correspondence should be addressed to Maryam Hashemi mhashemi63yahoocom

Received 10 July 2021 Revised 29 August 2021 Accepted 25 September 2021 Published 7 October 2021

Academic Editor Barbara Speranza

Copyright copy 2021 Maryam Hashemi et al is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

e color of fresh pistachio is used as a postharvest quality indicator e present study was performed to investigate the chemicalproperties of fresh pistachios coated with different sodium alginate concentrations (1 and 15) various amounts of Shirazi thymeessential oil (03 and 05) and their combination during storage (2plusmn 1degC and 85plusmn 5 RH) Over the storage duration chemicalparameters were measured on days 13 26 and 39 e results showed that although the application of sodium alginate incombination with thyme essential oil decreased polyphenol oxidase activity in comparison with other treatments the highest totalphenolics and phenylalanine ammonia lyase activity were found in pistachios coated with alginate (1) + thyme essential oil (03and 05) In general it was proven that treatments containing 1 alginate + 03 essential oil had the ability to maintain thequality of fresh pistachio fruit approximately over 39 days of storage

1 Introduction

Pistachio nuts contain considerable amounts of essentialminerals phenolics essential fatty acids proteins and vi-tamin A [1] and are known as healthy food Pistachio iscommonly used in the form of a dry product as nut but theconsumption of fresh pistachio has become more popular inthe last decades [2]

Weight loss lipid oxidation browning and microbialgrowth of fresh pistachio play important roles in its finalappearance and quality during marketing [3] Studies haveshown that after harvesting fresh pistachio it immediatelybecomes brown and decayed that affect its final marketacceptability [4] Browning is one of the most importantphenomena that occurs in the pistachio hull during pro-cessing and storage [3] It is a common color change among

fresh vegetables and fruits and takes place because of thereaction of phenolic compounds oxygen and polyphenoloxidase (PPO) enzyme Biochemical studies have shown thatthe oxidation of polyphenols (mainly the conversion ofortho-diphenols into quinones and semiquinones) is thereason for hull browning [4]

Edible coating of fresh products is applied to avoidquality deterioration of fresh fruits [5] It can control gasexchange from the fruit surface decrease respiration rateand control water evaporation from fruits thereby reducingmoisture loss [6] Furthermore edible coating technologyimproves product quality along with its shelf life by changingthe internal atmosphere and reducing microbial prolifera-tion [7] However choosing suitable formulations for ediblecoatings considerably affects their effectiveness Azarakhshet al [8] reported that respiration rate and weight loss were

HindawiJournal of Food QualityVolume 2021 Article ID 3193573 7 pageshttpsdoiorg10115520213193573

decreased in alginate-coated pineapples compared withcontrol fruits Ribeiro et al [9] showed that alginate washelpful in delaying color change weight loss and softeningof coated plums ey concluded that edible coatings actedas barriers on the surface of fruit and reduced its perme-ability to gases (CO2 and O2) and water vapor is de-creased the rate of respiration and transpiration and delayedthe ripening process

e efficacy of edible coating could be improved by theaddition of antibrowning and antimicrobial agents [10]Nowadays functional additives such as essential oils (EOs)are mainly added to edible coating formulations to enhancethe appearance integrity microbial safety and mechanicalstrength of food [11]

Direct surface application of antifungal and antibacterialcompounds has slight benefits because active ingredients areneutralized at contact or are diffused into the bulk of fruiterefore the addition of EOs into edible coating formu-lations is an efficient strategy to improve the functionality ofcoatings [12]

Shirazi thyme (Zataria multiflora Boiss) has a highpercentage of essential oil with antibacterial and antifungalactivities Application of Zataria multiflora essential oil invarious antimicrobial edible coatings including alginate[13 14] gum arabic [15] chitosan [16] and carboxymethylcellulose [17] showed to increase total phenolic compoundsand as a result antioxidant activity of films e resultsshowed that films containing essential oil could be poten-tially applied in active biodegradable packaging materials toinhibit or delay deterioration and oxidation and preventmicrobial activity [17]

Considering limited studies on fresh pistachio storabilityand the potential of sodium alginate and Z multiflora es-sential oil to prevent the activity of PPO and oxidation ofphenolics treatment with sodium alginate and Z multifloraessential oil was applied to decrease browning e presentstudy aimed to investigate the possible potentials of variousformulations of sodium alginate and Z multiflora essentialoil and their combination for suppressing the browning offresh pistachio fruits

2 Materials and Methods

21 Materials Fresh pistachio (Pistacia vera L) fruits cvlsquoAhmad-Aghaeirsquo were harvested manually on October 10from 30-year-old pistachio trees ey were instantlytransported to the laboratory of postharvest and thosewithout crack and with uniform size color and shape wereseparated from the clusters

Food grade sodium alginate glycerol and sunflower oilwere obtained from Sigma-Aldrich Chemicals (Germany)Zataria multiflora essential oil was purchased from BarijEssence Company (Kashan Iran)

22 EdibleCoating Solutions Sodium alginate edible coatingwas prepared according to the method reported by Azar-akhsh et al [18] To prepare 1 and 15 (wv) edible coatings1 and 15 g sodium alginate powder (Merck Germany) were

dispersed in 100ml distilled water respectively e solu-tions were heated at 70degC and stirring was carried out untilthe clear appearance of the mixture en 15 (wv)glycerol was added followed by 0025 (wv) sunflower oilen Zataria multiflora Boiss EO at concentrations 0(control) 03 and 05 (wv) was added Finally thesemixtures were homogenized for 5min

23 Edible Coating Treatments and Storage Edible coatingswere applied according to the method reported by Azar-akhsh et al [18] e fruits were immersed in coating so-lutions for 3min and then air-dried for 1 h at 25plusmn 2degCenthey were immersed in calcium chloride (2 wv) for 2minto allow gel formation and air-dried at 25plusmn 2degC 200ndash250 gpistachio fruit was placed in each polypropylene containerwith dimensions 12times155times105 cm Coated pistachios werestored at 2plusmn 1degC and 85plusmn 5 RH for 39 days Fresh pistachiocharacteristics were determined every 13 days duringstorage

24 Total Phenolics (TPs) TPs were measured by theFolinndashCiocalteu reagent [19] 05 g flesh tissue of the pis-tachio hull was homogenized with 3ml methanol (85) andthen centrifuged at 12000times g for 20min at 4degC to removeany undesirable impurities e supernatant was separatedand used as the extract 300 μL extract was mixed with1200 μL 7 sodium carbonate and maintained at roomtemperature for 5min en 1500 μL 10 FolinndashCiocalteureagent was added and the mixture was shaken for 90min indarkness at room temperature Absorbance was read at760 nm by using a spectrophotometer (Epoch BiotechGermany) Gallic acid was used for drawing the standardcurve e concentration of the total phenolic content wasexpressed as mg gallic acid equivalents per 100 g FW

25 DPPH Radical Scavenging Activity Antioxidant activity(AA) was measured according to the 22-diphenyl-1-pic-rylhydrazyl (DPPH) radical scavenging method described byBrand-Williams et al [20] 01ml fruit hull extract 1mlDPPH (01mM) and 1ml Tris-HCl (pH 75) buffer weremixed using a vortex e final mixture was incubated for30min in a dark room en mixture absorbance was readat 517 nm by using a spectrophotometer (Epoch BiotechGermany) and AA percentage was calculated using thefollowing equation

AA() 1 minusAsampleAcontrol

1113890 1113891 times 100 (1)

26 Enzyme Activities 05 g frozen fresh fruit hull waspowdered in a chilled pestle using liquid nitrogen andhomogenized in 1mL 100mM phosphate buffer (pH 7)containing 05mM EDTA and 6 (wv) poly-vinylpolypyrrolidone (PVPP) e mixture was centrifugedat 15000times g for 20min at 4degC and the supernatant was usedfor the measurement of enzyme activities

2 Journal of Food Quality

27 Polyphenol Oxidase (PPO) Activity Assay Polyphenoloxidase (PPO) activity was determined using the methodsproposed by Koushesh Saba et al [21] Aliquots of thesupernatant were added to two solutions containingcatechol and pyrogallol at concentrations of 005M and002M respectively Absorbance increase was monitoredat 420 nm for 1min at room temperature and enzymeactivity was expressed as unit per gram of fresh weight perminute

28 Phenylalanine Ammonia Lyase (PAL) Activity AssayFor the measurement of phenylalanine ammonia lyase(PAL) activity 01mL supernatant was added to a mixturecontaining 05mL 10mM L-phenylalanine 1mL 50mMphosphate buffer (pH 7) and 04ml double-distilled waterAfter mixture incubation at 40degC for 1 h the reaction wasstopped by adding 05mL 6mM HCl PAL activity wasmeasured by the absorbance of the mixture at 290 nm basedon the production of cinnamic acid PAL enzyme activitywas expressed as mg of cinnamic acid per gram of freshweight per min [22]

29 Statistical Analysis e experiment was set as factorialbased on randomized complete block design with ninetreatments and three replications e source of variationincluded edible coatings essential oils and storage durationAnalysis of variance (ANOVA) was performed using SASsoftware (version 91) e mean values were comparedaccording to Duncanrsquos multiple range test at Plt 005

3 Results and Discussion

31 Total Phenolic Concentration and DPPH Radical Scav-enging Activity e effects of edible coating essential oiland essential oil-enriched edible coatings on the TP of thefresh hull are illustrated in Figure 1(a) Among differenttreatments fruits covered with 1 sodium alginate + 03thyme showed the highest TP content (5701mg100 g freshweight) after 39 days of storage However fruits treated with05 thyme essential oil showed the lowest TP content(4991mg100 g fresh weight) among all treatments(Figure 1(a)) As shown in Figure 1(b) initial DPPH radicalscavenging activity of the fresh pistachio hull was 3977During the storage DPPH radical scavenging activities of alltreated and control fruits were dramatically decreased andreached the lowest level after 13 days of storage e DPPHradical scavenging level started to increase with increasingstorage period up to 26 days and then decreased at the end ofstorage but it was higher in all storage times in treated freshpistachios than control ones (Figure 1(b))

e reduction of antioxidant capacity in fruits could beattributed to fruit senescence and higher respiration rate dueto the degradation and loss of some phenolic compoundsHashemi et al [13] showed that sodium alginate ediblecoating enriched with Zataria multiflora essential oil in-creased phenolic compounds in the kernels of coated freshpistachio fruits Other studies have shown that the appli-cation of Zataria multiflora Boiss essential oil-enriched gum

arabic coated on fresh pistachio resulted in higher TPcompared to control fruits [15] Ali et al stated decreasedphenolic content is a natural part of senescence which canalso be due to cell wall degradation when fruit is stored overlong periods [23]

Hashemi et al [24] reported that apricots coated withbasil seed gum (BSG) +Origanum vulgare essential oil(2ndash6) showed the highest antioxidant activity whilecontrol and BSG-coated samples gave the lowest amount ofantioxidants at the end of storage timeese effects could bethe result of the oxygen barrier properties of edible coatingsand the capacity of essential oil components to retain fruitquality factors along with the inhibition of enzyme activitythat degrades antioxidant compounds [25] us the in-crease of antioxidant capacity is related to the increase in theTP content Oms-Oliu et al [26] observed that the increaseof phenolic compounds increased the antioxidant capacityof lsquoPiel de Sapo melon during 14 days of storage period at4degC Our results clearly revealed the increment of TPcompounds of fruits coated with alginate + thyme oilSimilarly thyme oil added to packaging materials increasedthe amount of TPs and flavonoids (catechin) in avocadofruits [27] A similar trend was also stated by Ali et al [28]for tomato fruits coated with gum arabic (5) ediblecoatings However the increase of the total phenolic contentmight also increase due to the essential oil component inbasil seed gum coating which could delay the oxidationprocesses of phenolic compounds by scavenging free radicalsand oxygen [29]

32 PPO and PAL Activity As shown in Figures 2(a) and2(b) the activity of enzymes associated with the browning ofthe fresh hull ie PAL and PPO enzymes was significantlyaffected by edible coating formulations e activity of thePPO enzyme in fresh hulls was increased during storage sothat the highest activity of PPO was observed in control(uncoated) pistachios and those coated with 15 sodiumalginate + 05 essential oil after 39 days of storage while thelowest levels were obtained in fruits treated with 1 sodiumalginate solution + 03 thyme essential oil and 03 es-sential oil (Figure 2(a))

According to Figure 2(b) PAL enzyme activity in treatedand control fruits was increased during the storage periode lowest activity of the PAL enzyme was observed incontrol fruits e fruit samples treated with 1 sodiumalginate + 03 essential oil showed the highest level of PALactivity however it had no significant differences with othertreatments except for 15 sodium alginate + 05 essentialoil (Figure 2(b))

PPO is a key enzyme in the texture browning of fruitsand vegetables Some assessments reported a significantincrease in PPO activity during storage [30] Enzymaticbrowning is often accompanied with damage to the cellmembrane in texture [31] When the integrity of themembrane is reduced phenolic compounds are exposed tooxygen and oxidized by the catalytic activity of the releasedpolyphenol oxidase [31] Kader [32] reported that enzymaticbrowning can be reduced at low levels of oxygen An

Journal of Food Quality 3

increase of PPO activity was observed in pistachio duringstorage and as a result the oxidization of phenolic com-pounds occurring during this process led to lower amountsof polyphenol compounds [33] In contrast higher phenoliccontents of samples coated with 1 alginate + 03 thymemight be attributed to lower PPO enzyme activities Itseemed that alginate in solutions acted as a barrier foroxygen needed for PPO activity In addition de Sousa [34]reported that mushrooms coated with alginate enriched witheugenol essential oil and cinnamic acid reduced polyphenoloxidase activity which resulted in lower enzymatic brown-ing and alginate coating formed a protective barrier on thesurface of samples reducing the supply of O2 which can helpreduce PPO activity Previous studies have shown that theapplication of Arabic gum and sodium casein in combi-nation with cinnamon and lemongrass essential oils on

guava [11] was effective in reducing the activity of the PPOenzyme A previous study examining the effects of gumarabic in combination with Zataria multiflora essential oilon fresh pistachio fruits also showed that these treatmentswere effective in reducing PPO activity [15] Regarding thePAL enzyme several studies have shown that the accu-mulation of phenols and anthocyanins was correlated withthe increase of the activity of this enzyme in some fruitsisis the first key enzyme involved in the biosynthesis ofphenols in fruits and vegetables [35] In addition herbalessences have not only antimicrobial properties but also theability to increase TP compounds [36] is may be becauseessential oils play positive roles in secondary plant metab-olites and stimulate the biosynthesis of phenolic compoundsand anthocyanins by inducing an increase in the activity ofthis enzyme [37] In addition Chiabrando and Giacalone

a-c a-

ca-

c a-c

a-c

a-c

a-c

a-c

a-c a-

ca-

ca-

c a-c

a-c a-

ca-

ca-

c

b-d b-

dcd

abde de

e

a

a

ab

46

48

50

52

54

56

58

60

harvest 13 26 39Storage time (days)

UncoatedEC (1)EC (15)

Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

Tota

l phe

nolic

(mg

100

g-1 F

W)

(a)

ab

ab

b

ab

a

ab

b

a

ab

10

15

20

25

30

35

40

45

harvest 13 26 39

DPP

H ra

dica

l sca

veng

ing

activ

ity (

)

Storage time (days)

00305

Zm

(b)

Figure 1 Total phenolics (a) of the fresh pistachio hull coated with sodium alginate +Zataria multiflora and DPPH radical scavengingactivity (b) in the fresh pistachio hull treated with Zataria multiflora during storage at 3plusmn 1degC Means (n 3) with the same letters are notsignificantly different according to Duncanrsquos test (plt 005) EC alginate-based edible coating Zm Zataria multiflora


[34] reported that fresh-cut apple coated with alginateenriched with cinnamon and rosemary essential oils reducedpolyphenol oxidase activity which resulted in lower enzy-matic browning and alginate coating formed a protectivebarrier on the surface of samples reducing the supply of O2which can help reducing PPO activitylowast should replace theprevious text

4 Conclusion

One of the most important issues associated with the storageof fresh pistachios is their short storage life Fresh pistachioslose their quality shortly after harvest because the pistachiohull is very perishable and is rapidly spoiled and brownedApplication of edible coatings is an important protectionmethod However this method alone is not enough Certainfunctional and bioactive compounds can be incorporated intoedible coatings thus enhancing the safety of coated productsand bringing benefits to the health of consumersus edible

coatings based on the incorporation of active ingredientsespecially essential oils are considered as one of the ap-proaches with the greatest interest for managing the quality offresh products Such a strategy can inhibit enzymatic orbiochemical damage during postharvest storage is studyshowed that the application of alginate coating enriched withZataria multiflora could reduce the browning of fresh pis-tachios during storage Based on our findings control (un-coated) fruits showed the most intense hull browningfollowed by samples treated with 05 essential oil but itshould be noted that careful selection of thyme concentrationwas required in coating formulations to improve the stor-ability of fresh in-hull pistachio fruits Also the lowest PPOenzyme activity was observed in the samples coated with 1sodium alginate + 03 Zataria multiflora essential oil Inaddition a higher TP content in the hull was also obtained infruits coated with 1 sodium alginate + 03 Zataria mul-tiflora essential oil which was selected as the best formulationfor increasing the storage life of fresh pistachio

a-g

g-i f-i

d-h

d-h

a-d

a-f a-

fa-

g a-g

a-g a-

f

a-c

d-h

a-c

a-e

b-g

f-i

c-g

e-h

a

hi

ab

i

aa a

23456789

1011

harvest 13 26 39

PPO

activ

ity (u

nit p

er g

FW

per

min

)

Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(a)

ijf-j

f-jg-

j f-j f-j f-jg-i

d-g

e-g

h-j

e-g

e-h

c-f c-f

e-g d-

f

h-j

aba-

d a-c

a-d

b-e

ab a ab

j

030507091113151719212325

harvest 13 26 39

PAL

activ

ity (u

nit p

er g

FW

per

min

)

Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(b)

Figure 2 PPO (a) and PAL activity (b) of the fresh pistachio hull coated with sodium alginate +Zataria multiflora at 3plusmn 1degC Means (n 3) withthe same letters are not significantly different according to Duncanrsquos test (pgt 005) EC alginate-based edible coating Zm Zataria multiflora


Data Availability

e data belong to a project and the authors do not have thepermission to publish andor share the data and provideappropriate attribution

Conflicts of Interest

e authors declare no conflicts of interest

Acknowledgments

is research was supported by the University of Hor-mozgan and the Pistachio Research Center of Rafsanjan

References

[1] I Ozturk O Sagdic H Yalcin T D Capar and M H Asyalildquoe effects of packaging type on the quality characteristics offresh raw pistachios (Pistacia vera L) during the storagerdquoLWT-Food Science and Technology vol 65 pp 457ndash463 2016

[2] A Sheikhi S H Mirdehghan and L Ferguson ldquoExtendingstorage potential of de-hulled fresh pistachios in passive-modified atmosphererdquo Journal of the Science of Food andAgriculture vol 99 no 7 pp 3426ndash3433 2019

[3] H Tavakolipour and A Kalbasi-Ashtari ldquoEstimation ofmoisture sorption isotherms in Kerman pistachio nutsrdquoJournal of Food Process Engineering vol 31 no 4 pp 564ndash582 2008

[4] S Gheysarbigi S H Mirdehghan M Ghasemnezhad andF Nazoori ldquoe inhibitory effect of nitric oxide on enzymaticbrowning reactions of in-package fresh pistachios(Pistaciavera L)rdquo Postharvest Biology and Technology vol 159 ArticleID 110998 2020

[5] J Synowiecki and N A Al-Khateeb ldquoProduction propertiesand some new applications of chitin and its derivativesrdquoCritical Reviews in Food Science and Nutrition vol 43 no 2pp 145ndash171 2003

[6] J Duan R Wu B C Strik and Y Zhao ldquoEffect of ediblecoatings on the quality of fresh blueberries (duke and elliott)under commercial storage conditionsrdquo Postharvest Biologyand Technology vol 59 no 1 pp 71ndash79 2011

[7] S Benıtez I Achaerandio M Pujola and F Sepulcre ldquoAloevera as an alternative to traditional edible coatings used infresh-cut fruits a case of study with kiwifruit slicesrdquo LWT-Food Science and Technology vol 61 no 1 pp 184ndash193 2015

[8] N Azarakhsh A Osman H M Ghazali C P Tan andNMohdAdzahan ldquoOptimization of alginate and gellan-basededible coating formulations for fresh-cut pineapplesrdquo Inter-national Food Research Journal vol 19 pp 279ndash285 2012

[9] C Ribeiro A A Vicente J A Teixeira and C MirandaldquoOptimization of edible coating composition to retardstrawberry fruit senescencerdquo Postharvest Biology and Tech-nology vol 44 no 1 pp 63ndash70 2007

[10] M A Rojas-Grau R Soliva-Fortuny and O Martın-BellosoldquoEdible coatings to incorporate active ingredients to fresh-cutfruits a reviewrdquo Trends in Food Science amp Technology vol 20no 10 pp 438ndash447 2009

[11] S B Murmu and H N Mishra ldquoOptimization of the Arabicgum based edible coating formulations with sodium caseinateand tulsi extract for guavardquo LWT-Food Science and Tech-nology vol 80 pp 271ndash279 2017

[12] L Sanchez-Gonzalez M Vargas C Gonzalez-MartınezA Chiralt and M Chafer ldquoUse of essential oils in bioactive

edible coatings a reviewrdquo Food Engineering Reviews vol 3no 1 pp 1ndash16 2011

[13] M Hashemi A M Dastjerdi A Shakerardekani andS H Mirdehghan ldquoEffect of alginate coating enriched withshirazi thyme essential oil on quality of the fresh pistachio(Pistacia vera L)rdquo Journal of Food Science and Technology-Mysore vol 58 2020

[14] A Shakerardekani M Hashemi M Shahedi andA MirzaalianDastjerdi ldquoEnhancing the quality of fresh pis-tachio fruit using sodium alginate enriched with thyme es-sential oilrdquo Journal of Agricultural Science and Technologyvol 23 no 1 pp 65ndash82 2021

[15] M Hashemi A M Dastjerdi S H MirdehghanA Shakerardekani and J B Golding ldquoIncorporation ofZataria multiflora boiss essential oil into gum Arabic ediblecoating to maintain the quality properties of fresh in-hullpistachio (Pistacia vera L)rdquo Food Packaging and Shelf lifevol 30 p 100724 2021

[16] M Moradi H Tajik S M Razavi Rohani et al ldquoCharac-terization of antioxidant chitosan film incorporated withZataria multiflora boiss essential oil and grape seed extractrdquoLWT- Food Science and Technology vol 46 no 2 pp 477ndash484 2012

[17] A Dashipour V Razavilar H Hosseini et al ldquoAntioxidantand antimicrobial carboxymethyl cellulose films containingZataria multiflora essential oilrdquo International Journal of Bi-ological Macromolecules vol 72 pp 606ndash613 2015

[18] N Azarakhsh A Osman H M Ghazali C P Tan andN Mohd Adzahan ldquoLemongrass essential oil incorporatedinto alginate-based edible coating for shelf-life extension andquality retention of fresh-cut pineapplerdquo Postharvest Biologyand Technology vol 88 pp 1ndash7 2014

[19] V L Singelton and J A Rossi ldquoColorimetry of total phenolicswith phosphomolybdic-phosphotungstic acid reagentsrdquoAmerican Journal of Enology and Viticulture vol 16 no 39pp 144ndash158 1965

[20] W Brand-Williams M E Cuvelier and C Berset ldquoUse of afree radical method to evaluate antioxidant activityrdquo LWT-Food Science and Technology vol 28 no 1 pp 25ndash30 1995

[21] M Koushesh Saba K Arzani and M Barzegar ldquoPostharvestpolyamine application alleviates chilling injury and affectsapricot storage abilityrdquo Journal of Agricultural and FoodChemistry vol 60 no 36 pp 8947ndash8953 2012

[22] T Nguyen S Ketsa and W G van Doorn ldquoRelationshipbetween browning and the activities of polyphenoloxidaseand phenylalanine ammonia lyase in banana peel during lowtemperature storagerdquo Postharvest Biology and Technologyvol 30 no 2 pp 187ndash193 2003

[23] A Ali M Maqbool S Ramachandran and P G AldersonldquoGumArabic as a novel edible coating for enhancing shelf-lifeand improving postharvest quality of tomato (Solanumlycopersicum L) fruitrdquo Postharvest Biology and Technologyvol 58 no 1 pp 42ndash47 2010

[24] S M B Hashemi A Mousavi Khaneghah M GhaderiGhahfarrokhi and I Es ldquoBasil-seed gum containing Origa-num vulgare subsp viride essential oil as edible coating forfresh cut apricotsrdquo Postharvest Biology and Technologyvol 125 pp 26ndash34 2017

[25] O B Sogvar M Koushesh Saba and A Emamifar ldquoAloe veraand ascorbic acid coatings maintain postharvest quality andreduce microbial load of strawberry fruitrdquo Postharvest Biologyand Technology vol 114 pp 29ndash35 2016

[26] G Oms-Oliu R Soliva-Fortuny and O Martın-BellosoldquoUsing polysaccharide-based edible coatings to enhance


quality and antioxidant properties of fresh-cut melonrdquo LWT-Food Science and Technology vol 41 no 10 pp 1862ndash18702008

[27] P S Sellamuthu M Mafune D Sivakumar and P Soundyldquoyme oil vapour and modified atmosphere packaging re-duce anthracnose incidence and maintain fruit quality inavocadordquo Journal of the Science of Food and Agriculturevol 93 no 12 pp 3024ndash3031 2013

[28] A Ali M Maqbool P G Alderson and N Zahid ldquoEffect ofgum Arabic as an edible coating on antioxidant capacity oftomato (Solanum lycopersicum L) fruit during storagerdquoPostharvest Biology and Technology vol 76 pp 119ndash124 2013

[29] G K Jayaprakasha P S Negi B S Jena and L Jagan MohanRao ldquoAntioxidant and antimutagenic activities of Cinna-momum zeylanicum fruit extractsrdquo Journal of Food Compo-sition and Analysis vol 20 no 3-4 pp 330ndash336 2007

[30] M V Martinez and J R Whitaker ldquoe biochemistry andcontrol of enzymatic browningrdquo Trends in Food Science ampTechnology vol 6 no 6 pp 195ndash200 1995

[31] K Tano M K Oule G Doyon R W Lencki and J ArulldquoComparative evaluation of the effect of storage temperaturefluctuation on modified atmosphere packages of selected fruitand vegetablesrdquo Postharvest Biology and Technology vol 46no 3 pp 212ndash221 2007

[32] A A Kader ldquoPrevention of ripening in fruits by use ofcontrolled atmospheresrdquo Food Technology vol 34 pp 51ndash541980

[33] X Duan X Su Y You H Qu Y Li and Y Jiang ldquoEffect ofnitric oxide on pericarp browning of harvested longan fruit inrelation to phenolic metabolismrdquo Food Chemistry vol 104no 2 pp 571ndash576 2007

[34] V Chiabrando and G Giacalone ldquoEffect of essential oilsincorporated into an alginate-based edible coating on fresh-cut apple quality during storagerdquo Quality Assurance andSafety of Crops amp Foods vol 7 no 3 pp 251ndash259 2015

[35] G A Ojeda S C Sgroppo and N E Zaritzky ldquoApplication ofedible coatings in minimally processed sweet potatoes (Ipo-moea batatas L) to prevent enzymatic browningrdquo Interna-tional Journal of Food Science amp Technology vol 49 no 3pp 876ndash883 2014

[36] M Gao L Feng and T Jiang ldquoBrowning inhibition andquality preservation of button mushroom (Agaricus bisporus)by essential oils fumigation treatmentrdquo Food Chemistryvol 149 pp 107ndash113 2014

[37] P Jin X Wu F Xu X Wang J Wang and Y ZhengldquoEnhancing antioxidant capacity and reducing decay ofChinese bayberries by essential oilsrdquo Journal of Agriculturaland Food Chemistry vol 60 no 14 pp 3769ndash3775 2012


decreased in alginate-coated pineapples compared withcontrol fruits Ribeiro et al [9] showed that alginate washelpful in delaying color change weight loss and softeningof coated plums ey concluded that edible coatings actedas barriers on the surface of fruit and reduced its perme-ability to gases (CO2 and O2) and water vapor is de-creased the rate of respiration and transpiration and delayedthe ripening process

e efficacy of edible coating could be improved by theaddition of antibrowning and antimicrobial agents [10]Nowadays functional additives such as essential oils (EOs)are mainly added to edible coating formulations to enhancethe appearance integrity microbial safety and mechanicalstrength of food [11]

Direct surface application of antifungal and antibacterialcompounds has slight benefits because active ingredients areneutralized at contact or are diffused into the bulk of fruiterefore the addition of EOs into edible coating formu-lations is an efficient strategy to improve the functionality ofcoatings [12]

Shirazi thyme (Zataria multiflora Boiss) has a highpercentage of essential oil with antibacterial and antifungalactivities Application of Zataria multiflora essential oil invarious antimicrobial edible coatings including alginate[13 14] gum arabic [15] chitosan [16] and carboxymethylcellulose [17] showed to increase total phenolic compoundsand as a result antioxidant activity of films e resultsshowed that films containing essential oil could be poten-tially applied in active biodegradable packaging materials toinhibit or delay deterioration and oxidation and preventmicrobial activity [17]

Considering limited studies on fresh pistachio storabilityand the potential of sodium alginate and Z multiflora es-sential oil to prevent the activity of PPO and oxidation ofphenolics treatment with sodium alginate and Z multifloraessential oil was applied to decrease browning e presentstudy aimed to investigate the possible potentials of variousformulations of sodium alginate and Z multiflora essentialoil and their combination for suppressing the browning offresh pistachio fruits

2 Materials and Methods

21 Materials Fresh pistachio (Pistacia vera L) fruits cvlsquoAhmad-Aghaeirsquo were harvested manually on October 10from 30-year-old pistachio trees ey were instantlytransported to the laboratory of postharvest and thosewithout crack and with uniform size color and shape wereseparated from the clusters

Food grade sodium alginate glycerol and sunflower oilwere obtained from Sigma-Aldrich Chemicals (Germany)Zataria multiflora essential oil was purchased from BarijEssence Company (Kashan Iran)

22 EdibleCoating Solutions Sodium alginate edible coatingwas prepared according to the method reported by Azar-akhsh et al [18] To prepare 1 and 15 (wv) edible coatings1 and 15 g sodium alginate powder (Merck Germany) were

dispersed in 100ml distilled water respectively e solu-tions were heated at 70degC and stirring was carried out untilthe clear appearance of the mixture en 15 (wv)glycerol was added followed by 0025 (wv) sunflower oilen Zataria multiflora Boiss EO at concentrations 0(control) 03 and 05 (wv) was added Finally thesemixtures were homogenized for 5min

23 Edible Coating Treatments and Storage Edible coatingswere applied according to the method reported by Azar-akhsh et al [18] e fruits were immersed in coating so-lutions for 3min and then air-dried for 1 h at 25plusmn 2degCenthey were immersed in calcium chloride (2 wv) for 2minto allow gel formation and air-dried at 25plusmn 2degC 200ndash250 gpistachio fruit was placed in each polypropylene containerwith dimensions 12times155times105 cm Coated pistachios werestored at 2plusmn 1degC and 85plusmn 5 RH for 39 days Fresh pistachiocharacteristics were determined every 13 days duringstorage

24 Total Phenolics (TPs) TPs were measured by theFolinndashCiocalteu reagent [19] 05 g flesh tissue of the pis-tachio hull was homogenized with 3ml methanol (85) andthen centrifuged at 12000times g for 20min at 4degC to removeany undesirable impurities e supernatant was separatedand used as the extract 300 μL extract was mixed with1200 μL 7 sodium carbonate and maintained at roomtemperature for 5min en 1500 μL 10 FolinndashCiocalteureagent was added and the mixture was shaken for 90min indarkness at room temperature Absorbance was read at760 nm by using a spectrophotometer (Epoch BiotechGermany) Gallic acid was used for drawing the standardcurve e concentration of the total phenolic content wasexpressed as mg gallic acid equivalents per 100 g FW

25 DPPH Radical Scavenging Activity Antioxidant activity(AA) was measured according to the 22-diphenyl-1-pic-rylhydrazyl (DPPH) radical scavenging method described byBrand-Williams et al [20] 01ml fruit hull extract 1mlDPPH (01mM) and 1ml Tris-HCl (pH 75) buffer weremixed using a vortex e final mixture was incubated for30min in a dark room en mixture absorbance was readat 517 nm by using a spectrophotometer (Epoch BiotechGermany) and AA percentage was calculated using thefollowing equation

AA() 1 minusAsampleAcontrol

1113890 1113891 times 100 (1)

26 Enzyme Activities 05 g frozen fresh fruit hull waspowdered in a chilled pestle using liquid nitrogen andhomogenized in 1mL 100mM phosphate buffer (pH 7)containing 05mM EDTA and 6 (wv) poly-vinylpolypyrrolidone (PVPP) e mixture was centrifugedat 15000times g for 20min at 4degC and the supernatant was usedfor the measurement of enzyme activities
















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46

48

50

52

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58

60



Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

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Tota

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nolic

(mg

100

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W)

(a)

ab

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10

15

20

25

30

35

40

45

harvest 13 26 39

DPP

H ra

dica

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veng

ing

activ

ity (

)

Storage time (days)

00305

Zm

(b)




4 Conclusion



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harvest 13 26 39

PPO

activ

ity (u

nit p

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FW

per

min

)

Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(a)

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030507091113151719212325

harvest 13 26 39

PAL

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Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(b)



Data Availability




Acknowledgments


References
























































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Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

Tota

l phe

nolic

(mg

100

g-1 F

W)

(a)

ab

ab

b

ab

a

ab

b

a

ab

10

15

20

25

30

35

40

45

harvest 13 26 39

DPP

H ra

dica

l sca

veng

ing

activ

ity (

)

Storage time (days)

00305

Zm

(b)




4 Conclusion



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Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(a)

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Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(b)



Data Availability




Acknowledgments


References











































4 Conclusion



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PPO

activ

ity (u

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per

min

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Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(a)

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030507091113151719212325

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Storage time (days)


Zm (03)EC (1)+Zm (03)EC (15)+ Zm (03)

Zm (05)EC (1)+ Zm (05)EC (15)+ Zm (05)

(b)



Data Availability




Acknowledgments


References










































Data Availability




Acknowledgments


References










































research article effect of sodium alginate in combination

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