the effect of air-drying, freeze-drying and storage

7/27/2019 The Effect of Air-drying, Freeze-drying and Storage

http://slidepdf.com/reader/full/the-effect-of-air-drying-freeze-drying-and-storage 1/11

THE EFFECT OF AIR-DRYING, FREEZE-DRYING AND STORAGE

ON THE QUALITY AND ANTIOXIDANT ACTIVITY OF SOME

SELECTED BERRIES

MAGDALENA MICHALCZYK1

, RYSZARD MACURA andIWONA MATUSZAK

Department of Refrigeration and Food ConcentratesFaculty of Food Technology

Agricultural University of Krakow ul. Balicka 12230-149 Krakow, Poland

Accepted for Publication March 30, 2008

ABSTRACT

The aim of this study was to analyze the effects of air-drying and freeze-

drying and subsequent storage of dried products on the content of polyphe-

nols, anthocyanins and the antioxidant properties of selected berry fruits. The

material was raspberry (Rubus ideaus L.), strawberry (Fragaria ananassaDuch) and bilberry (Vaccinum myrtillus). Despite exposure to atmospheric

oxygen, the stored freeze-dried fruit retained the properties of the raw material

better than the air-dried product. In the case of the latter, there were consid-erable differences in the retention of total polyphenolic and anthocyanin

content as well as antioxidant properties in the three fruit species examined. In

particular, bilberry maintained a high polyphenol and anthocyanin content

and high antioxidant potential despite the greatest losses of these compounds.

PRACTICAL APPLICATIONS

Consumer demand for food with health-promoting qualities is increasing.The food industry has intensified its efforts to provide high quality, semi-processed products that fulfil this requirement. The results presented in thiswork indicate that even after long-term storage and despite exposure to atmo-spheric oxygen, freeze-dried berries retain the antioxidant properties of theraw material to a very high degree. Therefore, lyophilisates can satisfy thisparticular need. Air-dried berries are much less stable during long-term

1 Corresponding author. TEL: +48-12-622-47-58; FAX: +48-12-622-47-58; EMAIL: [email protected]

Journal of Food Processing and Preservation 33 (2009) 11–21.© 2009, The Author(s)

Journal compilation © 2009 Wiley Periodicals, Inc.

11

mailto:[email protected]











storage. The dynamics of the changes occurring during the storage of bothkinds of product are presented in detail.

INTRODUCTION

The ability of certain foods to protect human cells from the harmfuleffects of free radicals has attracted considerable interest and quickened thepace of research into the antioxidant potential of fruits and vegetables. Berryfruits, which have been estimated to provide 27.1% of total plant antioxidantsin the Norwegian diet (Halvorsen et al. 2002), have a particular role to play.Strawberries, raspberries and bilberries, all rich in health-promoting proper-ties, are the most popular fruits in this group. Strawberries contain anthocya-nins, catechins and quercetin, and kaempferol, as well as being a rich source of ellagic acid (Hannum 2004). Strawberries also contain large amounts of ascor-bic acid, about 60 mg/100 g fresh weight (Proteggente et al. 2002), the contentin raspberries being about 30 mg/100 g (de Ancos et al. 2000a; Proteggenteet al. 2002). The level of ascorbic acid in bilberries is relatively low.

The major phenolic compounds identified by Proteggente et al. (2002) instrawberry extracts were pelargonidin-3-glucoside and, in lesser quantities,cyanidin-3-glucoside; in raspberries, however, cyanidin-3-sophoroside was thedominant phenolic compound, with cyanidin-3-glucoside and cyanidin-3-rutinoside present in lesser amounts. The content of cyanidins in strawberriesis usually very minor (Kalt et al. 1999). Bilberries (Vaccinium myrtillus L.) areexceptionally rich in anthocyanins (about 300–530 mg/100 g of fresh fruit)(Prior et al. 1998). Faria et al. (2005) identified 15 of them in this fruit, withcyanidin-3-glucoside, delphinidin-3-galactoside, delphinidin-3-glucoside,cyanidin-3-galactoside, delphinidin-3-arabinoside and petunidin-3-glucosidepresent in the largest quantities.

Considerable research has been devoted to the ability of particular phenolcomponents, fruit extracts and lyophilisates to inhibit the development of neoplasms, coronary disease and other degenerative diseases. A great deal of the documented research carried out on animals has confirmed the efficacy of these substances; however, the findings were specific to the conditions of theexperiments, such as the choice of procancerogen, the species of animals usedfor testing and the choice of the monitored indicators (Aziz et al. 2002; Royet al. 2002; Joseph et al. 2003, Hannum 2004; Matchett et al. 2005). More-over, the anthocyanins in bilberries have been attributed with properties thatimprove microcirculation and reduce vision impairment (Morazzoni andBombardelli 1996; Murray 1997). Hence, apart from being traditionally usedto regulate the digestive system, bilberries are now used in preparations forimproving vision and circulation.

12 M. MICHALCZYK, R. MACURA and I. MATUSZAK



It is essential to determine what effect processing and storage have on theantioxidant and other health-promoting properties of berry fruits. It is widelyknown that sublimation drying is much more effective in preserving valuablefood compounds than traditional methods of drying. However, the effects arenot always long-lasting and the resulting products can be unstable duringstorage, with the initial high quality rapidly deteriorating (Uddin et al. 2002).The rapidity of this deterioration is sometimes greater than that observed intraditionally dried products of lower initial quality. The phenomenon is clearlyseen in, for example, carrots (Tang and Chen 2000; Yen et al. 2008). There-fore, the purpose of this study was to analyze the effect of air-drying, freeze-drying and subsequent product storage on the content of polyphenols,anthocyanins and the antioxidant potential of selected berry fruits.

MATERIALS AND METHODS

Samples

The raw material was raspberry ( Rubus ideaus L.), strawberry (Fragaria

ananassa Duch.) and bilberry (Vaccinum myrtillus). After stemming,

discarding the damaged fruit and cutting the strawberries into halves, theberries were divided into two groups. The first group was dried using tradi-tional air-drying at a temperature of 40C (raspberry and strawberry for 48 h,bilberry for 72 h). The second group was frozen to a temperature of -23C andthen freeze-dried in an OE-950 lyophilizer (Labor MIM, Budapest, Hungary)at a plate temperature of 35C for 24 h (strawberries, raspberries) and 36 h(bilberries). After drying, the fruit was packed into glass jars and stored for10 months at room temperature in a light-free environment. The analysis wasconducted on fresh fruit, 24 h after drying, and every 2 months during storage.

Methods

Extraction. Material extraction was conducted using acidified methanol(methanol: 2% HCl 95:5 v/v) (Benvenuti et al. 2004). The extractant wasadded to the dry material and left for 20 min. The samples were then homog-enized, stirred with a mechanical stirrer for 5 min and centrifuged for 15 minat 4,000¥ g. The residue then underwent the same procedure twice more.Finally, a 10% extract of the material was obtained (per weight of fresh rawmaterial), which underwent further investigation.

Determination of Total Phenolic Content. Total phenolic content wasdetermined according to the methodology developed by Singleton and Rossi

13QUALITY AND ANTIOXIDANT ACTIVITY OF SOME BERRIES



(1965) using the Folin–Ciocalteau reagent. Sample extracts (0.5 mL, threereplicates) were mixed with 2.5 mL of Follin–Ciocalteau reagent and 5 mLsodium carbonate solution (75 g/L). The mixture was brought to 50 mL withdistilled water and allowed to stand for 2 h at room temperature before theabsorbance was measured. This procedure is described in Benvenuti et al.

(2004). The measurements were conducted at a wavelength of 750 nm with aCecil CE 9500 spectrophotometer (Cecil Instruments, Cambridge, England).The result was expressed as gallic acid equivalents in mg/100 g fresh weight,on the basis of the calibration curve that had been constructed earlier for gallicacid.

Determination of Total Anthocyanins and Anthocyanins Degradation

Index. Total anthocyanin content was determined according to the method-ology described by Giusti and Wrolstad (2001). The extracts were appropri-ately diluted to 100 mL volume with two buffers, pH 1.0 (0.025 M potassiumchloride) and pH 4.5 (0.4 M sodium acetate). After 20 min incubation at roomtemperature, the absorption was measured at 510 and 700 nm. The anthocya-nin content was calculated using a molar extinction coefficient of cyanidin-3-glucoside of 26,900, a molecular weight of 449.2 and absorbanceA = (A510 - A700)pH 1.0 - (A510 - A700)pH 4.5.

The anthocyanin degradation index (DI) is defined as the ratio of the total(degraded and nondegraded) content of anthocyanins determined with thesingle pH method, divided by the content of nondegraded anthocyanins deter-mined using the pH-differential method. It was calculated on the basis of theabsorbance of the samples diluted with pH 1.0 and 4.5 buffers, DI = ApH1.0 / (ApH 1.0 - ApH 4.5). The anthocyanin DI calculated using this method is usefuleven if the anthocyanins are unidentified, or the extinction coefficients areunknown (Fuleki and Francis 1968).

Determination of the Scavenging Effect on 2,2-diphenyl-

1-picrylhydrazyl (DPPH). Antioxidant activity was measured by the colori-metric method, using DPPH free radical in accordance with the proceduredescribed by Brand-Williams et al. (1995). Extracts of different concentrations(0.1 mL) were added to a 3.9 mL methanolic solution of DPPH (0.00236 g/ 100 mL). Absorbances were measured at different time intervals until thereaction reached a plateau at 515 nm against methanol as the blank reference.Antiradical activity was expressed as the amount (in g) of raw material nec-essary to decrease the initial DPPH concentration by 50% (EC50 [g of freshmaterial/g of DPPH]) using the procedure described by Brand-Williams et al.

(1995).




Determination of Dry Matter Content. Dry matter content, necessaryfor calculations, was determined using a vacuum dryer in the presence of adehydrating agent at a temperature of 70C, drying the samples to a constantmass.

Statistical AnalysisExperiments were performed in triplicate and results were expressed as

mean Ϯ standard deviation (SD). SD and correlation coefficient were calcu-lated using CSS Statistica software (StatSoft, Tulsa, OK).

RESULTS AND DISCUSSION

The total polyphenolic (Fig. 1) and anthocyanin (Fig. 2) content of theanalyzed fruit were approximated to the content indicated in the literature,respectively: (1) bilberry 525–905 and 280–300 mg/100 g fresh weight; (2)raspberry 113–228 and 28–96 mg/100 g fresh weight; and (3) strawberry 230–530 and 8–14 mg/100 g fresh weight (Prior et al. 1998; de Ancos et al.

0

50

100

150

200

250

300

350

400450

500

raw

material

0 2 4 6 8 10

Time of storage (months)

P o l y p h e n o l s ( m g / 1 0 0 g )

0

100

200

300

400

500

600

700

800

900

P o l y p h e n o l s o f b i l b e r r y

( m g / 1 0 0 g )

strawberry strawberry fd

raspberry raspberry fdbilberry bilberry fd

FIG. 1. POLYPHENOLS CONTENT IN RAW MATERIAL AND IN DRIED

CONVENTIONALLY AND FREEZE-DRIED (fd) PRODUCTS AS GALLICACID EQUIVALENT




2000a,b; Proteggente et al. 2002; Faria et al. 2005; Rababach et al. 2005).Air-drying caused different percentage losses in the analyzed components of the various fruits. The relatively large decrease in the polyphenol and antho-cyanin content of bilberries may have been due to the relatively long dryingperiod (72 h), causing a naturally occurring waxy layer on the fruits. More-over, the degradation of anthocyanins depends, among other factors, onpolyphenol oxidase activity, organic acid content, sugar concentration, pH andthe content of more reactive anthocyanins, e.g., cyaniding-3-glucoside (deAncos et al. 2000b).

Lyophilization either slightly lowered the total polyphenolic (Fig. 1) andanthocyanin (Fig. 2) content, or slightly increased it, depending on the species.This slight increase could have resulted from improved extraction of thelyophilized material. Kwok et al. (2004), comparing the effects of freeze-drying and air-drying on serviceberry fruit, found considerably greater lossesof the abovementioned compounds in air-dried fruit.

During the storage of air-dried fruit, total polyphenolic content fell dra-matically, with the largest percentage decrease in bilberries. There was asimilar fall in anthocyanin content. The changes in the anthocyanin DI (Fig. 3),

0

10

20

30

40

50

60

70

raw

material

0 2 4 6 8 10


A n t h o c y a n i n s ( m g / 1 0 0 g )

0

50

100

150

200

250

300

A n t h o c y a n i n s o f b i l b e r r y

( m g / 1 0 0 g )


raspberry raspberry fd

bilberry bilberry fd

FIG. 2. ANTHOCYANINS CONTENT IN RAW MATERIAL AND IN DRIEDCONVENTIONALLY AND FREEZE-DRIED (fd) PRODUCTS ASCYANIDIN-3-GLUCOSIDE EQUIVALENT




which indicates the proportion of degraded anthocyanins in the sample, weremost significant for raspberries. According to Fuleki and Francis (1968), theDI is a better indicator of sample color than anthocyanin content. It is possibleto establish an index limit beyond which the degradation becomes so notice-able or so significant that the product should be disqualified. The values of thisindicator for fresh raw material were also highest in the case of raspberries. Inlight of these changes, the analysis of EC50 (Fig. 4) changes brought aboutsome surprising results. The value of this parameter increased considerably forstored dried strawberries and raspberries; however, despite very large losses inpolyphenols, there was a relatively insignificant (less than twofold) increase inthe EC50 value of stored bilberries.

The storage of lyophilisates resulted in considerably smaller losses inpolyphenols compared with traditionally dried fruits (Fig. 1), especially in thecase of bilberries and raspberries. Anthocyanins were also very well preserved(Fig. 2). No anthocyanin loss was observed in strawberries. In raspberries, theloss was slight, while in bilberries it was 50%. There was also very littlechange in the anthocyanin DI during the storage of lyophilisates (Fig. 3).Garzón and Wrolstad (2001) indicate that the chemical structure of anthocya-nins (e.g., glycosylation and acylation by different sugars and acids) is

1,0

1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

raw

material

0 2 4 6 8 10


A n

t h o c y a n i n s d e g r a d a t i o n i n d e x

.




FIG. 3. ANTHOCYANINS DEGRADATION INDEX IN RAW MATERIAL AND IN DRIEDCONVENTIONALLY AND FREEZE-DRIED (fd) PRODUCTS




believed to be a major factor affecting their stability. In their experiments, theyalso found a direct relationship between increasing water activity and theanthocyanin degradation rate.

During the 10-month storage of the freeze-dried products, the EC50increased only slightly, and in bilberries, despite this fruit showing the largestlosses in polyphenols and anthocyanins, it hardly changed (Fig. 4). Someauthors have observed a strong correlation between antioxidant properties, andphenolic ( R = 0.83– R = 0.95) or anthocyanin content ( R = 0.77– R = 0.92), butthis has been reported mainly for the raw material (Prior et al. 1998; Kalt et al.

1999; Kalt et al. 2000). The present work investigated the correlation coeffi-cients for processed and stored products. For air-dried berries, a strong inversecorrelation was found between the EC50 and phenolic or anthocyanin content(from -0.86 to -0.95 phenolic; from -0.72 to -0.87 anthocyanins). This wasnot so clear in the case of lyophilisates. Among freeze-dried products, asimilarly strong correlation was found only for bilberries (-0.83 and -0.90),while no correlation was observed for strawberries and raspberries.

Mastrocola et al. (1997) noticed that partially processed fruits are notreadily available to the food industry for desired end uses; despite the high costof obtaining them, lyophilisates can satisfy these specific needs. Moreover,products dehydrated in this way are commonly used in most Asian countries as

0

10

20

30

40

50

60

70

raw

material

0 2 4 6 8 10


E C 5 0 ( g f w / g D P P H )




FIG. 4. EC50 VALUE FOR RAW MATERIAL AND DRIED CONVENTIONALLY ANDFREEZE-DRIED (fd) PRODUCTS




ingredients in soups and are usually included in products such as instantnoodles (Nindo et al. 2003). It is widely accepted that freeze-drying is the bestdehydration method for preserving product quality (George and Datta 2002).The results of the present study indicate that, even after long-term storage,freeze-dried products retain the antioxidant properties found in the raw mate-rial to a very high degree despite being exposed to atmospheric oxygen.

CONCLUSIONS

Sublimation drying was far more effective in preserving valuable foodcompounds than traditional air-drying. Stored lyophilisates of fruits main-tained the properties of the raw material much better than air-dried products, inspite of exposure to atmospheric oxygen. There were considerable differencesbetween the three species examined in maintaining total polyphenolic content,total anthocyanin content and antioxidant properties. The highest percentagelosses of polyphenols and anthocyanins were found in stored bilberries, withvery little accompanying change in antioxidant potential. Air-dried strawber-ries and raspberries showed reduced antioxidant properties after storage

despite relatively high levels of polyphenols and anthocyanins.

REFERENCES

AZIZ, R.M., NINES, R., RODRIGO, K., HARRIS, K., HUDSON, T.,GUPTA, A., MORSE, M., CARLTON, P. and STONER, G.D. 2002. Theeffect of freeze-dried blueberries on n-nitrosomethylbenzylamine tumori-genesis in the rat esophagus. Pharm. Biol. 40(Suppl.), 43–49.

BENVENUTI, S., PELLATI, F., MELEGARI, M. and BERTELLI, D. 2004.Polyphenols, anthocyanins, ascorbic acid, and radical scavenging activityof Rubus, Ribes, and Aronia. J. Food Sci. 69, 164–168.

BRAND-WILLIAMS, W., CUVELIER, M.G. and BERSET, C. 1995. Use of a free radical method to evaluate antioxidant activity. Lebens. Wiss.Technol. 28, 25–30.

DE ANCOS, B., GONZÁLEZ, E.M. and CANO, M.P. 2000a. Ellagic acid,vitamin C, and total phenolic contents and radical scavenging capacityaffected by freezing and frozen storage in raspberry fruit. J. Agr. FoodChem. 48, 4565–4570.

DE ANCOS, B., IBAÑEZ, E., REGLERO, G. and CANO, M.P. 2000b. Frozenstorage effects on anthocyanins and volatile compounds of raspberryfruit. J. Agr. Food Chem. 48, 873–879.




FARIA, A., OLIVEIRA, J., NEVES, P., GAMEIRO, P., SANTOS-BUELGA,C., DE FREITAS, V. and MATEUS, N. 2005. Antioxidant properties of prepared blueberry (Vaccinium myrtillus) extracts. J. Agr. Food Chem.53, 6896–6902.

FULEKI, T. and FRANCIS, F.J. 1968. Quantitative methods for anthocyanins.Determination of total anthocyanins and degradation index for cranberry juice. J. Food Sci. 33, 78–83.

GARZÓN, G.A. and WROLSTAD, R.E. 2001. The stability of pelargonidin-based anthocyanins at varying water activity. Food Chem. 75, 185–196.

GEORGE, J.P. and DATTA, A.K. 2002. Development and validation of heatand mass transfer models for freeze-drying of vegetable slices. J. FoodEng. 52, 89–93.

GIUSTI, M.M. and WROLSTAD, R.G. 2001. Characterisation and measure-ment of anthocyanins by UV – visible spectroscopy. In Current Protocols

in Food Analytical Chemistry, (R.E. Wrolstad and S.J. Schwartz, eds.) pp.F1.2.1–F1.2.13, John Wiley and Sons, New York, NY.

HALVORSEN, B.L., HOLTE, K., MYHRSTAD, M.C.W., BARIKMO, I.,HVATTUM, E., REMBERG, S.F., WOLD, A.B., HAFFNER, K.,BAUGERØD, H., ANDERSEN L.F., et al. 2002. Systematic screening of total antioxidants in dietary plants. J. Nutr. 132, 461–471.

HANNUM, S.M. 2004. Potential impact of strawberries on human health: Areview of the science. Crit. Rev. Food Sci. 44, 1–17.

JOSEPH, J.A., DENISOVA, N.A., ARENDASH, G., GORDON, M.,DIAMOND, D., SHUKITT-HALE, B. and MORGAN, D. 2003. Blue-berry supplementation enhances signaling and prevents behavioral defi-cits in an Alzheimer disease model. Nutr. Neurosci. 6 , 153–162.

KALT, W. and MCDONALD, J.E. and DONNER, H. 2000. Anthocyanins,phenolics, and antioxidant capacity of processed lowbush blueberry prod-ucts. J. Food Sci. 65, 390–393.

KALT, W., FORNEY, C.H.F., MARTIN, A. and PRIOR, R.L. 1999. Antioxi-dant capacity, vitamin C, phenolics, and anthocyanins after fresh storageof small fruits. J. Agr. Food Chem. 47 , 4638–4644.

KWOK, B.H.L., HU, C., DURANCE, T. and KITTS, D.D. 2004. Dehydrationtechniques affect phytochemical contents and free radical scavengingactivities of Saskatoon berries ( Amelanchier alnifolia Nutt.). J. Food Sci.69, 122–126.

MASTROCOLA, D., DALLA ROSA, M. and MASSINI, R. 1997. Freeze-dried strawberries rehydrated in sugar solutions: Mass transfersand characteristics of final products. Food Res. Intern. 30, 359–364.

MATCHETT, M.D., MAC KINNON, S.L., SWEENEY, M.I.,GOTTSCHALL-PASS, K.T. and HURTA, R.A.R. 2005. Blueberry fla-




vonoids inhibit matrix metalloproteinase activity in DU145 human pros-tate cancer cells. Biochem. Cell Biol. 83, 637–643.

MORAZZONI, P. and BOMBARDELLI, E. 1996. Vaccinium myrtillus L.Fitoterapia LXVII , 3–29.

MURRAY, M.T. 1997. Bilberry (Vaccinium myrtillus). Am. J. Nat. Med. 4,18–22.

NINDO, C.I., SUN, T., WANG, S.W., TANG, J. and POWERS, J.R. 2003.Evaluation of drying technologies for retention of physical quality andantioxidants in asparagus ( Asparagus officinalis, L.). Lebensm. Wiss.Technol. 36 , 507–516.

PRIOR, R.L., CAO, G., MARTIN, A., SOFIC, E., MCEWEN, J., O’BRIEN,C.H., LISCHNER, N., EHLENFELDT, M., KALT, W., KREWER, G.,et al. 1998. Antioxidant capacity as influenced by total phenolic andanthocyanin content, maturity, and variety of Vaccinium species. J. Agr.Food Chem. 46 , 2686–2693.

PROTEGGENTE, A.R., SEKHER PANNALA, A., PAGANGA, G., VANBUREN, L., WAGNER, E., WISEMAN, S., VAN DE PUT, F.,DACOMBE, C. and RICE-EVANS, C.A. 2002. The antioxidant activityof regularly consumed fruit and vegetables reflects their phenolic andvitamin C composition. Free Radical Res. 36 , 217–233.

RABABACH, T.M., EREIFEJ, K.I. and HOWARD, L. 2005. Effect of ascor-bic acid and dehydration on concentration of total phenolics, antioxidantcapacity, anthocyanins, and color in fruits. J. Agr. Food Chem. 53, 4444–4447.

ROY, S., KHANNA, S., ALESSIO, H.M., VIDER, J., BAGCHI, D.,BAGCHI, M. and SEN, C.H.K. 2002. Anti-angiogenic property of edibleberries. Free Radic. Res. 36 , 1023–1031.

SINGLETON, V.L. and ROSSI, J.A. 1965. Colorimetry of total phenolics withphosphomolybdic-phosphotungstic acid reagents. Am. J. Enol. Viticult.16 , 144–158.

TANG, Y.C. and CHEN, B.H. 2000. Pigment change of freeze-dried caro-tenoid powder during storage. Food Chem. 69, 11–17.

UDDIN, M.S., HAWLANDER, M.N.A., DING, L.U.O. and MUJUMDAR,A.S. 2002. Degradation of ascorbic acid in dried guava during storage. J.Food Eng. 51, 21–26.

YEN, Y.-H., SHIH, C.-H. and CHANG, C.-H. 2008. Effect of adding ascorbicacid and glucose on the antioxidative properties during storage of driedcarrot. Food Chem. 107 , 265–272.


the effect of air-drying, freeze-drying and storage

Documents