r -

ELSEVIER Food ChemiHry 67 (1999) 389-397

Food Chemistry

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A comparison between Helianthus annuus and Eucalyptus lanceolatus honey

Parminder Kaur Bath, Narpinder Singh* Deparmeni of Food Saetee and Technology. Gurú Nanak Dev Unitemiy. Amritsar-14) 005. India

Received 15 March 1999. acceplcd 25 Maich 1999

AbstracI

A comparison between physico-cbemical. enzymatic activiucs artd rheological propcrües of Helianthus annuus and Eucalyptus lanceolatus honey was made. Eucalyptus lanceolatus honcy showed higher prolein. diastase and calalase activity than Helianthus annuus honey, while proline, conductivily. total acidity. free acids and laclonc contení were higher in Helianthus annuus honey Consistency coemcienl and activation energy for flow were lower for Helianthus annuus than Eucalyptus lanceolatus honey. Con-firmaiion of monofloral origin of honcy types was accomplished through microscopio examinalion. The erTects. of convectivo and microwave healing on hydroxymelhylfurfural (HMF) formation in both honey types were also investigated Total acidity. free ucids and lactone contení increased in both honcy types during healing H M F formation vaned linearly with tempersture ind lime of hcating in both honcy types. Microwave healing of both honcy types also caused an increase in H M F formation. Effecl of slorage of honey, healed under duTcrenl conditions, on H M F contení was also investigaled, Stttisücal analysis revealed ihat slorage duntlion liad Uic greaicsi eflect on H M F formaüon. folk>wed by healing durauon and bcaimg temperalurc. in Helianthus annuus honey. while healing duraiion showed the mosl pronounced efTect. followcd by healing temperatura and durauon, in Eucalyptus lanceolatus boney. © 1999 Elsevier Science Ltd. All rights reserved.

Keyworas: Honey; Composiüon; Healing; Microwave healing, Hydroxymelhylfurfural; Slorage

I. Introduction

The physico-chemical propertics of honcy produced in difTcrent gcographical localions have been rcporled by severa 1 rcscarchcrs (Langridge, 1977; Maieos-Ncvado, Sacnz De La Maza & Mateos-Nevado. 1994; Siddiqui, 1970; Singh & Bath, 1997). Somc of Ihc pop­ular types of honey available in India are of monofloral origin, which inelude Trifolium spp, Helianthus annuus, Eucalyptus lanceolatus, and Brassica júncea. The com ;

position and properttes of honcy vary with the floral sources utilized by the honey-bees, as wcll as regional and climatic conditions (Abu-Tarboush. Al-Kahiani & El-Sarragc, 1993; Perez-Arquilluc. Conchello, Arino, Juan & Herrcsa. 1994; Salinas. Montero De Espinosa. Osorio & Lozano, 1994). Hcating of honey is an essen-tial step during processing lo prevent granulation and fermentation (Singh, Singh, Bawa & Sckhon, 1988). Healing of honey resulis in hydroxymelhylfurfural (HMF) formaüon. The temperalurc and duraiion of hcating musí be controlled. because any excessive

• Cofresponding aulhor.

amouni of H M F indícales excessive heating and loss of freshness of honey (Isbell, Frush, Wade & Hunier, 1969; Thrasyvoulou, 1986; White, 1978). Temperalurc and duration of healing during processing musí be con­trolled in relation lo the floral so urce from which the honey has been extracted (Singh & Bath, 1997). Higher valúes of H M F also suggesi the possibiliiy ihat the honey has been adulteratcd by invert syrup (Doner. 1977). H M F in honcy has also been rcporled lo depend on slorage icmpcrature and duraiion (Gupla. Kaushik & Joshi. 1992; Papoff. Campus, Floris, Proia & Farris. 1995; Sancho, Muniatgcui. Hudiboro & Sima!, 1992; While, Kushnir & Subcrs, 1964). On Ihc olher hand, Chcrchi, Porcu. Spancdda and Tuberoso (1997) did nol observe significanl changes in H M F , acidity. moisture contení diastase índex in threc types of honey or cven after a sto-rage period of 24 months al referigration and ambicni lemperalure. The objectíves of the present study were lo: (1) compare physico-chemical propcriies of Helian­thus annuus and Eucalyptus lanceolatus honcy, (2) investigate the cffcct of convccüvc and microwave hcat­ing on H M F formaüon in honcy types and (3) study the cfTccl of slorage of honcy types, hcalcd under different conditions. on H M F formation.

0308-8146799/S - aee froni malier © 1999 Elsevier Science Ud All righi» reaerved. PII: S0308-8M6(99)OOI32-6

P.K. Baik. N. Singh IFood Chemuiry 67 f19991 3&9~J97

2. M a l c r i á i s and mclhods

2.1. Collection and preparaUon o/samples

Samples of honcy were coltected lo rcprescnl lwo dií-fercnl sources, viz_ Helianthus annuus and Eucalyptus lan­ceolatus. from ihe 1997 season. Honcy used in the present sludy was npe honey, harvcstcd from hives, which were located in the arcas wherc Helianthus annuus and Euca­lyptus lanceolatus constitulcd the niajor flora, for the col­lection of néctar. Extraction of honey was carried out by filtration and squcczing the honcy Ihrough muslin cloth and stored in air-tight plástic jar» for further analysis.

2.2. Analysis

*Brix was dclenmncd using an Abbemal Digital Automatic Refractometer (Dr. Wolfgang Kerochen G M B H , Scelzc, Gcrmany). Refractive Índices of honey lypei were measured using an Abbemal Refractomctcr al 20DC and corresponding moislurc contení (%) was calculatcd using ihc relationship between refractive índex and water contení (AOAC, 1990). Colour was determined al 420 nm using a Specironic-20D (Millón Roy. USA) añer diiuling S g honey lo 20 mi with dis-tilled water. Total acidity, pH. free fatty add, lactonc and proline conients were mcasured in fresh boney sampics using A O A C mclhods (Hdrtch, 1990). Changa in pH. total acidity, free aads and lactonc contents in honey sampics beated at 80"C for I h were also mcasured. To determine conductivity, 20 g of cach honey sample was dissolved in 100 mi of distilled water and conductivity (mhos) was measured using a digital conductivity meter, model NDC-732 (NAINA Electronics, Chandigarh).

2J. Pollen morphology

For floral idcmiincation of honey samples, 5 g of diluted honey sample was centnfuged at 10.000 rpm for 15 min to sepárate the pollcns. Samples of separated pollen grains were spread with the help of a brush on a slidc containing a drop of lactophenol. The slides were examined microscópica!ly at 45 x using a brighi-held microficopc (Olympus, Tokyo).

2.4. Protein. diastase and cal alase activity

Proian contení of honey was determined by the Lowry method (Lowry. Rotebrough. Farr & Randall. 1951). Diastatic number was determined using the A O A C method (Helrich. 1990). Catatase activity of honey sampics was determined following the method of Luck (1965), with minor modifications. Phosphate buf-fer (110 mM) of pH 7 was made by mixing equal parís or KHjPO* (1.496 g/100 mi) and K 2 H P 0 4 (1-914 g/100 mi). H¿>2 (6.5 mi) of I .25xl0 ' a M was diluted to 25 mi

using phosphate buffer. The reference sample contuincd 1.6 mi H 2 0 ¡ solution plus 400 ul of distilled water. The test samples (2 m!) consisted of 1.6 mi H ; 0 : and dis­tilled waicr-containing honey (50, 100 and 150 ul). A Shimadxu UV-1601 spectrophotomelcr wiih TCC (elec-tronic aulomatk temperalurc control) equilibrated al 37*C with an enzyme kinetics software package was used to monitor the d ce rea se in absorbance at 240 nm after 0, 15, 30,45 and 60 s. Catalasc activity (umol/min) was calculated using the following expression:

Changcinabsorbancc/min • total reaction mixture (2 mi) x dílution factor

Extensión coefTicicnlof HjO- x amountof sample takcn

2J. Conrea i re heating

To sludy the effect of temperature and duraiion of hcating on H M F formation, 5 g of honey was placed in a beaker and heated at 50.60,70 and 80*C for 15. 30,45 and 60 min. immcdiutely cooled to room temperature and analy2cd for H M F contení.

2.6. Microwave healing

Honey samples (5 g) were poured into Tcflon beakers and heated al 70. 140, 210 and 280 W powcr levéis for 30,90, 150,210 and 270 s io a domestic microwave oven (Kelvinator, Modcl*T 23) Afler cach test, the door of the microwave oven was kept open for 5 min lo facil­ítate cooling. The power ouiput of ihc magnetron of the microwave oven, specifted by the manufacturer, was 700 W and the operaling frequeney was 2450 MHz. The dclerminalion of H M F was carried oui using A O A C mclhods (Helrich, 1990).

2.7. Rheological properttes

Rheological properties of honcy samples were measured using a Brookficld viscometer (Brookñcld Engineenng Inc., Model DV-II) as described earlicr (Singh k Bath, 1997)

2.8. Slorage

Honey samples (200 g) were heated at 50. 60. 70. and 80*C for 15, 30. 45 and 60 min in a waicrbath. cooled, sealed in air-tight glass conlainers and stored at room temperature. After 1, 2 and 3 montbs of storage, sam­pics were analyzed for H M F contcnt.

2.9. Stalistical analysis

The dala reported are nverages of triplícate observa-tions. The data were Bubjected to slatístical analysis using Minítób statislícal software (Slate College. PA).

f>.K tkiil. /V Smzh ¡ Food Chemuiry 67 fl999) i&> 397 m

3. Resalís and dbcusaoa

3.1. Composition

Moisture cootenls of honey types diñered sig* niñcantly, which mainty depends on the harvest season and degrec of maturity in the hivc (Pérez-Arqui lie et al., 1994). Honey samples with high moisture contents are more prone to fermenta!ion. so it is an importan: para* meter, when consider.ng the shelf Ufe of honey during storage (Sanz, Gradillas, Jimeno, Pérez & Juan. 1995). Moisture contents from 16 to 18% indícate a proper degrec of maturity, and stern from ihc current use of modern hives by beckeepers. Helianthus annuus honey had moisture, Bnx and prolme contení of 19.5%, 77.9 and 19.3 mg/100 g, rcspectively against 16.5%, 81 and 30.4 mg/lOOg, rcspectively in Eucalyptus lanceolatus honey. Lunigo. Ciurlo. BaUetto, Novan and Malerba (1993) reportcd a prolme contení from 19.55 to 65.3 mgy 100 g (mean valué 36.3 mg/100 g) for honcy samples imported from Argentina. Helianthus annuus honcy had a darker colour than Eucalyptus lanceolatus honey. as indicated by its higher opucal density (OD) mcasured at 420 nm (Table 1). The colour of honcy is an indicator of its mineral contení, the higher the mineral conient, the darker would be the colour and vice versa (Perez-Arquille et al. 1994). Total acidity, free ackb and lac­tonc contents of Helianthus annuus honey were higher than Eucalyptus lanceolatus honey. Heating of both honey types at 80°C for 1 h resuited in an increase in total acidity. free acids and lactonc contents and decrease in pH (Table 2). Honey obtained during the spnng flowcnng season. i.e. Fcbruary-Junc, is often more acidic than in the auiumn season. when it usually

contains more honeydcw (Pérez-Arqui lie et al.. 1994). Similar effeets of hcating honey on total acidity, free acids and lactonc contents have been reponed earlicr (García el al., 1997) The preaence of organic aads. particularly gluconic aad in equilibrium with lactones or estos, and morganic lons, such as phosphate and chloride, contribute to the acidity of honey (Echigo & Takcnaka, 1974). Conductivity valúes of Helianthus annuus and Eucalyptus lanceolatus honey were 1455 x 10 and 545x10 mhos, rcspectively. Vahations in con­ductivity valúes of the honcy types may be attnbutcd to the variation in conccntraiion of inorganic salts. Henee. Eucalyptus lanceolatus honey is less iomc than Helian­thus annuus honcy. The conductivity of honey depends. m addition to minerals, on organic acids, prolein, com-plcted sugars and polyols (Crane, 1975).

3J. Protein contení and enzymatic activities

Protcin contení, diastatic number and cal a lase activ­ity of Eucalyptus lanceolatus were found lo be higher Lhan Helianthus annuus honey (Table 3}. Protein con­tents of Helianthus annuus and Eucalyptus lanceolatus honey were 0.036 and 0.6%, rcspectively. This variation may be tiitributcd lo the lypc of flora. Protein contení of honey from flowers of Tilia, Ziiiphus jujuba. Robinia. Litchi, Astragalus stnicus, Codonopsis. Sesame. and cotton plañís has been reportcd to vary bctween 0.048 and 0.42%, with the highest valué in honcy from Tilia flowers and the lowcst in Robinia flowers (Pcng & Pan, 1994). Eucalyptus lanceolatus honcy showed higher dia­stase and catalase adliviües than Helumthus annuus honcy. Schcparlz (1966a) described a direct correlation betwccn catatase and diastase activity. Pollens have

Table I Pbytico<hernicaJ properties of booey types*

Type M Matura (%>* •Bm* C o W Prolme (mg/100 gj*

Hehmitm « a u a l*.SbstOM T1Ja±04 0611a i 0006 19 3a S0.0I Emmtnuui lamroiaiMj 16.5a * 025 ai obs i o* 0.683b* 0.010 3046*032

Valúa wiUi nnulai tallen do noi dtffec tigiúAcanily \j> • 0.( '•. Higher ranked taller» are ugruficanily differenl fiotn lower ranked letten in Ihc following fonn h > a.

Tabk2 Chemica! eharacteriilioi of honey lypc**

Type PH' Free acsdil» imeqtksjí' Laaone • meo.le* Total aadHy (meq \gr

Helumttm mmtB 367 30c± 14 40c* I . » 70c, | 4

lleho-ihu gMftta* 324 40d±2.4 40d*I.O 824*14 Eutalrpim loiKeoloiui 4 48 I5a±0.8 3 3 a ± 0 4 48a* 12 Enea!roiia kmceoiomr* 4 13 25b ¿0.15 35b*0.S 60b» 16

• Vahío wilh aína bu íeitrr» do DO< dificr Bgnin¿anir> (/ < 0.05). • Healed al 80*C for I h. ' Higher ranked leiicrs are agnihcantly difíereni from lower ranked taller» in ihc fohovnng form d >e>b>a.

392 P.K. Bath. N. Singh ¡ Food Chemutry 67 (1999) 389-39?

been reportcd lo be ihe main source of catalasc (Sche-partz, 1966b). whik Vansell and Freeborn (1929) and Lolhrop and Paine (1931) asscrt thal diaslasc in honcy mainly comes from ihe bce. pollcns and ihc néctar. High activity of catalase in Helianthus annuus honey may be attributcd lo the type of flora.

3J, Pollen morphology

Pollen grains of Helianthus annuus honey were char-actcrizcd by a thick, coarsely granular cxine. bcaring sharp conical spincs (Fig. 1). whíle pollen from Euca­lyptus lanceolatus honey (Fig. 2) had a smooth form,

exinc without spincs or flccks or other decorations. tri­angular in oullinc and with three promincnl germ pores (Wodchouse. 1965).

3.4. Heating

Helianthus annuus honcy showed an initial H M F contení of 4.45 mg/100 g against 1.23 mg/100 g for Eucalyptus lanceolatus honey. Thesc valúes are higher than thosc reponed previously (Doner. 1977; Lungo el al.. 1993). Honey produced in subtropical climates has been reponed to have higher H M F contení (LaGrangc and Sandcrs, 1988). Healing at 70°C for 60 min resullcd

Tnble 3 Piolein and enzyme activity of honcy lypes"

Type Protón (mg/l00g/ Diaitatk number* Caula.-* (uinol/inin)k

lltlianihtu annuut 36a* 0.30 31.4. ±0.32 IS8a*4.0 Eucalyptus lanceolatus 60b* 1.6 42.9b* 0.73 366b* 5.0

* Valúes wiib similar letiers do nol difTcr signi&cantly (j>< 0.05). * Higher ranked letiers are tignificanlly differcnl from lower ranked leiters in ihc following form b>a.

O

•y ta» lh>

Fifi. 1 Pollen» wnarated from Helianthus annuus honey al (a) 10* and (b) 45x under lighi miaoscope

rtH

Fíg. 2. Pollen» separaied from Eucalyptus Umciolaius honey as seen al (a) lOx and (b) 4Sx under lighi microvcopc

P.K. Baih. N. Singh / Food Chantar, 67 {1999) 3S9-S9? 393

Tabk 4 Table 5 Analysis of vi nance ofdaia shown in Figs. 3 and 4 Rcgrcasion analysis for HMF formation in honey types

Type So urce DF MS F-vmlue» Type Temperature Regres-uon & rQ equalion*

Htlianihus Temperature 3 624 547.8— rQ equalion*

annuui Heating duraikin 3 31.28 2743— Helionihut annuui 50 r-A.uixo.or7x 0.982 Tempcraturexheating duration 9 0.142 12.45-w 60 Y -4.186 «0.044X 0.929 Error 32 0.0114 70 Y -5.420 xO.036* 0.986 Toml 47 80 K - 7 475x0039r 0.912

tjxalyptia Temperature 3 9.13 3 0 8 8 » . Eucalypim ianctolaim 50 Y -0.996 *0.036* 0.935 lanceolalui Heating duraiion 3 14.30 4 8 3 9 . » 60 Y -4.186x0 023* 0.922

Temperaturexheaung duraiion 9 1.62 5 4 8 . » 70 Y-5.420 * 0.026* 0.870 Error 32 0.003 80 r-745x0099* 0.982 Toul 47

Y. HMF<mg/IQ0g); * , healing duraiion (minutes) ' « V < 0 . 0 0 5

in an increase in H M F formation from 4.45 lo 7.66 mg/ 100 g. in Helianthus annuus honcy and from 1.23 to 3.1 mg/100 g under similar conditions in Eucalyptus lan­ceolatus honcy. The effeets of heating temperalurc and duraiion on H M F formation in Helianthus annuus and Eucalyptus lanceolatus honey are shown in Figs. 3 and 4. The higher rale of H M F formation in Helianthus annuus honcy may be attríbutcd to its lowcr pH. It has aiready been reportcd that honeys with low pH valué produce more H M F on heating (Hase, Suzuki, Odatc & Suzuki, 1973; Singh & Bath, 1997, 1998). The siaiistical analysis showed significan! effeets of temperature and duration of heating on H M F formation in both honey types (Table 4). Howevcr, temperalure showed a grcater effect on H M F formation in both honcy types. The interac-tion effect of temperature and duration of heating, on H M F formation, was also highly significant. The regression models for the formation of H M F as a func-tion of temperature and duration of heating showed a linear rclationship with R 3 valué in the range of 0.91-0.98 in Helianthus annuus and 0.86-0.98 in Eucalyptus lanceolatus honey (Table 5).

Ghazali, Tan and Hashim (1989) reponed that microwave heating could be used (in small-scalc industries)

for preventing deterioration of honey. They did not observe any signiñeant changes in pH, total acidity, ash, glucosc, fructose and sucrose contents of honcy during microwave heating. Thesc authors did not repon the effect of microwave hcating on H M F formation. The effeets of heating the honey types in a microwave oven al differcnl power levéis and durations are reponed in Table 6. H M F content increased with increase in ihc microwave power levéis and duration of heating in both the honey types (Figs. 5 and 6). The statistical analysis, shown in Table 7, rcvealed that power levéis had a greater effect on H M F formation, in both the honcy types, than duration of hcating. The variation in H M F formation during microwave heating may be altributed to differences in dielcctríc constan! and loss factors of the honey types. The differences in thesc propenics may be due to differences in composilion of honcy types. The absorpuon of microwavcs by a material has been reponed to depend on its loss factor. The greater the loss factor, the greater the absorplion and faster is the risc in temperature (Hudtara, 1998). Helianthus annuus honcy is more ionic, as indicated by its higher con­ductivity. The ionic or conductivity contribution to the loss factor, can be expressed by the following equa­lion (Buffler, 1992):

15 30 45 60 Heating duration ( minutes)

Fig. 3 Eflcct of healing lemperaiurc and duraiion on HMF forma-lion ín Helianihus annuui honey.

7.5

6.5

15

4 5

3.5

2.5

1.5

Temperalure

50°C 60* — - 7 0 ° C 80°C X -

i * *

15 30 45 60 Heating duration (minutes)

Ra. 4. Effeci of heating temperalure and durauon on HMF forma­tion in Lucalypiui ¡anctotatui honey.

394 M Baik S Smgl:

Tabfc6 Effect of nucrowave heating on HMF formaüon

Type Heaünf lune(i)

Power levdi(W)

10 140 210 280 llelwtho amnmu 30 11.19075 1400 13431 17.061

90 12.938 14258 17454 19.452 1 » 13.385 17.461 19.456 20.145 210 16.091 18 038 19 932 22.234 270 16.850 19.10 II oto 25.789

Eueatypiuj lanctuíutui 30 4.775 5.4715 4.7775 5.3742 90 4.903 5.4865 5.9206 6J1I9 150 5.1197 5.6511 6.0927 '• 20M 210 5.6137 5.7559 6.8263 8.4805 270 6.244* 62533 8.5104 í-5478

67 11999, U9-J97

TaNe 7 AnalyM* of vanante of data m Table 6

Type Souice DF MS f-value-

Lucalvpiui laituoiaiui Power leweb 3 1326 678.4--. Time 4 9 57 4 9 0 » .

12 0678 34.7... Error 40 00195 Toul 59

Htlumihm j ' . - - . , • Power eveU 3 123 078 6699 35— Time 4 65 267 3532.61..-Power levett«lime 12 2.378 129 4 5 » . Error 40 0018 Toul 59

• " V < 0 . 0 0 S .

c = °/2*r (i)

whcrc a re presen ts Ihc dircct currcnt conduciiviiy (mhosi,/is the frequeney in Hcrlz and c is permiltivity of free spacc • - 5 x l 0 1 J f/m). Eq. (l)can be wnuen m Ihc following more simple form:

- 1 .80a// (2)

where a and f are in mmhos/cm and Chz (more com-monly used units), respectively.

Thcrefore, ai 2.45 GHz, a syslem wiih greater con­ductivity contributes more to the lo» factor as com­pared to the system with lower conductivity.

3-5. flow behatiour

Consistency coefficient. flow behaviour índex and aclivation energy of flow, for both ihe honcy types, are shown in Table 8. Helianthus annuus honcy had a lower consistency coefficient than Eucalyptus lanceolatus honey. Thesc results are in agrccmcni wiih ihose reponed cartier (Singh & Bath. 1997). Consistency coernaen:

Tabtt 8 Flow behaviour and aaivauort enerjy for flow of honcy type*

Type Temperalure Contiatency Fio* c co coeffiocni behaviour (kcal/mol)

(Til*] •odei

Hrhmtkmamm m 15 1439 0.94 7.90 25 0640 095 35 0430 0.99 45 0O95 1.00 55 0.0313 1.30

kutalyptui 15 5J70 0.93 22.80 lanctoiatut 25 1.981 0.99

35 1.164 0.95 45 0-J94 0.92 55 0.185 090

progrcssivcly decreased with mercase in temperature in both honey types. The effect of lempcrature on con-sisteney coeflicient can be correlated by an Arrhenius-lypc cquaiion:

1 » 0 * e x p ( J W * n (3)

26 -

o I 2lL

Power levéis 70W 140W 210W 280W .y'

30 90 150 210 270 Hcating duration í seeonds)

Fk> 5. Eflect of power leveli and beato* Uoo ir. Hthanthms amaina boney dunnf .

on HMF forma-

8.6

7.6

Power levéis >• 70 W liOW / / 210W - -VM.' /

e> 66 £

U

30 90 150 210 270 Heating durationt seconds)

Fif 6. Eflea of power krvcb and beaüng duration on HMF forma­tion m EMca/rpuu ¡amceaiaha honey donog microwive heaunj

P K Bath. S Stitgh I

Tabk 9 linca of Rorage on HMF (mg/100 gj contení of honcy type»

Temperature ( ' O

Hcaung Stofigc duraooo ( m ) uaac (mon

Hrlumi ka) mmm

•O E*calrpna

50 13 1 11.9 5.30 50 15 2 13.1 5.14 50 15 3 160 505 50 15 1 11.7 (•0(1 50 30 2 150 5.27 50 30 3 154 5.16 50 45 1 12.7 601 50 43 2 154 6-52 50 45 3 15.7 6.84 60 15 1 12.0 5.55 60 15 2 15.5 4.97 60 15 3 15.9 5.23 60 30 1 130 6.14 60 30 2 15.7 64 60 30 3 160 716 60 45 1 13.4 6.97 60 43 2 16.7 7.0 60 45 3 164 7.39 70 15 1 124 4.93 70 15 2 154 30 70 15 3 162 60 70 30 1 142 644 70 30 2 16.1 545 70 30 3 16.7 6.13 70 45 1 166 619 70 45 2 165 6.53 70 43 3 161 6.74 M IS 1 14.3 3.68

• IS 2 15.2 607 80 IS 3 154 6.18 10 30 1 14.7 694 10 30 2 16.6 7.13 B0 30 3 166 7.65 N 45 1 IB.I 7.31 M 45 2 18.0 731 10 45 3 18.0 7.75

whcre n is ihc viscosity. rjoo is a pre-exponential Tactor. £„ is the aclivation encrgy for flow. R is the perfect gas constanl (1.987 cal g m o l - 1 k~') and 7 is the absolule temperature (K). Eq. (1) can be expressed in the loga-ríthmk form in order to estímale the parameter £¡, for both honey types. Scrru-log plots. of consistency coeffi­cient versus inversc of absolute temperature, gave sig-nificant correlation coerncients when plotted using the linear regression analysis. Estimated valúes for Em for both honey types are reponed in Table 8. It was observed that HeUanihus annuus honey had a lower aclivation encrgy for flow than Eucalyptus lanceolatus honey. These differences may be attributed to the diffcr-crices in soluble solids as indtcatcd by BBnx valúes. The results are in accordance with those reponed previously. Giner. Ibarz. Garza and Xhian*Quan (1996) reponed an Ea valué of 14.6 kcal/mol for danfied cherry juice al 74'Brix.

ntstry 67 11999) SS9 J97 J95

Tabk 10 \n»!yw. of vi nance of dala in Table 9 for Helkmthui

Source DF ss P

Temporaturr 3 70.15 1051 0 000 MeaUng duraiion 2 56.22 1251 0.000 Slorage 2 127.45 2836 0.000 Temperature»healing duration 6 12.42 92.12 0.000 Temperature • llora ge 6 24.54 182.06 0.000 Du r a t ion x Horage 4 969 107 83 0 000 Temperature • heating durauon 12 1451 5345 0 000 «Horage Error 72 1417 Total 107 317.33

Tabk II Analyu* of vamnee oí dau m Tabk 9 fot Eucalnnui i T I l l l

Source DF SS avahar p

Temperalure 3 21.52 1569 0.000 Hcating duration 2 3940 4318 0000 Slorage 2 2.28 250 0.000 Tcmperatuie • heating duraiion 6 4.22 153 0.000 Tempera ture • it erige 6 I 15 41 0.000 Hcauag duratKMiKitoragr 4 0.61 33 0000 Temperalure • beaúog durauon 12 525 95 0000 • ttnaji Error 72 0J2 Toul 107 74.90

3.6. Slorage

H M F contents in honcy lypes. stored for 1. 2 and 3 monlhs aflcr heating at 50, 60. 70 and 80°C for differeni durations, were also determined (Table 9). The dala reponed in Table 9 were subjected lo analysis of var­iarlos. This signiñeant efTect of slorage durauon. heaüng temperature and heating durauon on H M F formaüon in both honey types is shown m Ta bies 10 and 11 Slo­rage duration showed the most pronounced cfTcct. fol-lowed by hcating duration and healing temperalure. on H M F contení in Helianthus annuus honcy. while healing duration showed the grealest clfect on H M F formation in Eucalyptus lanceolatus honey. foliowcd by heating temperature and slorage duration. The interacüon erTect of all thrce factors. with cach other. on H M F contení was also signiñeant in both honey types. Heating tem­perature interaelion efTect with slorage duration. in Helianthus annuus. and with heating duraiion. in Euca­lyptus lanceolatus honey, on H M F formaUon, was highly signiñeant. The effeets of storage duration on H M F formation in honey types heated under differcnl conditions are illustralcd in the interacüon plots plotted using Minilab statistical software (Figs. 7-10). The more pronounced efTect of storage duraiion on H M F formation in Helianthus annuus than m Eucalyptus lan­ceolatus honey may be attributed to the composiüonal

396 F.K. Baik. N. Smgh / Food ChenUstry 67 (1999¡ ¡89-397

Temperature 5 0 * — - 6 0 *

Z 1 7 r - - " 7 0 ° C - ~ 8 0 ° C

o* E »

u.

16

15h

Heating duration (minutes)

Fig. 7. Inicraction ploi ahowing effect of temperature and durauon o! hcating OD HMF formaüon in «ored Helianthus annuus honey

16.5-

| , 5 . 5

o. 1A.5

£ 13.5 x

12.5 •

Heating duraron -I5min 30min 65 min

Storage (months)

Fig. 9. InlerBCtioo plot ihowmg erTect of «oragc and hcating duraiion on HMF formaüon in Heliantkus annuus honey.

en o 8 6.5 en E

7 5 - Temperature — 5 0 * ^ - - 6 C * y — ? o * y r

r — 8 0 * ' '

1 5 5

15 30 45 Heating duration (minutes)

Fig. 8. Imeracilon plot inowing effect of temperature and duration of bealing on HMF formation in llored Eucalyptus lanceolatus honey.

7.0 o

§ 6.5

CP . E . 6.0 3 X 5.5

Hea t ing duration 15mln 30mín í.5mln .— "

Storage (months)

Fig. 10. Interacüon plot ahowing effea of storage and heating dura­tion on HMF formation in Eucalvptui lanccolaim honcy.

differences in honey lypes. Hclianihus annuus had higher moisture. free acids and total acidity than Eucalyptus lanceolatus honey. All these constituents have been rcporled to créate favourable conditions for degrada-lion of reducing sugars by promoling cnolizalion (Papoff el al.. 1995; Schadc & Marsh. 1958; Toribio & Lozano, 1987).

4. Conclusión

lanceolatus honey under similar heating and storage conditions.

Acknonled|:eincnts

P.K..B. acknowledges a CSIR Sénior Fcllowship from the Council of Scicntific and Industrial Research. New Dclhi.

Helianthus annuus and Eucalyptus lanceolatus honey diffcr significanüy in their physico-chemical, cnzymatic and rheological properties. The intcnsity of H M F for­mation in both ihc honcy íypcsalso varied significantly. H M F formation in honcy during storage depends on source and healing conditions under which the honey has been processed. Thcreforc. heating conditions, sto­rage duration and source of honcy must be considered together during processing of honcy. Helianthus annuus honey showed greater H M F formation than Eucalyptus

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