the effect of ozone and air on off-odors in beet … documentation/volatile fatty acids/vfas in...

2004 SPRI Conference on Sugar Processing Research

THE EFFECT OF OZONE AND AIR ON OFF-ODORSIN BEET SUGAR

Emmanuel Duffaut 1 , Mary An Godshall' and Casey C. Grimm2

Sugar Processing Research Institute, Inc.New Orleans, Louisiana, USA

2 Southern Regional Research Center, Agriculture Research ServiceU. S. Department of AgricultureNew Orleans, Louisiana, USA

ABSTRACT

This study investigates ozone and air as potential polishing agents for the elimination of offodors periodically found in beet sugars.

Ozone and air were directly circulated through a bed of crystalline sugar to oxidize and/orremove volatile compounds responsible for off-odors. Various experimental parameters, such astreatment time, temperature, pressure and ozone concentration were tested to determine theoptimum conditions for ozone or air action. Volatile off-odor compounds were analyzed using

(SPME-GC-MS). The

effect of ozone and air on the volatile fatty acids (VFA) profile was closely monitored, since ithas been established by SPRI and other researchers that VFA, when present in beet sugar, are asignificant source of off-odors and off-flavors, even at very low levels.

Results showed that air was more efficient than ozone in removing odoriferous compound fromcrystalline beet sugar. At optimal conditions, air removed all compounds to a very large extent,whereas ozone did not and ultimately induced formation of acetic acid. Air treatment is also a

more economical solution.

193


INTRODUCTION

Good sensory quality is of major economical importance in the sugar industry and in the foodindustry in general. Off-odors and off-flavors, even at low levels, greatly affect the perceivedquality of sugar, diminishing its potential utilization by the food industry, leading to a decreasein its selling value or even to rejection by the customer.

Off-odors exuding from white beet sugars can be caused by a wide array of over 50 differentvolatile compounds, such as pyrazines, aldehydes, alcohols, furans, phenolics and carboxylicacids (1). Short chain volatile fatty acids (VFA), in particular, acetic, propanoic, isovaleric andbutanoic acids were found to be off-odor compounds of major importance for they can causeodor and flavor at very low concentrations in crystalline beet sugar (I ,2). Malodorous chemicalsin beet sugars originate from the activity of soil microorganisms or from the beet itself(indigenous or absorbed) or are formed during the manufacturing process (caramelization,Maillard reaction) (1,2,6).

The bulk of the odoriferous organic compounds is located at the surface of the crystals, trappedin a thin film of concentrated syrup surrounding the crystals. Sugar crystals grow insupersaturated syrup, which is removed by centrifugation once the proper crystal size is attained.Most of the syrup is separated from the crystals using water or steam spraying, but a very thinlayer of syrup always remains around the crystals. This surface layer of saturated syrup containsmost of the impurities and water present in the whole crystal, including the volatile odoriferouscompounds (6).

Research on off-odors in white sugar concerns essentially the analytical dimension of theproblem, and great efforts have been made to develop a rapid technique to extract and analyzetrace volatile compounds from crystalline white sugar. GC-MS is the ideal method to identify theoff-odor volatile compounds, and, in spite of some limitations, headspace analysis (3) is the bestway to extract the volatiles from the sugar. SPME (Solid Phase Micro Extraction) offersrapidity, economy, and concentration benefits over simple headspace (4).

SPME utilizes a fiber coated with an adsorbent material that is placed in the headspace of asample for a specific period of time and temperature. During this time, the volatiles in theheadspace are concentrated on the thin film of the fiber. The fiber is subsequently desorbed withheat into a gas chromatograph-mass spectrometer (GC-MS) for sample analysis andidentification of the volatiles (Figure 1).

A recent S.P.R.I. comparative study showed that SPME is a more sensitive extraction techniquefor volatiles in crystalline sugars than headspace (3). SPME had especially high sensitivity forVFA, which are some of the main odoriferous agents (3). SPME GC-MS is an environmentallyfriendly procedure that requires a small amount of sample, uses no solvents, and is accurate,efficient, economical, simple, quick and allows semi-quantitative analysis (5).

194


Solid Phase Micro Extraction

ri 4- Handle

................

Syringe Needle

Fiber

Sample VialSugar Sample

Figure 1. Solid PhaseMicroextraction principle.

It

Very little literature has been published concerning the process side on how to eliminate orattenuate off-odors in white beet sugars. It was reported that partial elimination of malodor wasachieved by ventilation of the beet sugar during bulk storage (6) as well as by air sweep in silos.Various other treatment suggestions included porous absorbent, additional washing in thecentrifuge and treatment with polishing carbon (7). In recent years SPRI had begun to investigatepotential applications of ozone in the sugar industry, looking to the time when ozone might beeconomically viable due to modern ozone generation plants being able to produce ozone cheaply,reliably and in high concentrations, favoring good reaction kinetics (8). Ozone receivedclassification as a GRAS (Generally Recognized as Safe) substance by the U.S. Food and DrugAdministration in 1982, allowing its broad use in the food industry.

It was decided to test ozone as a polishing agent for removal of off-odors in beet sugar. Theprinciple of air sweep or air circulation in silos was used in the experimentation as it seemed tobe the most practical way to apply ozone.

The primary objectives of this study were to determine and optimize the potential action ofozone treatment for off-odor removal in beet sugars, using SPME GC-MS as a qualitativemeasurement system. A parallel study was conducted with air treatment.

EXPERIMENTAL

Ozone was supplied by an electrical generator (120-V, 60-Hz, 0.45-A), which produced 0.45 g/hr

of ozone, using an ambient air supply of 20-SCFH (Standard Cubic Feet per Hour). Duringtreatment, the sugar samples were placed in a vertical double-jacketed glass column connected toa water bath to heat the sugar. The ozone and air streams circulated through the sugar bed fromthe bottom to the top of the column. 50 g of sugar was treated in each experiment. Aftertreatment the sugars were spread on a glass dih for cooling and stored in glass containers.

195

2004 SPRI Conference on Sugar Processing Research -7Five sets of 4 to 7 beet sugars from five different North American locations (A, B, C, D, E) wereused in the experiments. Each sugar was sensory scored by three individuals, looking at a set ofdescriptors. Each sugar was given an over-all sensory rating, based on resolving the sensory datainto three categories: Acc = acceptable; Bor = borderline; Rej = reject.

SPME GC-MS was performed on 5 g samples placed in 10 ml air sealed vials. The vial wasagitated for 15 minutes at 65°C at 100 rpm (10 seconds of agitation separated by 1 secondpauses). The fiber was exposed to the headspace for 15 minutes, with the same agitation andtemperature. GC and MS conditions have been described earlier (3). The fiber was desorbed for2 minutes in the injection port of the gas chromatograph at 270°C. The fiber was regenerated bybaking it in a fiber heater in the presence of a helium purge at 270°C for 1 minute.

RESULTS AND DISCUSSION

All untreated sugars used in this study had similar chromatographic patterns, with two majorgroups of volatile products detected (Figure 2). The first group included short-chain volatile fattyacids of rather low abundance (concentration), with retention times of I to 7 mm. The secondgroup, with longer retention times, was made up of compounds with higher molecular weightand greater abundance, with retention times of 22 to 30 mm. There were only a few intermediatecompounds of significant abundance in between those two groups. (Peaks marked ascontaminant arise from the SPME fiber or the column.)

Abundance

I0-VV leuu 20.00 2200 24.00 26.00 28.00

6500000

6000000

5500000

5000000

4500000

4000000

3500000

3000000

2500000

2000000

1500000

1000000

500000

0

Tim e-'

Figure 2. Sugar D6ACC , no treatment at room temperature (RI), total ion chromatogram (TIC).

196


For better definition, the mass fragment of molecular weight 60 (mlz 60) was used to scanspecifically for VFA and other fatty acids. With the exception of propanoic acid, the base peak ofshort-chain fatty acids is mlz 60 (4). Analysis at ion mlz 60 showed that all the sugars had fourVFA in common: Acetic acid, butanoic acid, 3-methyl butanoic acid (isovaleric acid) andpentanoic acid (valeric acid), as shown in Figure 3.

These fatty acids have strong, characteristic odors (9) and are responsible for some of the majoroff-odors in beet sugar (1). Several sugars (E4BOr, C4Bor and CS BOr) also presented hexanoic acid(9.5 mm) and traces of heptanoic acid, octanoic acid and nonanoic acid (E4 801 and C4or).Hexanoic, heptanoic, octanoic and nonanoic are also odorous agents but less powerful than theVFA (9).

The second group of volatiles was composed mainly of alkanes and compounds of various natureand abundance (Figure 4). They have not been fully identified at the present time.

Effect of Ozone Treatment at Room Temperature.The ozone generator was supplied with air by a pump with a flow-rate of 0.8 liters/min or 3.3SCFH, thus producing 0.074 g ozone/hr. In this experiment, three ozone concentrations weretested at room temperature (20-25 1 C): 240 (10 mm), 480 (20 mm) and 960 (40 mm) ppm (w/w).Only the results at 480 and 960 ppm are discussed because no significant changes were noticedat 240 ppm. Six and beet sugars were treated with 480 ppm ozone: E3 13Or, C7 Bor, E4Bor, CSBor,

C4Bor, D6ACC ; and five were treated with 960 ppm ozone: D3 Bor, CI ACC , B2 Bor, AS RCJ , ElRej.

Treatment with ozone showed definite action on the VFA (Figure 3). Tables 1 and 2 show thedifference between each VFA peak area before and after treatment for each sugar. The generaltrend was that acetic, butanoic, 3-methyl butanoic and pentanoic acids were partially removedfrom the sugar, and hexanoic, heptanoic, octanoic and nonanoic acids were increased or formed.Ozone action increased as ozone dosage was increased.

'l.

etic ac itanoic ac 86.4%Me Butanoic ac 30.6%ntanoic ac 29 8 %

exanoic ac 268 O/

eptanoic ac 61:O%ctanoic ac 71 5onanoic ac 95M

1 FIncreased l Decreased

VFA removal/formatioliC4B0r C5Bor -

14.5% 12.8 %93.1% 92.6% -63.1% 28.4%74.5% 54.3%

E3

66.2%42.5 %22.0%

area).D6ACC51.8%94.4%71.4%36.8%

C78or42.0%85.8%76.5%82.3%

Table I. Ozone 480 ppm RT:E4

197

area).ElRej

44.8%49.5%20.7 %35.6%93:5%Formed

EHI

Decreased }

Untreated @ Room Temp

aj0.2

H00 00

=0.6

200000

20000

150000

100000

600 000 1000 I2HE

.uiji ol corrcctco areas: ii

2000 V® 2400 2000 OIZ

Ozone 960 ppm (40 mm) @ Room Temp

0.10000 0.6

7.

MOM

000000

20000

200000

10

00000

0

um or corrected areas: 6477642

2004 SPRI Conference on Sugar Processing Research'I

m RT: VFA removal/formation (% peASReJ

3̂1

ClA C D3BOT.55.8 %' 11.6 % 24.2 %

50.8 % 89.1 % 86.0 %

20.7 %91.1 % 88.2 %

85.0% 89.1% 64.8%61.8% 44.1%

I 6:4% . 33.8 % 39.9 %Frmed 6.5% 14.2 %

Ii Table 2. Ozone 960

cenc acutanoic ac-Me Butanoic acentanoic ac[exanoic ac[eptanoic acctanoic aconanoic ac

It appeared that ozone removed the highly odoriferous VFA (acetic, 3-methyl butanoic andbutanoic acids) and had formed less odoriferous acids (hexanoic, heptanoic, octanoic andnonanoic acids) through oxidation reactions. However, this was not true for all sugar. Forexample, acetic acid increased in E4BOr, E3 Bor, A5RCJ and El Rej and in quite high proportion forthe last 3 sugars cited (>45%). Additionally, hexanoic and heptanoic acids were formed in CIA,,as well as heptanoic and octanoic acids in D3BOT.

Figure 3. Sugar B280 , ozone treated, 960 ppm at room temperature m/z 60.

Ozone had a marked effect on the compounds of the second group (Figure 4). The primaryobservation was that, with the exception of butyl-butanoate, which increased in a few cases, allof the HMW compounds were well removed and some were completely eliminated (Table 3-4).

198


On the other hand, several new compounds of intermediate molecular weight appeared on thehromatographs with low to moderate abundance. These compounds were very likely ozone

oxidation products created from the HMW compounds, especially the alkanes. The mostsignificant of the newly formed compounds were nonanal and decanal, which are listed in Tables3 and 4. These were common to all the sugars tested. Dodecanal consistently increased withozone treatment or was significantly formed. Dodecanal was detected at very low level in someuntreated sugars and was absent in the others (Tables 3 and 4).

Unlike butyl-butanoate, the three aldehydes (nonanal, decanal, and dodecanal) are powerfulodoriferous agents (9), especially nonanal and decanal, and are likely to cause off-odors in thetreated sugar. Hence, although HMW compounds were substantially decreased or eveneliminated, the ozone action was not satisfactory under these conditions since mild or strongodoriferous agents were newly formed probably due to incomplete oxidation of other compoundsalready present. Despite the presence of new compounds, sensory analysis of treated sugar didnot detect off-odors, probably because they were present in subthreshold concentrations.

9000000

8000000

7000000

6000000

5000000

4000000

3000000

2000000

1000000

01300

Tim>A bun da mm ce

Untreated @ Room Temp

CE

CeLi

14.00 1500 1600 17.00

C

C -LC

C

1800L

40

19,00

I.--

"

20.00 2100 2200

C

tC

9000000 -

8000000 Ozone 960 ppm (40 mm) @ Room Temp7000000

C6000000

5000000

4000000

3000000 cc2000000

1000000

01300 1400 1500 16.00 17.00 18.00 19,00 20.00 21.00 22.00

Tirm'e

Figure 4. Sugar A5ReJ , ozone treated, 960 ppm at room temperature, TIC.

199

iseu onD6ACC

Fömjèd100.0%

Fórñd12.8%

100.0%100.0%65.2%

area).C7Bor:rohièd

52.2%100.0%100%

58.4%

100.0%697% Decreased


Table 3. Ozone 480 ppm @ RT: HMW removal/formationE4 j C4Bor C5Bor E3 orNonanal Formed 'Formed Formed Formed

Decanal 'Forniéd Fthied FohnêdPentadecane 100.0% 100. A0/_ 100.0% 100.0%Butyl butanoate 32.6% 3. 60 0 375% 8 3%Dodecanal.11yumuopecane -[eptafHexadecanePhenolLOctadecane

Table 4. Ozone 960

IonanalThdecanal

j ntadecane -I J tyl butanoate

decanalyclododecane

Heptafflexadeca nePhenolOctadecane

1K area).ElRejriéd. I

fiied1 Li

100.0Frthed 4 LreasTj

68.6% 16.4% 3.2% 59.5%100.0% 100.0% 100.0% 100.0%100% 100% 100% 100%100% 46.4% 64.6% 39.4%

i @ RT: HMW removal/formation (%A5ReI B2Bor CIACC D31.

Fithd •Et j Fd Thid.

100.0 0/0 100.0% 100.0% 100.0%83.7% 34.6% g•4

24.8% 57.8% 65.3% 61.9%567

100.0% 100.0% 100.0% 100.0% 100.0%

100.0% 100.0% 100.0% 100.0% 100.0%

25.0 % 49.3 0/- 74.5 % 49.7% 35.7%

Effect of Heat on Ozone Treatement.In this experiment, the effect of the temperature of sugar during ozone treatment was tested. Thegoal in increasing the temperature of the sugar was to reduce the viscosity of the syrup layersurrounding the crystals to facilitate the mobility of the off-odor compounds to make them moreaccessible to the action of ozone as well as to increase the sweeping action. Sugars 133 BOr, C 1 Acc,132 13or , A5 Rej , El Rej were used, with the same experimental conditions as above, except that,before ozone treatment, the temperature of the sugar was raised to 75-80°C by circulation of hotwater in the column jacket.

Increasing the temperature greatly improved the removal of VFA (Figure 5). As shown in Figure6, all HMW compounds were also eliminated. After treatment with 960 ppm ozone at 75-80°C,all VFA were largely or even totally removed except acetic acid which concentration was at leastdoubled in each sugar (Table 5). This indicates that acetic acid may be the final oxidationproduct of the HMW compounds by ozone. Sensory analysis showed that all the treated sugarswere odor-free after treatment, indicating that the acetic acid was below the sensory detectionthreshold.

200

2004 SPRI Conference on Sugar Processing Research -"ql

Table 5. Ozone 960 p m@ 80°C: VFA removal/formation (% peak area).

A561 I B2or C!ACC D3BOr ElRe1j

69:5% 50;2 % 54:r% .593% ... 51.5%Acetic ac

10.1 % 48.1 % 35.4% 365%crSe

icaC _tanic Ac I 54.4 % 72.1 % 82.3% 64.5% 65.0

19.4% 51.6% 73.9% 43.5% 483%Pentanoic ac

oic ac 22.3% 58.1 % 84.0

Iflentaflolcac 100% 100% 100% 100% 100%

100% I 100% 100%

100% 100% I 100% 100% 100%Nonanoic WC

MW

Untreated Room Temp600202

4

500002U U

400202

0Or

::gr

JL

202 402 602 802 1000

ME

600202 Ozone 960 ppm (40 mm) @ 80 C

500202

400202

320002

200200

1000002 402 1200 1400 16

Figure 5. Sugar C1 ACC , ozone treated, 960 ppm at 80°C, mlz 60.

201

16

. .'

II

I•


AL'un(lanoe

VUntreated@ Room Temp U! =.9

CeC -

. IIU

H'- Cii CJ - Iii UII . U

m&1600 1700 1800 1900 2000

I 6e+07

14e+07 E128+07

1e407

8000000

6000000

4000000

2000000

01300 1400 1500

ALn(la(p

Ozone 960 ppm (40 mm) @ 80 C'9C

C

ACCU

1600 1700 1800

I 6e.07

I 4e+07 El2e.07

C1e407 c)

8000000

6000000

4000000

2000000

1300 1400 1500

Figure 6. Sugar C 'ACC, ozone treated, 960 ppm at 80°C, TIC.

202

2004 spRl Conference on Sugar Processing Research

Air Treatment.onsider1ng that air is the major portion of the ozone stream and since air ventilation is alreadyused in some factories to remove off-odors, the deodorizing effect of air sparging alone wasexamined. One sugar, El containing a wide variety of volatile compounds and rated "borderlineto reject" in sensory quality, was treated with air for 40 mm, both at room temperature and at80°C (Figure 7). There was very little effect at room temperature on the VFA and some decreaseof the compounds at the higher retention times. With elevated temperature, there was asignificant decrease observed in all the volatiles, to the extent that most of them were eliminated,especially VFA (Figure 8) with even acetic acid being largely removed. Unlike ozone at 480

and 960 ppm, no new compounds were formed.

•tl

uted@RomT30MOOD

loom

0 VL 2,0.06.00

Pate

14. 16.03 18.03 23.03

1= Air40Mn9R00MTen1P

loomLL 1Z03 14.03 16.03 18.03 23(X)4 6.03 8.03 10.03

Tre-Pate

rüTe->

500DODO Air 4Onin@8OC403XXX)

I

lcxmX)1Z03 L

LI—^

. 18.03 23(X)06.03 8.00

Figure 7. Sugar El Rej, treated with air at room temperature and 80°C, TIC.

203


Sensory analysis showed that El Rej still had a faint residual off-odor after air treatment.However, air treatment produced a sugar that was no longer in the "reject" category, but veryclose to commercial quality. This may suffice to treat sugars with less odor than ElRej.

AbtiflOaf Ice

450000400000 7

Untreated Room Temp350000300000250000200000150000100300500000 ....

200 4,00 6W &00 - 1800 2000 2200 2400 2600 2800

A r, u Or rice

450000400300 Air 40 mm @80C35030030000025030020030015000010030050000

01_,___,200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800

TrnrerFigure 8. Sugar El Rej , air treated 40 min at 80°C, mlz 60.

These results indicate that ozone and air treatment at elevated temperature (80°C) may holdpromise as deodorizing agents for refined beet sugar. This is a very simple process that couldeasily be installed in a sugar factory. Ozone or air treatment would be most efficient energy-wise if applied to the sugar coming out of the centrifugal in the factory, which is approximately65-70°C, hence saving heating energy. However, the relatively high humidity of the sugarcoming out of the centrifuges may pose a problem. Hence, ozone and air would most likely beapplied batch-wise either at the factory subsequently to the dryer (25-30°C), or by the industrialuser (ambient temperature), as needed. In both cases some heating would be required.

The formation of acetic acid with ozone treatment is a major drawback to its use, for it isunlikely that ozone will have any oxidative effect on acetic acid due to its chemical structure(CH3CO2H). Ozone primarily breaks phenol rings, amines and double bonds in the carbon chain(10), none of which are present in the acetic acid molecule

204 1

Table 6. Ozone 960

Acetic acButanoic ac3-Met ButanoiC acPentafloiC ac

Air 20'80.7%87.5%91.9%90.6%

IVI

t!I.


Effect of Pressure on Air and Ozone Treatments.Additional testing was conducted in order to confirm the results obtained above for both air andozone treatments. Malodorous sugars were treated with an excess of ozone for maximumoxidation. Pressurized air was used instead of the pump in order to increase the generator'sozone production. Although the production rate was not known, for a given amount of sugar, byvarying either the duration of treatment or the inlet pressure and leaving the other one constant, arelationship between the ozone dosage of several experiments could be established. Air speedwas measured through a pressure gauge placed before the sugar bed. Sugar E2, rated "reject" bysensory analysis was treated at 80°C. The amount of sugar (50 g) and the air pressure before thesugar bed (25 in) were kept constant and only the treatment duration time was varied

(20 and 40

mm). Air experiments were realized with the same experimental conditions.

As previously observed, ozone and air treatments thoroughly removed the HMW at either 20 and40 mm. Also, air largely eliminated VFA (>80 %) at 20 mm (Figure 9), and this removal wasonly slightly increased during 40 min treatment. On the other hand, ozone did not have a positiveeffect on VFA as can be seen in Table 6. First, ozone increased the amount of acetic acid at 20mm (>40%) and 40 mm (>55%). Except for 3-methyl butanoic acid, which was well removed atboth dosage rates (>35 %), removal rates for the others VFA were very low at 20 mm (<10 %)and these appeared to be formed at 40 mm.

VFA removal/formation

N

O3 20'_

10.4%41.8%

92.5% 7.3%

Dased on area).

03 40'sed

--711 :A 01

—34.6% 1EEThese results confirmed that air alone has a more thorough action than ozone since air greatlyremoved the VFA whereas an excess of ozone did not and even caused their formation. No off-odors were detected by sensory analysis after treatment with ozone.

205

"3PR1109 0

E2 untreated, RT

8.00 10.00 1200 14,00 16.00 18,00''.,) 'i.c.& b.W

I2004 SPRI Conference on Sugar Processing Research

Abundance

45000040000035000030000025020000015010000050000

0

Tirre- ->Abundance

Ion 6000(5970106030) SPRI110 D()

E2, air 20 1, 25 in, 80 C

20) 4.00 6.00 8.00 10(X) 1200 14'00

Figure 9. Sugar E2RCJ , air treated 20 min at 25 in and 80°C, m/z 60

Effect of Storage on Treated Sugars.As mentioned in earlier discussion, despite the formation of acetic acid, sugars treated withozone had little detectable odors. Acetic acid has a higher sensory threshold than other VFA,which would account for sugars with measurable amounts of acetic acid having little or no odor.Since ozone and air treatment are essentially surface treatments, it is possible that volatilespresent deeper in the syrup layer around the crystal or even inside the crystal may eventuallydiffuse to the surface and again cause the sugar to have an odor. To test this, three beet sugars,A6ACC, B2Bor, B6RCJ , were treated with ozone and air for 40 min at 25 in pressure and at 80°C. 50g of sugar were used in each experiment. After treatment, each sugar was cooled on plasticdishes and then put into clean, oven-dried 250 ml sealed glass containers. Sniff tests wereperformed right after treatment when sugars had cooled and on days 1, 5, 12 and 20.

As shown in Table 7, off-odors became noticeable in the ozone-treated sugar in less than 20days. There was little odor re-appearance on the 201h day in air-treated sugars. This is furtherdemonstrated in Table 8, where air showed much higher percentage of removal after 20 dayscompared to ozone, except for the borderline sugar for which acetic acid removal was a littlehigher with ozone than with air. This result may indicate that residual ozone in the sugartermporarily masks some of the off-odors.

45040035000030000025c0200150000100000

500DO0

Time-->

206

Decreased

ReAir82.5

37.5 90.0

65.2 91.0

46.8

90.0

7.8 90.9

207

25 in82.286.889.892.7

25 in70.478.181.988.597.8

5 in89.792.494.195.7

15 in84.288.692.194.2

15 in88.391.096.994.499.3

5 in89.694.596.798.399.6

25 in77.379.378.897.595.8

15 in82.687.784.993.698.3

5 in87.293.793.897.098.6

B iReAcetic ac

Butanoic ac3-Met Butanoic ac

Pentanoic ac

Acetic acButanoic ac

3-Met Butanoic acPentanoic acHexanoic ac

Acetic acButanoic ac

3-Met ButanoicaCPentanOiC acHexanoic ac


Table 7. Reappearance of off-odor after air and ozone treatment: Sniff tests.

A6 eptable t B2 borderhn____L B6 (reject)

M Ozone Air Ozond Air 'bzone

No tätnit '. . -_- - - -

Da " O; - - - - - -Dal' - + + -Da'5 - + - + - +

Da 12

+ -H- + I ++ +

(-)

no off-odor; (+) very subtle off-odor; (++) light but clearly noticeable; (+++) off-odor;

(++++) strong off-odor

.1.

Table 8.VFA's removal (%) after 20 daAcceptable j

- 03AiJAcetic ac 76.1

tanoic ac 24.4 82.9[3-Met Butanoic ac 39.1 83.5PentanoiC ac 15.7 85.9

Iliexanoic ac

Air vs. OzoneBorderlineT

Effect of Air VeIocityConsidering that air speed through the sugar bed might have an effect on off-odor removal, 40min tests at 80°C with air were performed on sugar B 1 Rej , C3 Bor and C6130r at three different air

velocities, which were represented by the pressure measured at the column inlet: 5, 15 and 25 in.

Table 9.VFA removal rate (%) for combined ozone/air treatment.


Results showed that the slower the air speed in the sugar bed, the better the removal of VFA(Table 9). At higher speed it is possible air flow is not uniform throughout the sugar bed and thatpreferential passageways are created, diminishing the contact between air and sugar. Thephenomenon is moderate and the removal decreases less than 10 % while the speed triples.

CONCLUSIONS

Air was shown to be superior on every level to ozone in removing/eliminating volatile off-odorsfrom beet sugars. On the first hand, ozone can totally eliminate high molecular weightcompounds at high dosage but only partially removed most of the VFA, ultimately producingacetic acid which accumulates in the sugar resulting in potential off-odor, whereas air removedall the HMW compounds as well as all VFA, including acetic acid, by up to 95%. Air treatedsugars remained stable over 20 days unlike the ozone treated sugars.

Both incomplete ozone treatment and treatment with an excess of ozone resulted in the formationof oxidation products.

The second major advantage of air over ozone is economical. Ozone utilization requiresexpensive equipment and demands specific safety regulation.

It was established at a lab scale that the best air action occurs when the sugar to be treated is hot(80-85°C), combined with very low air velocity through the sugar bed. Further tests need to bedone to determine the effect of hot air on cold or wet sugar for, on the factory side, it is easierand more economical to heat air than a large amount of sugar.

REFERENCES(1) Godshall, M.A., Grimm, C.C., and Clarke, M.A. (1995) Sensory properties of white beet sugars,Intemat. Sugar J., 97:296-343.(2) Marsili, R.T., Miller, N., Kilmer, G.J., and Simmons, R.E. (1994) Identification and quantitation ofthe primary chemicals responsible for the characteristic malodor of beet sugar by purge and trap GC-MS-OD. J. Chromatographic Sci., 32:165-171.(3) Moore S.J., Godshall M.A., and Grimm C.C. (2003) Comparison of two methods of volatile analysisfor determining the causes of off-odors in white beet sugars -- SPME and Headspace. Internat. Sugar J.,105:224-229.(4) Batista, R.B., Grimm, C.C., and Godshall, M.A. (2002) Semi quantitative determination of short-chainfatty acids in cane and beet sugars. J. Chromatographic Sci., 40(3):127-132.(5) Grimm C.C. and Godshall M.A. (2002) Solid Phase Microextractjon (SPME) for the evaluation of thesensory quality of sugar. SPRI Res. Conf. Proceedings, p 42-50.(6) Van der Poe] P.W., Schiweck H., Schwartz T. (1998) Sugar Technology, Beet and Cane SugarManufacture.(7) Colonna, W.J., Mc Gillivray, T., Samaraweera, U. and Torgeson, T. (1996) Odor in beet sugar: somecausative agents and preventive measures. SPRI Res. Conf. Proceedings, p 198.(8) Patel M.N. and Moodley M. (1991) Decolorisation with hydrogen peroxide, ozone and otherchemicals. SMRI Technical Report No. 1598.(9) Fenaroli's Handbook of Flavor Ingredients, Vol II, 2d Edition. (1975) CRC Press, Inc.(10) Davis S.B, Moodley M., Singh I. and AdendorffM.W. (1998) The use of ozone for color removalat the Melelane refinery. Proc South African Sugar Technol Assoc. 72:255-260.

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