DIACETYL TEST AS A QUALITY CONTROL TOOL IN FROZEN CONCENTRATED ORANGE JUICE

Transcription

1 3 FLORIDA STATE HORTICULTURAL SOCIETY, 966 DIACETYL TEST AS A QUALITY CONTROL TOOL IN PROCESSING FROZEN CONCENTRATED ORANGE JUICE D. I. MURDOCK Lactic acid bacteria are rganisms f sani tary significance in prcessing frzen cncen trated range juice. They impart flavrs and drs which have been characterized as similar t buttermilk (3) (7). The bacteria respnsible are principally thse rganisms belnging t the genera Lactbacilhts and Leucnstc. They are present n and in the fruit when it arrives at the plant and grw well in single strength and partially cncentrated range juice. T pre vent a buildup f these rganisms during the l Staff Bacterilgist, Minute Main Cmpany, A Divisin f The CcaCla Cmpany. prcessing peratin, an efficient sanitatin pr gram must be maintained. It sn became apparent amng the early investigatrs that a rapid methd was needed t detect the presence f lactic acid bacteria. The direct miscrscpic methd was first used. It cnsisted f cunting the number f cells present n a stained slide preparatin. The difficulty in distinguishing between the bacteria and the debris present n the smear left much t be desired. Then in 95, Hill et al. () and Byer () intrduced t the citrus industry a rapid methd fr the detectin f diacetyl and acetylmethylcarbinl (AMC), the metablic DIACETYL VALUES OF ORANGE JUICE Sample Obtained Frm Finishers HELD AT ROOM TEMPERATURE. 3.. Characteristic f Juice " Brix.33 Acid as Citric %.66 Brix/Acid Rati 7. > O a E ± IS Hurs at Rm Temperature (76 F)

2 MURDOCK: DIACETYL TEST 33 prducts f the grwth f lactic acid bacteria in range juice. The test, a mdificatin f the VgesPrskauer (VP) reactin, is extremely sensitive t diacetyl and will detect cncentra tins f less than. Mst prcessrs f frzen cncentrated range juice, as indicated by a survey made by Murdck and Dennis in 96 (8), use sme frm r mdificatin f the VP test fr the detectin f diacetyl and AMC in range juice. Variatins in preparatin and handling f VP reactants were reprted by Mur dck in 965 (9). The purpse f this paper is t shw hw the diacetyl test, which requires less than nehalf hur t perfrm, can be used as a quality cntrl tl t determine the micrbial activity in prcessing frzen cncentrate range juice. Prcedure The diacetyl test used in this investigatin was described by Murdck (Fla. State Hrt. Sc. Prc, Nv. 965). Briefly, it cnsisted f adding 3 ml f single strength r recnstitu ted range juice ( Brix) t a large biling flask cnnected t a water cndenser, cllecting 5 ml f distillate, adding the VP reagents, and reading the clr reactin n a Lumetrn clr imeter 6 secnds after additin f the reagents. The results are expressed as f diacetyl in the distillate. Results and Discussin Relatinship f fruit quality t diacetyl val ues. A study was made t determine the rela tinship f fruit quality t diacetyl values. It cnsisted f cllecting at the cncentrate plant Vz bx (apprx. 5 lbs.) f sund acceptable fruit (ranges) and a similar amunt f reject fruit, the latter cnsisting f splits, partially decmpsed, sft spts, etc. The fruit was brught t the labratry where the juice was extracted frm each lt by means f a hand extractr. The fllwing diacetyl values were btained: Fig. RELATIONSHIP OF DIACETYL VALUES IN EVAPORATOR FEED JUICE TO PUMPOUT ORANGE CONCENTRATE FOR 966 VALENCIA SEASON TASTE EVAPORATOR g JJ Standard errr f estimate.7 5 Observatins O.I..3.. Evapratr Feed Juice

3 3 FLORIDA STATE HORTICULTURAL SOCIETY, 966 Type f Fruit Brix Brix /acid Rati Sund Reject (Gd) (Bad) Beisel et al. () als fund that juice frm defective fruit was higher in diacetyl than it was frm sund fruit. Murdck et al () fund that there was a direct crrelatin between fruit quality and the micrbial cntaminatin f freshly extracted juice. Therefre, it is quite evident that if unsund fruit entering the plant is nt remved during the grading peratin it will nt nly "seed" the plant with micrrgan isms but will als result in an immediate surge in diacetyl during the prcessing peratin. as an index f plant sanitatin. In citrus prcessing plants, as in ther fd plants, juice may ccasinally remain stagnant in an unused pipeline; r a dead pcket may ccur as a result f a change in the piping arrangement. Als, pulp adhering t finisher chutes may nt always be remved during a flush peratin. It was fund that pulp under ptimum cnditins adhering t equipment, such as finisher chutes, wuld develp a sur dr in apprximately 6 hrs. if nt remved (). When this ccurred, the pulp usually had a ttal viable cunt f,, rganisms per gram and a diacetyl cncentratin f ne r mre (6). Fig. shws that diacetyl values f range juice held at rm temperature (76 F) in creased frm.3 t.9 in hrs. The greatest increase in diacetyl ccurred after hrs. Frm these data, it is apparent that if range juice is held in a drmant cnditin, such as in an unused pipeline and the equipment is nt kept in a sanitary cnditin, an increase in diacetyl will ccur. values during evapratr peratin. Hill and Wenzel in 957 (5) reprted n the diacetyl values btained in prcessing range cncentrate in a lw temperature pilt and cm mercial evapratr. They nted an increase in diacetyl ccurred during the cncentrate prcess, usually after the evapratr had been perated hrs. r mre. The citrus industry within the last year r tw has replaced nearly all f their lw temperature evapratrs with high temper ature shrt hlding time units, generally refer red t as a TASTE evapratr (Thermal Ac celerated Shrt Time Evapratr). A study was made under cmmercial cndi tins cmparing a TASTE unit with a 6stage lw temperature Buflvak evapratr in prcess ing wash pulp cncentrate. Samples fr diacetyl analyses were drawn every hrs. while the evapratrs were in peratin. Juice was cl lected befre it entered the evapratr (evapra tr feed) and when it left the units (pumput cncentrate). The Buflvak units were cleaned n a 87 hr. cycle and the TASTE evapratr every hrs. A table f frequencies f di acetyl values (evapratr feed juice and pumput cncentrate) fr the perid the TASTE and Buflvak evapratrs were in peratin is pre sented in Table. It can be seen frm the data that fr the perid April 63, 8 f the TASTE evapratr feed juice diacetyl values were in the range f. t.5. The distributin f the values leaving the evapratr were in the range f. t.5, tw in the range f. t.5, and tw in the range f.3 t.35. The average diacetyl values fr the test perid and the percent change between evapra tr feed juice and pumput cncentrate is shwn in Table. Nte that the average lss f diace tyl between these tw pints fr the TASTE evapratr was 36%, which cmpares with a 5% increase in diaetyl fr the Buflvak evap ratr. In anther study, which was made at Plant A frm April 9 thrugh June, the range juice entering the TASTE evapratr (evapr atr feed) and pumput cncentrate 6 Brix were checked fr diacetyl every hrs. while the evapratr was in peratin. A ttal f 5 analyses were made. The average lss f diace tyl fr the seasn between the evapratr feed juice and the pumput cncentrate was 3% (Table ). A table f frequencies f the diacetyl data fr the test perid is shwn in Table 3. Als included are the diacetyl values btained at Plant B while prcessing range cncentrate. In analyzing the diacetyl data btained frm Plant A, the fllwing regressin equatin was derived: PumpOut =. +.5 x Evapratr Feed This equatin shws the functinal relatinship between the level f diacetyl in the evapratr feed juice entering the TASTE evapratr and the level f diacetyl in the 6 Brix cncen trate pumput. Frm the equatin, it can be estimated that if the evapratr feed juice cn tains. diacetyl there will be n the aver age.3 diacetyl in the pumput cncen trate. The relatinship fr ther diacetyl values

4 MURDOCK: DIACETYL TEST 35 Table, Distributin f diacetyl data in prcessing wash pulp cncentrate during 966 Valencia seasn TASTE EVAPORATOR April 63 Evapratr Feed Juice PumpOut Cncentrate (6 Brix) Range Range,, , Ttal Freq. Frequencies.,,5.3,,35 9,,,5 8,,,5 35 BUFLOVAK EVAPORATOR April May..5 5 a in evapratr feed juice t pumput cncen trate is shwn in Fig.. Using the standard errr f the estimate f.7, a 95% cn fidence interval was calculated t shw the vari ability assciated with the estimate. Fr an evapratr feed juice diacetyl f., we wuld expect 95% f the estimates f pumput diacetyl t fall within a cnfidence interval f.9 t.37. Althugh the strength f the regressin equa tin fr the ther TASTE evapratrs was weak due t the limited number f samples cllected, it appears that the same functinal relatinship applies. Bilgical Cntrl Prgram. We have seen that diacetyl can be used as presumptive evi dence f the quality f the incming fruit and as an index f sanitatin in a citrus cncentrate plant. Since the diacetyl test will detect the end prducts f micrbial grwth in range juice during prcessing peratins, it can be used ef fectively as a quality cntrl tl. In develping a bilgical cntrl prgram, the fllwing shuld be cnsidered:. Sample statins : Select definite check pints t adequate ly cver the prcessing peratin.

5 36 FLORIDA STATE HORTICULTURAL SOCIETY, 966 Table. Average Values fr Test Perid Avg. f Prduct Evapratr N. Tests Evapratr Feed Juice PumpOut Cncentrate % Change Wash pulp (6 Brix) TASTE % () Wash pulp (6 Brix) Buflvak HU % (+) Orange Cne. (65 Brix) TASTE () 5.37U.5 3% () Orange Cne. (65 Brix) TASTE () % () (), lb. evapratr Plant A () 5, lb, evapratr Plant B. Frequency f tests Check prduct frm each statin every hrs. r mre frequently if necessary. 3. Recrding f data Lg all diacetyl values. An example f a lg in which the data can be pltted graphically as it is accumulated is shwn in Fig. 3.. Interpretatin f data Be able t crrectly interpret the data as it is btained. In rder t assist Minute Maid persnnel in this regard, a Guide fr Interpretatin f Analyses has been develped (Fig. ). values during nrmal and abnrmal perids. Fig. 3 is a cpy f a lg shwing diacetyl values btained during a nrmal plant run which started n May, 966. Nte the values remain mre r less cnstant within a very narrw range. Fig. 5 is a cpy f a lg shwing a diacetyl buildup. Observe the steady increase in diacetyl in the wash pulp discharge liqur starting at n March 3 and the large increase in diacetyl between 9 n April and 3 n that same day. During this time interval the diacetyl increased frm. t.8 in hurs. This wuld indicate the cntaminating rganisms were in their ptimum grwth phase. If preventive measures are nt immediately tak en, spilage will ccur in a shrt time. In this instance, the juice rm was shut dwn and the equipment thrughly cleaned with a detergent slutin. The surce f cntaminatin, when cnditins exist as illustrated in Fig. 5, usually will be fund in the juice rm. It may Occur frm sur pulp in finisher chutes, stagnant juice in trughs r header lines, etc. If fund, a flush dwn with chlrinated water is indicated and/r the equipment shuld be thrughly cleaned with detergent slutin. Anther abnrmal cnditin is a sudden surge in diacetyl. This usually ccurs when: () A "slug" f sur juice is diverted int the system, ie. frm an unused pipeline nt cleaned prir t use, () prduct remaining in an evapratr feed tank that has becme stagnant, r (3) a lad f pr fruit being prcessed. Frtunately, a sudden increase in diacetyl is us ually fllwed by a crrespnding decrease as the slug f cntaminated prduct passes thrugh the system. If diacetyl des nt return t nr mal, a flush dwn r a clean up is indicated. We have seen hw the diacetyl test can be used as an effective quality cntrl tl in the prcessing f frzen cncentrated range juice. It can als be used t a lesser degree as an indicatin f the quality f bulk cncentrate which, at times, is purchased n the pen mar ket. If the prduct was prduced in a TASTE evapratr, it must be remembered that ap prximately Vs f the diacetyl present in the evapratr feed juice will be lst during the

6 MURDOCK: DIACETYL TEST 37 Table 3, Distributin f diacetyl data in prcessing range cn centrate in TASTE evapratr during 966 Valencia range seasn* PLANT A April 9 June Evapratr Feed Juice PumpOut Cncentrate (6 Brix) Range Range, , » MMM Ttal Freq. Frequencies PLANT B April May ,3,35,.5 L3 9.,5 8 6 Te cncentrate peratin. Therefre, if high diace tyl is fund in bulk drummed prduct, the as sumptin can be made that the prduct was prduced under insanitary cnditins prir t evapratin. Summary Data are presented t shw that the diacetyl test can be used as an index f juice quality and pr sanitatin in prcessing frzen cncentrated range juice. Apprximately Vz f the diacetyl present in the evapratr feed juice was lst in a TASTE evapratr during the cncentrate p eratin. An increase in diacetyl usually ccur red when a lw temperature evapratr was used.

7 38 FLORIDA STATE HORTICULTURAL SOCIETY, 966 Fig. 3 DIACETYL VALUES OBTAINED DURING NORMAL OPERATION DIACETYL LOG Plant PrnHnrt Orange Cncentrate 7 A \ B r A "N Date Start up :_ Time Start up :_ A s/ A k Ty y r 7 N _.. Date 5/ Time Hurs Bact. Yeast Ttal Diac. Tech. 8 O CSi Remarks Samples analyzed every fur hurs.

8 MURDOCK: DIACETYL TEST 39 Fig. GUIDE FOR INTERPRETATION OF DIACETYL ANALYSIS IN PROCESSING FROZEN CONCENTRATED ORANGE JUICE DIACETYL H NORMAL MICROBIAL Q) bo ACTIVITY DURING SAFE WORKING RANGE PROCESSING CQ IF OR MORE ROUTINE,3 75 ANALYSES ARE HIGHER IN ( rh Q G, DIACETYL CONCENTRATION, 5 THAN THE PRECEDING TEST,5 TAKE CORRECTIVE ACTION AREA OF CAUTION UNDER "DANGER",75 DETERMINE SOURCE OF TROUBLE, O c H,5 FLUSH DOWN EQUIPMENT IN AF,5 5 FECTED AREA WITH HIGHLY DANGER u P,55 CHLORINATED WATER OR O C,5 75 DETERGENT SOLUTION,6 SHUT DOWN AND THOROUGHLY DANGER OR CLEAN EQUIPMENT INVOLVED SPOILAGE MAY RESULT HIGHER WITH DETERGENT SOLUTION IF OPERATION CONTINUES Develpment f bilgical cntrl prgram Acknwledgment using the diacetyl test as a quality cntrl tl is discussed. Interpretatin f the diacetyl data The authr gratefully acknwledges Mr. W. and preventive measures used in a cncentrate J. Hepburn fr the statistical analyses f the plant t prevent spilage during perids f high data and Quality Cntrl persnnel fr the micrbial activity are mentined. diacetyl determinatins.

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10 EDWARDS ET AL: CONCENTRATE COLOR 3 LITERATURE CITED. Beisel, C. Grdn, R. W. Dean, R. L. Kitchel, K. M. Rwell, C. W. Nagel, and R. H. Vaughn. 95. Surce? and detectin f VgesPrskauer reactants in Califrnia Valencia range juice. Fd Research. 9: Byer, E. M. 95. Visual detectin f either diacetyl r acetylmethylcarbinl in frzen cncenterated range juice. Fd Technl. 8: Hays, G. L., and D. W. Riester. 95. The cntrl f "ffdr" spilage in frzen cncentrated range juice. Fd Technl. 6: Hill, E. C, F. W. Wenzel, and A. Barret. 95. Clrimetric methd fr detectin f micrbilgical spil age in citrus juices. Fd Technl. 8: Hill, E. Cm and F. W. Wenzel The diacetyl test as an aid fr quality cntrl f citrus prducts. I. Detectin f bacterial grwth in range juice during cn centratin. Fd Technl. : Minute Maid Cmpany. Labratry data (Unpublish ed). 7. Murdck, D. I., V. S. Try, and J. F. Flinazz. 95. Develpment f ffflavr in Brix range cncen trate inculated with certain strains f lactbacilli and Leucnstc. Fd Technl. 6: Murdck, D. I., and R. E. Dennis. 96. Detectin f diacetyl and acetylmethylcarbinl in prcessing frzen cncentrated range juice a preliminary reprt. Prc. Fla. State Hrt. Sc. 77: Murdck, D. I Detectin f diacetyl and acetylmethylcarbinl in prcessing frzen cncentrated range juice an investigatin f methds emplyed. Prc. Fla. State Hrt. Sc. 78: Murdck, D. I., and C. H. Brkaw Sanitary cntrl in prcessing citrus cncentrates. I. Sme specific surces f micrbial cntaminatin frm fruit bins t extractrs. Fd Technl. : Murdck, D. I. Persnal beservatins f authr. COMPARISON OF SUBJECTIVE AND OBJECTIVE METHODS FOR DETERMINING THE COLOR OF RECONSTITUTED FROZEN CONCENTRATED ORANGE JUICE Gerge J. Edwards, F. W. Wenzel, R. L. HUGGART3 AND R. W. BARRON3 Abstract One subjective and tw bjective methds were used t determine the clr f recnsti tuted frzen cncentrated range juice. The USDA clr scres fr samples ranged frm 3 t 37 pints when this subjective methd was used. Tw bjective methds were used: (a) the Hunter Clr and Clr Difference Meter t b tain tristimulus clr values and (b) the Bausch and Lmb Spectrnic 55 recrding spectrphtmeter t btain spectral curves. Hunter Rd values ranged frm.3 t 7.; the a values values frm 7.5 t.8; and the b values frm 8. t 9.8. Dminant wavelengths cmputed frm the spectral curves fr the recnstituted juices, ranged frm 576 t 58 m^; purity frm 59 t 9%; and brightness frm.3 t 33.8%. As the visual clr scre increased, the Hunter a value increased and the Rd value decreased; als, brightness decreased but n trend was evi dent between either the dminant wavelength r purity and the clr scre. Flrida Agricultural Experiment Statins Jurnal Ser ies N. 59. lcperative research by the Flrida Citrus Experiment Statin and Flrida Citrus Cmmissin. Flrida Citrus Experiment Statin, Lake Alfred. 3Flrida Citrus Cmmissin, Lake Alfred. Intrductin Clr t different disciplines f science means varius things. T the chemist it is dye and pigments. T the physicist clr is a phenmena in the field f ptics and electrmagnetc radia tin. T the physilgist and psychlgist clr dentes a sensatin t the human bserver. There are many prcedures in use tday that cmpare the clr f ne bject with that f anther r give a value fr the clr difference between them. Such methds are either sub jective r bjective, the frmer depending upn a visual evaluatin while the latter uses differ ent instruments. Subjective methds. The Maerz and Paul Dictinary f Clr (5) cntains examples f many clrs. Plate n page 3 f this bk shws varius clrs that culd apply t range juice. The MacbethMunsell Disk Clrimeter (3, ) can be used s that verlapping clr wedges are spun and the resulting clr cmpared t that in samples f range juice. By varying the amunt f white, gray, yellw, and range, the clr f range juice may be matched. Anther example f a subjective methd is the use f USDA clr cmparatr tubes t btain a clr scre fr range juice. A trial set at such tubes cnsisted f clred viscus plastic in capped glass tubes. These were avail