Determination of Niacin in Orange Juice with Lyophilized Lactobacillus arabinosus ATCC 8014

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Vol.20, No. 4 PrintedinUS.A.

Determination of Niacin in Orange Juice with

Lyophilized Lactobacillus arabinosus ATCC

80141

N. GORIN,2 E. J. S. MEULENHOFF, AND D. YARROW

Food Inspection Service,Amsterdam, CentraalbureauvoorSchimmelcultures, YeastDivision,andLaboratory for Microbiology, Technological University, Delft, The Netherlands

Received forpublication21July1970

The determination of niacin inorangejuice withlyophilized Lactobacillus arabi-nosusATCC 8014has theadvantageovertheusual method ineliminating the delay caused by the necessity of cultivating cells of L. arabinosus for the inoculum and also in eliminating the periodical cultivation on agar slopes.

Theniacincontentoforangejuiceisfrequently

determinedbytheFoodInspection Serviceas an

aid in the detection of adulteration (3, 4). For the

analysis,

we employed the microbiological

method withLactobacillus arabinosus ATCC 8014 asdescribedin theDifcoManual(1) and by Freed (2) with slight modifications. This method is in-TABLE 1. Analysisofniacin inorange juice (sample

2231) with inoculum prepared in the usual way and with inoculumprepared with lyophilized

cellsa

Determination Xb SC s(s of X) Usual inoculum... 0.37 40.01 ±3

Cells 6 months after

lyophilization... 0.38 ±0.01 ±3 Usual inoculum... 0.38 ±0.02 45

Cells 15 months after

lyophilization... 0.38

±0.01

±3

aPortionsof thesamples were kept at -20 C andbroughtto room temperature 1daybeforeuse.

Determinations were performed simultaneously. bX = the average offivevalues, inmilligrams

per100 ml.

cS = (2d2/n - 1)512.

convenient in that it is necessary to prepare the

inoculum 24 hr before performingthe assay. To

eliminate thisdelay,wedecidedto uselyophilized cellsas theinoculum.

Cellsweresubculturedfrom a stock cultureon Micro AssayCulture Agarintotubes containing 10 ml of Micro Inoculum Broth (MIB). After 24 hrof incubation at 30C, thetubes were

cen-trifugedand the supernatant wasdiscarded

asep-'Published with the authorization of J. Weits, Director of the FoodInspection Service, Amsterdam.

2Presentaddress:Sprenger Institute, Wageningen.

tically. The cells in each tube were suspended in 0.2 to 0.3 ml of MIB and pipetted into tubes (100by8mm) which were then constricted in the

middletoaid sealingin thefinalstage.The tubes were placed in the chamber of a freeze-dryer (Martin Christ, modelDelta), and, after freezing

TABLE2.Determination ofniacin in various samples

of orange juice in the usual way and with inoculum prepared with lyophilized cells"

Sample Usual Lyophilized

2108 0.16 0.14

2455 0.10 0.10

2505 0.11 0.09

2902 0.11 0.12

aResults areexpressed as mill

per 100 ml of orange juice. igrams of niacin

TABLE 3. Determination ofrecoveryfactorsa

Determination Usual inoculum lInoculumdwitlh

1 0. 50 (104)b 0.49 (102)

2 0.50

(104)

0.49

(102)

aNiacin (0.10 mg) was added to sample 2231 (100ml). Theexpectedvaluewas0.48mg of nia-cin per 100 ml of orange juice.

bValues in parentheses represent percentages. for 1hr at -10 to -12C,the vacuumpump was switched on automatically. The tubes were left overnight (ca.18hr) andplacedonthesecondary drying

manifold;

after3 to4hr,theywere

flame-sealedand stored at 5 C. To prepare the

inocu-lum, a tube was openedaseptically and the cells

were washed and suspended in isotonic sodium

chloride. 641

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APPL. MICROBIOL.

The results of assays carried out in the usual

mannerand withlyophilized inoculaarerecorded

inTables 1 and 2. Therewas nopractical differ-encebetween theresultsof thetwomethods, and cellscanstill be used 15 months after

lyophiliza-tion. Table 3 shows that the recovery factors of usual inocula and lyophilized cells are also similar.

Weconclude that theuseoflyophilized cells of

L. arabinosus is suitable for the assay of niacin

and that this method has the advantage of elimi-nating thedelay caused by the necessity of culti-vating cells for the inoculum and also of

elimi-nating the periodical cultivation on agar slopes.

This method could probably also be applied to

theassay of niacin in samples other thanorange

juice.

LITERATURE CITED

1. Difco Laboratories. 1953. Difco manual, 9th ed., p. 216-217. Reprinted 1966. DifcoLaboratories, Detroit.

2. Freed, M. 1966. Methods of vitamin assay, 3rd ed. Inter-sciencePublishers, Inc.,NewYork.

3. Goddijn, J. P. 1970. Mogelijkheden tothetaantonen van de vervalsingvansinaasappelsap. Voedingsmiddelentechnologie

1:366-369.

4. Sawyer, R. 1963. Chemicalcomposition ofsome natural and processedorangejuices. J. Sci. FoodAgr. 14:302-310.