Food Protection Trends - January/February 2021 - 155

TABLE 2. Core method conditions and associated validated matrix categories for five rapid
screening methods and three reference methods for Salmonella
Enrichment core conditions

Reference

Test
portion
size

AOAC
OMA
2011.03
(8)

Follow
BAM or
MLG

AOAC
OMA
2013.01
(9)

25 g, 375 g,
30 mL,
sponge,
swab

AOAC
OMA
2014.01
(11)

25 g, 100 g,
325 g,
375 g,
sponge

AOAC
OMA
2016.01
(12)

100-375 g,
325 g,
30 mL,
sponge,
swab

Single

AOAC
OMA
2017.06
(14)

25 g, 375 g,
30 mL,
sponge,
swab

FDA BAMe
Chap. 5
(34)

25 g,
sponge,
frog legs,
pig ears

USDA
25 g, 100 g,
MLGf
325 g,
Chap. 4.10
30 mL,
(29)
sponge
ISO 65791:2017
(24)

Enrichment
Ratioa
stage
Primary

Broth
identity

Categories
Time
(h)

Temp
(°C)

Follow FDA BAM or USDA MLG

Secondary

SX2

22-26

42 ± 1

Dairy
products

Meat
Egg
Fruits and Miscellaneous Animal
Environmental
and
Seafood
Spices
products
vegetables
foods
feed
samplesb
poultry

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

s, p, t

X

X

X

X

X

Single

0.1,
0.25

BPW +
proprietary
supplement

22-24

42 ± 1

Primary

0.1

BPW

18-24

41.5 ± 1

RVc

24c

41.5 ± 1c

ISO BPW

24

37 ± 1

X

41.5 ± 1c

X

Secondary
0.1
0.25

ISO BPW
18-24
(prewarmed)

Single

0.1,
0.25,
0.5

21 ± 1
BPW
(prewarmed) 10 ± 2d

Primary

0.1

Secondary
Primary

0.1, 0.2,
0.5

Secondary
Primary

25 g
Secondary

0.1

36 ± 1d

24 ± 2

35

RV and TT

24 ± 2

42 ± 0.2
35 ± 2

BPW

22-24

35 ± 2

RV and TT

22-24

42 ± 0.5

BPW
18 ± 2
(prewarmed)

34-38

24

s

X

X
s, c, t

37 ± 1

Lactose

RVS and
MKTTn

X

X

41.5
37

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

s, t, p, c

X

X

X

X

X

X

X

X

Core enrichment ratio varies for sponges and swabs and may vary for different test portion sizes.
b
s, stainless steel; p, plastic; t, ceramic tile; c, sealed concrete.
c
For materials with high background counts.
d
For simultaneous detection of E. coli O157:H7.
e
;FDA BAM has many specific variations; the most common core method is shown here.
f
USDA-FSIS Microbiology Laboratory Guidebook (MLG) data for core conditions of the most common enrichments. BPW, buffered peptone water; ISO BPW, buffered peptone water (ISO formula);
lactose, lactose broth; MKTTn, Muller-Kauffman tetrathionate-novobiocin broth; RV, Rappaport-Vassiliadis broth; RVS, Rappaport-Vassiliadis broth with soy; SX2, a proprietary selective Salmonella
enrichment broth similar to RV; TT, tetrathionate broth.

Fit-for-purpose approach: Matrix Evaluation Level
Assessment Tool
Although matrix grouping and similarity of enrichment
approaches are helpful in reducing the burden of test method
validation, these factors are only half of the story. Both
options rely on knowing the composition of the matrix to be
tested and understanding how that composition may affect
method performance. With current matrix grouping schemes
(e.g., ISO, AOAC, FDA), defining the matrix is essential
to determining the level of evaluation required for a matrix

addition. However, intrinsic properties of the matrix may be
unknown to the food producer or testing laboratory, making
assessment of the matrix difficult when quick turnaround
times are essential. Rather than starting with the question
" To which food category does my matrix belong? " , a riskbased assessment approach could be used.
With the variety of products that are produced or come
through the door for testing, how do you decide how much,
if any, evaluation is needed? To help address these questions,
we have developed a Matrix Evaluation Level Assessment
January/February Food Protection Trends

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