In vitro digestibility of beta-casein and beta-lactoglobulin under simulated human gastric and duodenal conditions: a multi-laboratory evaluation.
Initially the resistance to digestion of two cow's milk allergens, beta-casein, and beta-lactoglobulin (beta-Lg), was compared using a "high-protease assay" and a "low-protease assay" in a single laboratory. The low-protease assay represents an alternative standardised protocol mimicking conditions found in the gastrointestinal tract. For the high-protease assay, both proteins were incubated with either pepsin or pancreatin and digestion monitored by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and reverse phase-high performance liquid chromatography. The low-protease assay involved gastroduodenal digestion in the presence or absence of phosphatidylcholine (PC). Both beta-casein and beta-Lg were susceptible to hydrolysis by pepsin and pancreatin in the high-protease assay. In contrast, the kinetics of beta-casein digestion in the low-protease assay were slower, beta-Lg being pepsin resistant. During duodenal digestion, beta-Lg was gradually degraded and addition of PC slowed digestion. Subsequently, the reproducibility of the low-protease assay was assessed in 12 independent laboratories by visual assessment of the gels and densitometric analysis: the inter- and intra-laboratory variability was affected by sampling and electrophoresis method employed. The low-protease assay was shown to be reproducible. Future studies will extend these findings using a broader panel of proteins.
Mandalari
G
G
Institute of Food Research, Norwich Research Park, Colney, Norwich, NR4 7UA, UK. giusy.mandalari@bbsrc.ac.uk
Adel-Patient
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K
Barkholt
V
V
Baro
C
C
Bennett
L
L
Bublin
M
M
Gaier
S
S
Graser
G
G
Ladics
G S
GS
Mierzejewska
D
D
Vassilopoulou
E
E
Vissers
Y M
YM
Zuidmeer
L
L
Rigby
N M
NM
Salt
L J
LJ
Defernez
M
M
Mulholland
F
F
Mackie
A R
AR
Wickham
M S J
MS
Mills
E N C
EN
D000485:Allergens / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D002364:Caseins / Q000276:immunology / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004063:Digestion; D004386:Duodenum / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005753:Gastric Mucosa / Q000378:metabolism; D006801:Humans; D007782:Lactoglobulins / Q000276:immunology / Q000378:metabolism*; D008892:Milk / Q000737:chemistry / Q000276:immunology; D010194:Pancreatin / Q000378:metabolism; D010434:Pepsin A / Q000378:metabolism; D015203:Reproducibility of Results; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry
D000485:Allergens; D002364:Caseins; D007782:Lactoglobulins; D012967:Sodium Dodecyl Sulfate; D010194:Pancreatin; D010434:Pepsin A