Quantitative X-ray diffraction determination of alpha-lactose monohydrate and beta-lactose in chocolate.
Lactose is a constituent of milk chocolate. During processing and cooling, lactose may precipitate as alpha-lactose monohydrate and beta-lactose. The presence of alpha-lactose monohydrate has a deleterious effect on the quality of milk chocolate. A quantitative X-ray diffraction method for determination of alpha-lactose monohydrate and beta-lactose in chocolate is described. The alpha-lactose monohydrate signal at 19.9 degrees 2theta with Cu-Kalpha X-rays is a cubic function of concentration. The beta-lactose signal at 20.9 degrees 2theta is a linear function of concentration. alpha-Lactose monohydrate is detectible at about 0.1 weight% and can be quantified at >0.5 weight%. beta-Lactose is detectible at about 1 weight% and can be quantified at >3 weight%. About 10 min is required to prepare and run a sample.


CONCLUSIONS
The crystalline form of lactose affects the quality of chocolate. A rapid method for quantifying crystalline forms of lactose in chocolate is described. The method can be used for quality control and for improving chocolate quality.
Thomas
Nathan R
NR
Dept of Chemistry and Biochemistry, Brigham Young Univ, Provo, UT 84602 USA.
Shumway
Logan S
LS
Hansen
Lee D
LD
D002099:Cacao / Q000737:chemistry*; D002138:Calibration; D002182:Candy / Q000032:analysis*; D003460:Crystallization; D007785:Lactose / Q000032:analysis* / Q000737:chemistry; D011786:Quality Control; D013237:Stereoisomerism; D014961:X-Ray Diffraction / Q000379:methods*
D007785:Lactose