Some abstracts do not have video files because ASAS was denied recording rights.
559
Prediction of fat globule particle size in homogenized milk using mid-FTIR
Our objectives were to develop partial least squares (PLS) prediction models using data from Fourier transform MIR (mid-FTIR) spectra to predict the particle size distributions d(0.5) and d(0.9), surface volume mean diameter D[3,2], and volume moment mean diameter D[4,3] of milk fat globules and to validate the models. Five in-line IR homogenizers with different homogenization efficiency were used to homogenize pasteurized modified unhomogenized milks and farm raw bulk tank milks. Homogenized milks were collected from the homogenizer outlet and then run through a mid-FTIR milk analyzer without an in-line homogenizer to collect an infrared spectra of the homogenized milks for modeling. A separate portion of each homogenized milk was analyzed with a laser light scattering particle size analyzer to obtain particle size reference values. The study was replicated 3 times with 3 independent sets of modified milks and farm raw bulk tank milks. Validation of the models was done with a set of 34 milks that were not used in the model development. The PLS model factors, standard error of cross validation (SECV), and R-square for d(0.5), d(0.9), D[3,2], and D[4,3] were: factors (12, 10, 12, 10); SECV (0.03, 0.12, 0.02, 0.09); R-square (0.93, 0.88, 0.92, 0.68), respectively. The validation mean difference (MD), standard deviation of the difference (SDD), and relative standard deviation (RSD) for d(0.5), d(0.9), D[3,2], and D[4,3] were: MD (-0.024, 0.019, -0.012, -0.029 μm); SDD (0.036, 0.148, 0.022, 0.110 μm); RSD (5.47, 9.10, 4.32, 12.67%). The basis for the ability to model particle size distribution of milk fat emulsions was hypothesized to be the result of the PLS modeling detecting absorbance shifts caused by light scattering in mid-FTIR spectra of milk fat due to the Christiansen effect. The independent sample validation of particle size prediction models found that there was more variation in d(0.9) and D[4,3] predictions than the d(0.5) and D[3,2] predictions relative to laser light scattering reference values and this may be due to variation in particle size among different pump strokes. The accuracy of the d(0.9) prediction would be fit-for-purpose for routine quality assurance to determine if the homogenizer within an mid-FTIR milk analyzer was near the failure level (i.e., d(0.9) > 1.7 μm) and needed to be replaced. This could be done as a monitoring for the daily average of the particle size performance (i.e., d(0.9)) of a homogenizer based on the mean for the day.
Keywords: particle size, homogenization, mid-FTIR