Assessment of the rennet coagulation of skim milk: A comparison of methods

Monitoring of rennet-induced coagulation of milk reconstituted from low-heat or medium-heat skim milk powders with or without calcium enrichment (6.25 mmol kg−1) was carried out by five analytical methods. The four types of milk samples allowed evaluation of these methods on substrates characterized by very different rennetability. Thirteen parameters describing the coagulation process were extracted from the various measurements for each sample and compared. The visual flocculation and gelation times evaluated by the Berridge test and dynamic small amplitude oscillatory rheometer (DSAOR), respectively, were not significantly different from specific parameters identified from near-infrared (NIR) spectra analysis. DSAOR, piezoelectric rheometer, and NIR spectrometer allowed and evaluation of the beginning of gel firming. It clearly appeared that NIR spectroscopy, an on-line sensor, could best assess rennet-induced coagulation of studied samples.