Turbidimetry for crystalline fractionation of lard

Abstract

Development of specific properties of lard, a well‐known edible animal by‐product and one which plays an important role in Chinese‐style foods, was studied by means of multiple‐step crystalline fractionation. A method for monitoring the crystallization temperature and crystallization time of lard by spectral turbidity was also studied. The capabilities of the proposed method were experimentally demonstrated through recovery of the fat crystal mass. Six significant changes in turbidity spectra, which correspond to the formation of fat crystals, were observed at various temperatures while cooling the melted lard from 50°C to the final vessel temperature at a constant cooling (0.5°C/min) and agitator rate (50 rpm). Crystallization time for each lard fraction was determined while the peak in turbidity was observed in the process of cooling at a specific temperature. Determination of crystallization time by means of turbidimetry correlated with the increase in deposition of fat crystals. No significant increase in fat crystal mass was observed when cooling prolongation after the turbidity peak for the sample was measured. Attributes of lard fractions were characterized by iodine value, saponification value, fatty acid composition, and melting profile of crystallization temperature. Based on the results, turbidimetry might be suggested as a fast and inexpensive method for monitoring the crystallization temperature and crystallization time for the routine crystalline fractionation process.