The effect of cooling on crystallization and physico-chemical properties of puff pastry shortening made of palm oil and anhydrous milk fat blends

摘要

Commercial shortenings and margarines are mainly produced via rapid cooling with scraped surface heat exchangers (SSHE) and therefore, controlling fat crystallization in the cooling process of these systems plays an important role. In this study, four batches of puff pastry shortening were produced from palm oil blends containing 25% and 50% anhydrous milk fat (AMF) using a bench-top SSHE. The outlet temperature of SSHE was investigated at 20 degrees C and 12 degrees C relating to the difference of crystallization temperature between palm oil and milk fat. Physico-chemical properties, crystal morphology and fat stability of these shortenings during storage at 5 degrees C were determined by various classical technologies including differential scanning calorimetry (DSC), polarized light microscopy (PLM), rheological and texture analyzer. Our results showed that fat blends crystallized at 12 degrees C had a stronger crystal network after production but the discrepancy of hardness diminished after the first storage week at 5 degrees C. Besides, the change of crystallization temperature did not affect significantly melting behavior as well as fat polymorphism of products. Upon storage, some big aggregates were detected in shortenings as a combined result of the recrystallization of palm fat crystals and the post-crystallization of milk fat triacylglycerols (TAGs).