Alkaline earth metal and alkali metal hydroxide effects on transesterification and subsequent crystallization of butter oil

Formation of monoglycerides (MAG) and diglycerides (DAG) has been shown to be a product of transesterification of butter oil. Crystal formation is crucial in butter production, as it directly dictates the texture, hardness, spreadability, and overall physical stability of the final product. The intricate 3-dimensional network formed by fat crystals in the liquid oil phase is the primary determinant of these properties, affecting both consumer appeal and processing efficiency. The use of different catalysts may influence the chemistry of the partial glycerides that are formed and thus influence the crystals formed in the butter oil. This work seeks to determine the differences that arise when using alkali metal hydroxides as catalysts versus alkaline earth metal hydroxides. Butter oil was transesterified with Ba(OH)₂, Ca(OH)₂, Mg(OH)₂, KOH, and NaOH to determine the effect of different catalysts on the reaction and subsequent crystal formation. The use of KOH and NaOH as catalysts causes fewer larger triglycerides and overall more DAG to form in the sample after the reaction compared with using Ba(OH)₂ and Ca(OH)₂ as catalysts. Transesterification of the butter oil causes an increase in crystallization temperature and a decrease in melting temperature compared with the blank butter oil. The crystals from transesterified butter oils contain the most stable β polymorph, whereas the blank sample lacks it. Butter oils transesterified with KOH and NaOH contain an extra polymorphic state attributed to MAG crystallization. Transesterification of butter oil affects the morphology of the crystals, causing nonspherulite crystals to form and grow. This research finds that transesterification of butter oil affects the chemistry and crystallization of the butter oil and that alkali earth metal hydroxides have a different effect compared with alkali metal hydroxides when used as catalysts.