Oli goglycerol fatty acid esters (OGEs) are an important kind of polyglycerol fatty acid esters (PGEs) which have been widely used as emulsifiers in food, medicine and cosmetic industries. The aim of this study was to investigate the preparation of OGEs by the esterification of olig oglycerol with linoleic acid in a solvent-free system using Lipozyme 435 as the catalyst. The effects of substrate molar ratio, reaction time, reaction temperature, enzyme dosage, and water addition on the efficiency of esterification (EE) were studied. Single factor experiments and response surface methodology (RSM) were employed to optimize the reaction parameters. The optimum conditions were obtained as follows: reaction time 4.52 h, reaction temperature 90 °C, enzyme dosage 2 wt% (based on the total substrate mass), the molar ratio of oligoglycerol to linoleic acid 1.59:1 and no water addition. Under these conditions, the experimental EE (95.82±0.22%) fitted well with that predicted by RSM (96.15%). Similar results were obtained when the process was scaled up to a production of 500 g in a pilot bubble column reactor (BCR). The enzyme maintained 98.2% of the relative activity after 10 batches of reaction in the BCR. Electro spray ionization mass spectrum was employed to rapidly analyze the esterification products, and most species of OGEs have been identified. KEYWORDS: Biocat alysis; Bubble column reactor; Esterification; Immobilized enzyme; Lipase; Oligoglycerol fatty acid estersRESUMEN: Optimización de la preparación de ésteres grasos de oligoglicerol catalizada por Lipozyme 435. Los ésteres grasos de oligoglicerol (OGEs) son una clase importante de ésteres de ácidos grasos de poliglicerol (PGE) que han sido ampliamente utilizados como emulsionantes en alimentación, medicina y en la industria cosmé-tica. El objetivo de este estudio fue investigar la preparación de OGEs mediante la esterificación de oligoglicerol con ácido linoleico en un sistema libre de disolvente utilizando Lipozyme 435 como catalizador. Se estudiaron los efectos en la eficiencia de esterificación (EE) de la relación molar de sustratos, de los tiempos de reacción, las temperaturas de reacción, la dosis de la enzima, y de la adición de agua. Se realizaron ensayos factoriales individuales y metodología de superficie de respuesta (RSM) para optimizar los parámetros de la reacción. Las condiciones óptimas se obtuvieron como sigue: tiempo de reacción 4,52 h, temperatura de reacción 90 °C, dosis de enzima 2% en peso (basado en la masa total del sustrato), la relación molar de ácido linoleico:oligoglicerol fue de 1,59:1 sin adición de agua. Bajo estas condiciones, el EE experimental (95,82±0,22%) se corresponde bien con lo predicho mediante RSM (96,15%). Se obtiene un resultado similar cuando el proceso se escaló a una producción piloto de hasta 500 g en un reactor de columna de burbujas (BCR). La enzima mantiene el 98,2% de su actividad relativa después de 10 lotes de reacción en el BCR. Se empleó un espectrómetro de masas de ionización mediante electrosp...
Liquid oils containing high‐melting diacylglycerols (DAGs) are more likely to cause precipitation than triacylglycerol‐based oils during long‐term storage, which is not desired for consumer products. Therefore, we attempted to retard the crystallization of high‐melting DAGs by adding emulsifiers, diglycerol esters of fatty acids (DGEs), which were synthesized by esterification of diglycerol and linoleic acid using Novozym 435. The reaction product was isolated by silica gel column chromatography to obtain pure mono‐, di‐, and triesters of diglycerol, and the composition was analyzed by HPLC and ESI‐MS. Further structural analysis of the purified products was performed by 1H‐ and 13C‐NMR. The retardation effect of DGEs with a different esterification degree on the crystallization of DAGs was investigated using solid fat content, differential scanning calorimetry, polarized light microscopy, and X‐ray diffraction. The results reveal that addition of 0.5 % (w/w) DGEs could effectively retard the crystallization of high‐melting DAGs by inhibiting the nucleation process and delaying the crystal growth, but their addition did not alter the crystal forms of DAGs. Moreover, the retardation effect was enhanced as the esterification degree of DGE decreased.
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