Partial coalescence in double (W1/O/W2) emulsions prepared with skimmed milk, polyglycerol polyricinoleate, and different fats

Partial coalescence was studied in double (W-1/O/W-2) emulsions prepared with skimmed milk, polyglycerol polyricinoleate (PGPR) as lipophilic emulsifier, and different fats. Microstructural and rheological analyses were performed. Encapsulation efficiency (as a parameter of inner water retention) and solid fat content were estimated by differential scanning calorimetry. The presence of PGPR in dispersed lipid phase promoted partial coalescence especially at higher concentration. This promotion of partial coalescence may have been produced by the increase of collision frequency due to protein displacement by PGPR at the outer interface and/or the increase of capture efficiency due to the modification of fat crystals by PGPR. Partial coalescence was also favored when inner water droplets were released as a consequence of an osmotic unbalance between inner and outer aqueous phases. Thus, the addition of glucose in dispersed aqueous phase decreased the partial coalescence degree due to the higher encapsulation efficiency given by the balanced osmotic pressures. With respect to the effect of the employed fat on partial coalescence, the obtained data indicate that the phenomenon was favored at higher solid fat content in lipid phase. Results led to the conclusion that inner osmolality, encapsulation efficiency, and inhibition of partial coalescence were correlated. Practical applications: The originality of this work resides on boarding the subject of partial coalescence in W-1/O/W-2 emulsions. The studied systems are proposed as potential lipid-reduced substitutes of dairy creams, with the employment of alternative non-dairy fats such as low trans vegetable fat. The combined analysis of partial coalescence and encapsulation efficiency allowed studying their reciprocal effects and evaluating the potentiality of the systems for the encapsulation of hydrophilic compounds. The variations of relative osmotic pressures in inner and outer aqueous phases, lipophilic emulsifier concentration, and solid fat content may lead to desirable or undesirable rheological properties depending on the required texture of the food emulsion. The findings of this work could be an important step pointing to control the factors leading to partial coalescence in W-1/O/W-2 emulsions for food applications. The stability against partial coalescence in W-1/O/W-2 emulsions containing polyglycerol polyricinoleate (PGPR) and solid fat in lipid phase is linked to the retention of inner water droplets or the encapsulation efficiency of the system. The higher the inner osmolality the higher the encapsulation efficiency; and the higher the encapsulation efficiency the lower the partial coalescence degree. This aggregation of fat globules is attributed to the increase of collision frequency due to protein displacement by PGPR at the outer interface and/or the increase of capture efficiency due to the modification of fat crystals by PGPR.