Nonenzymatic browning in dehydrated food liposomes

MARÍA LAURA GAGLIANO; MARCELA AGUDELO; CAROLINA SCHEBOR; MARÍA DEL PILAR BUERA

Mar del Plata

Congreso; Interim Meeting of the International Color Association AIC 2010 “Color and Food”; 2010

Microencapsulation of food ingredients is a very valuable technique in order to improve delivery, stability and controlled release of many beneficial food components. Liposomes are common microencapsulation systems, composed by phospholipids. Many functional phospholipids contain amino groups, making them reactive in the browning development. The most studied browning reaction involves sugars and proteins. The nonenzymatic browning involving phospholipid components has been less explored. The objective of this work was to analyze color changes in dehydrated liposome model systems containing soy lecithin, as a source of phospholipids, considering different drying methods and storage conditions. Model systems contained soy lecithin liposomes (prepared by sonication or extrusion) in phosphate buffer pH 6, with the addition of either glucose or glycine or both reagents. Each liposome system was dehydrated by two different drying techniques: freeze-drying or spray-drying. The samples were then humidified at different relative humidites (RH). Afterwards, the samples were stored at the temperatures 45 and 60ºC. Color was measured using a photocolorimeter, using the CIELab color space, 2º observer and D65 illuminant. During storage, L* values decreased while a* and b* values increase in all the analyzed systems. These color changes and the chromatic displacement in the CIELab color space were characteristic of non-enzymatic browning reactions. The changes were more pronounced at 60ºC than at 45ºC and at the higher RH analyzed. No significant differences of color changes between were observed in samples dehydrated by the two drying methods employed. Many dehydrated foods and ingredient formulations, especially liposomes contain lipidic compounds like phospholipids that can participate in non-enzymatic browning reactions causing color changes that might be deteriorative. Therefore, it is important to analyze the conditions for the occurrence of such reactions. This work shows that both freeze-dried and spray-dried food model systems containing soy lecithin liposomes can develop browning even in mild storage conditions.