Furosine content, loss of o‐phthaldiadehyde reactivity, fluorescence and colour in stored enteral formulas

Abstract

Heat effects induced during the storage of enteral formula under laboratory and industrial conditions were evaluated using the following indicators: furosine; loss of available amino groups, measured by decrease in o‐phthaldialdehyde (OPA) reactivity; fluorescence associated with the Maillard reaction (345 nm excitation, 415 nm emission); and colour (absorbance at 420 nm). The storage of formulas A and B (with different protein content) at 4, 20 and 30°C during 12, 24 and 36 weeks produced an increase in furosine values. Under industrial storage conditions at 55°C for between 1 and 12 weeks the behaviour of furosine differed between the two types of formulas. In Formula A (lesser protein content), there was a decrease in furosine level after the third week, whereas in formula B (greater protein content) a decrease was observed after the eighth week.The loss of OPA reactivity reached 18% and 22%, respectively, for formula B and formula A stored at 30°C for 36 weeks. In adverse storage conditions (55°C), the loss of OPA reactivity reached 50%.Fluorescence intensity (FI) and absorbance at 420 nm increased at all time/temperatures assayed. It reached values of 22.5 and 27.5 for FI and 0.161 and 0.173 for A420, respectively, for formula A and B, stored for 36 weeks at 30°C.Furosine, loss of OPA reactivity, fluorescence intensity and colour are useful indicators of nonenzymatic browning during storage of enteral formulas.