Colour measurement as indicator for controlling the manufacture and storage of enteral formulas

Reflectance colour measurement was used to control the browning reaction during the manufacture (untreated, UHT, standardisation and bottle sterilisation) and storage (4, 20, 32 and 55 °C from 1 to 36 weeks) of two types of enteral formula (3.7% and 5.4% protein). Precision studies showed coefficients of variation of 0.19%, 4.77% and 1.02% for L∗, a∗ and b∗ parameters respectively. The a∗ and b∗ parameters proved useful to monitor the manufacture of these products. No statistically significant changes were observed during storage at 4 °C. At 55 °C the parameters a∗ and b∗ increased for both types of formula. However, at 20 and 32 °C, the a∗ parameter was useful for the formula with 3.7% protein and the b∗ parameter for that with 5.4%. Colour measured as reflectance was strongly correlated with colour absorbance at 420 nm, especially during storage at 20 °C. Likewise, a strong correlation was observed between nutritional value (measured as lysine loss) and colour. Colour measurement is a simple and fast method to control different processing and storage conditions of enteral formulas, and may also be useful as an indirect measurement of nutritional value.