A simple method for determining light transmittance of polymer films used for packaging foods

Sensitive components of food may undergo degradation reactions when subjected to light. The packaging of the food may slow down such reactions by absorbing and reflecting a fraction of the incident light. Riboflavin is a light‐sensitive vitamin and undergoes first‐order degradation when subjected to visible light. Rate constants of this reaction were evaluated under 20 W coolwhite light at pH = 9.0 at 25 °C, with no light shielding or by shielding the light with methylcellulose films. Based on this photodegradation reaction, a new model was proposed to define percentage light transmittance of methylcellulose films. Depending on composition, the percentage transmittance was in the range 66–96%. Variation of light transmittance was explained in terms of solubility and crystallinity.