Light Transmission Characteristics of Wrapping Materials and Oxidation of Butter by Fluorescent Light

Butter was wrapped in 10 materials as 454-g prints and exposed to Cool-White fluorescent light. Four treatments were different combinations of light intensity and time (lx/d, 400/1, 400/6, 2000/2, 2000/4). The wappers were 5 polyethylene-based plastics, 2 parchment papers, 2 metallized aluminum papers, and an aluminum foil paper laminate. Only the laminate completely protected butter from oxidation. Oxidation occurred on the light-exposed butter surface with all wrappers in the three strongest light treatments. There were linear relations of the level of oxidized flavor with flavor score (r = -.99) and of logarithms of peroxide values with oxidized flavor and with flavor scores (r = .90 and -.91, respectively). Oxidation was similar whether butter was fresh or stored at -18C for 8 mo before light exposure. After 2000 lx for 4 d and storage for 8 to 12 wk, oxidized flavor had penetrated 20 mm, or one-third, of the print.