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

Abstract

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 −18°C for 8 mo before light exposure. After 2000 lx for 4 d and storage for 8 to 12wk, oxidized flavor had penetrated 20mm, or one-third, of the print.Wrappers differed markedly in their transmission of light. The foil laminate transmitted no measurable light. Yellow plastics transmitted very little light below 500nm; this did not appreciably reduce oxidation, indicating that longer wavelengths are important. Values for peroxide on the surface with the different wrappers and light treatments were linearly related to the logarithm of light intensity and to the square root of time. Thus, oxidation was greater at lower intensities of light and at shorter times of exposure than expected from that observed at higher intensities and longer time exposures. The 2 metallized papers transmitted less than 10% of light and did not prevent oxidation, indicating that wrappers should transmit even less light for protection of butter from the higher light exposures used in this trial.