Does vitamin fortification affect light oxidation in fluid skim milk?

Abstract

Off-flavors in milk related to light oxidation form due to photoxidation of native riboflavin and tetrapyrroles, resulting in an array of lipid oxidation compounds. Recent work has established that fortification with waterdispersible vitamin A can result in off-flavors in fluid skim milk caused by vitamin A degradation products in the vitamin premix. The objective of this study was to determine the role of vitamin fortification on light oxidation of high temperature, short time pasteurized fluid skim milk. First, the aroma profiles and aromaactive volatile compounds in light-exposed vitamin premixes were determined by exposing the premixes to fluorescent (FL) or light-emitting diode (LED) light at 2,000 lx at 4°C for 0, 2, 4, 8, or 24 h. A trained panel (n = 6) documented aroma profiles of each vitamin premix at each time point. Headspace solid-phase microextraction followed by gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS) were performed to characterize aroma-active compounds in light-exposed vitamin premixes. In the second experiment, commercial vitamin premixes (vitamin A and vitamin D in oil and water matrices) were used to fortify skim milk (vitamin A: 3,000 IU/946 mL; vitamin D: 600 IU/946 mL). Skim milk was pasteurized, homogenized, and packaged in 946-mL high-density polyethylene jugs. Milks were exposed to FL or LED light at 2,000 lx at 4°C for 4, 12, 24, or 48 h. Controls with and without vitamins and light shielding were included. Riboflavin and vitamin A and D degradation were quantified via ultra-high-performance liquid chromatography. A trained panel (n = 8) documented sensory profiles of milks at each time point. Lipid oxidation volatile compounds were quantified via solid-phase microextraction with GC-MS. Vitamin degradation volatile compounds were quantified via solvent-assisted sorptive stir bar extraction with GC-MS. Riboflavin, vitamin A, and vitamin D degradation were consistent with that reported in previous studies. We found no effect of vitamin fortification on development of typical light oxidation-related off-flavors (cardboard and mushroom) or lipid oxidation-related volatiles (hexanal and heptanal). A perfumey/floral flavor was documented in the oil-based vitamin A-fortified milk, suggesting that light exposure affected the off-flavors contributed by water-versus oil-based vitamin fortification. These results show no evidence that vitamin fortification at current levels provides any protection against light oxidation-related off-flavors in fluid milk.

Short communication: Effect of purple corn pigment on change of anthocyanin composition and unsaturated fatty acids during milk storage

“…Milk antioxidants have been shown to play a crucial role in preventing lipid peroxidation. The addition of antioxidants to milk to prevent milk oxidation has been reported in a previous study (Schiano et al, 2019).…”

The role of heat treatment in light oxidation of fluid milk

“…Following 48 h at 4°C, milks were placed into 1 of 2 light boxes (88 × 57 × 31 cm) constructed as described by Schiano et al (2019). Light boxes were covered with laser cloth (BK5 blackout fabric, ThorLabs Inc., Newton, NJ) to eliminate ambient light from reaching samples during exposure.…”

“…Sensory profiling of milks was approved by the North Carolina State University Institutional Review Board for Human Subjects. A trained panel of 8 descriptive analysis panelists (2 men, 6 women; ages 21-55 yr), each with at least 150 h of prior experience profiling fluid milk and dairy products, profiled intensities of typical milk flavor attributes (Jo et al, 2018) and light oxidation-specific flavors such as cardboard and mushroom (Schiano et al, 2019) using the spectrum method 15-point intensity scale (Meilgaard et al, 2007; Table 1). Aliquots (40 mL) of milk from each treatment were dispensed into 65-mL soufflé cups labeled with random 3-digit blinding codes and were subsequently lidded and equilibrated to 15°C.…”

“…Experiments by van Aardt et al (2005) reported that addition of α-tocopherol decreased hexanal formation during storage, whereas additions of butylated hydroxyanisole and butylated hydroxytoluene decreased pentanal, hexanal, heptanal, and 1-octen-3-ol, although consumer-relevant intensities of LOF were not assessed. The addition of vitamin premixes was found to have no effect on LOF development in HTST skim milk (Schiano et al, 2019). Flavor and sweetener addition, although not directly oriented at the mitigation of oxidation, has also proven effective in protecting fluid milk from the negative sensory effects of LOF develop-ment.…”

The effect of intense pulsed light on the sensory properties of nonfat dry milk

“…Light‐induced flavor increased with the extended periods of light exposure (Dimick, 1973; Dunkley et al., 1962; Harwood et al., 2020; Jung et al., 1998; Van Aardt et al., 2001; Whited et al., 2002). The exposure time required to produce off‐flavors differed depending on the types of light sources (Brothersen et al., 2016; Chang & Dando, 2018; Schiano et al., 2019). In general, decreased storage temperature retarded the development of the flavor and color changes of milk caused by light (Dunkley et al., 1962; Hong et al., 1995; Lieberman & Warne, 2001; Mortensen et al., 2003; Sattar et al., 1977).…”