# Intrinsic and Extrinsic Factors Affecting the Color of Fresh Beef Meat--Comprehensive Review
## 3 Results and Discussion
### Extrinsic Factors
#### 3.2.3 Slaughtering Season  
Heat or cold stress might have different effects on the physical and psychological status of the animals, especially shortly before being slaughtered, which might result in meat with high pH and DFD-like conditions. Hot temperatures might impair the body's heat dissipation and increase animal stress, while cold temperatures might increase muscular shivering, which can rapidly deplete pre-mortem glycogen reserves. Slaughtering cattle during wintertime produced meat with significantly lower L*, a*, and b* scores and higher pH due to harsh average temperatures (\(-3.3\)\({}^{\circ}\)C) and low relative humidity (57.73%) during this season. It was also recommended that when cattle were processed at temperatures higher than 5 \({}^{\circ}\)C, the L*, a*, and b* beef values also increased [72]. It was demonstrated that longer showering times (2 h, water at 10 to 15 \({}^{\circ}\)C) during cold days increased the incidence of DFD meat due to higher muscle pH and lower L* and b* values [103]. Another study concluded that winter temperatures (12 \({}^{\circ}\)C) slightly produced more stress in the animals than summer temperatures (21 \({}^{\circ}\)C), but no significant differences were observed in meat color [33]. It was also reported that increased stress in bulls started at daily temperatures higher than 18 \({}^{\circ}\)C during the summer months, resulting in higher DFD-meat incidence than in winter months [31]. Lower L*, a*, and b*, and higher pH values were also found when animals were slaughtered during summer months with an average temperature of 23 \({}^{\circ}\)C [104]. Similarly, it was reported that cattle were more susceptible to reaching DFD conditions during summer months (average pH = 5.92), compared to winter months (average pH = 5.8), probably due to higher stress caused by heat [66]. Another study determined that there was a higher probability of obtaining DFD meat during the summer months (15.7%), compared to spring (13.32%) and winter (12.63%), due to temperatures that reached up to 35 \({}^{\circ}\)C [67]. It was also documented that slaughtering animals during the hot season (average temperature = 34 \({}^{\circ}\)C) drastically depleted the glycogen amounts pre-mortem and increased the probability of obtaining DFD carcasses up to 59% versus none during the cool season [105]. It was also found that 15.4% of the carcasses were classified as DFD during the hot season, where temperatures in the lairage pens attained values up to 48 \({}^{\circ}\)C versus only 8.15% during the cold season [106]. It seemed that cattle were overall more stressed for hot rather than for cold temperatures. Harvesting cattle at temperatures higher than 18 \({}^{\circ}\)C might be problematic in increasing animal heat stress, thus increasing the probability to produce DFD meat. Unnecessary stressors like long cold showers during cold days should be strictly avoided to increase beef color values. Pre-mortem conditions should guarantee a comfortable environment for the animals to reduce temperature-induced stress and improve meat color.