## 1 Introduction  
Numerous natural antioxidants have been shown to be effective against lipid oxidation in a variety of meat products. In poultry, plum extract [1], green tea extract [2, 3] and grape seed extract [3], sage and oregano [4], as well as pongemastre fruit juice [5] are some of the natural antioxidants found to be effective. Correspondingly, e.g., cranberry powder [6], lutein, season, ellagic acid, and olive leaf extract [7], along with grape seed extract [8, 9] rosemary [10, 11], and green tea [10] have proven to be effective natural antioxidants in pork. Synthetic antioxidants such as butylated hydroxyanisole, butylated hydroxtoluene, and propyl gallate have been approved for use in foods by the United States Department of Agriculture, USDA, since 1955 [12]. However, safety and toxicity issues with synthetic antioxidants are leading to stricter regulations [13, 14]. Consequently, consumers are increasingly demanding more natural products free from chemical preservatives [15], and, hence, employing antioxidant extracts from natural sources such as herbs, spices, seeds, fruits, and tea in meat and meat products fits well into this trend as also evidenced by a number of recent reviews and studies on the subject [16, 17, 18, 19, 20, 21, 22].  
Phenolic compounds such as phenolic acids, phenolic diterpenes, flavonoids, and volatile oils in the natural antioxidants are responsible for the antioxidant effect [23]. Phenolic compounds can function as primary antioxidants, i.e., chain breakers, which react with free radicals generated during lipid oxidation by donation of a hydrogen atom [24].  
Rosemary is among the most commonly used natural antioxidants in meat products [25] with its antioxidative effect mainly being due to phenolic diterpenes and phenolic acids [23]. Green tea owes its antioxidative effect mainly to flavonoids, especially catechin, but also tannins and vitamins [23].  
Degree of lipid oxidation can be measured in a variety of ways such as peroxide value (primary lipid oxidation products) [26], thiobarbituric acid reactive substances (TBARS) (secondary lipid oxidation products) [26; 27], headspace hexanal (the most abundant secondary lipid oxidation product [28]) e.g., via solid-phase microextraction gas chromatography (SPME-GC) [29], and sensory detection of oxidation [26]. Sensory methods have the advantage of detecting levels of oxidation perceivable by humans [30]. However, sensory analyses are expensive and time-consuming. Hence, being able to correlate a laboratory method with sensory analysis could save both time and money [31].  
In this study, an antioxidant screening was performed by evaluating the effects of up to three different commercial natural antioxidants from rosmary (Guardian(tm) 09, StabilEnhance(r) OSR D 2.5, and StabilEnhance(r) OSR 4) and green tea (Guardian(tm) 20S), respectively, in three deli-style, commercially produced meat products, namely, cured deli turkey (CDT), chicken fillet (CF), and pulled pork (PP). The purpose was to determine the most efficient antioxidant and addition level for each investigated product and the potential to replace phosphate with a natural antioxidant in commercial deli-style meat products. This was done by measuring the degree of lipid oxidation in the form of headspace hexanal via SPME-GC after 1, 7, and 13 weeks of refrigerated storage and comparing the results to oxidation flavor as determined at the same time points by a trained sensory panel and determining a potential correlation between the two analyses. Performing sensory analysis is expensive and time-consuming, yet, important with regard to e.g., consumer acceptance and detection threshold [26].