**1. Introduction**

The consumer demand for healthy products is expected to grow in the coming years, frankfurter sausages being one of the most popular, with a large market worldwide for their convenience and price. Even though their intrinsic characteristics can vary significantly, pork frankfurters may contain up to 23% fat and 8.7% saturated fatty acids (SFA) [1], which converts them into less attractive meat products. It is a well-known fact that SFA and trans fatty acids (TFA) provide a suitable texture and juiciness in meat processed products, but they have detrimental effects on human health, such as cardiovascular disease or metabolic syndrome [2]. For this reason, the WHO recommends reducing the energy intake of total fats to less than 30% of the total daily diet and preventing SFA and TFA in the diet [3]. As animal fats are richer in SFA and TFA than those from a vegetal source, the partial replacement has become a strategic target for the meat industry in order to develop healthier meat

products [4–8]. Indeed, vegetable oils in sausage formulations have been used for the production of low/improved fat frankfurters [9,10]. However, since vegetable oils are liquid at room temperature, this constitutes a major problem, resulting in substantial di fferences in texture, color, and flavor with regard to beef or pork backfat.

Trying to address these issues, food researchers have shown an increased interest in edible oleogels. The formation of oleogels requires an oleogelator that will form a network allowing the conversion of liquid oil to a solid substance, and it may also include bioactive compounds [11,12]. The properties of the oleogels are a ffected by the type, concentrations, and crystallization temperature of the oleogelator, by the oil medium and presence of other additives [2]. Oleogels based on canola oil and ethylcellulose as the organogelator have proven to be an alternative lipid phase in comminuted meat products [13,14], meat batters [15], and breakfast sausages [16]. However, temperatures required to dissolve ethylcellulose in oil are above 130 ◦C, which makes the whole process more complex. Alternatively, beeswax is certainly regarded as one of the most commercially valuable waxes, used to wrap cheese or as a food additive, which also can be used as an oleogelator. Beeswax was evaluated with di fferent types of oils [11,17], but there is still insu fficient data in meat processed products with few exceptions, such as beef burgers [18] or pâtés [19]. On the other hand, linseed oil is widely used in functional food because of its high level of α-linolenic (~55%), which is converted into long chain *n*-3 fatty acids (FA). Moreover, Fayaz et al. [20] have reported that textural properties of oleogels composed by beeswax and linseed oil were stable, showing greater firmness and stickiness than those from other oilseeds (canola, sesame, and sunflower). In addition, meat products enriched with linseed oil enhance the FA profile in health terms. Recently, Gómez–Estaca et al. [19] tested a mixture of olive, linseed, and fish oil together with beeswax to replace animal fat in pork liver pâtés, concluding that stability, texture, color, and sensory attributes were not significantly a ffected.

Therefore, the aim of this research was to study the e ffect of replacing pork backfat with di fferent substitution levels with oleogels, elaborated using linseed oil and beeswax, on the main quality attributes of frankfurters (color, texture, and sensory properties).

#### **2. Materials and Methods**

### *2.1. Oleogel Elaboration*

For the production of beeswax-based oleogel, a commercial linseed oil Vitaquell ® with 72% polyunsaturated (approx. 55% of α-linolenic), 19% monounsaturated, and 9% saturated FAs was used as the oil phase. Oleogels with 8% ( *w*/*w*) gelator were produced for all the fat replacement experiments. To ensure the solubilization of beeswax in linseed oil, the gelator was dispersed under stirring at 80 ◦C (above wax melting point) for at least 30 min. After that period of time, the oleogels were left cooling at ambient temperature until gel formation.

### *2.2. Frankfurter Production*

Three di fferent batches (1.5 kg per batch) were produced: A control batch (CO), elaborated only with pork backfat, two batches of sausage frankfurter (SF), SF-25, and SF-50 with 25% and 50% of pork backfat replaced by oleogel, respectively. The amount of pork backfat added was 172.5 g, 129.4 g, and 86.25 g for the CO, SF-25 and SF-50, respectively, and the amount of linseed oleogel added was 43.1 g and 86.25 g for SF-25 and SF-50, respectively. These formulations were selected according to previous works developed in our lab. The other components were added in the same proportion: Pork jowl (438.8 g), pork lean (198.8 g), pork heart (240 g), water (172.5 g), ice (418.1 g), sodium caseinate (18.8 g), salt (11.2 g), and commercial mix (189.4 g). The commercial mix (Ceylamix PT-F, Laboratorios Ceylamix, Valencia, Spain) consisted of potato starch, salt, milk, and soy protein, polyphosphates (E-450i, E-452i), dextrose glutamate monosodium (E-621), sodium ascorbate (E-301), sodium, nitrite (E-250), and paprika extract (E-160c).

The meat batter was elaborated as follows. The sodium caseinate and water at 60 ◦C were homogenized in a Ultraturrax T25 basic (IKA-Werke, Staufen, Germany) for 2 min at a ratio of 5:1. Pork backfat or oleogel were then added and emulsified for 3 min. Once the emulsifying process was finished, the mixture was refrigerated at ambient temperature. Meat batters were elaborated by chopping the pork lean, jowl, and heart in a cutter (Cutter K30, Talsa, Talsabell S.A., Valencia, Spain) at a low speed for 1 min. Afterwards, the pork backfat or oleogel mass was added and chopped for 1 additional min. Finally, the commercial mix was included in the meat batter and mixed for 5 min. During this process, the overall temperature did not exceed 8 ◦C. After emulsification, each batch of meat batter was stuffed into 25 mm collagen casings and divided into sausages of 8 cm of length.

The sausages were cooked in a water bath (Marmite Mera 120 × 70, Talsa, Talsabell S.A., Valencia, Spain) at 90 ◦C for 20 min. The sausages were then immersed in an ice water-bath for 5 min, placed in polyethylene bags, vacuum packaged, and pasteurized at 90 ◦C for 30 min. Finally, the sausages were transferred to a cooler at 2 ◦C and stored for 24 hours until analysis. A total of 30 sausages of 100 grams (five samples per each batch × three batches × two replicates) were analyzed for different quality traits. Before analysis, sausages were minced in a blender (Moulinex, Barcelona, Spain).
