*2.1. Materials*

Fresh post-rigor pork meat (a mixture of *M. biceps femoris*, *M. semimembranosus*, *M. semitendinosus*, *M. gracilis* and *M. adductor*) (30 kg) (23.7% ± 0.2% protein, 3.89% ± 0.49% fat) and pork back fat (5 kg) (0.87% ± 0.1% protein, 92.99% ± 0.80% fat), both from different animals, were obtained from a local market on different days. The meat was trimmed of visible fat and connective tissue. The meat and pork backfat were minced through a grinder with a 0.6 cm plate (Van Dall SRL., Milano, Italy). Lots of approximately 1000 g for meat and 500 g for fat were vacuum packed, frozen and stored at −20 ◦C until used.

The SUN, donated by the company Planetarians (Palo Alto, CA, USA), was used as an animal fat replacer. This ingredient has been reported to have 38% protein, 1.8% fat and 4.6% moisture, as well as high total phenolic content [8].

Other ingredients and additives used were sodium chloride (Panreac Química, S.A., Barcelona, Spain), sodium tripolyphosphate (Manuel Riesgo, Madrid, Spain), sodium nitrite (Fulka Chemie GmbH, Buchs, Germany) and flavouring (Gewürzmüller, Julio Criado, Madrid, Spain).

#### *2.2. Preparation of Frankfurters*

Three different types of frankfurter were prepared (Table 1).


**Table 1.** Formulation (%) of frankfurters.

Additives added to all the samples per 100 g of product: 2 g NaCl; 0.5 g flavouring; 0.3 g sodium tripolyphosphate and 0.012 g sodium nitrite. \* Frankfurters formulated with all animal fat (F/AF), half of the animal fat and replacing the rest of fat with 2% (F/2SUN) or 4 % (F/4SUN) of defatted sunflower seed flour (SUN). \*\* Upcycled defatted sunflower seed flour.

One, used as a reference, was formulated with 15% of pork back fat (F/AF) to obtain a final product with about 20% of fat similar to commercial products and other frankfurters [14,15]. The other two samples were elaborated with proximately half of the pork backfat (8%). In these 2 reformulated frankfurters, to replace the rest of pork backfat (7%), SUN was used in 2 levels, 2% (F/2SUN) and 4% (F/4SUN), and the difference was made up with water, according to the formulations shown in Table 1.

Meat and fat were thawed at 3 ± 1 ◦C prior use. Frankfurters were elaborated according to Jiménez-Colmenero, et al. [18], using the formulation described in Table 1. Briefly, all meat was homogenized and ground for 1 min in a chilled cutter (Stephan Universal Machine UM5, Stephan Söhne GmbH and Co., Hameln, Germany). Then, pork backfat for all samples and the corresponding amount of SUN according to the formulation (Table 1) for each type of frankfurter (F/2SUN or F/4SUN), along with the rest of the ingredients (additives and water) (Table 1) were added to the cutter and mixed for 2 min. Finally, under vacuum and chilled conditions, the mixture was homogenized for 2 min. The final meat batter (<14 ◦C), was stu ffed into 20 mm diameter Nojax cellulose casings (Viscase S.A., Bagnold Cedex, France). Samples were hand-linked and heat processed in a smokehouse (model Unimatic 1000, Micro 40 Eller, Merano, Italy). Then, frankfurters were cooled to room temperature, casings were removed, and samples were vacuum-packed in plastic bags (Cryovac ® BB3050, Sealed Air S.L., Sant Boi de Llobregat, Barcelona, Spain) and stored (4 ± 1 ◦C) until use.

#### *2.3. Composition Analysis and Energy Value*
