**3. Results**

#### *3.1. Chemical Composition of Frankfurters*

The statistical analysis showed significant di fferences for all evaluated parameters; however, the numerical values among batches were similar, with the exception of cholesterol content (Table 1). These outcomes can be explained by the fact that the amount of ingredients in all formulations was in fact the same, except the subcutaneous fat from pork which was replaced by the linseed oleogel. These slight observed differences could be attributed to the lack of homogeneity (backfat, jowl, lean, and heart) in the frankfurter elaboration procedure.

**Table 1.** Chemical composition of a frankfurter, expressed in percentage (mean values ± standard deviation of 10 samples).


Saturated fatty (SF), Standard error of mean (SEM), a–c Means in the same row with different letters differing significantly (*p* < 0.05).

Differences in moisture content ranged between 55.55–56.74% for all the batches, while the protein percentage varied from 10.62 to 11.19%, resulting in slightly higher values for the control samples. In addition, the replacement with linseed oleogel had a significant (*p* < 0.05) effect on protein content. Ash content was significantly affected by replacement of pork backfat, ranging between 4.04 and 4.24%. Regarding the fat content, the differences among batches were small (18.35–20.03%), although they reached statistical (*p* < 0.05) relevance and the cholesterol amount varied significantly (*p* < 0.001) among batches, with the highest content (25.08 mg/100g) in the control sausages.

#### *3.2. Fatty Acid Profile of Frankfurters*

The influence of the partial replacement of pork backfat at two levels by linseed oleogel on the FA profile is shown in Table 2. As expected, this partial substitution caused a significant effect in all FAs with the exception of α-linoleic acid (C18:2*n*6c). This is due to the healthy FA profile of the linseed oleogel. However, the most predominant FAs in all batches were monosaturated fatty acid (MUFA), followed by SFA and polyunsaturated fatty acid (PUFA).

Regarding individual FA, oleic acid (C18:1*n*9c) was the most considerable FA followed by palmitic acid (C16:0), α-linoleic acid, and stearic acid (C18:0). The replacement of pork backfat by linseed oleogel reduced the SFA content from 35.15 g/100 g obtained in control sausages to 33.95 and 32.34 g/100 g in SF-25 and SF-50, respectively. The most predominant SFA was palmitic acid (C16:0), followed by stearic acid (C18:0). The palmitic content decreased significantly (*p* < 0.05) from 22.23 to 20.07 g/100 g for the control and SF-50 treatment, respectively. Moreover, stearic content showed a significant reduction from 10.92 to 10.37 g/100 g. The MUFA content was also affected by linseed replacement, presenting the highest values in the control sausages (48.06 mg/100 g). Differences are mainly due to oleic content variation along the three batches. In this sense, linseed seed is poor in this FA, causing a significant decrease in the final formulation.

Concerning PUFA, their content was significantly (*p* < 0.05) affected by linseed inclusion. Indeed, the PUFA content increased from 16.77 mg/100g for the control to 20.10 and 25.46 mg/100 g for SF-25 and SF-50, respectively. The linoleic acid did not show significant (*p* > 0.05) differences among batches; however, variations in PUFA content are directly associated to the linolenic content. This was a desired consequence, which had immediate consequences on *n*-3 PUFA content as well as in PUFA/SFA and *n*-6/*n*-3 ratios. Indeed, control sausages had the lowest PUFA/SFA ratio (0.47) and the higher *n*-6/*n*-3 (14.92). Thus, these ratios could be significantly (*p* < 0.05) increased to 0.78 and decreased to 1.61, respectively, with replacement of 50% of pork backfat by linseed oleogel.


**Table 2.** Fatty acid profile (g/100 g of fat) of frankfurter (mean values ± standard deviation of 10 samples).

Standard error of mean (SEM), the saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), atherogenicity (IA), thrombogenicity (IT), a–c Means in the same row with different letters differing significantly (*p* < 0.05).

Finally, replacing pork backfat with a linseed oleogel also had a significant effect (*p* < 0.001) on the IA and IT and on h/H. Sausages with a replacement of 25% and 50% obtained the lowest values for IA and IT (0.42 vs. 0.40 vs. 0.36; *p* < 0.001 for control, SF-25 and SF-50, respectively, in the case of IA and 0.98 vs. 0.75 vs. 0.53; *p* < 0.001 for control, SF-25 and SF-50, respectively), showing the better nutritional fatty acid profile. Regarding the h/H ratio, sausages replaced with 50% of lineseed oleogel obtained the highest values, with the highest percentage of hypocholesterolemic FA, α-linolenic, and the lowest amounts of hypercholesterolemic FA (C14:0 and C16:0). On the contrary, control sausages displayed an opposite trend in respect to the amounts of hypocholesterolemic and hypercholesterolemic FA, resulting in the lowest h/H values. However, for all sausage batches studied this ratio was higher than 2.5, which is considered as favorable.

#### *3.3. Quality Parameters: pH and Color Assessment of Frankfurters*

The pH values were significantly (*p* < 0.001) influenced by replacement with linseed oleogel, although numerical values were very similar. Regarding color parameters (L\*, a\*, and b\*), they were significantly (*p* < 0.001) influenced by substitution of pork backfat with linseed oleogel. Specifically, luminosity and yellowness increase with the amount of linseed oleogel (L\* from 61.47 to 69.37 and b\* from 16.61 to 18.85 for the control and SF-50, respectively). On the contrary, redness value decreased from 12.50 to 9.06 for control and SF-50, respectively (Figure 1).

**Figure 1.** Color parameters of frankfurters, a–c Different letters indicate statistically significant differences (*p* < 0.05), (mean values ± standard deviation of 10 samples).

#### *3.4. Texture Profile Analysis of Frankfurters*

The textural profile analysis shows that the replacement of pork backfat with linseed oleogel led to significant variations in the following textural parameters: Hardness, cohesiveness, gumminess, and chewiness (Figure 2). Cohesiveness, gumminess, and chewiness significantly increased in SF-50, with respect to control sausages, but the differences were relatively slight.

**Figure 2.** Textural parameters of frankfurters. Hardness (Kg), Springiness (mm), Gumminess (Kg), and Chewiness (kg mm), a–c Different letters indicate statistically significant differences (*p* < 0.05), (mean values ± standard deviation of 10 samples).

#### *3.5. Sensory Attributes of Frankfurters*

Sensory analysis indicated that there were significant differences in the preference (*p* < 0.05), influenced by the replacement of pork backfat with linseed oleogel (Table 3). The appearance is significant to consumer preference and acceptability of products. Panelists showed a clear preference (*p* < 0.05) for control samples over SF-25 and SF-50 samples. Regarding color parameters, the control sample obtained the lowest yellowness value, suggesting a higher acceptability. In meat products, the yellow color is associated with rancid foods caused by lipid oxidation. A significant difference (*p* < 0.05) was detected between the control and the remaining samples for the odor and taste. The control sample was the most preferred in both cases. Hardness only showed a slightly higher value in the 25% substitution sausage without significant influence in the evaluation for ranking preference. In the case of juiciness, a significantly lower score (*p* < 0.05) showed for the SF-50, whereas no differences were detected between the control and SF-25. Finally, control samples obtained higher scores for global perception compared to other samples (86 vs. 58 and 48 for control, SF-25, and SF-50 batches, respectively).


**Table 3.** Preference data: Rank sums. Ranking preference: 1 the lowest, 3 the highest preferred.

> a–b Different letters indicate statistically significant differences (*p* < 0.05).
