## 3 Results and Discussion
### Analysis of Interesterified and Noninteresterified Mixtures
MF:RSO—noninteresterified mixture of milkfat and rapeseed oil, iMF:RSO—interesterified mixture of milkfat and rapeseed oil, MB_C—control meat batters with pork jowl, MB_MF:RSO—meat batters produced with a noninteresterified mixture of milkfat and rapeseed oil and MB_iMF:RSO—meat batters produced with an interesterified mixture of milkfat and rapeseed oil. in Figure 2. On the course of the curve of the initial blend, two distinct peaks can be observed: peak 1 corresponding with lower-melting TAGs from rapeseed oil and peak 2 corresponding with higher-melting TAGs from milkfat. This is in agreement with the fact that rapeseed oil is able to remain in liquid form at a wide range of temperatures due to the low content of saturated fatty acids [11]. The gradual decrease of peak 1 and appearance of a new peak 3 corresponding to a high-melting TAG was the main consequence of the intereesterification. Peak 2 in the medium melting fraction became more pronounced. That can be attributed to the formation of new trisaturated and disaturated triacylglycerlevels after intereesterification [24; 29]. In the case of peak 3, the temperature associated with newly formed TAGs was very high, and a lot of energy was needed to melt the newly formed triacylglycerlevels, which also contributed to the increase of these blend melting points. Previous studies also indicated that the enzymatic intereesterification process can cause changes in the melting profile [13; 18; 24; 29; 30]. The quality of the oils and fats used as raw materials in the intereesterification is related to the free fatty acid (FFA) content, peroxide index, moisture and soaps content [24]. In the initial mixtures of milkfat with rapeseed oil, the acid value was at the level of 1.31-mg KOH/g fat, and the oxidative stability expressed as the induction time reached 85.29 min (Figure 3). The interesterified mixture was characterized by a significantly higher acid value (7.56 mg KOH/g fat) than the initial mixture. Other research also reported that enzymatic interesterification caused an increase of the free fatty acids content [10; 17; 31]. It can be due to the fact that two opposite reactions occur in the process of enzymatic interesterification: partial hydrolysis and the resynthesis of esters, which means that, in the final product, some amount of free fatty acids are present [32]. [PERSON] et al. [31] state that the duration of the process significantly affects the FFA content. [PERSON] et al. [24] in research on the interesterification of palm stearin and patawa oil mixtures suggested that chemical interesterification, in turn, reduced the FFA content in fat blends, because during filtration, FFA could be removed with the catalyst. Figure 2: Melting curves of the initial and interesterified mixtures of milkfat with rapeseed oil. MF:RSO—noninteresterified mixture of milkfat and rapeseed oil and iMF:RSO—interesterified mixture of milkfat and rapeseed oil. The interesterified mixture was also characterized by a significantly lower induction time (18.2 min) than the noninteresterified blend (Figure 3). The main reason for the lower oxidative stability for structured lipids is the loss of the antioxidant during the intereesterification reaction [33; 34]. An important factor affecting the oxidative stability of interesterified fats is the distribution of fatty acids in triacylglycerollolecules. Most studies have shown that PUFA placed at the sn-2 location of TAG are more favorably oxidized than in the sn-1 and sn-3 locations [35; 36]. [PERSON] et al. [34] claimed that the effect of location of the fatty acids in the triacylglycerollovel position did not seem to be conclusive of the oxidative stability of the interesterified fats. Generally, most literature records a report that enzymatic interesterification caused a decrease in oxidative stability, regardless of the type of starting fats and reaction conditions [13; 17; 18; 31; 34].