A) Average values of the total fat content of the mealworm as a novel food by individual breeders do not differ by more than ±10% from the total average fat content of all selected suppliers. B) The total fat content of the mealworm as a novel food is comparable to other commodities of animal origin from common livestock. C) The results of comparison of the fat sensory evaluation of mealworm as novel food with other fats of animal origin using a simple electronic nose will be different.

The aim of this work was to evaluate some aspects gained and analyzed during the monitoring of nutritional values of mealworm, especially for fat. The work observes and compares the total fat content of mealworm from different breeders including the determination of its average value and the standard deviation and its comparison with other fats of animal origin commonly used. Furthermore, the aim was to obtain initial information on the comparison of the sensory properties of the fat of the mealworm with other fats of animal origin using a simple electronic nose.

Mealworm (Terebrio mollitor) larvae in the last and the penultimate developmental stages (full length of the body just before the pupae) were used. The larvae were taken from the breed, left to starve for 48 hours, killed with boiling water (100 °C) and immediately dried at 105 °C. The samples prepared this way were homogenized and stored in a refrigerator at 4 – 7 °C until analysis.

The larvae were purchased from three companies in the Czech Republic. In addition, the data of the author described in (Adámková et al., 2016; Adámková et al., 2017) were used for comparison. Furthermore, the average values and standard deviations from available literature were compared with a focus on breeding and sales in the Czech Republic.

The data were analyzed using Excel 2013 (Microsoft, USA). Results were expressed by average ± standard deviation. For the calculation of the general average fat values for mealworm and their comparison, also the values from the available literature complemented by the optimal conditions of breeding focused on the breeding area in the Czech Republic were used together with the measured values.

In case of measurement by E-nose, data was evaluated using Excel 2013 (Microsoft, USA) and Gnuplot 5.0: an interactive plotting program (Williams et al., 2016).

To determine the overall value of the total fat content of the mealworm larvae and its comparison, the total fat content in samples from three suppliers (2 direct breeders + 1 supplier with unknown breeder) was determined in the first step. The basic results determined by the Soxhlet method are shown in Table 1.

From the results shown in Table 1. average values and standard deviations for individual suppliers were calculated and these values were compared with other literary sources focusing on the area of the Czech Republic, as shown in Table 2.

Table 2 shows that even under optimal breeding conditions, the total dry fat content of mealworm larvae (Tenebrio molitor) samples may differ statistically, even if the breeders are from one geographical area. By random purchase, the consumer gained insect with a total fat content ranging from 170 mg.g^-1 to 360 mg.g^-1 of fat in dry matter. The mean value calculated from the experimental values and available literature sources for Europe for the optimal breeding conditions stated is 243 ±57 mg.g^-1.

From a standard deviation of 23.4% of the average total fat content, it can be estimated that the consumer is not able to estimate the amount of fat in a particular insect sample with sufficient accuracy. The real extreme values can occur in breeds where welfare is not respected by the breeder and especially the seller (Adámková et al., 2017).

The analyzed data show the total fat content of mealworm is not affected by the area of breeding. The content of the fat will be influenced by the breeding temperature, seasons, stress and nutrition in managed breeds Broekhoven et al. (2015); Nowak et al. (2016). Here, too, it is confirmed that nutrition is one of the important factors influencing the quantity and variability of fat as it is for other commodities of animal origin (patent). The fat content of mealworm can be compared with the fat content of the parts of the body of common livestock (Figure 1) (Pipek, 1995; Steinhauser, 1995). Due to the size of the insect, from the whole body of the insect, whereas in common livestock it is possible to extract the fat from individual parts thereof. In addition, it is necessary to consider that fat consumption from ordinary livestock can take place after a short heat treatment or even in the raw state, insect fat can be used for food purposes only after chemical extraction. This increases the cost of this raw material. On the other hand, in the longterm storage process there are no significant biochemical and microbiological changes and no specific storage conditions (Adámek et al., 2018).

When comparing the total fat content in the dry matter of the mealworm with the total fat content of the conventional meat, the analyzed values for the mealworm are in a wide range from 16% to 36%. This can be compared with both lean chickens (14%) and, for example, salmon (37.6%). This range includes, for example, beef sirloin, mackerel or turkey meat.

From the health point of view, not only the total fat content but also the fatty acid profile, especially linoleic acid and linolenic acid, is important. EFSA Recommendation on fat and other lipophilic substances ingestion from 2010 (EFSA, 2010) no longer state recommendation for the n-6: n-3 ratio but, indicate that linoleic acid intake should not fall below 4% and linolenic acid below 0.5% of total energy intake. In the case of mealworm meal consumption and required energy intake of 10,000 kJ.day^-1, linolenic acid in the amount of 205 g and 708 g of linolenic are needed. Considering the linolenic acid intake, the quantity contained in the dry matter is insufficient and must be supplemented from other sources. On the contrary, the amount of linoleic acid is sufficient, and the dry matter can serve as the source of this acid (Adámková, 2017). Although mealworm is included among livestock since 2015 (EFSA, 2015), it must be considered a specific species with special biological properties. For this reason, insect has to be bred under the defined breeding conditions to achieve the desired properties.

In the next part, the flavor of raw pork and beef fat was measured with a simple electronic nose and compared with fat obtained by the extraction from mealworm larvae. The results in Figure 2 show the difference between insect fat and pork and beef fat.

The most significant difference was recorded by the MQ-8 type sensor, which responds in particular to Hydrogen (H₂), next to alcohol, LPG and cooking fumes. Therefore, the difference between fats can be caused by the treatment of fat from insect during extraction or different fat composition.

In today's food industry, modern techniques such as electronic nose, eye or tongue are used to capture sensory properties. The disadvantage of these techniques is that they cannot replace the human sensory organ in full. The advantage is good repeatability even in longterm measurements (human can be tired) and in some cases a better sensitivity, resolution or range wider than a human can possess (e.g. electronic eye). An electronic nose used to record flavors from commodities of animal origin is described, for example, by Gopal (2015), who in his study used the Peres' electronic nose to assess the freshness and durability of the meat. The electronic nose plays another important role in detecting food counterfeiting and assessing its authenticity (Peris and Escuder-Gilabert, 2016). In the case of edible insect as a novel food that is being introduced to the market, however, this technology has been used only minimally. The introduction of this technology is one of the arguments for persuading the Czech (European) consumer that food from edible insect is safe and has properties similar to other commodities of animal origin. It is necessary to bear in mind that the insect fat is extracted.