Teodora Popova

The study aimed to investigate the effect of the inclusion of Tenebrio molitor meal (TM) in the diet of layer hens on the quality characteristics of eggs and their fatty acid profile. A total of 90 layers (age 33 weeks) were involved in the trial. They were allocated to 5 dietary groups, each consisting of 6 replicate cages with 3 layers per cage. The layers were fed a basal diet (C) and diets including TM in amounts of 1% (T1), 2% (T2), 3% (T3), and 4% (T4) for a period of 10 weeks. The dietary incorporation of TM was associated with decreased weight of the eggs (p < 0.0001), albumen (p < 0.0001), yolk (p = 0.0008), and shell (p < 0.0001) as well as decreased shell thickness (p < 0.0001), corresponding to the deteriorated performance indicators. Additionally, the yolks of the hens receiving TM had a darker colour (p < 0.0001). The diets containing the insect meal led to significant decrease in the saturated (SFA) (p = 0.0019) and increase in monounsaturated fatty acids (MUFA) (p < 0.0001) in the yolks. The content of polyunsaturated fatty acids (PUFA) declined in the groups fed TM (p = 0.0028), particularly T3 and T4. This was, however, compensated by the favourably lower peroxidability (PI) (p = 0.0137), atherogenic (AI) (p = 0.0111) and thrombogenic (TI) (p = 0.0070) index and raised ratio between hypo- and hypercholesterolemic fatty acids (h/H) (p = 0.0039).

The study aimed to investigate the effect of the incorporation of Tenebrio molitor meal (TM) as partial replacement of soybean meal in the diet of layer hens on the production performance and quality characteristics of eggs. The trial included 90 layers at the age of 33 weeks allocated to 5 dietary groups. Each group consisted of 6 replicate cages with 3 layers per cage. The layers were fed a basal diet (C) and diets including TM in amounts of 1% (T1), 2% (T2), 3% (T3), and 4% (T4) for a period of 6 weeks. The results demonstrated different effect of the incorporation of TM in the layers' diet depending on the dose. After the first week of the trial, it was associated with significant reduction of the egg production and impaired feed conversion ratio in the birds fed 2% TM, which was also observed in T4 from the 4th till the 6th week of the experiment. The weight of the eggs and the albumen showed linear response to the inclusion of the TM in the diet, as both decreased with the increasing levels of the insect meal. The latter also affected the colour of the yolk, which was lighter in all the groups consuming TM in comparison to the control group.

The study aimed to explore the changes in hydrolytic and oxidative changes in broiler meat during frozen storage as affected by the dietary levels of low-fat Tenebrio molitor meal (LFTM). A total of 120 male one-day-old Ross 308 broilers were involved in the trial and allocated to 5 groups. After 14 days of adaptation, the broilers were fed a basal diet (C) and diets including LFTM in amounts of 2.5% (T2.5), 5% (T5), 7.5% (T7.5), and 10% (T10). After 35 days, the broilers were slaughtered. For the purposes of the experiment 18 broilers per dietary group wеre used. The carcasses were frozen into freezing cabinet (-18 °C). Six of the carcasses were stored for 1 month, another 6 were stored for 3 months, and the last 6 were stored for a period of 5 months. Breast and thigh meat of the broilers were used to analyze the effect of the dietary LFTM and storage on the changes of pH, color, lipid and protein hydrolysis and oxidation. The results of this study demonstrated а strong interaction effect of the dietary LFTM and the storage on the quality traits and stability of the lipids and proteins of the meat in broilers, also depending on the type of meat. Overall, the higher levels of LFTM (7.5% and 10%) reduced pH and led to brighter color of the breast during the storage. Furthermore, the insect meal in levels higher than 5% decreased the hydrolysis and primary lipid oxidation in the breast during the later stages of the storage, as well as the initial proteolysis. However, in thighs, such levels of LFTM promoted lipid hydrolysis and secondary oxidation during the earlier storage periods. The results point to future research, which will help to establish the most appropriate conditions so that LFTM can exert its positive effect and help restrict the hydrolysis and oxidation in meat to preserve its healthy and nutritional value.

A meta-analysis of the effect of gamma irradiation on the accumulation of primary and secondary products of oxidation, as well as pH and instrumental colour characteristics (lightness—L*; redness—a* and yellowness—b*) in beef stored at different temperatures and packaging was performed. A total of 15 studies were included, each concerning at least one of the examined indicators. The number of independent experiments according to the covariates (dose of irradiation, temperature of storage, and packaging) varied between 16 and 25 for the individual traits. The heterogeneity between studies determined the selection of the random effects model to be applied on the raw mean difference (effect size) in the analysis of the data. The results of the meta-analysis showed that the gamma irradiation of beef is associated with a significant increase in the peroxide value (POV) (p = 0.046) and the content of thiobarbituric acid reactive substances (TBARS) (p < 0.001) as well as a decrease in pH (p < 0.001). The colour parameters L*, a*, and b* varied insignificantly. While no effect of the dose of applied radiation and the type of packaging was found on the studied parameters, the storage conditions affected the TBARS content, which, however, remained at acceptable levels without negative influence on the high nutritional value of the meat.

The study aimed to investigate the effect of the inclusion of low-fat Tenebrio molitor meal (LFTM) as partial replacement of soybean in the diet of broilers on the physical properties, chemical composition and fatty acid profile of the meat. The trial included a total of 120 male one-day-old Ross 308 broilers allocated to 5 groups. After 14 days of adaptation, the birds were fed a basal diet (C) and diets including LFTM in amounts of 2.5% (T2.5), 5% (T5), 7.5% (T7.5), and 10% (T10). At 35 days of age, 8 birds per group were sacrificed and subjected to analysis of the meat quality. The higher dietary levels of LFTM were associated with decrease in pH₂₄ (linear, P<0.0001), but increased L* (linear, P=0.0004), drip loss (linear, P=0.0001) and cooking loss (linear, P=0.0058) in the breast. Furthermore, increasing the LFTM concentrations led to decline in protein (linear, P<0.0001), but increase in fat (linear, P<0.0001) and moisture (linear, P=0.0006) of the breast meat. The inclusion of the LFTM in the diet affected the fatty acid composition in breast and thigh meat in a dose dependent manner. Increasing the dietary levels of LFTM increased the saturated (SFA) fatty acids in the breast (linear, P=0.0012) and thigh (linear, P<0.0001) as well as the content of monounsaturated (MUFA) fatty acids in both cuts (linear, P<0.0001). This was associated with decrease in the polyunsaturated (PUFA) fatty acids in the meat of the birds fed higher levels of LFTM (linear, P<0.0001), thus producing higher atherogenic (AI) (linear, P<0.0001) and thrombogenic indices (TI) (linear, P<0.0001). The results of this study suggest that LFTM might be included in amount up to 5% in the diet of broilers without adverse effects on meat quality.

Rabbit meat is very susceptible to spoilage due to its high moisture and protein content. Hence, the application of natural antioxidants is important to restrict the deterioration and maintain its high quality and shelf life. This study was designed to investigate the effect of edible films and coatings made of chitosan and containing rosemary extract on the pH, colour and lipid oxidation in rabbit meat during low temperature storage. Samples of the loin and hind leg derived from New Zealand rabbits were divided in five groups – control (C), F1 – wrapped into chitosan film; F2 – wrapped into chitosan + rosemary film; S1 – immersed into chitosan solution, S2 – immersed into chitosan + rosemary solution. The meat was stored at 4 °C for 7 days and then at –20$ °C up to day 90. The values of pH increased overtime in the loin and leg, and were higher in the treated groups, especially F1 and F2. The higher values of pH in F1 and F2 corresponded to the decreased lightness (L*) in these groups in both loin and leg. The redness (a*) and yellowness (b*) remained unaffected by the treatment and storage in the loin. In the leg, we observed decreased a* in S1 and S2 after 7 days, and in F2, S1 and S2 after 90 days. The lowest value of b* in the leg was exhibited in F2 after frozen storage. Regardless of the treatment and storage period, TBARS remained lower in the meats with edible films and coatings, demonstrating their high potential to restrict oxidation.

The valorisation of underutilized male layer-type chickens offers a sustainable and ethically aligned opportunity for the poultry industry. This study evaluated the feasibility of male layer-type chicken meat in the production of chicken pâtés and compared the effects of different meat sources—commercial broiler (CP), and 5 (5wP) and 9-week-old (9wP) male layer-type chickens—on product quality during refrigerated storage using the general linear model with the Tukey–Kramer post-hoc test. Pâtés made from 5wP meat exhibited the most favourable technological properties, including the lowest (p < 0.05) total expressible fluid (TEF), highest (p < 0.05) water retention (TEF_Water), and lowest (p < 0.05) fat content (TEF_Fat) than CP and 9wP indicating superior emulsion stability. The 5wP pâtés also presented the lowest (p < 0.05) TBARS values on day 1, along with reduced colour deterioration (ΔE) over 7 days of storage. CP samples demonstrated the greatest (p < 0.05) hardness, cohesiveness, and gumminess, but lower (p < 0.05) springiness and resilience compared to 5wP and 9wP, yielding softer and elastic pâtés. Overall, pâtés formulated with 5wP can be a promising option for the development of value-added poultry products. The incorporation of male layer-type chicken meat into commercial formulations will encourage further research of their market potential.

Tenebrio molitor is considered a sustainable protein source for diets in poultry. It has been investigated in regard to the performance, health status, and product quality in different poultry species. This study was designed to evaluate the effect of low-fat Tenebrio molitor meal (LFTM) included in the broilers’ diet on the growth performance and carcass composition of the birds. The trial was conducted at the Institute of Animal Science-Kostinbrod, Bulgaria. A total of 120 male one-day-old Ross 308 broilers were allocated to 5 groups. After an adaptation period of 14 days, the birds were fed a basal diet (C) and diets including LFTM in amounts of 2.5% (T2.5), 5% (T5), 7.5% (T7.5), and 10% (T10). The growth performance of the birds was measured during the trial. At 35 days of age, 8 birds per group were slaughtered, and their carcass quality was evaluated. We found a linear response of BWG and FCR towards the inclusion of Tenebrio molitor meal (TM) in the diet. For the whole period (14–35 d), the BWG decreased (p = 0.0002), while the values of FCR increased (p = 0.0001) with the increase in the levels of the insect meal. The doses of 7.5% and 10% of the insect meal were associated with lower carcass weight and also decreased the yield of the breast. The results of the study indicated that the incorporation of LFTM, especially in amounts of 7.5–10%, could not be appropriate for broilers due to adverse effects on the growth performance and carcass composition.

This study aimed to assess the effect of the addition (2%) of soybean protein (SP) and insect flours derived from house crickets (Acheta domesticus, HCF) and yellow mealworm (Tenebrio molitor, YMF) in cooked sausages. The technological characteristics of the batter, the chemical composition of the sausages, their technological traits and lipid stability during refrigerated storage, as well as their sensory properties, were investigated. The SP, HCF and YMF batters displayed higher pH (p = 0.0025) and stability (p < 0.0001) but a darker colour (p < 0.0001) than the control samples. The addition of SP increased the plasticity of the batter (p = 0.0017), while YMF decreased its structural strength (p = 0.0274). Higher pH and darker colour were detected in SP-, HCF- and YMF-containing sausages; however, the effect of the alternative proteins depended on the duration of storage. The plasticity decreased in the insect-containing sausages (p = 0.0010) and increased over time (p = 0.0136), whereas the elasticity was lower in the YMF group (p < 0.0001). The protein and fat contents were higher (p < 0.0001) in the sausages containing alternative protein. TBARS content decreased over time in these groups. The HCF and YMF sausages received lower scores for their appearance, colour, texture, flavour and taste, suggesting the need for further technological interventions to make such products more attractive to consumers.

The increasing production of edible insects on an industrial scale makes it crucial to implement appropriate technologies after harvesting to process safe and high quality insect products. The aim of this work was to compare the impact of different drying treatments used in the production of flour from Tenebrio molitor larvae. The larvae were subjected to freeze-drying (FD), conventional drying (CD), microwave drying (MWD), microwave drying without freezing prior blanching (MWDL), and microwave drying with addition of 0.1% butylated hydroxytoluene (BHT) during the blanching of the larvae (MWDA). The studied parameters included water activity (a_w), instrumental colour, chemical composition, lipid oxidative processes, antioxidant activity, as well as microbiological status. The freeze-drying and conventional drying of the larvae reduced the a_w of the derived flours (p < 0.0001); however, their nutritional profile revealed lower protein (p < 0.0001) and considerably higher fat content (p < 0.0001) compared to the flours after microwave treatments. The conventional drying and microwave treatment with BHT induced significantly darker colour (p < 0.0001) in comparison to the other methods. Despite the advantages of the microwave drying as a fast and energy efficient method, it displayed some negative effects associated with low lipid stability such as higher acid value (AV) and secondary products of lipid oxidation (TBARS) (p < 0.0001). This was also observed in the MWDA flour, indicating a certain pro-oxidative effect of the BHT. Regardless of the drying method, all the flours had a low microbial load.