Improving the citric acid production by mutant strains Aspergillus niger using carbohydrate-containing raw materials as a carbon source

The demand for citric acid (CA) as a component of food products, pharmaceuticals, and cosmetics is increasing yearly. The use of adapted micro-organisms that convert naturally occurring carbohydrates into organic acids makes it possible to increase annual CA production significantly. The research aim was to study CA production by the Aspergillus niger strain in the medium based on carbohydrate-containing raw materials as a carbon source. We used a fermentation by A. niger. Starch hydrolysates were chosen as a nutrient medium. To improve the CA production of A. niger, multi-step mutagenesis was performed. This resulted in mutant strain A. niger R5/4, which had the highest acidogenic activity among the samples. The study evaluated the effect of temperature on the productivity of the mutant strains. The quantitative content of citric acid was analyzed at different incubation times (144, 168, and 192 h). The effect of the initial medium pH (4.5, 5.0, and 5.5) on acid formation was also investigated. The strain's optimum temperature, pH, and cultivation time parameters were determined. A three-factor, three-level Box-Benken design (BBD) was used to optimize CA production by A. niger strain R5/4 on a starch-containing medium. When assessing the impact of temperature on CA production, the ideal range was between 29 and 31 °C

Substitution of Pork Fat with Beeswax-Structured Oleogels in Semi-Smoked Sausages

The expansion of the assortment of low-saturated-fat sausages is a trend in healthy eating, and the use of alternative ways to reduce their saturated fat content is required. This study aimed to partially substitute pork fat with 7% and 10% oleogel, obtained by structuring sunflower oil with a two-component mixture of monoglyceride and beeswax, in the recipe for semi-smoked sausage. The physicochemical characteristics of the sausages were evaluated, and the fatty acid profile and sensory properties were analyzed. In the samples where pork fat was partially replaced with oleogel at 7% and 10%, there was a decrease in the content of saturated fatty acids (SFA) by 35% and 38%, respectively. The addition of oleogel to sausages significantly reduced the content of stearic and palmitic acid, increased the content of linoleic acid, and improved the fatty acid profile. The microstructure of the sausages showed a more homogeneous structure with a lower content of large lipid granules as the amount of oleogel added increased. The sensory analysis showed that the addition of 7% oleogel did not deteriorate the organoleptic properties. Therefore, the partial substitution of pork fat with 7% oleogel can be recommended to produce healthy sausages with improved fatty acid profile and sensory properties

Effects of Freeze-Drying on Sensory Characteristics and Nutrient Composition in Black Currant and Sea Buckthorn Berries

Fresh berries contain numerous components that can undergo complex changes during the drying process. This study aims to investigate the effect of freeze-drying on the sensory and chemical properties of black currant and sea buckthorn berries. Freeze-drying was performed at a shelf temperature of 35–55 °C with a step of 5 °C and durations of 18, 20, 22, and 24 h. Comparing the final freeze-dried berries with their fresh counterparts, it was observed that at a shelf temperature of 50 °C and a drying time of 18 to 20 h, there was a minimal loss in the content of vitamins, organic acids, and carbohydrates. However, based on organoleptic evaluations, the best results were achieved after drying for 20 h. Furthermore, the preservation of citric and malic acids in black currant berries, along with citric, tartaric acids, and sucrose in sea buckthorn berries, was only at 45.6% when the freeze-drying time was extended to 22 h. Considering the physical and chemical properties of listed freeze-dried berries, the optimal parameters were identified as a shelf temperature of 50 °C and a drying time of 20 h. The findings from this study serve as a foundation for selecting appropriate freeze-drying parameters for various types of berries