To study the factors and mechanisms involved in microorganisms' death or resistance to temperature in low-water-activity environments, a previous work dealt with the viability of dried microorganisms immobilized in thin-layer on glass beads. This work is intended to check the efficiency of a rapid heating-cooling treatment to destroy microorganisms that were dried after mixing with wheat flour or skim milk. The thermoresistance of the yeast Saccharomyces cerevisiae and the bacterium Lactobacillus plantarum were studied. Heat stress was applied at two temperatures (150 or 200 degrees C) for treatments of one of four durations (5, 10, 20, or 30 s) and at seven levels of initial water activity (a(w)) in the range 0.10 to 0.70. This new treatment achieved a microbial destruction of eight log reductions. A specific initial water activity was defined for each strain at which it was most resistant to heat treatments. On wheat flour, this initial a(w) value was in the range 0.30-0.50, with maximal viability value at a(w)=0.35 for L. plantarum, whatever the temperature studied, and 0.40 for S. cerevisiae. For skim milk, a variation in microbial viability was observed, with optimal resistance in the range 0.30-0.50 for S. cerevisiae and 0.20-0.50 for L. plantarum, with minimal destruction at a(w)=0.30 whatever the heating temperature is.

The study aims to compare three methods used for the evaluation of water absorption of wheat flour: a) a direct method consisting of a standard procedure on a Farinograph-E device and b) two indirect methods, namely NIR spectroscopy and centrifugation. Forty-four samples of Czech food wheat were collected from the harvest year 2021. Namely, 23 samples of food wheat from the standard maturity collection ‘SM2’ and 21 samples from the early maturity collection ‘EM2’. All wheat samples were ground to obtain wheat flour of fine granulation. The flour samples were characterised by protein and ash content of 10.55-14.75% and of 0,59-0.63%, respectively. The water absorption ranged from 55.7% to 63.2% flour weight (Farinograph standard procedure), 60.1-67.1% flour weight (NIR spectroscopy), and 67.6-77.2% flour weight (centrifugation). Based on the results obtained by ANOVA statistical analysis, no significant difference was found for all qualitative parameters of SM2 and EM2 (p = 95%). According to the mentioned methods for both indirect determinations of water absorption in the sets SM2 and EM2, the prediction of the standard farinograph water absorption was more accurate using the NIR technique (minimal and maximal pair differences of 1.01 and 6.86 percentage points, in contrast to 1.78 and 14.87 percentage points for the centrifugation method). Linear regression confirmed the primary importance of protein content for the water absorption values. Also, the ash content should be considered because it reflects the dietary fibre level, and the fibre influences the water absorption values as well.

Fungal growth on solid foods can make them unfit for human consumption, but certain specialty foods require fungi to produce their characteristic properties. In either case, a reliable way of measuring biomass is needed to study how various factors (e.g. water activity) affect fungal growth rates on these substrates. Biochemical markers such as chitin, glucosamine or ergosterol have been used to estimate fungal growth, but they cannot distinguish between individual species in mixed culture. In this study, a real-time polymerase chain reaction (rt-PCR) protocol specific for a target fungal species was used to quantify its DNA while growing on solid food. The measured amount of DNA was then related to the biomass present using an experimentally determined DNA-to-biomass ratio. The highly sensitive rt-PCR biomass assay was found to have a wide range, able to quantify the target DNA within a six orders-of-magnitude difference. The method was used to monitor germination and growth of Penicillium chrysogenum spores on a model porous food (cooked wheat flour) at 25°C and different water activities of 0.973, 0.936, and 0.843. No growth was observed at 0.843, but lag, exponential and stationary phases were identified in the growth curves for the higher water activities. The calculated specific growth rates (μ) during the exponential phase were almost identical, at 0.075/h and 0.076/h for aw=0.973 and 0.936, respectively. The specificity of the method was demonstrated by measuring the biomass of P. chrysogenum while growing together with Aspergillus niger on solid media at aw=0.973.

The effect of different levels of feed moisture (12-17%) during extrusion cooking, using a co-rotating twin-screw extruder on selected nutritional and physical properties of extruded products was investigated. Four different formulations were used based on wheat flour and corn starch with the addition of 10% brewer's spent grain (BSG) and red cabbage (RC) trimming reducing the flour and starch. The samples were: wheat flour+BSG (WBSG), corn starch+BSG (CBSG), wheat flour+red cabbage (WRC) and corn starch+red cabbage (CRC). Process conditions utilised were: constant feed rate of 25kg/h, screw speed 200rpm and barrel temperature of 80 and 120°C. The results indicated that increasing the water feed to 15% increased the level of total dietary fibre (TDF) in all the extrudates while extrusion processing increased the level of TDF in WBSG, CBSG and CRC but decreased in WRC products. Extrusion cooking increased the level of total antioxidant capacity (TAC) and total phenolic compounds (TPC) in WRC and CRC. In addition to water feed level affecting the TDF of the extrudates, also affected were the expansion ratio, bulk density, hardness, WSI, SME and colour. The protein level of the products and hardness of extrudates were related to the different formulations.

Summaries (En, Ru) | 2 ill. | The influence of fruit food additives "Yabochnaya" and "Grushevaya" obtained from secondary resources of fruit processing, on the forms of water connection in the wheat flour dough was evaluated. The additives are added to the test samples from wheat flour of the 1st grade in the amount of 6, 8 and 10% by weight of flour. Measurement of the nuclear magnetic relaxation characteristics of dough samples was performed using an NMR-analyzer AMV-1006M at a temperature of 23 deg C. It was found that the introduction additives "Yabochnaya" and "Grushevaya" to the dough samples in an amount of 10% by weight of flour allows increasing the content of strongly bound water in the dough by 6.5 or 4.9% respectively, which is explained by the higher content in the additive "Yabochnaya" compared to the additive "Grushevaya"of pectin (3.7% vs. 2.1%), largely showing water-retaining ability. The results, obtained using the NMR method, correspond to the data obtained in the study of the effect of these food additives on the water absorption capacity of the dough. Increasing in the dough the content of water, which is in a strongly bound state, will allow for further baking of dough blanks to reduce baking loss and, consequently, increase yield of products. | 6 ref. | Оценено влияние фруктовых пищевых добавок "Яблочная" и "Грушевая", полученных из вторичных ресурсов переработки фруктов, на формы связи воды в тесте из пшеничной муки. Добавки вносили в образцы теста из пшеничной муки 1-го сорта в количестве 6, 8 и 10% к массе муки. Измерение ядерно-магнитных релаксационных характеристик образцов теста осуществляли на ЯМР-анализаторе АМВ-1006М при температуре 23 град. С. Установлено, что внесение в образцы теста добавки "Яблочная" или "Грушевая" в количестве 10% к массе муки позволяет повысить содержание прочносвязанной воды в тесте на 6,5 или 4,9% соответственно, что объясняется более высоким содержанием в добавке "Яблочная" по сравнению с добавкой "Грушевая" пектина (3,7% против 2,1%), в значительной степени проявляющего водоудерживающую способность. Результаты, полученные с применением метода ЯМР, согласуются с данными, полученными при исследовании влияния указанных пищевых добавок на водопоглотительную способность теста. Повышение в тесте содержания воды, находящейся в прочносвязанном состоянии, позволит при дальнейшей выпечке тестовых заготовок снизить упек хлебобулочного изделия и, следовательно, увеличить его выход.

A simple and green ultrasound liquid-liquid microextraction method based on low viscous hydrophobic deep eutectic solvent (ULLME-LV-HDES) was proposed for the preconcentration and separation of selenium prior to HG-AAS detection. Six different DESs were prepared for the extraction of selenium. Quercetin was used complexing agent for Se(IV) ions. Various analytical parameters such as pH, quercetin amount, DES type and its volume, sonication time, sample volume were optimized. Tolerance limits of anion, cation and transition metal ions were studied. Preconcentration and enhancement factor were found 62.5 and 121. Under the optimum conditions, limit of detection was found 0.25 ng L⁻¹ with calibration range of 0.8–120 ng L⁻¹. Relative standard deviation was found 3.2%. The accuracy of the method was confirmed with certified reference materials (NIST 1567a Wheat flour and NIST 1548a Typical diet). Finally, the developed method was successfully applied to food and water samples.