Linda Rusalepp

Climate change is expected to alter air temperature, humidity, and soil water availability in forests, with important consequences for ecosystem carbon (C) cycling. The combined effects of atmospheric and soil drought on C fluxes and allocation remain poorly understood. We investigated how six realistic growing season weather scenarios affect C pools and fluxes in four-year-old Picea abies. Saplings were subjected to elevated air temperature (+6 °C) or reduced relative air humidity (-10%) for 30 days in the middle of growing season, each combined with either well-watered or water-stressed soil conditions. We quantified net ecosystem exchange (NEE), ecosystem and soil respiration (Re and Rs), photosynthetic assimilation four times during the growing season, and root respiration, exudation, and biomass allocation at the end of the experiment. Combined weather and soil water conditions significantly altered the seasonal dynamics of NEE, Re, Rs and fine root area growth, with Rs showing the strongest response. Total C accumulation in saplings biomass and root-related C fluxes was not affected following different weather scenarios. Combined atmospheric and soil drought reduced shoot respiration, suggesting persistent physiological effects of drought stress. All sapling ecosystems were net C sinks; the weakest C uptake was in well-watered ambient conditions with NEE of -144 mgCm-2h-1 compared to twice higher NEE following the heatwave. ,Growing-season weather extremes combined with soil-water conditions can reshape seasonal C dynamics in hemiboreal trees without necessarily affecting annual C accumulation, indicating substantial functional plasticity of saplings. However, shifts in C partitioning, particularly strong response of Rs, may alter future forest C cycling.

Consumer interest in healthier meat products has grown in recent years. Therefore, the use of plant powders as natural preservatives in the composition of pork and beef products could be an alternative to traditional meat products. This study aimed to assess the effect of different powders, such as blackcurrant, chokeberry, rowan berries, apple, tomato, garlic, and rhubarb, on the microbial growth dynamics in minced pork and beef during refrigerated storage. The total counts of aerobic microorganisms, Pseudomonas spp., yeasts, and molds were examined according to ISO methods. The polyphenolic profiles of plant powders and supplemented minced pork and beef samples were determined by HPLC-MS. The antioxidative capacity of the plant powders was analyzed using a spectrophotometric method. The findings of the study revealed that supplemented minced pork and beef samples had similar polyphenolic profiles and microbial growth dynamics. The highest antioxidative capacity was observed for anthocyanin-rich berry powders. In both minced pork and beef, rhubarb powder was the most effective plant material for inhibiting microbial growth, followed by blackcurrant pomace powder. In conclusion, all of the plant powders used in the present study can be used for the valorization of minced meat products, providing both antimicrobial and antioxidant effects.

It is commonly accepted that dietary nucleotides should be considered as essential nutrients originating mainly but not exclusively from meat and fish dishes. Most research in food science related to nutrition nucleotides is focused on raw products, while the effects of thermal processing of ready-to-eat food on nucleotide content are largely overlooked by the scientific community. The aim of this study is to investigate the impact of thermal processing and cold storage on the content of dietary nucleotides in freshly prepared and canned ready-to-eat meat and fish food. The concentrations of ATP, ADP, AMP, IMP, Ino, and Hx were determined using NMR, HPLC, FPMLC, and ATP bioluminescence analytical techniques; freshness indices K and K₁ and adenylate energy charge (AEC) values were estimated to assess the freshness status and confirm a newly unveiled phenomenon of the reappearance of adenylate nucleotides. It was found that in freshly prepared at 65 °C ≤ T ≤ +100 °C and canned food, the concentration of free nucleotides was in the range of 0.001–0.01 µmol/mL and remained unchanged for a long time during cold storage; the correct distribution of mole fractions of adenylates corresponding to 0 < AEC < 0.5 was observed compared to 0.2 < AEC < 1.0 in the original raw samples, with either a high or low content of residual adenylates. It could be assumed that heating at nonenzymatic temperatures T > 65 °C can rupture cell membranes and release residual intracell nucleotides in quite a meaningful concentration. These findings may lead to a conceptual change in the views on food preparation processes, taking into account the phenomenon of the free adenylates renaissance and AEC bioenergetics.

The chemical composition of berries and berry pomaces is diverse, containing polyphenolic components that may have both antibacterial and antioxidative properties. In the present study, in vitro antibacterial effect of the extracts of chokeberry, blackcurrant, and rowan berries and berry pomaces against L. monocytogenes, S. aureus, E. coli, and C. jejuni was studied. In addition, the polyphenolic profile and antioxidant activity of these extracts were investigated. The polyphenolic profiles in the aqueous and 30% ethanolic extracts were determined chromatographically by HPLC-MS, and the total polyphenol content was estimated spectrophotometrically by HPLC-DAD-UV. The minimal inhibition concentrations (MICs) of the extracts against tested bacteria were determined by the broth microdilution method. The content of total polyphenols was highest and good antioxidative properties of the extracts were determined for chokeberry and blackcurrant berries and their pomaces. The highest proportions of total quercetin derivatives and anthocyanins were found in the extracts of chokeberry berry/pomace and blackcurrant berry/pomace, respectively. The sensitivity of tested microbes to the extracts of berries and berry pomaces was as follows: S. aureus > L. monocytogenes > E. coli and C. jejuni. In vitro antibacterial activity of tested extracts depended on the extraction solvent, mainly for the ethanolic extracts. Findings suggest that chokeberry and blackcurrant berries and their pomaces can be used as a good source of polyphenols with antioxidative properties, and they also have antibacterial activity against some foodborne pathogenic bacteria. It is important that the valuable compounds are extracted from juice press residues before their disposal.

Fast protein and metabolite liquid chromatography (FPLMC) was introduced years ago to enable the easy separation of high-molecular compounds such as proteins from small molecules and the identification of the low-molecular substances. In this paper, the method is applied for the rapid evaluation of freshness and monitoring the aging of animal meat and fish. A novel chromatographic sensor was developed with a deep UV LED-based photometric detection unit (255–265 nm), an original flow cuvette and registration scheme; the processing of a chromatogram with the sensor takes approximately 15 min. Strict isochronism between the elution of ATP metabolites, mainly hypoxanthine (Hx) and inosine monophosphate (IMP), and the time of maturation of meat or fish, was discovered. A new freshness index H* = [Hx]/[IMP] was introduced, which is proportional to the instrumental delay time in the FPMLC chromatograms: the H* index < 0.5 indicates the presence of inosine monophosphate (IMP) and the high quality of the meat or fish. Reasonably strong correlations were revealed between data obtained by FPMLC and total volatile basic nitrogen TVB-N (for fish) or volatile fatty acids VFA (for meat) content. Moreover, putative nucleotide salvage and an increase in the concentration of IMP were observed in fish after heat treatment using the FPMLC sensor and NMR technique.