Adjunctive application of solid-state culture products and its freeze-dried powder from Aspergillus sojae for semi-hard cheese.

BACKGROUND: Species belonging to the genus Aspergillus have been used in traditional Japanese fermented foods. Aspergillus sojae is a species responsible for strong proteolytic activity. Freeze-drying treatments followed by physical disruption enables the pulverization of the mycelia of A. sojae RIB 1045 grown in whey protein-base solid media. Intracellular proteases were extracted using this protocol to compare extracellular protease activity in terms of the reaction's pH dependence in the presence or absence of inhibitors. RESULT: With different sensitivities to inhibitors, intracellular and extracellular proteases showed the strongest activity under acidic conditions, which were considered suitable for cheese application. The raw culture product (CP) and its freeze-dried product (FDP) were mixed with cheese curds, prepared according to Gouda-type cheese-making methods, and were allowed to ripen for 3 months. Chemical analysis of the products showed 13.3% water-soluble nitrogen (WSN) in the control, which had received noncultured media, whereas 20.0% and 21.1% WSN was found in the CP and FDP experimental cheeses, respectively. Although these adjuncts significantly increased WSN, an insignificant difference was found between CP and FDP. Free fatty acids in all experimental cheeses were similar, showing that CP and FDP caused no rancid defects. CONCLUSION: The introduction of freeze-drying treatments accompanied by cell disruption resulted in a negligible effect in terms of WSN. However, the application of A. sojae can be beneficial when it comes to increasing the level of WSN compared with A. oryzae, as shown in our previous study. © 2020 Society of Chemical Industry.

Technical note: Feasibility of near infrared transmittance spectroscopy to predict cheese ripeness.

The aim of the study was to evaluate the feasibility of near infrared (NIR) transmittance spectroscopy to predict cheese ripeness using the ratio of water-soluble nitrogen (WSN) to total nitrogen (TN) as an index of cheese maturity (WSN/TN). Fifty-two Protected Designation of Origin cow milk cheeses of 5 varieties (Asiago, Grana Padano, Montasio, Parmigiano Reggiano, and Piave) and different ripening times were available for laboratory and chemometric analyses. Reference measures of WSN and TN were matched with cheese spectral information obtained from ground samples by a NIR instrument that operated in transmittance mode for wavelengths from 850 to 1,050 nm. Prediction equations for WSN and TN were developed using (1) cross-validation on the whole data set and (2) external validation on a subset of the entire data. The WSN/TN was calculated as ratio of predicted WSN to predicted TN in cross-validation. The coefficients of determination for WSN and TN were >0.85 both in cross- and external validation. The high accuracy of the prediction equations for WSN and TN could facilitate implementation of NIR transmittance spectroscopy in the dairy industry to objectively, rapidly, and accurately monitor the ripeness of cheese through WSN/TN.

Deciphering the impact of nitrogen morphologies distribution on nitrogen and biomass accumulation in tobacco plants.

Background and aims: Nitrogen (N) distribution in plants is intricately linked to key physiological functions, including respiration, photosynthesis, structural development, and nitrogen storage. However, the specific effects of different N morphologies on N accumulation and plant growth are poorly understood. Our research specifically focused on determining how different N morphologies affect N absorption and biomass accumulation. Methods: This study elucidated the impact of different application rates (CK: 0 g N/plant; T1: 4 g N/plant; T2: 8 g N/plant) of N fertilizer on N and biomass accumulation in tobacco cultivars Hongda and K326 at different growth stages. Results: Our findings emphasize the critical role of N distribution in various plant parts, including leaves, stems, and roots, in determining the complex mechanisms of N and biomass accumulation in tobacco. We found that in relation to total N, a greater ratio of water-soluble N (N w) in leaves facilitated N accumulation in leaves. In contrast, an increased ratio of SDS (detergent)-insoluble N (N in-SDS) in leaves and non-protein N (N np) in roots hindered this increase. Additionally, our results indicate that a greater proportion of N np in leaves has a negative impact on biomass accumulation in leaves. Furthermore, elevated levels of N in-SDS, N w, and N np in roots, and N np in leaves adversely affected biomass accumulation in tobacco leaves. The Hongda cultivar exhibited greater biomass and N accumulation abilities as compared to K326. Conclusions: Our findings highlight the significant role of distribution of N morphologies on plant growth, as well as N and biomass accumulation in tobacco plants. Understanding N distribution allows farmers to optimize N application, minimizing environmental losses and maximizing yield for specific cultivars. These insights advance sustainable agriculture by promoting efficient resource use and reducing environmental impact.

Thinning effect on photosynthesis depends on needle ages in a Chinese fir (Cunninghamia lanceolata) plantation.

Canopies in evergreen coniferous plantations often consist of various-aged needles. However, the effect of needle age on the photosynthetic responses to thinning remains ambiguous. Photosynthetic responses of different-aged needles to thinning were investigated in a Chinese fir (Cunninghamia lanceolata) plantation. A dual isotope approach [simultaneous measurements of stable carbon (δ13C) and oxygen (δ18O) isotopes] was employed to distinguish between biochemical and stomatal limitations to photosynthesis. Our results showed that increases in net photosynthesis rates upon thinning only occurred in the current-year and one-year-old needles, and not in the two- to four-year-old needles. The increased δ13C and declined δ18O in current year needles of trees from thinned stands indicated that both the photosynthetic capacity and stomatal conductance resulted in increasing photosynthesis. In one-year-old needles of trees from thinned stands, an increased needle δ13C and a constant needle δ18O were observed, indicating the photosynthetic capacity rather than stomatal conductance contributed to the increasing photosynthesis. The higher water-soluble nitrogen content in current-year and one-year-old needles in thinned trees also supported that the photosynthetic capacity plays an important role in the enhancement of photosynthesis. In contrast, the δ13C, δ18O and water-soluble nitrogen in the two- to four-year-old needles were not significantly different between the control and thinned trees. Thus, the thinning effect on photosynthesis depends on needle age in a Chinese fir plantation. Our results highlight that the different responses of different-aged needles to thinning have to be taken into account for understanding and modelling ecosystem responses to management, especially under the expected environmental changes in future.