Comparison of MCFA and Other Methods of Terminating Alcohol Fermentation and Their Influence on the Content of Carbonyl Compounds in Wine

Effect of Indigenous Non-Saccharomyces Yeasts on Lipid Compositions of Maraština Wine

This study is the first to investigate the impact of indigenous non-Saccharomyces yeasts, including Hypopichia pseudoburtonii, Metschnikowia sinensis/shanxiensis, Metschnikowia chrysoperlae, Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora uvarum, Hanseniaspora guilliermondii, Hanseniaspora pseudoguilliermondii, Pichia kluyveri, and Starmerella apicola on the lipid composition of sterile Maraština grape juice and wines using the UHPLC-MS/MS method. Yeasts were tested in monoculture and sequential fermentations alongside commercial Saccharomyces cerevisiae. Indigenous non-Saccharomyces yeasts showed the potential to improve fermentation performance and enable the development of new wine styles through the biosynthesis of an unsaturated fatty acid pathway, which was identified as the most significant pathway. In monoculture fermentations, L. thermotolerans, H. uvarum, H. guilliermondii, H. pseudoguilliermondii, and P. kluyveri significantly reduced lignoceric acid, potentially influencing wine aroma through the formation of esters and higher alcohols. Hyp. pseudoburtonii, M. chrysoperlae, M. pulcherrima, P. kluyveri, and S. apicola increased the demand for lipids, such as stearic acid, which may help preserve membrane permeability by integrating into the membrane in response to ethanol shock. The most significant impact on free fatty esters was observed in fermentations with H. pseudoguilliermondii. Furthermore, L. thermotolerans in sequential fermentations significantly reduced arachidic, stearic, and palmitic acid. P. kluyveri reduced the content of erucic and linoleic acid.

Causes and consequences of endogenous hypoxia on growth and metabolism of developing maize kernels

Maize (Zea mays) kernels are the largest cereal grains, and their endosperm is severely oxygen deficient during grain fill. The causes, dynamics, and mechanisms of acclimation to hypoxia are minimally understood. Here, we demonstrate that hypoxia develops in the small, growing endosperm, but not the nucellus, and becomes the standard state, regardless of diverse structural and genetic perturbations in modern maize (B73, popcorn, sweet corn), mutants (sweet4c, glossy6, waxy), and non-domesticated wild relatives (teosintes and Tripsacum species). We also uncovered an interconnected void space at the chalazal pericarp, providing superior oxygen supply to the placental tissues and basal endosperm transfer layer. Modeling indicated a very high diffusion resistance inside the endosperm, which, together with internal oxygen consumption, could generate steep oxygen gradients at the endosperm surface. Manipulation of oxygen supply induced reciprocal shifts in gene expression implicated in controlling mitochondrial functions (23.6 kDa Heat-Shock Protein, Voltage-Dependent Anion Channel 2) and multiple signaling pathways (core hypoxia genes, cyclic nucleotide metabolism, ethylene synthesis). Metabolite profiling revealed oxygen-dependent shifts in mitochondrial pathways, ascorbate metabolism, starch synthesis, and auxin degradation. Long-term elevated oxygen supply enhanced the rate of kernel development. Altogether, evidence here supports a mechanistic framework for the establishment of and acclimation to hypoxia in the maize endosperm.

Observation of Residues Content after Application of a Medium-Chain Fatty Acids Mixture at the End of Alcoholic Fermentation

This study focused on applying a patented medium-chain fatty acids (MCFAs) mixture at the end of alcoholic fermentation and monitoring its residues. MCFAs are a promising agent that has the potential to increase the efficiency of sulfur dioxide and ultimately minimize its doses, which is one of the important goals of wine research today. Detailed octanoic, decanoic, and dodecanoic acid contents were observed during the experiment. The MCFA mixture was applied at doses of 0, 10, 20, and 60 mg/L. GC–MS determined the content of individual fatty acids. The results showed that the use of the investigated mixture of fatty acids at doses of 10 and 20 mg/L did not cause an increase in the content of individual fatty acids residues. The octanoic acid content after application of the 20 mg/L MCFA mixture was 8.24 mg/L after 744 h, while the untreated control variant showed a value of 7.71 mg/L. The performed sensory analysis also did not show a negative effect of MCFA application on the sensory properties of wine. Therefore, applying an MCFA mixture at 10 and 20 mg/L can be recommended as a safe alternative following alcoholic fermentation. However, the results obtained can also serve as a valuable basis for permitting the use of MCFA in the proceeding OIV approval process. The research thus opens the possibility of expanding a new oenological agent capable of reducing SO2 doses.

Medium chain fatty acids and fatty acid esters as potential markers of alcoholic fermentation of white wines

Aroma components of wines play an important role in the sensory quality of wines. In our paper we investigate the effect of commercially available yeast nutrients under different fermentation parameters. Caproic acid, caprylic acid, capric acid, and different fatty acid esters were used as markers of the alcoholic fermentation process. The optimal temperature for the fermentation of different white wines was at 15–16 °C, in the case of examined wines lower concentrations of fatty acids and fatty acid esters were found at this temperature. At 25–26 °C fermentation temperature very high concentrations of fatty acids and fatty acid esters were detected. Applying different nitrogen-containing wine additives we managed to achieve better aroma profiles for white wines even using musts of lower quality.