Extraction of tannin, colour and aroma compounds in pinot noir wines as affected by clone selection and whole bunch addition.

Our previous study revealed stem inclusion fermentation reduced anthocyanin, and increased tannin and aroma compounds responsible for green notes. This study further investigated the effect of clone selection and whole bunch fermentation on Pinot noir wine composition, with focus on tannin composition. Three treatments were conducted using two clones (AM10/5 and UCD5) in 2021 and 2022: 100% destemmed (DS), 30% whole bunch (WB30), and 60% whole bunch (WB60). WB60 increased stem and skin derived tannins but reduced seed derived tannin proportion in wines. Clone selection had an impact on tannin composition and an even greater impact on tannin concentration, colour, and aroma compounds. AM10/5 produced wines with higher tannin, polymeric pigments and darker colour. AM10/5 wines also had higher concentration of phenylethyl alcohol, but lower concentrations of 3-isobutyl-2-methoxypyrazine and ethyl esters, indicating more floral but less fruity and green notes.

Development of Tannins and Methoxypyrazines in Grape Skins, Seeds, and Stems of Two Pinot Noir Clones during Ripening.

Two Pinot noir clones (AM10/5 and UCD5) were analyzed for tannin and methoxypyrazines (MPs) in different grape tissues during berry development using liquid chromatography and two-dimensional gas chromatography-mass spectrometry. On a per berry basis, skin tannins reached the maximum level about 2-3 weeks after véraison, seed tannins at around véraison, and stem tannins 4 weeks before véraison. Clone AM10/5 showed significantly higher levels of seed and stem tannins on a per berry basis at harvest. Tannin concentration and composition varied among the different tissues. On a per berry basis, stem tannin levels were comparable to skin tannins but were 3 to 4 times lower than seed tannins, while stem tannins had an intermediate galloylation (5-7%) between seed tannins (12-18%) and skin tannins (2%) and lower prodelphinidin (4-7%) than skin tannins (31-36%). The mean degree of polymerization of stem tannins was similar to seed tannins but lower than skin tannins. MPs, including 3-isopropyl-2-methoxypyrazine (IPMP), 3-s-isobutyl-2-methoxypyrazine (SBMP), and 3-isobutyl-2-methoxypyrazine (IBMP), showed significantly higher concentrations than their sensory thresholds in grape stems but not in skins. The MPs development in stems showed an increasing trend toward véraison and then a decreasing trend toward harvest. Compared to AM 10/5, UCD5 stems showed a higher level of MPs, especially significantly higher concentrations of IPMP and IBMP at harvest. The extraction of MPs from grape stems could contribute negative green and vegetative characters to Pinot noir wines.

Studies on the Effect of Oxidation on Bioactivity of Phenolics and Wine Lees Extracts.

It is expected that any processing and handling of lees (e.g., drying, storage or removal of residual alcohol using various concentration techniques) will expose the material to oxidation and the consequences of oxidation on the biological activity of the lees and the lees extracts are unknown. The effects of oxidation (using horseradish peroxidase and hydrogen peroxide model system) on phenolic composition and their antioxidant and antimicrobial activities were investigated in (i) a flavonoid model system composed of catechin and grape seed tannin (Cat:GST) extracts at various ratios and (ii) in Pinot noir (PN) and Riesling (RL) wine lees samples. For the flavonoid model, oxidation had a minor or no impact on total phenol content but increased (p < 0.05) total tannin content from approximately 145 to 1200 µg epicatechin equivalent/mL. An opposite observation was found in the PN lees samples where oxidation reduced (p < 0.05) the total phenol content (TPC) by approximately 10 mg GAE/g dry matter (DM) lees. The mean degree of the polymerization (mDP) values of the oxidized flavonoid model samples ranged from 15 to 30. The Cat:GST ratio and interaction of the Cat:GST ratio with oxidation were found significantly to affect the mDP values of the flavonoid model samples (p < 0.05). Oxidation increased the mDP values in all oxidized flavonoid model samples except for Cat:GST 0:100. The mDP values of the PN lees samples ranged from 7 to 11 and remained the same after oxidation. There was no significant reduction in the antioxidant activities (DPPH and ORAC) of the model and wine lees after oxidation except the PN1 lees sample (decreased from 3.5 to 2.8 mg Trolox equivalent/g DM extracts). In addition, no correlation was observed between mDP (approximately 10 to 30) and DPPH (0.09) and ORAC assay (-0.22), which indicates that the higher mDP resulted in a poor ability to scavenge DPPH· and AAPH· free radicals. Antimicrobial activities of the flavonoid model were found to be improved after the oxidation treatment against S. aureus and E. coli with minimum inhibition concentration (MIC) of 1.56 and 0.39 mg/mL. This may indicate that new compounds were formed during the oxidation treatment, and these compounds showed more effective microbicidal activity. LC-MS work is required in the future to identify the compounds that are newly formed during the oxidation of the lees.

Characterization of Bioactive Compounds in Lees from New Zealand Wines with Different Vinification Backgrounds.

Wine lees are one of the main by-products produced during winemaking. Little is known about the effect of the vinification technique on the phenolic compounds and the biological activity of wine lees extracts. Wine lees collected at varying vinification sources of two grape varieties, Riesling (RL) and Pinot Noir (PN), were analyzed for total phenolic content (TPC), tannin content (TTC), their anthocyanin and phenolic profile, and the antioxidant and antimicrobial activities of their extracts. The results showed a low TPC and TTC in RL lees, which could be attributed to the varietal characteristic of RL grapes and to less skin contact during vinification. Vinification techniques modified the composition of the phenolic compounds in the lees. The results showed a good linear relationship between the antioxidant activities and the TPC and TTC, indicating that PN lees were better sources of phenolics and antioxidant activity than RL lees. The antimicrobial activity of wine lees was related to the phenolic composition rather than the quantity of total phenolics. Knowing the grape and wine processing conditions can provide some insights into the potential composition of wine lees and, hence, determine the potential economic use of the by-product.

Epigenetic Changes in Saccharomyces cerevisiae Alters the Aromatic Profile in Alcoholic Fermentation.

Epigenetic changes in genomics provide phenotypic modification without DNA sequence alteration. This study shows that benzoic acid, a common food additive and known histone deacetylase inhibitor (HDACi), has an epigenetic effect on Saccharomyces cerevisiae. Benzoic acid stimulated formation of epigenetic histone marks H3K4Me2, H3K27Me2, H3K18ac, and H3Ser10p in S. cerevisiae and altered their phenotypic behavior, resulting in increased production of phenylethyl alcohol and ester compounds during alcoholic fermentation using wine as a representative model system. Our study demonstrates the HDACi activity of certain dietary compounds such as sodium butyrate, curcumin and anacardic acid, suggests the potential use of these dietary compounds in altering S. cerevisiae phenotypes without altering host-cell DNA. This study highlights the potential to use common dietary compounds to exploit epigenetic modifications for various fermentation and biotechnology applications as an alternative to genetic modification. These findings indicate that benzoic acid and other food additives may have potential epigenetic effects on human gut microbiota, in which several yeast species are involved. IMPORTANCE The manuscript investigates and reports for the first time utilizing a non-GMO approach to alter the fermentation process of Pinot Noir wines. We have experimentally demonstrated that certain dietary compounds possess histone deacetylase (HDAC) inhibiting activity and can alter the wine characteristics by potentially altering yeast gene transcription, which was resulted from epigenetic effects. We have previously proposed the term "nutrifermentics" to represent this newly proposed field of research that provides insights on the effect of certain dietary compounds on microbial strains and their potential application in fermentation. This technological approach is a novel way to manipulate microorganisms for innovative food and beverage production with quality attributes catering for consumer's needs. Using a multidisciplinary approach with an emphasis on food fermentation and biotechnology, this study will be substantially useful and of broad interest to food microbiologists and biotechnologists who seek for innovative concepts with real-world application potential.

Effect of elevated temperature on membrane lipid saturation in Antarctic notothenioid fish.

Homeoviscous adaptation (HVA) is a key cellular response by which fish protect their membranes against thermal stress. We investigated evolutionary HVA (long time scale) in Antarctic and non-Antarctic fish. Membrane lipid composition was determined for four Perciformes fish: two closely related Antarctic notothenioid species (Trematomus bernacchii and Pagothenia borchgrevinki); a diversified related notothenioid Antarctic icefish (Chionodraco hamatus); and a New Zealand species (Notolabrus celidotus). The membrane lipid compositions were consistent across the three Antarctic species and these were significantly different from that of the New Zealand species. Furthermore, acclimatory HVA (short time periods with seasonal changes) was investigated to determine whether stenothermal Antarctic fish, which evolved in the cold, stable environment of the Southern Ocean, have lost the acclimatory capacity to modulate their membrane saturation states, making them vulnerable to anthropogenic global warming. We compared liver membrane lipid composition in two closely related Antarctic fish species acclimated at 0 °C (control temperature), 4 °C for a period of 14 days in T. bernacchii and 28 days for P. borchgrevinki, and 6 °C for 7 days in both species. Thermal acclimation at 4 °C did not result in changed membrane saturation states in either Antarctic species. Despite this, membrane functions were not compromised, as indicated by declining serum osmolality, implying positive compensation by enhanced hypo-osmoregulation. Increasing the temperature to 6 °C did not change the membrane lipids of P. borchgrevinki. However, in T. bernacchii, thermal acclimation at 6 °C resulted in an increase of membrane saturated fatty acids and a decline in unsaturated fatty acids. This is the first study to show a homeoviscous response to higher temperatures in an Antarctic fish, although for only one of the two species examined.