Biogenic Amines in Wine: Understanding the Headache

The presence of biogenic amines in wine is becoming increasingly important to consumers and producers alike,due to the potential threats of toxicity to humans and consequent trade implications. In the scientific field, biogenicamines have the potential to be applied as indicators of food spoilage and/or authenticity. Biogenic amines can beformed from their respective amino acid precursors by various microorganisms present in the wine, at any stageof production, ageing or storage. To understand the large number of factors that could influence the formation ofbiogenic amines, the chemical, biochemical, enzymatic and genetic properties relating to these compounds have tobe considered. Analytical and molecular methods to detect biogenic amines in wine, as well as possibilities that couldenable better control over their production levels in wine will also be explored in this review

The Effect of Micro-oxygenation on the Phenolic Composition, Quality and Aerobic Wine-Spoilage Microorganisms of Different South African Red Wines

The effect of micro-oxygenation treatments on the composition of different South African red wines was evaluated.  In some wines, micro-oxygenation led to an increase in colour density, with a corresponding change in colour, due to the formation of polymeric pigments. This increase also led to the red colour becoming more resistant to the bleaching effect of SO2. Micro-oxygenation also seemed to be more effective in increasing the colour densities of younger red wines than the older ones, although total red pigments were found to be highest in an older red wine that had received micro-oxygenation. Differences in the gelatine index were also observed over time. The micro-oxygenated and barrel-matured wines also had lower concentrations of catechin and the procyanidin B1, and showed a corresponding increase in polymeric pigment and polymeric phenols. Micro-oxygenation led to higher acetic acid bacteria counts, although no increase in volatile acidity was observed in these wines. A tasting panel preferredyounger red wines that had undergone micro-oxygenation. In an older red wine prolonged micro-oxygenation led to the wine becoming over-aged, with an increase in the barnyard/medicinal character, which corresponded with an increase in Brettanomyces counts. Micro-oxygenation can be used to increase the quality of young red wines, but further research is needed in this area

Oxygen in Must and Wine: A review

Oxygen can play an important role during the winemaking process. It can influence the composition and quality of the must and wine. Phenolic compounds are the main substrates for oxidation in must and wine. Oxygen addition leads to colour changes and the polymerisation of phenolic molecules in wine. Oxygen can, however, also influence the flavour and microbial composition of wine drastically, with certain off-flavours being formed and spoilage micro-organisms able to grow at too high oxygen additions to wine. A state-of-the-art, up-to-date review on the effects of oxygen in must and wine has, however, not been published recently. This review focuses on the effects of oxygen in must, during alcoholic fermentation, extended lees contact and during ageing of white and red wines. The effects it has on acetic acid bacteria and Brettanomyces are also discussed, as well as micro-oxygenation, a relative new technique used in wine production

Research Note: Effect of Simulated Shipping Temperatures on the Sensory Composition of South African Chenin Blanc and Sauvignon Blanc Wines

This work investigated the effect of constant and simulated shipping temperatures on the sensorycomposition of Chenin blanc and Sauvignon blanc wines. Wines exposed to elevated temperatures duringthe trial developed unwanted aromas, such as over-aged, sulphur-like and a yellow colour, while those leftat a cooler temperature retained tropical aromas. However, varying temperatures did not lead to largearoma differences in wines compared to those left at a constant lower temperature. It thus seems thataverage temperatures play a larger role in the development of unwanted over-aged aromas in certainSouth African white wines than temperature variations

Correlations between South African Red Grape and Wine Colour and Phenolic Composition: Comparing the Glories, Iland and Bovine Serum Albumin Tannin Precipitation Methods

Phenolic compounds in red grapes might give an indication of phenolic and colour compositions ofthe resulting wine. This work compared the Glories, Iland and Bovine Serum Albumin (BSA) tanninprecipitation methods for phenolic characterization of South African Pinotage, Merlot, Shiraz andCabernet Sauvignon red grape samples (n=31). Significant positive correlations were found for certainphenolic characteristics in the grapes measured by these methods. Levels of phenolic compounds in thegrapes and correlating wines were in line with literature. Merlot samples often associated more with higherconcentrations of seed tannins, which were also reflected in the wines. Significant correlations were alsofound with the colour characteristics of the resulting wines and some anthocyanin related measurementsin the grapes with the Glories and Iland methods, with the latter correlating slightly better. Significantpositive correlations were also found between grape and wine tannins as measured with the BSA method.However, malolactic fermentation changed some of these correlations and this needs to be investigatedfurther. This work might give wine producers as well as wine analyses laboratories valuable informationregarding the suitability of these methods to characterize the phenolic composition of South African redgrapes and their resulting wines

Sauvignon Blanc Wine: Contribution of Ageing and Oxygen on Aromatic and Non-aromatic Compounds and Sensory Composition : A Review

Oxidation and the capacity for sufficient ageing potential of white wines are constant problems forwinemakers worldwide. In general, it is accepted that certain grape varieties are especially sensitive tooxidation, suggesting that some of the chemical components key to their sensory attributes are stronglymodulated by oxygen exposure. Sauvignon blanc is a well-documented example of an oxygen-sensitivewine, and understanding the stability of various compounds is crucial in order to preserve the fresh andfruity characters of Sauvignon blanc wines while preventing the formation of off-odours over a longperiod of time. Compounds such as the volatile thiols and methoxypyrazines are key aroma compoundsresponsible for the typical Sauvignon blanc aroma, while other aroma compounds, such as esters, alcoholsand acids, can also contribute to the wine aroma. Oxidation-related compounds (such as aldehydes) canoccur under certain conditions and it is essential to understand the chemistry behind oxidation to controland manage the development of various characteristics in wine. The sensory interactions occurringbetween various compounds (both aromatic and non-aromatic) are also important due to enhancing orsuppressive effects that can mask certain aroma nuances. This review focuses on the stability of certaincompounds of Sauvignon blanc wines during oxidation and ageing and how it affects the aromatic andnon-aromatic composition of these wines

Monitoring the Effect of Micro-oxygenation before Malolactic Fermentation on South African Pinotage Red Wine with Different Colour and Phenolic Analyses

The use of micro-oxygenation and its effect on the quality of the red wine varietal, Pinotage, is largelyunknown. The influence of adding different oxygen dosages before malolactic fermentation on thephenolic composition and colour stabilisation of wine made from Pinotage was studied, and thesuitability of certain spectrophotometric and RP-HPLC analyses to determine these changes wereassessed in tanks of commercial lengths. Total oxygen dosages of 0 mg/L, 16 mg/L and 32 mg/L wereapplied, after which the wines underwent malolactic fermentation and maturation in the same tanks fortwo additional months. Decreases in anthocyanin concentration showed a strong inversely proportionalcorrelation with increasing polymeric pigment concentration. This suggests that the addition ofoxygen contributed to the early stabilisation of wine colour in Pinotage red wine. Overall, tanninconcentrations were not significantly influenced by the oxygen treatments, although lower levels wereobserved in wines treated with oxygen. An important finding of the study was that there appeared to belittle difference in the colour and phenolic composition of the wines between the 16 mg/L and 32 mg/Loxygen treatments. Good correlations were found between certain spectrophotometric techniques andthe RP-HPLC analysis used to study changes induced by micro-oxygenation (total anthocyanins, totalphenols). The colour and phenolic composition of Pinotage wine can be influenced before malolacticfermentation by micro-oxygenation. Some spectrophotometric phenolic analyses showed the sametendencies as observed with RP-HPLC (anthocyanins, monomeric flavan-3-ols, tannins), indicating theirsuitability to follow phenolic and colour changes induced by micro-oxygenation in Pinotage red wine

Do Differences in the Colour and Phenolic Composition of Young Shiraz Wines Reflect During Ageing?

This study investigated the evolution of colour and phenolic compounds of Shiraz wines during wine ageing. Wines made from the same vineyard, but with a different phenolic composition, were used in this study. Analyses included colour density, anthocyanins, tannin, hydroyxycinnamic acids, flavan-3-ols, polymeric pigments and polymeric phenols. Differences in phenolic compositions observed in the young wines were generally still observed after 6 and 12 months of ageing. These results indicate that significant differences in terms of phenolics and colour in young Shiraz red wines might thus be expected to be reflected in the wines after ageing as well

Attempted Identification of Causal Constituents of Pink Discolouration in White Wines

The pinking phenomenon has been known in the wine world for the past 50 years. The phenomenonoccurs when a white wine turns pink under certain conditions. Since then, a Portuguese study foundmalvidin-3-O-glucoside in Siria grapes making a connection to anthocyanin as the causing agent. Control(K), naturally pinked (NP) and pink induced (PI) Sauvignon blanc wine samples were analysed by LCMSand WineScanTM (Fourier Transform Infrared – FTIR) after Solid Phase Extraction. The monomericanthocyanins were analysed by a pH differential method, and CieLab was used to differentiate colourdifferences between the control and pinked samples. It was found that malvidin-3-O-glucoside was belowthe threshold values to facilitate pinking in Sauvignon blanc wines. Petunidin-3-O-glucoside showed aslight peak in the LC-MS analysis, and together with the malvidin-3-O-glucoside, the potential to pinkthe white wines increased. FTIR results showed that phenols and anthocyanins absorption could not bedistinguished and that there were possibly other compounds involved in the pinking of white wines. Analysisby CieLab expressed the PI wines as a darker pink colour than the control wine and the absorbency valueat 500 nm was at least three times higher for PI than the control, showing the aggressive oxidative natureof H2O2 on wine

Sensory Evaluation of Pinked Sauvignon Blanc Wines

Sensorial studies on pinked white wines have never been carried out. The aim of this study was to establishthe probability of an aroma and taste difference in pinked Sauvignon blanc wines using a triangular test.The issue of at which point a wine consumer can perceived the wine as pink was analysed using a rankingexperiment. The probability that a wine taster can detect oxidised and pink wines as a wine fault was alsoanalysed. It was found that the panellists could not detect anomaly samples by taste and aroma alone,although some noticed an oxidised aroma on the nose. The pink detection point was established at 0.03 AU.This point can be used to refine the detection point and the assay used. It was established that more than50% of the panellists could detect oxidised and pink wines as a wine fault. The study data can be used toeither train panellists to detect pinking as a wine fault, or to establish a potential new category for pinkSauvignon blanc wines