*Wine Stabilisation: An Overview of Defects and Treatments DOI: http://dx.doi.org/10.5772/intechopen.95245*

*Chemistry and Biochemistry of Winemaking, Wine Stabilization and Aging*

Chardonnay wine by 81% [161].

**5.2 Biogenic amines**

generation of its precursors. Significant advances have been made via genetic technologies in modifying fermentation strains that produce less EC precursors. Genetic modification approaches have the potential to provide safe, affordable, and effective methods to decrease EC formation. Several studies have shown that the modification of catalytic enzymes, such as urea carboxylase, arginase, and allophanate hydrolase, showed the ability to reduce the concentration of EC [156]. Additionally, the modification of urea permease and amino acid permease, which are regulated by several factors and directly affect the generation of EC precursors have been explored [160]. Since the metabolism pathways related to urea have been fully considered for the high-efficiency minimisation of EC, enhancing the gene expression of DUR1,2 and DUR3, which encode urea degradation enzymes and permease, respectively, is considered to be a viable strategy. In this way, the modification of permease has led to the construction of functionally enhanced urea-importing wine yeast cells, which can continuously express the DUR3 gene and reduce EC level in

Biogenic amines (BAs) are low molecular weight organic bases that have adverse physiological effects on humans when absorbed at high levels [162]. BAs are formed by decarboxylation of the corresponding amino acids by microorganisms such as LAB [162]. *Pediococcus,* as well as *Lactobacillus,* have been implicated in the production of BAs in wines that have undergone spontaneous MLF [162]. The final BAs levels in wine depend on the availability of the precursor amino acids and the BAs producing bacteria [162]. The only currently available simple and efficient solution to avoid or minimise BAs formation in wine is the use of MLF starter cultures [163]. After inoculation, the selected strain becomes dominant during MLF. Another recommendation is to avoid the practices that increase amino acid and peptide levels in musts. This also implies that LAB have more substrates, not only for producing BAs but also to survive better and longer after MLF [164]. Although there are currently no official values for the maximum limits for histamine and other BAs, the maximum value imposed for the levels of histamine, has been established through wine purchase and sale contracts, with the German companies demanding a maximum level of 2 mg/L of histamine. For these reasons, strategies for the reduction/elimination of BAs in wine are necessary, especially histamine. Until now, there are not useful treatments for reducing BAs levels especially, in red wines. However, it has been shown that uncommon wine LAB strains have amine oxidase activities that degrade histamine, tyrosine, and putrescine [165]. Also, non-*Saccharomyces* yeasts, such as *Schizosaccharomyces*, can decrease malic acid content in wine, they can be an excellent alternative to LAB, avoiding the MLF. Also, the use of *Schizosaccharomyces* reduces the risk of BAs production [166]. According to the OIV Resolution [19], only bentonite is applied in already contaminated wines to reduce the content of the BAs in the final wine [167]. Bentonite has a negative surface charge density, being able to exchange the cations adsorbed on its surface by the wine BAs. However, due to the negative impact on wine aroma combined with the high wine losses due to the high volume of lees, bentonite is presently not an adequate solution and other options need to be studied. Till now, there is no effective way of removing BAs in the finished wine.

Mycotoxins are secondary metabolites produced by several fungi that grow in food, including wine, under particular circumstances, with ochratoxin A (OTA) being one of the most important [168]. In 1993, the International Agency for

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**5.3 Mycotoxins**

Research on Cancer (IARC) classified OTA as possibly carcinogenic for humans (group 2B) [169]. Since 2006, the maximum limit for OTA in wine is 2 μg/kg [170]. OTA has been related to wine contaminations since 1996 [171] and after that, the occurrence of OTA in wine samples has been described in several works. Blesa et al. [172] found an OTA incidence in wines of 53% in 521 red wines, 69% in 98 rosé wines, and 61% in 301 white wines. These data show that it is important to prevent and control the occurrence of this mycotoxin in wines. To eliminate this toxin, several chemicals, microbiological and physical methods have been described [168]. Nevertheless, in the case of wines, effective removal processes are limited, and at present, the use of adsorbents is the most common. OTA content can reduce in the final wine from 70 to 32% by fermenting with selected yeast [173], *Non-Saccharomyces*, such as *Schizosaccharomyces*, are also promising in reducing the OTA content by about 70% during fermentation [173]. Several fining agents have been evaluated concerning their ability to remove OTA from wines, and it was found that AC presented a good adsorption capacity for OTA [174]. Filtration before bottling about 0.45 μm of wine can easily reduce the final content in OTA by about 80% [174], but none of them is 100% efficient in removing OTA from wines.

Aflatoxins are a group of highly toxic secondary metabolites produced by fungi of the genus *Aspergillus* [175]. AFB1 is the most predominant and toxic aflatoxin. It is classified as a Group 1 human carcinogen (IARC) [169]. Aflatoxins and Aflatoxinsproducing strains [176] have been detected in grape and musts [177]. The presence of aAFB1 in wines is caused by fungi that grow on grapes in the vineyards. In the literature, there are few studies regarding aflatoxins contamination in wines [177]. One of them is from Di Stefano et al. [178] that studied the occurrence of aflatoxins in 30 sweet wines from five winemaking in the Sicilian regions, Italy. The presence of aflatoxin in wines has been documented in recent years, largely because of the adaptability of aflatoxigenic fungi, such as *A. flavus*. At present, the EU has not set a maximum allowable limit for aflatoxins in wine, but this does not mean that the problem can be ignored. Therefore, it is essential to develop technological solutions to reduce/eliminate the levels of aflatoxins in wines. Recently the work from Cosme et al. [179] shows the high efficiency of bentonite in the removal of aflatoxin B1 and B2.
