Bio-protection in winemaking is no longer just a buzzword; it is a reality. Many winemakers worldwide have started experimenting with the available commercial products, and can testify to their success.
Bio-protection is well-established in the food industry, with various microbes commercially available. In the wine industry, many microbes are under investigation, and some have already been commercialised to reduce or replace the use of sulphur dioxide. It should be noted that bio-protection is also an active area of research in viticulture, focusing specifically on the inhibition of fungal diseases.
The concept of bio-protection is to use ‘good’ microbes or Bio Protective Cultures (BPCs) to prevent, inhibit or kill the ‘bad’ microbes and thereby prevent wine spoilage in a more ‘natural’ way than using chemical additives.
Passive and active competition strategies
Bio-protective yeasts and bacteria have antagonistic mechanisms ensuring their success as BPCs. These competition strategies, as they are also known, can be passive or active. Examples of passive strategies are fast nutrient uptake, high growth rate, short lag phase, biofilm formation and the production of pulcherrimic acid. Examples of active strategies include the production of ethanol, SO2, toxic compounds, antimicrobial peptides and lytic enzymes.
The most well-known and utilised BPC is commercially produced and inoculated Saccharomyces cerevisiae due to its profound dominance (because of its passive and active competition strategies) over uninoculated non-Saccharomyces yeasts and wine bacteria; the good, the bad and the ugly.
However, the growth of ‘good’ non-Saccharomyces yeasts is often desired since they can have various positive impacts on wine quality, even though they only exhibit active growth or metabolism during the first parts of fermentation. These positive impacts include a reduction of alcohol content, an increase of glycerol content, a release of mannoproteins and polysaccharides, the production of fruity esters, thiols and terpenes and an increase in titratable acidity. The use of high concentrations of SO2 can also suppress the proliferation and contribution of non-Saccharomyces yeasts.
Enter the non-Saccharomyces BPCs. These bio-protective non-Saccharomyces yeasts can be inoculated into grape juice to reduce, delay or replace the use of SO2. They suppress the proliferation of the ‘bad’ non-Sacch yeasts whilst allowing the growth or metabolism of the ‘good guys’.
Non-Saccharomyces wine yeasts already commercialised for this purpose include Zymaflore Égide (Torulaspora delbrueckii and Metschnikowia pulcherrima), Zymaflore Khio (Metschnikowia pulcherrima), LEVEL2 INITIA (Metschnikowia pulcherrima), IOC Gaïa (Metschnikowia fructicola) and Viniflora Prelude (Torulaspora delbrueckii).
A recent laboratory scale study investigated the use of Viniflora FrootZen (Pichia kluyveri) and Viniflora NoVA (Lactiplantibacillus plantarum, the fancy new name for Lactobacillus plantarum) as potential BPCs. The researchers studied the efficacy of these two microbes (separately) as BPCs, with and without SO2 additions. They concluded that these two commercial products could form part of a strategy to reduce, not replace, SO2 usage in the pre-fermentative stage, as they have no anti-oxidative activity. Compared to an uninoculated control, the inoculation with either of these two microbes led to the production of wines with lower concentrations of acetic acid and ethyl acetate, compounds that can be damaging to wine quality. Further research is needed to investigate the potential bioprotective abilities of the two microbes under commercial winemaking conditions.
Winemakers who wish to reduce their use of SO2 to meet consumer expectations must contact their suppliers for more detailed practical information on using the mentioned yeasts and bacterial starter culture. It is possible that other pre-fermentative bio-protection yeasts and bacteria also exist.
Vasileios Englezos, Paola Di Gianvito, Lorenzo Peyer, Simone Giacosa, Susana Río Segade, Nathalia Edwards, Luca Rolle, Kalliopi Rantsiou, Luca Cocolin. Bioprotective effect of Pichia kluyveri and Lactiplantibacillus plantarum in winemaking conditions. Am J Enol Vitic. July 2022: ajev.2022.22008; published ahead of print July 07, 2022; https://www.ajevonline.org/content/early/2022/06/30/ajev.2022.22008
Paola Di Gianvito, Vasileios Englezos, Kalliopi Rantsiou, Luca Cocolin. Bioprotection strategies in winemaking. International Journal of Food Microbiology, Volume 364, 2022, https://doi.org/10.1016/j.ijfoodmicro.2022.109532