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5 0 V I N E YA R D & W I N E RY M A N A G E M E N T | J u l y - A u g 2 016 w w w. v w m m e d i a . c o m Gordon Specht of Canada-based Lallemand Inc., which specializes in the production of yeasts and bacteria. "In the case of selected yeast, we've studied their nutri- tional demands and can supple- ment what's necessary for reliable and complete fermentations. Indig- enous microbe fermentations are trickier, as we don't know if it will be spoilage organisms benefiting from a nutrient addition or the fer- menting yeasts. It's basically a roll of the dice, but what we normally advise to winemakers who insist on relying on indigenous microbes is to carefully monitor their fermenta- tion progress and, if they like what they're smelling, add nutrients. If they don't like what they're smell- ing in their indigenous ferments, we advise them to intervene and inocu- late with a selected rescue yeast." Specht suggests that one of the advantages of working with cul- tured yeasts selected from nature is that, because they've been charac- terized, winemakers can know their nutrient requirement. "Experiences products such as inactivated dried yeast hulls. "For managing wine fermenta- tions, whether using selected or indigenous microbes, nutrients are helpful, especially under stress- ful fermentation conditions," says in our own yeast production fer- mentations laid the groundwork for our nutrient formulations," he says. "We've also collaborated with oth- ers in the area of yeast growth nutri- tion and fermentation to attempt to understand the complex and often frustrating interactions in grape must." Lallemand markets a num- ber of products, including GoFerm, GoFerm Protect evolution and Fer- maid O. The basis of these products is inactivated yeasts. "All three con- tain 100% yeast-derived ingredients and no added ammonia salts such as DAP," says Specht. "All three are also OMRI [Organic Materials Review Institute] listed, so they have the potential to be used in organic winemaking programs." " D u r i n g t h e g r o w t h p h a s e , yeast need vitamins, minerals and nitrogen," says Jose Santos of Enartis USA. "The presence of alcohol inhibits transport of amino acids through cell membranes and reduces their consumption." San- tos points out that, to optimize their absorption and efficiency, amino Nitrogen metabolism plays an important role for yeast nutri- tion in alcoholic fermentations. The nitrogen amount in terms of YAN, and source, either mineral or organic, are both important factors — but they aren't the only impactful parameters. When yeast are awakened from their dehydrated state and placed in grape must, they're far from their optimal fermentative condition. They must reestab- lish their metabolic balance and adapt to their new environment. Establishing the proper mem- brane transport potential is criti- cal for the yeast to achieve rapid metabolic balance. Rehydration of yeast in a cell-friendly solution that con- tains the proper survival factors, vitamins and minerals can facili- tate the metabolic equilibrium needed for optimal fermentative performance, including rapid growth and cell populations high enough to carry the fermenta- tion to a strong completion. Addition of high-nitrogen nutri- tional supplements during rehy- dration can be detrimental to yeast performance and should not be used, specific supple- ments rich in survival factors but low in nitrogen are recommend- ed for healthy yeast rehydration. The challenges yeast face in terms of membrane transport and structural integrity are dif- ferent in white and red must environments. While red must has more physical challenges — like high fermentation tem- peratures and increased tannin concentration — white musts share the challenges of high potential alcohol and low pH. Yeast in white wine fermenta- tions must ferment cleanly and aid in the revelation of delicate white wine aromatics. In addition to creation of a healthy balanced membrane t r a n s p o r t p o t e n t i a l , p r o p e r yeast rehydration with a supple- ment containing survival factors can actually improve the yeast nitrogen utilization efficiency s i g n i f i c a n t l y, a n d f a c i l i t a t e s clean, strong fermentations with increased aromatic expression. Peter Salamone, Ph.D., is technical manager at Laffort USA in Petaluma, Calif. Laffort holds many patents and regularly launches innovative products and processes for the wine industry. YEAST REHYDRATION By Peter Salamone, Ph.D. Lallemand Inc.'s Gordon Sprecht says nutrients are helpful for managing wine fermentations, especially under stressful conditions.