Issue link: http://winesandvines.uberflip.com/i/513570
54 P R A C T I C A L W I N E R Y & V I N E YA R D June 2015 W I N E M A K I N G tial, but they may contribute to growth. Pantothenic acid present in tomato, grape and apple juice is considered to be a growth factor for O. oeni and is an ingredient of laboratory culture medi- ums for the isolation and purification of wine LAB. 1,4 Minerals Certain minerals including magnesium, manganese, potassium and sodium are important as they are enzyme cofac- tors or they are involved with transport mechanisms. There have been limited studies examining the mineral require- ments of wine LAB. Techniques to ensure complete malolactic fermentation As the AF progresses toward completion, the level of organic nitrogen depletes, as do certain amino acids indispensable for the growth of O. oeni. V. Renouf showed that wines with the most amino acid deficiencies also exhibited the worst instances of MLF completion. 19 Malolactic fermentation activators It is generally accepted that efficient alcoholic fermentation is based on suf- ficient nutrients for the yeast. Malolactic fermentation also requires sufficient nutrients for the bacteria, and there are solutions for smooth and complete MLF today. Figure 4 shows the results of a Cabernet Sauvignon wine trial inoculated with selected wine LAB Enoferm Alpha. The control wine, which received no inocu- lum, exhibited a low bacterial population of 1x104 CFU/mL for the 21-day trial, and the L-malic acid concentration remained unchanged. In the wine inoculated with Enoferm Alpha and no added bacterial nutri- ents, the bacterial population maintained itself for the first seven days then began a slow decline. Ten days after inoculation, addition of this peptide has a stimulat- ing effect on the growth of four wine LAB strains utilized in the trial. Studies using O. oeni have shown that after peptides are transported into the cell, their constituent amino acids are released back into the medium. Although they were transported, the peptides were not necessarily con- sumed. 20 The hypothesis suggested this transport was carried out with the aim of saving energy. Indeed, it appears the transport of peptides requires less energy than would be required for free amino acids, 11,13 which can be trans- ported by different pathways. In addition, the excretion of free amino acids by proton symporters generates the proton-motive force necessary for ATP synthesis. Peptides could be advanta- geous from an energy perspective by improving the resistance of the bacteria in an acid medium (pH 3.2). Vitamins Wine LAB require the B vitamins pan- tothenic acid (vitamin B5), biotin (B8), thiamine (B1) and niacin (B3). Pyridoxine (B6) and riboflavin (B2) are not essen- O. oeni, Lalvin 31 and Enoferm Alpha, using the technique outlined above. 18 The results are in Figures 1 and 2. The number of essential amino acids required by strains of wine LAB is important. In a wine deficient in amino acids, undesirable strains of Lactobacillus sp. may develop more easily than desir- able strains of O. oeni. 21 Peptides In addition to free amino acids, peptides may constitute another distinct source of useable organic nitrogen for wine LAB. Wine LAB have the ability to degrade both proteins and peptides, and use the derived amino acids to fulfill their nitro- gen requirements. It is probable that certain peptides are more likely than others to be trans- ported into the cell then hydrolyzed by wine LAB. These peptides stimu- late wine LAB because they allow for energy production and may stimulate MLF under conditions of low pH and high molecular SO 2 . 2 Figure 3 shows results from experiments performed by Lallemand to assess the impact of add- ing a growth-stimulating peptide. The 0 5 10 15 20 25 Days Malic acid (g/L) 3.5 3 2.5 2 1.5 1 0.5 0 1.00E+08 1.00E+07 1.00E+06 1.00E+05 Bacteria Popula on (cfu/mL) Enoferm Alpha (malic acid) Enoferm Alpha + nutrients (malic acid) Enoferm Alpha + (bacteria popula on) Enoferm Alpha + nutrients (bacteria popula on) Control (malic acid) Figure 4. Impact on malolactic fermentation of adding Opti'Malo Plus bacteria nutrient to a Cabernet Sauvignon wine: ethanol 14%, pH 3.56, total SO 2 25 mg/L, free SO 2 5 mg/L Bauer Associates Geotechnical Engineers and Geologists Providing Geotechnical Engineering Services for Wineries, Commercial and Residential Projects Bryce@bauergeotech.com • 707-887-2505 Bryce Bauer