Issue link: http://winesandvines.uberflip.com/i/513570
June 2015 P R A C T I C A L W I N E R Y & V I N E YA R D 53 W I N E M A K I N G LAB a source of energy, it results in the formation of acetic acid, lipids, acetoin, butanediol and diacetyl. In O. oeni, the timing and speed of citrate decomposi- tion is strain-specific. While some strains that produce high levels of diacetyl begin to consume citric acid from the midpoint of the MLF, other strains do not start metabolizing citric acid until all of the L-malic acid has been depleted. 12 Nitrogen—amino acids and peptides Free amino acids and those arising from the hydrolysis of peptides are the main sources of the nitrogen used by wine LAB. Contrary to yeast, the amino acids required for wine bacteria cannot be synthesized from inorganic nitrogen. 17 They must either be supplied by the wine matrix or be synthesized by wine LAB metabolism from organic sources. Amino acids The amino acid requirements of wine LAB depend not only on the bacterial species but on the strain. The identifica- tion of essential amino acids for O. oeni growth has been the subject of numer- ous studies. The needs of 22 strains of O. oeni have been explored. 5,6,18,21 The technique used to determine the amino acid requirements consists of compar- ing growth of the bacteria in a complete medium containing all known required amino acids with growth of the bacteria in a medium from which these amino acids are individually eliminated. Arginine is an essential amino acid for the 22 strains studied. Amino acids such as glutamic acid, isoleucine, tryptophan, methionine, valine, cysteine, tyrosine, histidine and phenylalanine are also classified as essential for most strains. Proline and alanine do not affect the growth of most strains and are classified as indifferent amino acids. F. Remize et al. examined two commercial strains of Strain A Strain B Strain C Strain D Control 1.04E+06 1.35E+07 3.83E+06 1.94E+07 Wine + pep de at 5 mg/L 4.78E+06 1.93E+07 8.31E+06 2.81E+07 Wine + pep de at 20 mg/L 9.98E+06 2.30E+07 1.02E+07 5.54E+07 1.00E+05 1.00E+06 1.00E+07 1.00E+08 Bacteria popula on 7 days after inocula on (CFU/mL) Figure 3. Peptide growth stimulation OPTI'MALO ™ BLANC ML RED BOOST ™ For fast and secure Malolactic Fermentation www.lallemandwine.com Scott Laboratories: 707 765-6666 – info@scottlab.com – www.scottlab.com Energize your selected wine bacteria