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WineEast Solving sluggish MLF Occasionally a sluggish or resistant MLF can result even when SO2 , pH, temperature and alcohol are all in the proper range. If this hap- pens, it could be a result of the inhibitory effects of medium-chain fatty acids. Fining problematic wines with yeast hulls at about 0.5 grams per gallon, allowing a couple days to settle and re-inoculating with LAB will usually solve the problem. Additionally, protein-fined or over-clarified wines may lack proper nutrient levels to support LAB growth. A nutrient addition should be considered if these other limit- ing factors have been addressed and you are still not getting results. A natural source of nutrients in the form of fine yeast lees has been shown to stimulate LAB growth and, consequently, retaining some lees is standard operating procedure for MLF. Nevertheless, commercial preparations are available as additional assurance and are purported to "help the selected bacteria get a faster start, increase survival rates and lower the risk of problems from undesirable bacteria."10 As already mentioned, addition of SO2 the completion of MLF to help stabilize the wine. But don't rush to add SO2 as soon as bubbles stop rising. During the course of MLF, bacteria produce diacetyl. Diacetyl has a distinct buttery aroma. In fact, the food industry uses diacetyl in many of its concoctions for that very reason. Excessive diacetyl can be a fault, especially in whites. Fortunately LAB and even yeast can metabolize diacetyl into more benign end products. Diacetyl levels will usually fall into line in a week or two. Addition of SO2 effectively stops this evolution. Monitor the wine closely and keep your barrels well topped. At this point the wine is in a vulnerable state with no SO2 AS GOOD AS IT GETS. Natural Corks Champagne Corks Twinline Corks Bartops VISION® G-Cap® Wine Stopper Screw Cap Sales Representatives Chris & Liz Stamp info@lakewoodcork.com Lakewood Cork 4024 State Route 14 Watkins Glen, NY 14891 lakewoodcork.com 607-535-9252 607-535-6656 Fax 64 Wines & Vines JUne 2012 , elevated temperature Primary Tartaric Acid Primary Lactic Acid Malic Acid Solvent (from left), a 1-gallon wide-mouth jar, chromatography paper and micro pipettes are needed to test for malic acid (above right). and a raised pH. It is a prime candidate for spoilage bacteria (lactics as well as Acetobacter), Brettanomyces and surface yeast (Candida). should take place soon after Confirm completion of MLF The completion of MLF is usually confirmed with paper chroma- tography (above), enzymatically or with HPLC, the latter two being much more precise. Paper chromatography is still in wide use be- cause it is simple and inexpensive. The test involves a wicking pa- per (chromatography paper), solvent and a 1-gallon, wide-mouthed glass jar with a lid. The procedure is standard content in any winery lab manual. The important thing to note about this test is it shows a negative reading for malic acid at about 100mg per liter.11 H&W_Dec10.qxp 10/12/10 10:59 AM Page 1 is another reason to not be in too big a hurry to get SO2 This into your