UTILIZATION OF COMMERCIAL STARTERS FOR MLF

In addressing the issues of starter preparation and, subsequently, MLF, a distinction should be made between bacterial utilization of sugars for growth (population increases) and bacterial conversion of L-malate to L-lactate (the MLF). These two separate but related issues may be dramatically and differentially influenced by environmental conditions, such as pH, temperature changes, and increasing alcohol. 

Reliance on native MLF may represent an unpredictable situation, slowing the progress of processing and potentially leading to incomplete conversion of malate. As a result, most winemakers now utilize commercial LAB starters. As with yeasts, LAB starters accomplish the goal of immediate numerical superiority over potentially competitive native strains. Compared with MLF resulting from native strains, properly prepared and expanded inocula of commercial LAB generally yield more predictable results in terms of both the rate of conversion and final concentration of L-malic acid, as well as sensorially active metabolites. 

Several commercial freeze-dried LAB cultures have been available to winemakers over the years. Additionally, frozen concentrates ( 10 CFU/ mL) are also available. In the case of concentrates, viability requires that they be maintained in the frozen state rather than simply refrigerated until use. This may be troublesome, particularly where shipment may be inter- 

In their nationwide survey of over 100 wineries, Fugelsang and Zoeck-lein (1993) report that 43% of respondents used freeze-dried preparations, with an additional 8% using frozen concentrates. Already reactivated liquid cultures were being used by 34% of the winemakers and only 5% developed starters from their own cultures. Since that time, additional producers of freeze-dried cultures have emerged and the numbers of winemakers availing themselves of these more user-friendly sources of inocula has most likely increased. 

---