Grape Juice Medium

Add 250mL of fresh or reconstituted grape juice to a IL volumetric flask and dilute to volume with distilled water. It is important that the grape juice not have any preservatives such as SO2 or sorbate. 

If solidified agar is needed, add 20 g of agar to approximately 800 mL of the liquid medium. Boil to dissolve all ingredients, and then add back the remaining 200 mL of medium prior to autoclaving. 

---

Figure I. Photomicrographs of Leuconostoc oenos ML 34 grown on a grape juice medium for use as starter cultures.

A grape juice medium can be made as follows 1 volume grape juice, 1 volume water, 0.05% yeast extract titrate to pH 4.5 with NaOH. With some grape juices a supplemental addition of 0.005 to 0.05% Tween 80 is helpful. The media are sterilized by autoclave for 15 min at 15 psi. 

Starter cultures of L. oenos ML 34 for inoculating wine are obtained by inoculating the grape juice medium with 1 vol % of a subculture (or another starter culture). The subculture is prepared by inoculating 5 ml of the grape juice medium from a stab culture. The cultures are incubated at room temperature until turbidity is seen,... 

FIG. 5 Viability of Saccharomyces cerevisiae (o) and Oenococcus oeni strain EQ-54 ( ) inoculated into a Chardonnay juice with the bacteria prepared using a diluted grape juice medium (A) or a lyophilized culture (B). (Adapted from Semon et al, 2001 and with the permission of the Australian Journal of Grape and Wine Research.)... 

FIGURE 1 Yeast cell growth, viability, sugar consumption, and ethanol production patterns of a typical fermentation. In a synthetic grape juice medium. Triple M (Spiropoulos et al., 2000) was used and inoculated with a commercial strain of 5. cerevisiae. Glucose and fructose concentrations were determined by enzymatic assay, viable cell counts by plating on YPD medium, and cell mass by absorbance at 580 nm. 

Model Fermentations. A chemically-defined grape juice medium at pH 3.5, with amino acids as the nitrogen source, was used for the model experiments (72). Sugar (D(+)-glucose 200 g/L) was included unless ofiierwise indicated. For those model fermentations that were conducted in the presence of tannins (1.5 g/L), the medium was sonicated for 15 minutes at room temperature after the tannin addition, and the insoluble material was removed by centrifugation at 48000 g for 15 minutes. In ferments containing added anthocyanins, the enriched anthocyanin preparation was sterile filtered (0.2 pm), and 1.6 mL were added to 47.4 mL of sterile filtered chemically-defined grape juice medium for each model fermentation. 

Leong, S.-L., Hocking, A.D. Scott, E.S. (2006a) Effects of temperature and water activity on growth and ochratoxin A production by Austraiian Aspergillus carbonarius and A. niger isoiates on a simuiated grape juice medium. Int. J. Food Microbiol. 110, 209-216. 

Grape juice medium 9 off-flavours 10 mL grape juice medium, pH = 3.4, NaCl = saturation DVB/CAR/PDMS fibre, HS-SPME, 30 min, 50 °C GC-MS 0.0047 to 3 Morales- Valle et al., 2010... 

Starter culture prepared using diluted grape juice medium. 

Fig. 1.18. Yeast growth and survival curves in a grape juice medium containing killer toxin (Barre, 1992) +, 10% K2 strain active culture supernatant O, 10% supernatant inactivated by heat treatment, (a) White juice, pH 3.4 cells in exponential phase introduced at time = 0. (b) Same juice, cells in stationary phase introduced at time = 0. (c) Red juice extracted by heated maceration, pH 3.4 cells in exponential phase introduced at time = 0...

However, under normal white fermentation conditions, grape juice is very poor in fatty acids and fermentation is usually carried out under hypoxia conditions (Bertrand and Miele 1984). Under these conditions, yeasts cannot synthesize unsaturated fatty acids. Consequently, Saccharomyces cerevisiae need to use another strategy to fluidize their membranes and the only possibility is incorporating medium chain fatty acids (MCFA) within the phospholipids of the membrane (Roz6s 1992). The effect of a short chain is similar to that of the double bond of a long chain (Quinn and Chapman 1980) and, therefore, the increased synthesis of MCFA could also modulate membrane fluidity. 

Oenococcus is a facultative acidophilic anaerobe and grows at pH 4.8 with temperatures between 18 °C and 30 °C. It requires a rich medium supplemented with tomato juice or grape juice, and its growth is not inhibited in the presence of 10% ethanol. Glucose is fermented in lactic acid, carbon dioxide, acetic acid and ethanol (it is a heterofermenter). It converts malate into lactate and CO2 in the presence of fermentable carbohydrate. 

In addition to S02 and antibacterial proteins/peptides, medium-chain fatty acids produced by yeast during alcoholic fermentation have also been implicated in the inhibition of malolactic bacteria (Carrete et al, 2002 Edwards and Beelman, 1987 Lonvaud-Funel et al, 1985). Inhibition of Saccharomyces species and some LAB by medium-chain fatty acids has been reported in grape juice and silage (Pederson et al, 1961 Woolford, 1975). Although this hypothesis has not been conclusively shown, Lonvaud-Funel et al (1985) and... 

Metal spatulas. 8. Yeast Paste. 9. 100% Bleach. 10. Grape juice agar medium for embryo collection 227.5 mL grape juice, 43.5 g sucrose, 11 g Agar 5 mL of an 1.25 N NaOH solution, 5.5 mL acid mix (418 mL propionic acid, 41.5 mL 85% phosphoric acid, distilled H20 to make 1 L) (see Note 3). 

Used as a nonselective general growth medium for wine and juice microorganisms, grape juice agar is prepared as follows ... 

---