Een correcte sulfiet oplossing (voldoende hoge concentratie) bij de juiste pH (je moet dus zorgen dat er genoeg vrije SO
2beschikbaar is en dit is afhankelijk van de pH) is zeker een afdoende desinfectantia, en daar is wetenschappelijk onderzoek naar gedaan. De drogreden dat dit niet werkt daar er na een aantal weken al vast gesteld is dat daar schimmel op zo een oplossing komt is puur logisch, gezien de hoeveelheid vrije SO2 daalt in de oplossing over tijd en deze als dus danig zijn werking verliest.
6.7. Antimicrobial
At low concentrations, SO2 inhibits the development of microorganisms. At high concentrations, it can destroy a proportion of the microbial population. Molecular SO2 is the form responsible for antimicrobial action [Rahn and Conn, 1944; Rhem, 1964; Macris and Markakis, 1974; Beech et al., 1979; King et al., 1981].
Bound SO2 also possesses antimicrobial activity, though this is limited. The antimicrobial activity of bound SO2 depends on the compound that the SO2 is bound to [Rehm and Wittman, 1962]. For example, acetaldehyde, pyruvate, and acetone have a significant inhibition effect, whilst glucose has only a slight inhibition effect. Generally, the antimicrobial activity of bound SO2 is not significant.
Different yeast and bacteria strains have different levels of tolerance to SO2 [Cruess, 1912]. A number of studies have attempted to determine the levels required for inhibition or death for numerous strains. One study found a 1000-fold reduction in the number of viable cells of a Brettanomyces species, certain LAB species, and other spoilage organisms within 24 hours at a molecular SO2 concentration of 0.8 mg/l [Beech et al., 1979]. Another found total microbial inhibition in at 4 mg/l molecular SO2 [Delfini, 1984]. A classic study by Beech et al. [1979] assessed the SO2 required to reduce non-growing yeast and bacterial populations by 10,000 viable cells/ml over a 24 hour period in 10% ethanol buffered solutions. They found that 0.825 mg/l molecular SO2 was required for one Saccharomyces cerevisiae strain, 0.825 mg/l for a Brettanomyces strain, 1.50 mg/l for a Zygosaccharomayces bailii strain, and 4 mg/l for a Lactobacillus plantarum strain. Based on these figures it would seem that a level of 0.8 mg/l molecular SO2 is sufficient for the suppression of the majority of yeast and bacteria strains.
It should be noted, however, that strains can build up resistance to SO2. Older cultures tend to have more resistance to SO2 [Schimz, 1980; Katchmer, 1990].
Bacteria are more susceptible to SO2 than yeasts and are considered separately below.
6.8. Antiyeast
Molecular SO2, and to a lesser extent bisulphite (HSO3-), inhibit yeast. Free SO2 essentially has an antiseptic effect [Kielhofer, 1963], and the growth of Saccharomyces has been shown to be related to its concentration [Ingram, 1948].
6.8.1. Resistance adaptation
As stated above, different yeast strains are resistant to SO2 [Porchet, 1931] to varying degrees. Some may tolerate 700 mg/l free SO2 or more.
Yeast may also adapt to an SO2 environment and become resistant to SO2. Certain yeasts have been shown to permanently adapt to 10-12 times the SO2 concentration that the parent strain could tolerate [Scardovi, 1951, 1952, 1953]. Delfini [1988, 1989, 1992a] demonstrated that a variety of yeast strains (S.cerevisiae, S. ludwigii, Zygosaccharomyces baillii, and Schizosaccharomyces japonicus) could develop successive permanent (inherited) resistance to SO2 to a final level of 9.2-11.5 mg/l molecular SO2.
It is therefore important to limit SO2 additions, and to avoid adding successive doses, as this may result in increased SO2 resistance by the yeast strain.
6.8.2. Growth
Yeast growth exhibits an extended lag phase in the presence of SO2, but this is usually followed by normal growth following the end of the lag phase [Schanderl, 1959].
SO2 is more effective on yeasts in their resting/sporulating phase, since binding with aldehydes may occur latter.
6.8.3. Complete and partial inhibition
Scardovi [1951] showed that total S. cerevisiae strain cell death occurred with 4 mg/l molecular SO2 for non-resistant variants, whilst 40 mg/l was required for resistant strains. S. cerevisiae has been shown to be sensitive to 0.5-0.9 mg/l molecular SO2, with complete inhibition occurring at >0.5-1 mg/l [Beech, 1979]. In another study, approximately 30% cell death occurred at 18 mg/l molecular SO2, whilst 70% death occurred at 42 mg/l [Farkas, 1988]. SO2 can also reduce the viability of a yeast inoculum. One study found that 15-20 mg/l free SO2 reduced the population from 106 to 104 cells/ml [Lehmann, 1987]. Nevertheless, fermentation has been seen to commonly occur (evidenced by a 0.5-1% by volume alcohol production) with as much as 2000 mg/l free SO2 [Delfini, 1984].
Marcis and Markakis [1974] showed that 1.3 mg/l molecular SO2 was required to eliminate viable yeast cells in a medium. Another study showed that 1.56 mg/l was required [King et al., 1981]. Minarik [1978] found that 6.4 mg/l was required in juice, while Beech et al. [1979] found that 0.825 mg/l was required in a model wine solution, and Sudraud and Chauvet [1985] suggested 1.5 mg/l be used following fermentation and 1.2 mg/l be used during storage to prevent refermentation of residual sugar.
It may be generally accepted that 4-5 mg/l molecular SO2 can cause total inhibition of S. cerevisiae.
6.8.4. Time dependence
Total yeast death is also time dependent. Yeast uptake of SO2 is rapid, and can be complete within 3 minutes [Macris and Markakis, 1974]. It may, however, require longer periods of time for SO2 to become lethal. One study [Delfini, 1981] found total inhibition occurred at 0.29 mg/l molecular SO2 for Kloeckera apiculata, 0.67 for Pichia vini, and 1.59 for Candida vini. These concentrations became lethal after 24 hours of exposure with a cell population of 106 cells/ml. Macris and Markakis [1974] found that a population reduction of 90% took 83 minutes with 0.025 mg/l molecular SO2. In spite of these findings, Uzuka and Nomura [1986] found that, at 0.80 mg/l molecular SO2, over 50% of yeast viability was lost within 30 minutes. A similar reduction corresponds to 6 hours at 0.825 mg/l in the Beech et al. [1979] study and 20 hours in the King et al. [1981] study.
6.8.5. Yeast selective
To a certain degree, SO2 may be used as a yeast selector. At certain doses it promotes yeast selection by hindering the multiplication of non/low-alcohol producing yeasts such as apiculates, Torulopsis, and Candida more than that of elliptic yeasts [Romano and Suzzi, 1992]. Nevertheless, Heard and Fleet [1988] showed that apiculated yeasts (Kloeckera and Hanseniaspora) grew to substantial populations (106-107 cells/ml) in a few days before receding.
6.9. Antibacterial
Lactic bacteria are sensitive to free and, to a lesser extent, bound SO2 [Fornachon, 1963].
The primary antimicrobial effect of SO2 is attributable to molecular SO2, at least up to pH 5 [Scardovi, 1951, 1952; Macris and Markakis, 1974]. Though there is evidence that bound SO2 can contribute to bacterial control [Bioletti, 1912; Rhem, Wallnofer and Wittman, 1965; Lafon-Lafourcade and Peynaud, 1974; Hood, 1983] and inhibit LAB growth [Fornachon, 1963]. This is because LAB consume acetaldehyde, which subsequently releases SO2 from the bound acetaldehyde-SO2 form [Osborne et al., 2000]. Mayer et al. [1975] found Leuconostoc oenos sensitive to levels of acetaldehyde-bound SO2 levels of 20-60 mg/l. Hood [1983] showed that just 6 mg/l of acetaldehyde-bound SO2 could inhibit the growth of Leuconostoc oenos, Leuconostoc brevis, and Pediococcus pentosaceus at pH 3.4.
In one study [Delfini and Morsiani, 1992], ten strains of Leuconostoc and four of Lactobacillus were found to cease growth above 0.5 mg/l molecular SO2. A Leuconostoc population of 2 × 106 cells/ml in a buffered synthetic medium died within 22 hours after addition of 0.84 mg/l molecular SO2. However, a number of Leuconostoc and Lactobacillus strains survived SO2 additions and resumed multiplication after a 10-60 day lag phase at molecular SO2 levels under 0.8 mg/l.
Acetic acid bacteria are also sensitive to SO2. Research conducted on Acetobacter aceti, A. liquefaciens, A. hansenii, A. pasteurianus and Gluconobacter oxydans showed that some strains were more sensitive than others. Molecular SO2 levels of 0.1-0.65 mg/l were required to effectively kill strains in juice over a 4 day period, depending on the individual strain [du Toit, 2000]. The production of VA was also found to inhibit the growth of yeast (Vin 13). Some acetic acid bacteria strains were found to produce SO2 binding compounds such as gluconic, 2 ketogluconic and 2,5 diketogluconic acids. The addition of SO2 before fermentation may therefore be of increased importance, since this will inhibit acetic acid development which in turn will prevent inhibition of yeast growth.
Het gebruik van sulfiet als desinfectans voor je equipement kan volgens mij maar je moet je aan een aantal regels houden, pH is daar de belangrijkste van je moet een pH van 2 lager of lager hebben om voldoende SO
2 vrij te stellen. (hou hier rekening mee als je hard water hebt)
Je sulfiet oplossing is beperkt houdbaar door diffusie van SO
2 naar de lucht en binding aan de micro-organismen en eventueel nog achtergebleven vervuiling. Dus regelmatig verversen van je oplossing is een noodzaak.
Wees er van bewust dat er resistentie kan opgebouwd worden (net zoals bij Starsan) dus regelmatig een ander product gebruiken als desinfectans is de boodschap.
Het grote nadeel vind ik persoonlijk de ongezonde atmosfeer waar je je zelf aan blootstelt. Ik raad het ook om die reden niet aan om dit te gebruiken maar stellen dat dit onvoldoende werking heeft als desinfectans is incorrect.En nu mogen jullie mij allemaal afschieten
Topic: Al weer een discussie over reinigen en desinfecteren (gelezen 16501 keer)