The Use and Effects of Lactic Acid Bacteria in Malting and Brewing with Their Relationships to Antifungal Activity, Mycotoxins and Gushing: A Review

Turned and unturned outdoor floor malted sorghum were studied for their total microbial contamination, nature and extent of contamination by moulds, cytotoxicity (IC 50 ) and quality in terms of diastatic power (DP). The presence of aflatoxins, fumonisins, deoxynivalenol and zearalenone were also investigated. Total microbial counts were high (10 7 -10 8 cfu /g) in both turned and unturned samples. All samples showed contamination by different moulds, with the dominant being Mucor species, Rhizopus oryzae, Fusarium moniliforme and Phoma sorghina as well as Aspergillus flavus and Alternaria alternata. The latter four are known for producing mycotoxins. Malt samples had very low cytotoxicity (IC 50 from 62.5 to >1000 kg/kg), though all contained fumonisins, deoxynivalenol and zearalenone at levels of < 0.25-2 µg/g, 15-20 and 10-15 µg/kg, respectively. Malt DP was generally lower in turned samples compared to unturned samples probably because the heat conserved in the latter ensured better germination conditions. Overall, turning during germination did not affect the microbial load, mould population and levels of deoxynivalenol and zearalenone in sorghum malt but decreased sorghum malt DP. Thus, alternative methods of controlling the sorghum malt microbial load should be sought.

Section: Discussionmentioning

confidence: 99%

The Microbial Contamination, Toxicity and Quality of Turned and Unturned Outdoor Floor Malted Sorghum

Lefyedi

Marais

Dutton³

et al. 2005

“…They also contribute to the grain enzyme activity by being important producers of amylolytic, proteolytic and cell wall-degrading enzymes with potentially positive effects on malt characteristics 16,17,26,41,47,50,51,62 . In addition, malt-derived bacteria and fungi with known and carefully selected characteristics can be applied as starter cultures and they offer natural ways to improve the safety and processability of malt 4,31,35 .…”

Section: Introductionmentioning

confidence: 99%

Indigenous Microbial Community of Barley Greatly Influences Grain Germination and Malt Quality

Laitila

Kotaviita

Peltola³

et al. 2007

The present study was carried out to investigate the impacts of bacterial and fungal communities on grain germination and on the malting properties of good‐quality two‐row barley. In order to suppress the growth of bacterial and/or fungal communities, various antibiotics were added to the first steeping water of barley. This study was also designed to explore the dynamics of the bacterial community in the malting process after antimicrobial treatments by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE). The diverse microbial community played an active role in the malting ecosystem. Even previously undescribed bacterial species were found in the malting ecosystem. Suppression of the bacterial community mainly consisting of Gram‐negative bacteria was advantageous with respect to grain germination and wort separation. In addition, more extract was obtained after antibacterial treatments. The fungal community significantly contributed to the production of microbial β‐glucanases and xylanases, and was also involved in proteolysis. An improved understanding of the complex microbial community and its role in malting enables a more controlled process management and the production of high quality malt with tailored properties.

“…It is possible that the P. pentosaceus strain used in this study produced such antimicrobial compounds. It is also possible that the P. pentosaceus strain produced antifungal compounds, as it has been shown that numerous LAB exhibit antifungal activities and the active factors have been identified 18 . The inhibition of coliforms by other bacteria can also be attributable to competition for nutrients 13 .…”

Section: Cultures (Code Number) Original Culture Numbers Sourcementioning

confidence: 99%

“…Recently we have shown that these undesirable sorghum malt microflora can be controlled by steeping in dilute NaOH 16 . However, a recent development aims to inhibit the growth of unwanted bacteria and moulds by the addition of desirable microbial cultures as natural biocontrol agents in steeps 18 . Lactic acid bacteria (LAB) 15 and the yeast Geotrichum candidum 4 have been shown to be effective at inhibiting unwanted microorganisms in barley malting.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Control of the Growth of Coliforms and Moulds in Sorghum Malting by Bacterial and Yeast Cultures

Lefyedi

Taylor

2007

Traditional outdoor floor malted sorghum can be contaminated with high levels of coliform bacteria and moulds that can potentially produce mycotoxins. The effect of steeping with the addition of bacterial and yeast starter cultures on microbial contamination, toxicity and diastatic power (DP) of sorghum malt was investigated. Lactobacillus plantarum, Pedicococcus pentosaceus and Saccharomyces species were selected on the basis of inhibition of fungal species using the disc diffusion assay. Steeping the sorghum with the addition of these cultures at 10 7 -10 8 cfu /mL reduced the level of moulds by one to two log cycles, with the Saccharomyces culture appearing to be the more effective and L. plantarum the least effective. Coliforms, where present in significant numbers, were reduced to levels of <10 1 -10 2 by steeping with the cultures, with the P. pentosaceus culture appearing to be the most effective and Saccharomyces the least effective. There were no detectable amounts of mycotoxins and no significant cytotoxicity in the malts in either the controls or the culture-steeped malts. Steeping with the cultures did not affect malt DP. The use of such P. pentosaceus and Saccharomyces sp. cultures could be an alternative to chemical treatment for the control of microbial contamination in sorghum malt.