Isolation, Identification, and Characterisation of Beer-Spoilage Lactic Acid Bacteria from Microbrewed Beer from Victoria, Australia

Abstract

Lactic acid bacteria are the most frequently encountered beer‐spoilage bacteria, and they may render beer undrinkable due to the production of lactic acid, diacetyl, and turbidity. Microbrewed beer is typically sold unpasteurised, leaving it more susceptible to spoilage by lactic acid bacteria. In this study, the incidence of lactic acid bacteria in bottled microbrewed beer from Victoria, Australia was investigated. A total of 80 beers from 19 breweries were screened for lactic acid bacteria. Almost 30% contained culturable lactic acid bacteria, and many had lactic acid levels well above the flavour threshold. Ethanol, hops, and the pH levels of the beers were not predictors for spoilage in the beers examined, and contamination appeared to be more closely linked to the source brewery. The 45 lactic acid strains isolated from these beers were identified by RAPD‐PCR, with Lactobacillus brevis being the most frequently isolated species. All isolates were capable of spoiling beer and contained putative hop resistance genes. At typical beer levels, pH and ethanol had no effect on the growth of the particular spoilage bacteria isolated in this study.

The Occurrence of Beer Spoilage Lactic Acid Bacteria in Craft Beer Production

“…Beer is considered an unfavorable substrate of growth for many microorganisms due to several factors, such as: (i) the ethanol concentration ranging from 0.5% to 10% (w/w), (ii) the presence of hop compounds that have antimicrobial activity, (iii) the low pH (usually around 3.8 to 4.7), (iv) the reduced oxygen content and nutrient availability, and (v) the high CO 2 content (Sakamoto and Konings ; Manzano and others ; Rouse and Van Sinderen ; Menz and others ). Despite these hostile properties, there are a limited number of bacteria and yeasts, which are capable of growth and may spoil beer especially if it is not pasteurized or sterile‐filtered as craft beer (Sakamoto and Konings ; Hill ; Menz and others ). In particular, lactic acid bacteria (LAB) are well‐known as the main spoilage agents since it has been assessed that they are responsible for 60% to 70% of all cases of beer spoilage (Sakamoto and Konings ; Rouse and Van Sinderen ; Menz and others ).…”

“…Despite these hostile properties, there are a limited number of bacteria and yeasts, which are capable of growth and may spoil beer especially if it is not pasteurized or sterile‐filtered as craft beer (Sakamoto and Konings ; Hill ; Menz and others ). In particular, lactic acid bacteria (LAB) are well‐known as the main spoilage agents since it has been assessed that they are responsible for 60% to 70% of all cases of beer spoilage (Sakamoto and Konings ; Rouse and Van Sinderen ; Menz and others ). Among LAB, a few hetero‐ and homofermentative species belonging to Lactobacillus and Pediococcus genera are recognized as the leading causes of beer spoilage events (Rouse and Van Sinderen ).…”

“…Furthermore, these bacteria are generally characterized by resistance to hop compounds thus explaining their presence and growth in the final product (Rouse and Van Sinderen ; Haakensen and others ). The beer alteration caused by LAB spoilage consists in the production of off‐flavors (mainly due to diacetyl and lactic acid), changes in color and an increase in turbidity (Rouse and Van Sinderen ; Menz and others ). Furthermore, this detrimental effect on beer quality is also the cause of huge economic losses in the brewery sector (Sakamoto and Konings ).…”

“…Some papers have dealt with the detection of LAB spoilage in beers and breweries (Manzano and others ; Menz and others ), another focused on methods to control microbial contamination by the use of specific cleaning procedures (Manzano and others ), while others have been aimed at defining a rapid and sensitive method for the detection of beer spoilage bacteria before the beer is bottled and sold (Takahashi and others ; Asano and others ).…”

Microbiological Diversity and Prevalence of Spoilage and Pathogenic Bacteria in Commercial Fermented Alcoholic Beverages (Beer, Fruit Wine, Refined Rice Wine, and Yakju)

“…Korea is one of the largest manufacturers of Fermented and filtered alcoholic mash (mixture of malt, hops, water and grains, starch, or sugar) containing C 0 2 Beer served in a glass from large casks or kegs in pubs and other premises Beer produced in small breweries according to traditional recipes without pasteurization Beer commercially manufactured by canning or bottling after pasteurization Filtered and fermented alcoholic mash (fermented mixture of fruit, water, or both) stored in oak Fruit wine made from fermented grapes Fruit wine made from fermented fruits other than grapes (e.g., R. coreanus fruit, Korean wild grapes) Filtered and fermented rice wine mash (fermented mixture of rice, nuruk, and water), with or without other ingredients Filtered and fermented alcoholic mash (fermented mixture of starch-based materials, nuruk, and water) Yakju commercially or conventionally manufactured without pasteurization Yakju commercially manufactured after pasteurization FABs in the world, particularly of refined rice wine, fruit wine (e.g., Rubus coreanus fruit, plum, mulberry, and medicinal herbs), and yakju, and international exports have increased steadily (20). Although Asia is a big manufactur ing pool for diverse FABs, few studies have examined whether foodbome pathogens are present in traditional Asian products, although several have sought to identify harmful or beneficial microorganisms (11,29,49) or develop novel techniques to enrich beneficial microorgan isms or eliminate spoilage microorganisms (6,8,27,47) in these products.…”