International Commission on Food Mycology
International Commision on Food Mycology
Workshop 2010 -“Fungi in food and beverages: new research on spoilage, mycotoxins and prevention”
Freising, Germany,
7 – 9 June, 2010
Abstracts
Session 5: Fungi as Contaminants in the Beverage Industry (Chairperson Emilia Rico)
Posters
Spoilage of heat-processed beverages: an overview
Emilia Rico-Munoz1*
BCN Research Laboratories, Inc., 2491 Stock Creek Blvd., Rockford, TN 37853, U.S.A.
*Presenter: emilia.rico@bcnlabs.com
Heat-processed beverages can be classified as hot-filled and aseptically- or cold-filled. Since they are heat-processed, both groups can be spoiled by heat-resistant fungi (HRM) that produce ascospores. These ascospores not only survive the heat treatment given to these beverages but also can be activated and grow during storage. They are found in the ingredients such as the sweeteners, juice concentrates, juice purees, pectin, etc. Hot-filled beverages can incur additional spoilage due to the activation of ascospores of HRM such as Byssochamys spectabilis found in the empty PET bottles. They can also be environmentally contaminated at the cooling tunnel due to faulty closures. Cold- or aseptically-filled beverages can be exposed to a variety of non-heat resistant fungi such as Fusarium oxyporum, Exophiala sp., Cladosporium sp., Aureobasidium pullulans, and others at the filler. The eradication of some of these fungi from the aseptic filler or the aseptic filler room presents a challenge since they are involved in biofilm formation which protects them from the sanitizer. An overview of the sources of spoilage of these beverages as well as methodology and recommendations on how to reduce this type of spoilage will be presented.
Problems with potentially heat resistant moulds during validation of an aseptic filling machine
Michael Dahmen1*
1Krones AG, Process Technology R&D, Böhmerwaldstraße 5, 93073 Neutraubling, Germany
*Presenter: michael.dahmen@krones.com
After installation of an aseptic line in the beverage industry, typically the validation of the filling machine can be separated in two steps. First step is the validation of the individual sterilization processes, where for example the sterilization process of the packaging material is evaluated using packaging material (bottles and caps or seals) which is inoculated with standardized micro-organisms or using standardized spore strips for the machine surfaces. After treatment with the applied sterilisation technology, for example peracetic acid or hydrogen peroxide, the log reduction rate for each decontamination process can be calculated.
When all separate decontamination processes lie within the specifications, the commercial sterility rate of the whole process will be evaluated. This includes the thermal processing of the product, packaging decontamination, filling and closing of the bottle under aseptic conditions. Depending on the products to be filled, the failure rates of usually 1 microbiological failure in 10,000 bottles for low acid beverages and 1 failure in 30,000 bottles and up to 100,000 bottles for high acid beverages have to be observed and guaranteed by the machine supplier.
This acceptance test for high acid beverages is commonly performed with a clear juice or enrichment media with a pH value below 4.5. For the product treatment, usually the same parameters are used as under standard production conditions, predominantly between 92°C and 99°C for a few seconds.
To reduce the incubation time and achieve a fast result, bottles are very often half filled to increase the oxygen content and stored at temperatures above 25°C.
After an incubation time of 2 to 4 weeks, each filled bottle will be visually inspected. In case of a failed commercial sterility test because of microbiological growth, the organisms are plated for further investigations such as visual, microscopic or DNA analysis. With these results a troubleshooting in respect to the source of contamination is possible.
If the spoiling organism is described as a heat resistant species, the contamination is usually related to an insufficient product treatment. In cases where typical non heat resistant species occur, contamination is rather related to inadequate product handling or to problems with maintaining sterile conditions during bottle handling and filling.
Problems with interpretation of results occur in cases where spoiling organisms are found after heat treatment which have not yet been described as heat resistant in the literature. As an example for this, the validation of an aseptic filling machine is described in which spoilage by Tephrocybe sp. and Leohumicola sp. occurred in a large number of bottles. Both species have not been described as heat resistant moulds in the food industry before.
The class II hydrophobin FcHyd5p from Fusarium culmorum as gushing inducer and impact of hop compounds on its gushing potential
Georg Lutterschmid1*, Matthias Stübner1, Rudi F. Vogel1 and Ludwig Niessen1
1Technische Universität München, Lehrstuhl für Technische Mikrobiologie, Weihenstephaner Steig 16, 85350 Freising, Germany
*Presenter: georg.lutterschmid@wzw.tum.de
The phenomenon of gushing, i.e. the spontaneous over foaming of beer and other carbonated beverages immediately upon opening of a bottle, is a highly unwanted condition. It causes severe economical losses to breweries and producers of carbonated drinks and is resistant to unveiling the mechanisms and inducing agents involved. The origins of this problem are divided into primary gushing, which is associated with malt quality, and in secondary gushing, which is caused by technological failure. Secondary gushing can be prevented by good manufacturing practice and proper handling of the brewing equipment. However, mechanisms and inducing agents leading to primary gushing are not fully understood and identified. It has been suggested that fungal infection of the grain with Fusarium spp. is responsible for the problem. One consequence of the infection and growth of these moulds is the expression and secretion of hydrophobins, which are currently in focus as gushing inducing factors.
In our study, hydrophobin FcHyd5p from F. culmorum, which can be found in samples of infected barley and wheat, was heterologously expressed in Pichia pastoris and applied to induce the formation of bubble nuclei capable of inducing gushing in beer and other carbonated beverages. With the test system, hop compounds were evaluated for their potential to inhibit gushing. Bottled, non-gushing beer was chilled to 0°C, opened to add FcHyd5p and after sealing subjected to rotation (28 rpm) at ambient temperature. Subsequent to 16 h rotation and an hour rest the gushing volume was determined after opening by measuring the lost volume. Hop compounds were added together with the hydrophobin.
Addition of 2 mg hydrophobin to a 0.5 l bottle of beer resulted in strong overfoaming with max volumes up to 300 ml. An increased gushing volume was observed, if iso-α acid was added. Addition of hop oils and chemically modified iso-α acids lead to a significantly decreased loss of beer.
Based on the heterologously expressed hydrophobin FcHyd5p a system was established, in which compounds can be tested for their influence on gushing. This study shows, that some of the hop compounds tested here may be used to reduce the severity of gushing in beer. This system can further be developed for the evaluation of the effects of technological parameters on gushing reduction.
Acknowledgments:
This research was supported by Arbeitsgemeinschaft industrieller Forschungsvereinigungen "Otto von Guericke" e.V. (grant no. AiF 14551) and Weihenstephaner Jubiläums-Stiftung 1905
