Search: water sensitivity

Barley is steeped according to a defined scheme, and the absorption of the steeping liquor by the kernels at defined times is determined by calculating the moisture content. The moisture content after 72 h steeping time is used to assess the absorption of steeping liquor or the capacity for water imbibition in barley.

Analogous to the p and m values obtained in the determination of acid capacity (pH 8.2 and 4.3), this analysis is performed according to W-000.13.031 Acid Consumption (Alkalinity, p-Value and m-Value)/Acid Capacity to pH of 8.2 and/or 4.3 for Water. The alkaline capacity of the boiler water is determined through titration of the sample with 0.1 N sodium hydroxide (instead of hydrochloric acid) to a pH of 4.3 and/or 8.2.

Non-alcoholic beverages (NABs) can be divided into three main groups:

Juices and nectars

Soft drinks (e.g. spritzers, fruit juice drinks, lemonades, fizzy drinks, flavoured waters, sports and energy drinks, mixed drinks, etc.)

Waters (mineral water, table water, medicinal water, etc.)

Raw materials for non-alcoholic beverage production (fruit juice concentrates, base materials, flavourings, sugar syrups, etc.) are also listed.

Hot and cold drinks such as coffee, tea and milk are not included here.

With the exception of waters, this regulatory classification is based on their composition: mainly due to their juice content (0-100 %), flavouring (natural, natural-identical, artificial) and various ingredients such as caffeine, vitamins, minerals, etc.

Microbiological sensitivity of non-alcoholic beverages

The microbiological susceptibility of non-alcoholic beverages should be considered separately due to the diversity of the test matrix. It is characterised by the following key selective criteria:

Beverage ingredients:

The microbiological sensitivity of a beverage is expressed via the specific growth and inhibition substances. These include nutrient-rich substances such as carbohydrates, amino acids, minerals and vitamins etc., which provide the basis for microbiological growth. The presence of fruit acids, essential oils although also the lack of nitrogen sources, inhibit growth and thus provide additional inherent protection for non-alcoholic beverages.

pH value:

The pH value of a beverage plays a central role in beverage production and microbiological analysis. The acidification of the beverage is intended to prevent the growth of pathogenic microorganisms. However, there is no absolute limit value. In practice, a pH value of < 4.3 is considered sufficient protection, depending on the nature of the beverage and its ingredients. Vegetable juices, for example, are an exception.

Aerobiosis/anaerobiosis:

The carbonation of beverages creates an anaerobic environment to largely suppress the growth of aerobic microorganisms, for example. Depending on the type of packaging, sufficient CO₂ must be added to compensate for gas losses due to migration during the shelf life. For example, at least 3-4 g/l CO₂ is recommended when using lightweight PET bottles.

In general, the groups of acidophilic and acid-tolerant, aerobic and facultative anaerobic as well as anaerobic microorganisms are identified as potentially harmful to beverages in the NAB industry, provided that the pH value of the products is in the acidic range (pH value < 4.3). For NAB with more critical pH values (> 4.3), this increases the relevance of mesophilic and thermophilic microbes and potentially pathogenic microorganisms.

Osmophilic/osmotolerant microbes must also be taken into consideration. These can occur as spoilers, especially in highly concentrated raw materials for beverage production. These include, for example, fruit juice concentrates, fruit pulp, fruit preparations, base products, and also sugar syrups, etc.

The beverage-spoilage organisms in non-alcoholic still drinks are generally all yeasts, acetic acid bacteria, moulds and alicyclobacilli. Depending on the pH value, other germs such as Bacillus sp. become relevant.

In carbonated non-alcoholic beverages, fermentable and fermenting yeasts are particularly important, but also other microorganisms such as lactic acid bacteria. Depending on the pH value, other germs such as Bacillus sp. or potentially pathogenic germs such as Clostridium sp. can occur.

The listed groups of beverage spoilers can be categorised as primary contaminants from the corresponding raw ingredients or as secondary contaminants.

Due to the complexity and diversity in the NAB sector, the microbiological controls and analyses, both in the production process and in the end products, must be considered in a different way according to each product group. The requirements are always based on the specific selective criteria of the products in question.

In EU member states, Council Directive 80/777/EEC on the approximation of the laws of the Member States relating to the exploitation and marketing of natural mineral waters of 15 July 1980 became the basis for the implementation of existing laws at national level (current version dated 18 June 2009: Directive 2009/54/EC).

Article 5 of Directive 2009/54/EC regulates the requirements for mineral water both at the source and in the bottled water.

Paragraph 1 of Article 5 specifies the permitted total colony counts. At source, the total colony count (CFU) must not exceed 20 CFU/ml at 20 °C to 22 °C/72 h and 5 CFU/ml at 37 °C/24 h. These values are to be understood as GUIDE figures [3].

After bottling, LIMITS apply to both colony counts if the total bacterial counts were analysed within 12 hours of bottling. The maximum permitted concentrations are defined as 100 CFU/ml at 20 °C to 22 °C/72 h and 20 CFU/ml at 37 °C/24 h [3].

No limit values are set for the total colony count for the marketing stage in paragraph 3 of Article 5. This takes account of the fact that mineral water is not sterile and that, under appropriate conditions, there may be an increase in microorganisms (e. g . storage conditions in retail outlets or at the consumer's premises), but this may only originate from the natural microbial flora it had at source. In addition, the mineral water must be free from organoleptic defects [3].

Paragraph 2 of Article 5 defines the requirement that mineral water must be free from parasites and pathogenic microorganisms [3]. This is considered to be fulfilled if Escherichia coli, coliforms, faecal streptococci and Pseudomonas aeruginosa cannot be detected in a sample volume of at least 250 ml and sporulated sulphite-reducing anaerobes cannot be detected in any 50 ml sample examined ("indicator principle").

Annex I Section II Number 1.3. sets out the criteria for microbiological tests at the source (quantitative determinations of indicator bacteria, sample quantities, incubation temperatures, incubation times). In the author's view, these criteria also apply to the filling of mineral water, even if this is not explicitly stated.

The EU Directive does not specify (apart from quantitative determinations) which methods should be used for carrying out microbiological tests. This is therefore left to the discretion of each Member State within the framework of national implementation.

In Germany, the "Table Water Ordinance" of 12 November 1934 was replaced by the implementation of the EU Directive with the German Mineral and Table Water ordinance (MTVO) of 1 August 1984 (current version of 5 July 2017).

It should be noted that the German implementation deviates from the EU directive in some respects. The "quantitative determination" requirement is not fulfilled in the MTVO or in the corresponding chapter in the collection of official test methods (Section 64 of the German Food and Feed Code LFGB, L59.00) for "indicator organisms". Qualitative methods are listed here.

There is a further deviation in the incubation time for the total colony count of 20 °C to 22 °C. The EU directive specifies 72 hours [3], while the MTVO and § 64 LFGB specify 48 hours [1, 2].

There are also differences between the two German regulations with regard to the higher incubation temperature. The MTVO lists 37 °C ± 1 °C [1], whereas § 64 LFGB lists  36 °C ± 1 °C [2]. From the author's point of view, this deviation has no foreseeable significant relevance to the growth behaviour of the bacteria.

In the following explanations of the test methods, only one of the two temperatures is used, namely 37 °C ± 1 °C (however, 36 °C ± 1  C can also be used in daily laboratory practice).

Qualitative detection of faecal streptococci in mineral water, spring water, table water and other drinking water bottled for distribution to the consumer by means of enrichment culture in double-concentrated azide-glucose broth [1].

Membrane filtration (MF) and immersion of the filter in single-strength azide-dextrose broth (corresponds to the methods in Annex 2, point 2b of Section 4 (3) of the German Mineral and Table Water Ordinance [1] and ASU Section 64 LFGB L59.00-2) [2].