The use of bacterial strains to the relationship between the degree of contamination of flour bacterial spores and microbiological stability of bread

Human health is largely determined by the quality of products they consume. The concept of food quality includes not only their nutritional value, organoleptic properties, but also microbiological safety [1]. Obtaining and maintaining safe food - one of the main factors determining the health of the nation, because microorganisms are not only initiate food poisoning, but also produce highly toxic substances, including mycotoxins, which have mutagenic and carcinogenic properties [2].

Under current conditions the production of bakery products packed with long shelf life is one of the main directions of development of baking industry in Kazakhstan, which is caused by the need to enhance food safety of products, supply of ecological trouble areas, remote regions, in terms of man-made disasters, crises and emergencies.

Urgent problem of production of bakery products with extended shelf life is to increase their microbiological storage stability - to prevent molding.

The aim of this study is to investigate the effect of contamination of the main raw material - flour spores of bacteria in the molding process of bakery products and to establish of maximum permissible level of contamination for the production of baked goods in packaged form.

The work was conducted at the Research Institute "Food Safety" ATU, JSC "Kazakh Academy of Nutrition, " Department "Safety and quality of food," ATU, the bakery enterprises in Almaty and Almaty region.

In the study used the following materials: wheat flour Kazakhstan (ST RK 000000) high, the first and second grades, obtained from different areas in excess of 4 samples of the high grade flour, 1 sample of the first grade flour and 3 samples of the the second grade flour, baker's compressed yeast (Standard GOST 171), salt (Standard GOST 13830), sugar (Standard GOST 21), table margarine (GOST 240), sunflower oil (Standard GOST 1129) - obtained from the "Almaty margarine factory", drinking water (Standard GOST 2874), sorbic acid (E200). To conduct research used the following disinfectants: chlorinated lime. And the following culture of microorganisms: Bacillus subtilis, Aspergillus niger.

Microbiological resistance - the ability of the product to withstand the damaging action of microorganisms and to maintain their consumer properties within a certain time.

The problem of stability of the microbiology of bread includes issues prevent it from microbial spoilage, molding, and the potato disease.

The development of the potato disease of bread, as a rule, it eliminates musty, as bread, potato sticks infected with spores, the consumer retains its properties only for 2-3 days after baking, and molding process is the most intensively manifested in 4-5 days. Due to the fact that the study focuses on the microbiological stability of grain in storage, and storage of grain, potato disease affected not appropriate criterion for evaluating the stability of the microbiology of bread during storage was selected molding process.

Storing bread unpackaged is also not advisable, so bringing all experiments of this study were stored hermetically packaged bread in the sterile (to avoid additional contamination) polypropylene bags.

Today in our country produces two types of bread in the package: bread long-term storage -the shelf life of more than 20 days, and bread with extended shelf-life - the shelf life of less than 20 days.

Bread of long-term storage - is usually a special purpose (for the astronauts, divers, etc.). Usually it is done using special additives that slow the stale and microbial spoilage of the product packaging of certain quality, the use of conservation (sterilization), according to regulatory documents apply only to this type of product.

Bread, with extended-shelf-life, is produced manufacturer, as a rule, according to current regulations and generally accepted formulations using any packaging authorized by agencies of the State Committee of the RK for packaging food products. These products can be produced both in packed and unpackaged.

The composition of the microflora, the reproduction of which may cause deterioration of bakery products is diverse and includes two groups of microorganisms - are able to develop on the surface of the bread and its crumb.

Due to the fact that the baking temperature is high enough (250-280 ° C at the surface and 90-95 ° C in the center of the product), leaving the oven the surface of bread is practically sterile, and in the crumb of bread in a viable state there are only bacterial spores. The source of contamination of bakery products with the spores of bacteria, usually raw materials, mainly flour. Infection of the surface of the finished product with molds can occur only from the outside. Therefore, an important decision was made to investigate the microbiological status of flour.

Storage of bread, potato disease affected not feasible, so the first stage of the work was to investigate the microbiological status of flour in order to identify the relationship between the number of bacterial spores in her illness and disease of potato bread, as well as the establishment of maximum permissible level of contamination of flour for the production of bacterial spores with elongated grain shelf life.

Investigations to determine the overall level of contamination of flour with spores of bacteria and infection of bread with the potato illness.

The results are presented in Table 1.

It is known that the degree of conta-mination of raw bacterial spores cannot diagnose a disease of potato bread, because is essential not so much the number of spores, as their activity. However, the differentiation of flour for two levels of contamination ( 105 CFU / g, susceptible potato disease, apparently because this number of spores of the first stage of selection are presented in Table 2.

In the second stage of selection activity previously identified strains of bacteria tested by a laboratory test baking. In kneading the dough with a suspension of spores of bacteria have made in the amount of 105 CFU / g of flour. The results are shown in Table 3.

Due to the fact that in experiments to establish the relationship between the degree of contamination of flour by the spores of bacteria and the microbial resistance of bread were used strains of bacteria, which differ in their biochemical characteristics of the typical microflora of flour, to confirm the established relationships conducted additional experiments. Investigated the stability of the microbiology of the bread baked from flour with identical properties but with different degrees of contamination of bacterial spores (Table 4).

Table 1 - Relationship between the number of bacterial spores in flour and bread infected by potato disease

Wheat flour	Number of samples	% of samples of flour, infected with potato sticks, in the level of contamination, CFU / g
		<105	>105
Higher grade	72	31,8	100
First grade	98	36,2	100
Second gradeсорт		31,0	97,5
Total:	225	33,4	99.0

Table 2 – Activity of the spore-forming bacteria

Species of bacteria	strain	Duration of the dilution reaction of gelatin on the film, min	The degree of destruction by potato disease
Subtilis	1*	120	average degree
Subtilis	2*	105	average degree
Subtilis	3*	none	none
Subtilis	4*	90	average degree
Subtilis	5*		average degree
Subtilis	6*	90	average degree

Table 3 – The degree of destruction of bread by potato disease, contaminated with spores of the bacteria

Species of bacteria	strain	Evidence of potato disease		The degree of destruction by potato disease
		24h	36 h
Sublilis	0611-a	-		none
Subtilis	36-1	-		none
Sublilis	4/8	-	-	none
Sublilis	744-5	-		none
Sublilis	3*	-		average degree
Cereus	96-2			none
Cereus	45			none

Table 4 - Baking properties of flour with varying degrees of contamination

Contamination of flour with spores of bacteria CFU / g	Gluten content,%	Ндеф™ ед.прибора	Moisture content,%	Acidity, degree
50	31,0	68	13,5	2,5
150	29,5	70	14,0	2,5
420	28,7	65	13.8	2,5

Based on these data revealed that:

The level of contamination with bacteria spores of flour for making bread with extended shelf life by - no more than 101 CFU /