CN103397070A - Sensing and monitoring control method for escherichia coli water activity in bread - Google Patents
Sensing and monitoring control method for escherichia coli water activity in bread Download PDFInfo
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- CN103397070A CN103397070A CN2013103239005A CN201310323900A CN103397070A CN 103397070 A CN103397070 A CN 103397070A CN 2013103239005 A CN2013103239005 A CN 2013103239005A CN 201310323900 A CN201310323900 A CN 201310323900A CN 103397070 A CN103397070 A CN 103397070A
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Abstract
The invention discloses a sensing and monitoring control method for escherichia coli water activity (represented by Aw) in bread. The sensing and monitoring control method is characterized by comprising the following steps of inoculating escherichia coli into negative bread test samples to prepare a series of parallel escherichia coli positive bread samples, respectively placing the positive samples in constant temperature (for example, 2 DEG C) environments with different water activities for culture, taking out after a certain time, and detecting the escherichia coli count so as to obtain the linear relationship between an escherichia coli growth coefficient (represented by k) and the water activity in the bread; and taking the water activity when the growth coefficient k is 0, namely when the escherichia coli is not proliferated, as a key control point, proliferating the escherichia coli when the water activity is higher than the key control point, and inhibiting the proliferation of the escherichia coli when the water activity is lower than the key control point, thereby realizing sensing and monitoring control of the growth of the escherichia coli in the bread by monitoring the water activity. By adopting the method, the sensing and monitoring control of pathogenic microorganisms and the like in other matrix foods can be expanded.
Description
Technical field
The present invention relates to intestinal bacteria water activity (with Aw, representing) sensor monitoring control method in a kind of bread.
Background technology
Food safety concerns life with healthy, is the healthy basis with improving the human life quality of to protect mankind.At present, food safety has become global Major Strategic problem, and more and more is subject to countries in the world government and human consumer's great attention.Sanlu milk powder case, toxic capsule event and red-yolk duck egg disturbance, caused extensive concern both domestic and external.The ability of foods supervision department is being checked in each food-safety problem and crisis, how to ensure food safety and becomes the common subject matter of paying close attention to of the whole people.
Food is from raw material production, processing, storing, sale until all may there be unsafe factor in the links of consumption.Along with continually developing of new food resource, the increase gradually of food kind, production-scale continuous expansion, the increasing of the links such as production, processing, storing, sale, and the variation of Consumption patterns, it is day by day complicated that the mankind's food chain becomes.That food may be subject to is biological, the pollution of chemical and physical property hazardous and noxious substances, threatens human health.In research and grasp food and food processing process, issuable hygienic issues is conducive to take adequate measures, guarantees food safety.
Water activity is as the important indicator of a food safety control and quality control, and relevant GB is not made relevant regulations in China, wherein only moisture content has been done clear and definite mandatory regulation.Summary by the meaning for water activity relevant food industrial production and sanitary index control, the comparison of different measuring principle in the probing into of the studying carefully of water activity relevant criterion, water activity surveying instrument Principle Method, various standard both at home and abroad, obtained a kind ofly adopting food substrate directly to cultivate intestinal bacteria to determine the method for water activity standard in specific food products.Be intended to cause relevant departments and investigator's attention; domesticly be necessary progressively to launch the correlative study as the food microorganisms quality control index of water-activity and moisture absorption isothermal curve and water activity; thereby to can effectively monitoring and control, to protect mankind health and life security, maintain social stability the biological sanitary index relevant with some water activities of chemical unsafe factor in food production.
Control method to the intestinal bacteria in food and other microorganisms comprises physical means and chemical means.Although the Chemical Preservation mode take sanitas as representative can well be controlled microorganism in food, the risk of bringing to human health is also apparent.Therefore, the research of the anticorrosion means of physics become new focus.Moisture is one of important indicator that affects microorganism growth, and the growing state of microorganisms in the different in moisture envrionment conditions helps to instruct people effectively to control the vital movement of microorganism in food-processing, guarantees the security of food, extends Food Shelf-life.The mankind recognize between the easy putridness of food and water content very early close contacting.In food, the hydrogen-bonded ability of various nonaqueous components and water and size are all not identical.With moisture content detection food safety and quality, certain limitation is arranged.Take water activity as basis, embodied of overall importance, science and the unity of food safety with the Establishing that drying, refrigeration, seal-packed means extend effective period of food quality, the America and Europe is Japanese the major criterion of water activity as food safety control.The people such as Guernec have been found that intestinal bacteria in freezing meat or other solid substrates, and genetic expression and physiological compatibility are subject to the impact of the conditions such as low temperature.In affecting the research of intestinal bacteria inactivation condition, correlative study shows that intestinal bacteria are for the increase of high temperature resistance in the different solvents of low water activity; New research shows that intestinal bacteria also can increase for the resistance of hyperbaric environment in the different solvents of low water activity.The people such as Koseki have made some preliminary study to the growing state of listeria bacteria under different water activities, differing temps, acid-basicity condition.The people such as Abramson have set up mathematical model to the growth of flavus in cereal crop in wheat.But for the research that water activity is applied in practice, also be difficult to meet the food safety control demand.
Summary of the invention
, in order to obtain controlling the water activity control index that intestinal bacteria length is main purpose in foodstuff production, the invention provides intestinal bacteria water activity (with Aw, representing) sensor monitoring control method in a kind of bread.
The present invention adopts food substrate directly to cultivate intestinal bacteria to determine water activity standard in specific food products, wherein: said method comprising the steps of:
To not contain colibacillary food substrate through check and be placed in the moisture eliminator of different water activity environment, under the room temperature aseptic condition, balance is 48 hours, the food substrate of the different water activities of preparation;
Intestinal bacteria are seeded in appropriate matrix, are placed under former water activity condition and continue to cultivate, a taking-up at regular intervals detects colibacillary upgrowth situation, thereby draws the curve of corresponding food substrate Escherichia coli Growth process under different water activity conditions;
Find the logarithmic proliferation phase of every growth curve and it is carried out the logarithm match and obtain coefficient of growth;
The coefficient of growth of intestinal bacteria in this food substrate under different water activity conditions carried out linear fit, draw the linear relationship of Escherichia coli Growth coefficient and water activity in this food substrate;
Calculate the water activity when coefficient of growth is 0, this water activity is this food water activity reference mark.Namely lower than this water-activity, intestinal bacteria within a certain period of time can't fast breeding in food substrate, thereby makes the food quality microbiological indicator relevant with intestinal bacteria controlled.
In the present invention, take sliced bread as example, it is as using the common food of heating shortening as final technique, and it is essential items for inspection in its microbiological indicator that coliform detects.By artificial contamination's method, intestinal bacteria are inoculated in sliced bread, store under different water activity conditions and by method for counting colonies, analyze, draw the Escherichia coli Growth curve; Colibacillary process of growth under different water activities is studied, sets up colibacillary Prediction of survival model under 25 ℃ of room temperature conditions.The relation of Escherichia coli Growth coefficient and water activity has been discussed, has been obtained the quality control index of colibacillary water activity.The method that the present invention is based on water activity sensing observing and controlling food-borne pathogenic microorganism processed can be expanded the sensor monitoring for other kind pathogenic microorganisms of other food, the method is easy, quick, effective, and is significant to the mutual relationship between water activity and Food Quality, food safety in research food.
Description of drawings
Fig. 1 intestinal bacteria bacterial growth situation (water activity 0.95,0.96,0.97,0.98,0.99,1) in 48 hours in bread under different water activity conditions.
Fig. 2 is colibacillary propagation and attenuation (water activity 0.95,0.96,0.97,0.98,0.99,1, wherein the extinction curve length axis under water activity 0.92 condition is countershaft) in different water activity tangent plane bread.
Fig. 3 is the linear fit curve of Escherichia coli Growth coefficient and water activity in sliced bread.
Specific implementation method
, for further setting forth intestinal bacteria water activity (with Aw, representing) sensor monitoring control method in bread, below in conjunction with embodiment, be described in more detail.
The present invention adopts bread matrix directly to cultivate intestinal bacteria to determine in foodstuff production long as main purpose water activity control index to control intestinal bacteria.Concrete steps are as follows:
1, the relation of water activity and part microorganism experiment
By the inquiry related data (table 1) as can be known intestinal bacteria substantially can't grow in the medium matrix of the experimental situation of 0.95 water activity, therefore the bread matrix of 0.95,0.96,0.97,0.98,0.99,1 gradient water activity is set, 0h, 3h, 6h, 12h, 24h, 48h time point, utilize paper disk method to detect counting.In order to verify the method, measure three groups of panel datas, the related softwares such as employing Origin carry out data and image processing, as accompanying drawing 1, draw this method and can obtain stable and accurate data, and find out that intestinal bacteria (being Escherichia) can't grow substantially in the bread matrix environment of 0.95 to 1 water activity.
The relation of Fig. 1-water activity and part microorganism
2, sample preparation
Adjust distilled water Aw with glycerine solution, be placed in glass capsulation tank (specification 160mm), make it form water activity and be respectively 0.92,0.96,0.97,0.98,0.99,1.00 under 25 ℃ of room temperature conditions, standby.The recipe ratio following table of concrete different water-activity glycerine solution.
The water-activity of table 2-different concns glycerine solution
Remarks: after autoclaving
Under aseptic condition, to not contain colibacillary sliced bread under 25 ℃ of room temperatures through check, be placed in respectively the different moisture eliminator of water activity environment, place after the 48h balance and be prepared into water activity and be respectively 0.92,0.96,0.97,0.98,0.99,1.00 sample.Take the different sample 10g of different water activities, first get 5g and put into small beaker, intestinal bacteria are dripped to be inoculated on the sliced bread sample according to the order of magnitude concentration of 100cfu/mL mix, then add the 5g same sample and cover, put back in the moisture eliminator in former water activity environment.It is numbered respectively: 1 (sliced bread, water activity 0.92), 2 (sliced bread, water activities 0.96), 3 (sliced breads, water activity 0.97), 4 (sliced bread, water activities 0.98), 5 (sliced breads, water activity 0.99), 6 (sliced bread, water activities 1.00).Every kind of numbered samples in the sliced bread sample need to be made 11, so that standby when different time points (every 1 hour) taking-up measurement intestinal bacteria bacterium is counted.Utilize the water activity after VAS steam adsorption analysis instrument is measured positive bread sample balance, verify whether it conforms to ambient water activity in corresponding moisture eliminator; Wherein the condition that arranges of this instrument is: adopt the dew point condensation method, 25 ℃ of probe temperatures, wind speed 100mL/min are set, circulation is opened, time out is closed, tolerance range 0.010Aw;
3, data gathering
After a certain amount of intestinal bacteria being seeded to the serial negative bread sample of different water activities, be placed under former water activity condition and continue to cultivate, between detect at regular intervals colibacillary upgrowth situation, take out 1 part of sample every 1 hour in 10 hours and carry out enumeration with paper disk method, thereby draw bread colibacillary coefficient of growth under different water activity conditions;
Experiment measuring can obtain corresponding intestinal bacteria decay and growth curve, as accompanying drawing 2.Can find, be 0.96,0.97,0.98,0.99,1.00 o'clock at water activity, and intestinal bacteria can be exponential growth through the adjustment of one period short period of time, and along with the rising propagation phenomenon of water-activity is obvious gradually.Be 0.92 o'clock at water activity, intestinal bacteria can be exponential attenuation trend, and under this water activity, process stationary phase is not experienced in the bacterium decay.
, to above six groups of data, utilize Excel software and formula N=N
0E
Kt(1) carry out match, parameters N
0=100, N is ordinate zou, and t is X-coordinate, and e is constant, wherein N
0Represent initial colony number, N represents total number of bacterial colony, and t represents the time, and e represents the truth of a matter of natural logarithm.Above four data are known quantity, can go out corresponding coefficient of growth k value to the corresponding fitting of a curve of each water activity thus.
4, data processing
, by the k value under the different water activity environment of above-mentioned gained, utilize Excel software and formula k=aAw+b (2) to carry out linear fit, as accompanying drawing 3.Coefficient of growth k and its corresponding water activity are known quantity, and match draws corresponding a, b value, obtains the parameter formula, i.e. the linear relationship of Escherichia coli Growth coefficient and water activity in this food substrate.Drawn by accompanying drawing 3, when intestinal bacteria in the coefficient of growth k of exponential growth phase value less than or equal to 0 the time, intestinal bacteria do not breed, the water activity Aw of this moment is 0.93.
Claims (1)
1. intestinal bacteria water activity sensor monitoring control method in a bread, it is characterized in that: intestinal bacteria are seeded to serial negative bread sample and make the positive bread sample of intestinal bacteria of series of parallel, the isoperibol that positive sample is placed in different water activities is respectively cultivated, the interval certain hour takes out and detects coliform count, obtains accordingly the linear relationship of Escherichia coli Growth coefficient and water activity in bread; The coefficient of growth of using was that the intestinal bacteria water activity of not breeding is as critical control point as 0 o'clock, water activity during higher than this critical control point intestinal bacteria will breed, water activity during lower than this critical control point colibacillary propagation be suppressed, realize effective control to Escherichia coli Growth in bread by the monitoring water activity;
Said method comprising the steps of:
(1) preparation of negative bread sample: will not contain colibacillary bread through check and be placed in the different water activity environment of 25 ℃ of constant temperature, under aseptic condition, balance is 48 hours, the serial negative bread sample of the different water activities of preparation;
(2) preparation of the positive bread sample of different water activities: take negative bread sample 10g, first get 5g and put into small beaker, intestinal bacteria are dripped to be seeded on the sliced bread sample according to the concentration level of 100cfu/mL mix, add again the identical negative bread sample of 5g and cover, 11 parts, the positive bread sample of parallel preparation intestinal bacteria; Put every increment this continues to cultivate in water activity is respectively 0.92,0.96,0.97,0.98,0.99,1.00 airtight isoperibol;
(3) after a certain amount of intestinal bacteria being seeded to the serial negative bread sample of different water activities, be placed under former water activity condition and continue to cultivate, between detect at regular intervals colibacillary upgrowth situation, take out 1 part of sample every 1 hour in 10 hours and carry out enumeration, thereby draw bread colibacillary coefficient of growth under different water activity conditions;
(4) obtain coefficient of growth k under different water activity envrionment conditionss: utilize formula N=N
0E
KtCarry out the logarithm match, parameters N
0=100, N is ordinate zou, and t is X-coordinate, and e is constant, and above four data are known quantity, therefore can go out corresponding coefficient of growth k value to corresponding fitting of a curve under each water activity condition;
(5) utilize formula k=aAw+b to carry out linear fit, be known quantity according to previous step gained coefficient of growth k and its corresponding water activity, match draws corresponding a, b value, obtains the parameter formula, i.e. the linear relationship of Escherichia coli Growth coefficient and water activity in this food substrate
(6), according to previous step parameters obtained formula, make k=0 bring into and calculate corresponding Aw, be coefficient of growth k and be the water activity of 0 o'clock, the i.e. required pass key control water activity that obtains of this method for sensing, in this food substrate, lower than this water activity, intestinal bacteria will can not grow fully.
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| CN104198318A (en) * | 2014-09-09 | 2014-12-10 | 中国烟草总公司郑州烟草研究院 | Method for predicting water activity of mixed system of tobaccos and tobacco products as well as moisture content of each component |
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| US20100269601A1 (en) * | 2007-06-22 | 2010-10-28 | Decagon Devices, Inc. | Apparatus, method, and system for measuring water activity and weight |
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Cited By (1)
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| CN104198318A (en) * | 2014-09-09 | 2014-12-10 | 中国烟草总公司郑州烟草研究院 | Method for predicting water activity of mixed system of tobaccos and tobacco products as well as moisture content of each component |
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Application publication date: 20131120 |