阅读说明：本技术 一种检测猪肉新鲜度方法 (Method for detecting freshness of pork ) 是由 范东雨 李洁昆 蔡亦梅 高静 张瑜 任鲁风 于 2018-09-25 设计创作，主要内容包括：本发明公开了一种基于电子鼻技术的快速检测猪肉肉质新鲜度的方法,旨在提供一种操作简单,检测时间短,对被测样品无损的可应用于现场检测的方法。包括检测阈值的确定和现场检测两个步骤。其中,阈值的确定是根据国标中规定的肉质新鲜度的理化指标(挥发性盐基氮含量)拟合出电子鼻中各气体传感器的指标。现场检测包括现场基线的确定和检测两个分步骤,检测前5s数据作一次线性拟合,符合条件即可进行检测,否则不能,检测时将检测到的数据与基线方程作差值,再与之前确定的阈值作比较,以判断被测猪肉肉质的新鲜度。依据本发明一次阈值确定后可进行多次长时间的现场检测,检测过程简单,方便,为保证检测准确性,需定期进行阈值的确定步骤。(The invention discloses a method for rapidly detecting pork freshness based on an electronic nose technology, and aims to provide a method which is simple to operate, short in detection time and free of damage to a detected sample and can be applied to field detection. The method comprises two steps of detection threshold determination and field detection. Wherein, the threshold value is determined by fitting the indexes of each gas sensor in the electronic nose according to physicochemical indexes (volatile basic nitrogen content) of the freshness of the meat specified in the national standard. The field detection comprises two steps of field base line determination and detection, wherein the 5s data before detection is subjected to linear fitting once, the detection can be carried out according with the conditions, otherwise, the data cannot be detected, the detected data and a base line equation are subjected to difference value in the detection process, and then the difference value is compared with the previously determined threshold value, so that the freshness of the pork quality to be detected is judged. According to the invention, the field detection can be carried out for a plurality of times after the threshold is determined once, the detection process is simple and convenient, and the step of determining the threshold is required to be carried out regularly in order to ensure the detection accuracy.)

1. A method for rapidly detecting the meat freshness of pork by using an electronic nose is characterized by comprising the following steps:

a) keeping the distance between the electronic nose device and the tested sample to be more than 50cm, and preheating the electronic nose device for 5min or more than 5 min;

b) starting detection, keeping the distance between the electronic nose device and the detected sample to be more than 50cm for 5 ~ 10s, then enabling the electronic nose device to be close to the detected sample, enabling the duration time of the sampling inlet to be not more than 5cm in a downward inclined mode to be not more than 30s, and specifically carrying out a detection signal processing process:

i. continuously collecting gas sensor array signals in an electronic nose device;

respectively carrying out linear fitting on the sensor array signals acquired in the first 5s to obtain a series of linear equations, and determining the series of linear equations as a baseline series equation of the detection;

respectively calculating difference values of the sensor array signals acquired after 5s and the baseline series equation obtained in the previous step, respectively comparing the maximum value series of the obtained difference values with a preset threshold value series, and judging that the quality is deteriorated if the maximum value series exceeds the threshold value, otherwise, judging that the quality is not deteriorated;

c) and (5) after the detection is finished, keeping the electronic nose device away from the sample to a distance of more than 50cm, displaying the detection result and automatically recording.

2. The method for rapidly detecting the meat freshness of pork by using an electronic nose as claimed in claim 1, wherein the electronic nose device sensor array in step b) comprises one or more of amine sensors, ammonia sensors, sulfur-containing compounds sensors, ethanol sensors, alkane sensors and nitrogen oxide sensors.

3. The method for rapidly detecting the meat freshness of pork by using an electronic nose as claimed in claim 1, wherein the step b) is a stepThe obtained linear equation of the series should be in accordance with the goodness of fit R²Meets the requirement of more than or equal to 0.85, otherwise, the detection is invalidated.

4. The method for rapidly detecting the meat freshness of pork by using an electronic nose as claimed in claim 1, wherein the step of step b) isThe threshold value series in (1) is obtained by the following method:

a) according to a method for measuring salt-based nitrogen in GB5009.228-2016 in the measurement of volatile salt-based nitrogen in food safety national standard food, the content of volatile salt-based nitrogen contained in pork meat of different storage time is detected, and according to physicochemical indexes in GB2707-2016 in fresh (frozen) livestock and poultry products in the national standard of food safety, the freshness grade of the detected pork meat is determined;

wherein the content of basic nitrogen is less than or equal to 15mg/100g, and the content of basic nitrogen is not more than 15mg/100g, and the content is deteriorated pork;

b) separately detecting pork of different storage time in step a) of claim 4 by using an electronic nose device, operating according to step b) of claim 1 to obtain step b) of claim 1The series of maximum difference values in (a) are respectively matched and correlated with the content of the volatile basic nitrogen in the pork meat quality at different storage times in step a) in claim 4, and the correlation is used to determine the value of the series of maximum difference values of the sensor when the content of the volatile basic nitrogen in the pork meat reaches 15mg/100g, which is determined as the value in step b) in claim 1Is lower than the threshold value in (1).

Technical Field

The invention relates to a method for detecting the freshness of pork by an electronic nose, in particular to a method for rapidly detecting the freshness of pork on site at low cost.

Background

Fresh pork is deteriorated in the storage process, and along with the increase of the deterioration degree of the pork, certain contents of sulfur-containing compounds, ammonia and amine substances are volatilized from the pork, and the concentration of the sulfur-containing compounds, the ammonia and the amine substances is increased along with the increase of the deterioration degree.

The electronic nose technology is widely applied to food meat detection, detection signals are mainly obtained according to a sensor array formed by different gas sensors in an electronic nose system, then the types and the contents of corresponding sensitive gas components are calculated according to the obtained signals, and the freshness of a detected sample is determined. Most of detection processes need preheating equipment in advance for a long time, then flow through the cavity of specific volume according to specific and controllable gas velocity of flow and detect, and some settings require the clean air of logical certain time. The flow rate control and the volume control of the cavity have high requirements on equipment, certain precision and volume are required, analysis software generally needs to operate on independent equipment, the algorithm is complex, the whole detection time is long, and certain clean requirements on detection environments or places are met.

Disclosure of Invention

Aiming at the characteristics that the existing method for detecting the freshness of meat based on an electronic nose technology is too complex, tedious, long in time consumption, large in equipment volume and limited in detection place, the invention provides a method which is quick, simple to operate and applicable to field detection, and the method is realized by the following technical scheme:

a method for rapidly detecting the meat freshness of pork by using an electronic nose comprises the following steps:

a) keeping the distance between the electronic nose device and the tested sample to be more than 50cm, and preheating the electronic nose device for 5min or more than 5 min;

b) starting detection, keeping the distance between the electronic nose device and the detected sample to be more than 50cm for 5 ~ 10s, then enabling the electronic nose device to be close to the detected sample, enabling the duration time of the sampling inlet to be not more than 5cm in a downward inclined mode to be not more than 30s, and specifically carrying out a detection signal processing process:

i. continuously collecting gas sensor array signals in an electronic nose device;

respectively carrying out linear fitting on the sensor array signals acquired in the first 5s to obtain a series of linear equations, and determining the series of linear equations as a baseline series equation of the detection;

respectively calculating difference values of the sensor array signals acquired after 5s and the baseline series equation obtained in the previous step, respectively comparing the maximum value series of the obtained difference values with a preset threshold value series, and judging that the quality is deteriorated if the maximum value series exceeds the threshold value, otherwise, judging that the quality is not deteriorated;

c) and (5) after the detection is finished, keeping the electronic nose device away from the sample to a distance of more than 50cm, displaying the detection result and automatically recording.

In some embodiments, the electronic nose device sensor array in step b) comprises one or more of amine sensors, ammonia sensors, sulfur compounds sensors, ethanol sensors, alkane sensors and nitrogen oxides sensors.

In some embodiments, wherein step b) isThe obtained linear equation of the series should be in accordance with the goodness of fit R²Meets the requirement of more than or equal to 0.85, otherwise, the detection is invalidated.

In some embodiments, the step in step b)The threshold value series in (1) is obtained by the following method:

01) according to a method for measuring salt-based nitrogen in GB5009.228-2016 in the measurement of volatile salt-based nitrogen in food safety national standard food, the content of volatile salt-based nitrogen contained in pork meat of different storage time is detected, and according to physicochemical indexes in GB2707-2016 in fresh (frozen) livestock and poultry products in the national standard of food safety, the freshness grade of the detected pork meat is determined;

wherein the content of basic nitrogen is less than or equal to 15mg/100g, and the content of basic nitrogen is not more than 15mg/100g, and the content is deteriorated pork;

02) respectively detecting the pork with different storage time in the step 01) by using an electronic nose device, and operating according to the step b) to obtain the stepThe maximum difference value series in (b) are respectively fitted and related with the content of the volatile basic nitrogen in the pork meat of different storage time in the step 01), and the correlation respectively determines the value of the maximum difference value series of the sensor when the content of the volatile basic nitrogen in the pork meat reaches 15mg/100g, and the value determines the step in the step b)Is lower than the threshold value in (1).

The invention has the beneficial effects that:

1. the operation steps for detecting the freshness of the pork meat are simplified, and the detection time is greatly shortened;

2. namely, the base line is determined and the interference of the surrounding environment is removed, so that the method can be used in the field detection occasion.

Drawings

FIG. 1 is a flow chart of a method for detecting the meat freshness of pork by using an electronic nose;

FIG. 2 is the relationship between the gas components and contents volatilized from pork with different degrees of deterioration and the contents of volatile basic nitrogen in the meat.

Detailed Description

The invention is further elucidated with reference to the drawing.

The sensor array in the electronic nose system comprises a VOC (volatile organic compound) sensor, an ammonia sensor, an amine sensor and a nitrogen oxide sensor. The electronic nose system is used for detecting the freshness of pork quality according to the following method steps:

the threshold series for the 4 sensors were obtained by the following method:

taking 500g of fresh pure lean pork, crushing, placing and storing at the temperature of about 30 ℃ and the relative humidity of about 60%. And respectively detecting the content of volatile basic nitrogen in the sample at the time points of 0.5h, 1.5h, 2.5h, 4h, 6h, 8h and 10h, and detecting the volatile gas components and content of the sample by using an electronic nose system sensor array. Wherein the content of the first and second substances,

detection of the content of volatile basic nitrogen in the sample:

according to a method for measuring salt-based nitrogen in GB5009.228-2016 in the measurement of volatile salt-based nitrogen in food safety national standard food, the content of volatile salt-based nitrogen contained in pork meat of different storage time is detected, and according to physicochemical indexes in GB2707-2016 in fresh (frozen) livestock and poultry products in the national standard of food safety, the freshness grade of the detected pork meat is determined;

and (3) detecting volatile gas components and contents of the sample:

starting the electronic nose system device, keeping the distance between the electronic nose and the tested sample to be 50 ~ 100cm, preheating the electronic nose for 5min, and activating a gas sensor array of the electronic nose system;

keeping the distance between the electronic nose system device and the tested sample to be 50 ~ 100cm for 5s, respectively carrying out linear fitting on the sensor array signals acquired in the 5s to obtain a series of linear equations, and obtaining the goodness of fit R of the linear equations²If the linear equation is more than or equal to 0.85, determining a series of linear equations as a baseline series equation of the detection, and if not, detecting again; after the baseline equation is determined, the electronic nose device is close to the tested sample, and the sampling inlet is inclined downwards and is about 3cm away from the tested sample for 30 s; in this 30s the sensor array signals are acquired in real time and differenced with the corresponding baseline equation determined previously and the maximum value of the difference during the process is recorded.

The detection result is shown in figure 2, wherein the pork stored for 8h or less contains volatile basic nitrogen of less than 15mg/100g, and is non-deteriorated pork, and the pork stored for 8 ~ 12h contains volatile basic nitrogen of more than 15mg/100g, and is deteriorated pork.

According to the curve shown in the attached figure 2, an amine sensor curve, a VOC sensor curve, an ammonia sensor curve and a nitrogen oxide sensor curve are respectively related and fitted with a volatile basic nitrogen content curve, corresponding numerical values of the 4 sensor curves when the volatile basic nitrogen content is 15mg/100g are found, and the threshold value series for judging the pork freshness of the 4 sensors are determined.

Referring to the attached figure 1, the method for rapidly detecting the meat freshness of pork by using an electronic nose comprises the following steps:

starting the electronic nose system device, keeping the distance between the electronic nose and the tested sample to be 50 ~ 100cm, preheating the electronic nose for 5min, and activating a gas sensor array of the electronic nose system;

keeping the distance between the electronic nose system device and the tested sample to be 50 ~ 100cm for 5s, respectively carrying out linear fitting on the sensor array signals acquired in the 5s to obtain a series of linear equations, and obtaining the goodness of fit R of the linear equations²If the linear equation is more than or equal to 0.85, determining a series of linear equations as a baseline series equation of the detection, and if not, detecting again; after the baseline equation is determined, the electronic nose device is close to the tested sample, and the sampling inlet is inclined downwards and is about 3cm away from the tested sample for 30 s; in this 30s the sensor array signals are acquired in real time and differenced with the corresponding baseline equation determined previously and the maximum value of the difference during the process is recorded.

And comparing the recorded numerical values with the threshold values determined before the respective sensors, if the numerical values exceed the threshold values, judging that the detected sample is deteriorated pork, otherwise, judging that the detected sample is not deteriorated pork, and finishing the detection.