Homogenization of food samples plays an important role in the food microbiology testing, as it can not only affect the accuracy of the food microbiology testing, but also affect the detection rate.
The currently used methods for food homogenization are mainly rotary blade and impact homogenization. The rotary blade homogenization method involves adding the food sample into a sterile diluent and placing it in a sterile homogenization cup. The sample solution is then processed under a certain rotary blade speed to make it into a homogeneous solution. In contrast, impact homogenization involves placing the food sample and diluent into a homogenization bag, and using an impact method to beat the bag to prepare it into a homogeneous solution. Due to the significant difference in the impact of these two methods on the detection results, it is necessary to analyze the food characteristics and choose the appropriate homogenization method to ensure the detection effect.
To explore the comparison of two homogenization methods in the food microbiology testing, 24 food samples were selected for research.
According to the national standards for food safety microbiology detection methods, sample of the microbiological test in food industry needs to be prepared using both rotary blade and impact methods.
24 samples were taken under sterile conditions, with 25g each. They were then placed in a mixture of 225ml water, physiological saline, and 7.5% sodium chloride broth. After setting the frequency and gap of the impact homogenizer according to the solution form, the solution can be beaten for 1 to 10 minutes. The rotary blade homogenizer was set to a speed of 8000-10,000r/min, and homogenized twice according to the sample solution form to prepare a 1:10 homogenized solution.
24 samples were taken under sterile conditions, with 25g each placed in a 225ml 0.85% sterile physiological saline homogenization bag, and beaten for 2 minutes, during which the frequency and interval of the impact homogenizer were adjusted. Then a 1:10 homogenized solution was prepared, and molds and yeast, total colony number, and Staphylococcus aureus were measured. Afterwards, a sterile graduated pipette containing 9ml of physiological saline and 7.5% sodium chloride broth was used to aspirate 1ml of bacterial solution, mixed, and prepared again according to the above steps to prepare a 1:1000 diluent.
For foods with high fiber content, the rotary blade homogenization method may produce the best homogenization effect, while reducing the difficulty of operation. For larger and harder food, crushing should be done first before rotary blade homogenization to reduce the risk of sample rupture and ensure homogenization effect. For sticky or insoluble food, warm water bath treatment can be used before homogenization, and homogenization time should be kept within 2 minutes.
In summary, different homogenization methods may lead to certain differences in the results of food microbiology testing, and suitable homogenization methods should be chosen according to the situation during the detection process.