June 24, 2021
Rising globalization has increased the transportation of food and food ingredients worldwide. Food products are imported from and exported to different parts of the world and multiple stakeholders are involved in the food supply chain. This increases the chances of contamination in food and concerns people about the safety and quality of the food they consume. This has also led to the development and application of new analytical methods and techniques for food analysis. The analysis of food products involves certain steps, such as identification of an appropriate analytical procedure, sampling, preparation of samples for analysis, statistical analysis and reporting of test results.
Due to the complexity and diversity of food matrices, food samples cannot be analyzed without proper sample preparation. The process of concentrating a sample by homogenizing it and by removing contaminants and extracting target chemical residues is known as sample preparation. It ensures the removal of contaminants from a food sample that may interfere with the accurate analysis. Hence, this is one of the most important steps for sample analysis in food testing laboratories.
Sample preparation is one of the most important factors governing the reliability and accuracy of food analysis. Traditional sample preparation methods are expensive, time-consuming, labor-intensive, and require high solvent content that generates waste. Therefore, there is a need to replace traditional methods with easy, quick, cost-effective, and green techniques to improve food analysis.
Sample preparation involves certain steps and limitations at any step are likely to impact the final results. Although it is one of the most important steps in food analysis, it also brings few challenges along with it. The challenging steps involved in sample preparation include:
A food sample could be of anything from apples, oranges, honey, ketchup, or milk. Both inter-unit variations (differences in the properties of various units within a sample) or intra-unit variations (differences in the properties within individual units of a sample) are likely to be responsible for the heterogeneous property of a food sample.
Food testing labs need representative samples to generate high-quality, reproducible and accurate results. Hence, it is important to homogenize and pulverize food samples before analysis. Homogenization is the process of bringing uniformity in the composition of a food sample so that any fraction of the sample is identical in composition to any other fraction or the remaining sample. Various mechanical devices such as grinders and mixers, enzymatic methods such as proteases and cellulases, and chemicals such as strong acids and bases are used for homogenizing food samples.
Decreasing Sample Size
A sample should be small and manageable enough to perform accurate analysis. Hence, a small portion of the homogenous sample is selected for obtaining reliable and reproducible results.
Ensuring Consistency in Sample Properties
A sample must not undergo any significant changes such as enzymatic, chemical, microbial, or physical changes from sampling to analysis. Active enzymes and microorganisms in many food products could change their properties before analysis. This change tends to generate erroneous data and hence, should be prevented. Enzymatic activities are prevented through chemical preservatives or treatments such as freezing, drying, and heating, depending on the type and purpose of the food being analyzed. Additionally, the properties of a sample may alter after exposure to light, elevated temperatures, and oxygen or pro-oxidants. Therefore, it is important to store samples in refrigerated temperatures. This also helps in preventing any physical changes in the samples.
Every food sample in a laboratory must have proper labels containing the name and properties of the sample, collection time, the location from which it was collected, the details of the person who collected the sample, and the method used to select the sample. Laboratories must maintain complete records from sample selection to the generation of results. This makes the data easily retrievable during audits.
Laboratory personnel must judiciously choose the right technology to solve the pressing problems in sample preparation that can meet the changing needs of their laboratory. Considering the challenges in traditional sample preparation methods, new and environment-friendly methods have been discovered as an alternative. Modern microextraction methods such as solid-phase microextraction (SPME), stir bar sorptive extraction (SBSE), and liquid phase microextraction (LPME) are cost-effective methods. These methods involve extremely low or nonsolvent consumption.
Regulatory bodies such as the USFDA have determined sample preparation as one of the major steps in food analysis that greatly influences the reliability and accuracy of test results. Due to traditional sample preparation methods being expensive, time-consuming, and labor-intensive, new sample preparation techniques have been introduced which are rapid, easy, solvent-free, reliable, and cost-effective. Laboratories are encouraged to leverage automated and sustainable greener approaches to prepare samples. A LIMS can help food testing laboratories overcome operational challenges such as managing data associated with sampling and sample preparation, test results, generating CoAs, reducing turnaround time, and meeting regulatory compliance requirements with ease.