The Importance of Lab Testing for Food Products

Posted in: Applications, Electrodes

Author: Cristina Macarov, Derek Pedley

Date Posted: 14/04/2022


Why is laboratory testing for beverages and food products essential? Food quality testing laboratories help ensure suitability for consumption by checking them for any contaminants and perform quality analysis on parameters such as pH, consistency, nutritional levels, consistency of chemical composition, degradation (expiry dates), also test for storage conditions and microbiological activity. Metals, cleaning agents, pesticides and other additives can affect the overall safety, taste and quality of many foods. In addition, bacteria, such as e-coli and salmonella can make food unsafe to consume. Below are some of the testing processes that food laboratories carry out to ensure food products meet quality standards.

WHY pH LEVELS MATTER IN FOOD

While most people don’t consider how much pH affects their food, the fact is it can alter the properties of food in a number of ways. pH values can alter the nutritional value of food, can lead to decomposition or alteration of the chemical composition, can increase the bacterial activity over the accepted levels, and can also affect how long you can conserve it for. A wrong pH level can lead to unwanted chemical interaction between the existing ingredients, leading to unwanted negative reactions during consumption in worst cases.
pH values in foods are affected by the amount of free hydrogen ions present. The more acidic the food, the more free hydrogen ions are released. This can affect everything from the taste to the appearance of food, as well as their shelf life. Therefore, testing pH levels in a food quality testing lab is not only important in determining the quality of food, but also how safe it is. For example, some low acidic foods can generate dangerous bacterial spores if the pH level rises above 4.6. This is why pH testing needs to be so precise.

HOW pH LEVELS CAN AFFECT FOOD
  • Production Methods: The acidity levels found in ingredients can affect how we prepare different foods, such as bread and alcoholic beverages. The balance between the acid and the alkaline can alter the speed of the process as well as the duration of chemical reactions, e.g. in breadmaking the pH of the dough can affect the viscosity build up as well as preservation and microbial safety.
  • Flavour: The pH level of a food product can drastically alter how it tastes. The more acidic the food, the sourer the taste, which works well in foods that require that extra bite.
  • Texture: pH levels can also alter the feel of a food product, which can be just as important as the taste. This can mean the difference between a hard and crumbly cheese and a smooth and creamy soft cheese.
  • Appearance: pH levels can determine the colour and feel of a food product, such as the greenness of a cabbage or how orange a carrot is. Some manufacturers can play with a food product’s look by altering the pH levels.
WHY IS MEASURING pH IMPORTANT
  • It allows manufacturers to create food products with consistent qualities.
  • pH measurements allow manufacturers to find more efficient and cheaper ways of producing food.
  • Ensures any health risks, such as bacteria growth or food alteration, are not passed on to the consumer.
TESTING pH IN FOOD PRODUCTS

When conducting lab testing of food products, it is essential to determine the pH level for each product. pH affects all aspects of food including the texture, flavour, and aroma. pH also plays a role in the growth of microorganisms that can lead to illness if consumed.

When testing the pH in food, there are two primary methods used:

  1. Direct Testing – A pH reading is taken directly from the food product, usually using an electrode designed for the particular application. There is a shape, size and type of pH sensor for any application, perfectly designed to ensure application and sample compatibility. A measurement is taken by inserting the electrode directly into the food product. This type of testing can only be carried out on samples which do not have both solid and liquid parts, and have a uniform consistency. If pH measurement is required during the production process a sensor can be fitted to monitor the entire process (in-line).
  2. Sample Testing – A portion of the food is taken, tested, and then discarded.
SAMPLE TESTING USING THE SLURRY METHOD

The Slurry Method is a form of sample testing, which involves diluting a food sample with deionised water. As there is not a considerable number of ions present in distilled or deionised water, this does not significantly affect the pH readings of the sample. Slurries are particularly useful when testing semi-solid or solid food products with a spherical-tip electrode, as the sample can fully surround the electrode and provide a more accurate reading.

HOW TO CREATE A SLURRY
  1. Prepare 50g of your solid or semi-solid sample.
  2. Take 100g of deionised water.
  3. Combine the food sample with the deionised water to create a uniform paste. Further dilution may be required to the right consistency for pH measurement but it is recommended that as little water as necessary is used.
  4. Test using the relevant method below.
TESTING SOLID FOODS

Solid foods, such as raw meats and cheese, can be tested using the following method:

  1. Ensure that your electrode is calibrated. Conical-tip or knife probes would be the most suitable choice.
  2. Decide whether you are testing a sample or directly into the product.
  3. Rinse the electrode with deionised water.
  4. Insert the electrode into your sample. Leave until a stable reading can be taken, and record the pH.
  5. Rinse the electrode.
  6. Take a second reading, ensuring this is equal to your first reading.
  7. Rinse and clean the electrode before storing.
  8. Store in suitable cleaning solution to ensure hydration of the pH membrane. Ensure that the junction has been cleaned which is particularly important for dairy and meat products where proteins may block the reference junction. Cleaning solutions will often contain enzymes that digest/break down the proteins.
TESTING SEMI-SOLID FOODS

Semi-solid foods, such as soft cheeses, yoghurts, and bread dough, can be tested using the following method:

  1. Ensure that your electrode is calibrated. Either a spherical or conical-tip electrode can be used.
  2. Take a sample of your product and, if necessary, create a slurry following the method detailed above.
  3. Rinse the electrode with distilled water.
  4. Insert the electrode into your sample. Leave until a stable reading can be taken, and record the pH.
  5. Rinse the electrode.
  6. Take a second reading, ensuring this is equal to your first reading. This ensures that the mixture is homogeneous.
  7. Rinse and clean the electrode before storing.
  8. Cleaning overnight and in between measurements as above.
TYPES OF PROBES USED IN LAB TESTING FOR FOOD PRODUCTS

When it comes to probes used in food quality testing labs, Sentek supply the following:

  • Drinking Water Probe – A double junction Ag/AgCl probe used to measure the pH level of drinking water. Especially good in low temperature, low ionic strength samples.
  • Jam Probe – A single junction AgCl liquid filled probe with replaceable ceramic junctions. Used for pH measurement in jams, fruit juices and preserves.
  • Dairy Products Probe – A partial gel filled single junction AgCl probe with porous Teflon junction type. Used for measuring the pH level of dairy products such as milk and yogurt, as well as surface measurements for paper, skin and more. Also comes in an S7 variant.
  • Penetration Food Probe – An Ag/AgCl gel probe with porous Teflon junction type. Features a spear point probe for penetrating and testing meats, cheeses and fruits. Also comes in a Micro Food Penetration probe format.
  • pH Knife Probe – An Ag/AgCl gel probe with ceramic junction type. The stainless steel knife end protects the probe as it penetrates and measures frozen and defrosted meat products.
SENTEK

Here at Sentek we manufacturer and supply pH probes for a range of sectors. To find out more about our wide range of food probes, please get in touch with us today.

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