At The New Flavor, we understand that you are constantly striving to create new and innovative products that will delight your customers. One crucial aspect that can easily be overlooked for newcomers during the product development phase is water activity. Why? It’s a relatively unknown thing to those not knee-deep in the R&D, QA or manufacturing side of the business. Water activity is a critical parameter in food manufacturing that can greatly impact the quality, safety, and shelf life of your products. In this article, we will provide you with a comprehensive overview of water activity, including what it is, how it is measured, why it is important to your product or formula. We’ll also go over the safe limits for water activity in shelf-stable products and how you can control water activity to ensure the success of your food manufacturing operation so that even if you are new to the industry, you can start off on the right foot (and sound really knowledgeable!).
What is water activity?
Water activity (aw) is a measure of the amount of water available for microbial and chemical reactions in a food product. It represents the ratio of the vapor pressure of water in a food product to the vapor pressure of pure water at the same temperature and pressure. Water activity is expressed on a scale ranging from 0 to 1, with 0 being completely dry and 1 being pure water. Foods with higher water activity values have more available water, which can support the growth of microorganisms and degrade the quality of the product over time if other measures are not in place. An example of a high water activity food is fresh bread, compared to a low water activity food like crackers. Crackers are more shelf stable, whereas bread supports the growth of mold and yeasts more readily.
Measuring water activity allows you to understand the potential for microbial growth, enzyme activity, and chemical reactions in food products. There are several methods available for measuring water activity, including dew point depression, electrical impedance, and water activity meters. Water activity meters are the most commonly used method in the food industry due to their accuracy, speed, and ease of use. These instruments work by equilibrating the food sample with a controlled environment of known relative humidity and measuring the water vapor pressure of the sample. The water activity value obtained from these measurements provides critical information for determining the stability, safety, and quality of food products.
Why is water activity in food products important?
Water activity plays a crucial role in determining the shelf life, safety, and sensory characteristics of food products. Understanding and controlling water activity is essential for maintaining the quality and safety of your products throughout their shelf life. Too high of a water activity can promote microbial growth, leading to spoilage and food borne illnesses, and decreased shelf life. On the other hand, too low of a water activity can result in product drying (or a dry product to start with), loss of flavor, and changes in texture. Therefore, maintaining an optimal water activity level is critical for ensuring the stability, safety, and sensory attributes of your food products.
Water activity is also an important quality assurance measurement for your manufacturing operation. Monitoring and controlling water activity can help you maintain consistency in your product formulations, ensure the safety of your products, comply with regulatory requirements, and avoid potential food safety recalls and a damaged reputation or worse. Many food safety regulations and guidelines, such as the FDA's Hazard Analysis and Critical Control Points (HACCP) system, require the measurement and control of water activity as a critical control point in food manufacturing. Incorporating water activity as part of your quality assurance program is one step forward in ensuring that your products meet the highest standards of quality and safety.
What is the safe limit for water activity?
The safe limit for water activity in shelf-stable products depends on the type of food and the intended shelf life. In general, a water activity level below 0.85 is considered safe for most shelf-stable foods, as it inhibits the growth of most spoilage and pathogenic microorganisms. Many companies choose to go lower than 0.85 as a water activity limit and pair other means of food preservation along with water activity to employ what is called “hurdle technology”. However, some foods with low water activity, such as dried fruits or jerky, may have a longer shelf life even at slightly higher water activity levels due to their low moisture content and other preservation techniques such as smoking and salting. It is important to consult food safety regulations and guidelines, as well as conducting proper shelf-life studies to determine the specific safe limit for water activity in your particular food product.
How do I control Water Activity?
Controlling water activity in your food products is crucial to ensure their stability and safety. Fortunately, there are various ways to control water activity in your formulations. Here are five key strategies:
Ingredient Selection
Formula Optimization
Packaging
Storage Conditions
Quality Control
1. Ingredient selection
Choosing ingredients with lower water activity can help reduce the overall water activity of your product. For example, using dried fruits instead of fresh fruits, or using sugar or salt as preservatives can lower the water activity in your formulation. Additionally, rely on suppliers for assistance - you may find out they have a dried version of the ingredient you want that works in your formula and introduces no water. Lastly, determine if you need either natural or artificial preservatives in your formula to assist with the hurdle technology.
2. Formulation optimization
Adjusting the formulation of your product, such as modifying the recipe or processing conditions, can also help control water activity. This may include drying, baking, or adding water-binding ingredients to reduce the available water in the product. Sometimes you have the ability to optimize your formula, other times you may not or the solution may not be simple, but it never hurts to take another look at your formula or manufacturing process if you are struggling to control the water activity.
3. Packaging
Appropriate packaging selection can play a significant role in controlling water activity. Using moisture barrier materials, like a multi-later HDPE or adding desiccants can help prevent moisture ingress and reduce or maintain water activity over the expected shelf life. Selecting the right packaging for your brand and product during the product development process will help your formulators and manufacturers determine the any additional measures needed to control the water activity of your product once its packaged.
4. Storage conditions:
Proper storage conditions, including temperature and humidity control, are critical in maintaining the desired water activity level in your products. Storing your raw materials, work in progress (WIP) and finished products in a dry and cool environment can help prevent water activity from increasing over time and allowing for changes to your product. For example, powdered fruit ingredients are really prone to absorbing moisture from their environments and clumping. Ensuring you store your raw materials properly during all stages of production will prevent moisture migration, allowing you to keep them for their intended shelf life and reducing the potential for manufacturing problems and dollars wasted on unusable product.
5. Quality Control
Your quality team should be regularly measuring and monitoring the water activity of your raw materials and finished products using reliable and calibrated water activity meters to ensure that they remain within the safe limit. Additionally, you should perform shelf life and challenge studies to determine how the water activity may change throughout your product's expected shelf life. Lastly, it is not unreasonable to perform checks throughout your supply chain to ensure the water activity is stable. This will allow you to take corrective actions if necessary and maintain the quality and safety of your products, ultimately protecting your reputation and brand.
Water activity is a critical parameter in food manufacturing that can greatly impact the quality, safety, and shelf life of your products. Understanding and controlling water activity is essential for all food brands to ensure the success of their products and company reputation. By measuring, monitoring, and controlling water activity, you can maintain consistency, bolster the food safety of your product, comply with regulatory requirements, and extend your products shelf life.
At The New Flavor, we are committed to helping you navigate the complexities of food product development and quality assurance parameters and providing you with the knowledge and resources to create innovative and high-quality food and beverage products. Let us know if you want any assistance with your next project!
Comments