Food Dehydration Process Quiz

The amount of free water in a product, meaning water available for microbial growth and reactions. It's expressed as a ratio, with 1 being pure water and 0 being no free water.

Water that is tightly bound to molecules within a food. It doesn't behave like normal water and can't be easily removed.

Water that's free to move around within a food. It's easily removed and influences the product's properties like texture and shelf life.

A method of preserving food by removing moisture, extending its shelf life and making it easier to store and transport.

The process of converting fresh milk into a powdered form, increasing its shelf life and making it easier to transport and store.

The initial moisture content of a material, expressed as the mass of water per mass of dry solids. It's a measure of how much water is initially present in the product.

The moisture content at which the drying rate transitions from a constant rate to a falling rate period. It's the point where the rate of water evaporation starts to decrease.

The time it takes for the product to reach a constant drying rate. During this period, the surface temperature of the product remains constant at the wet bulb temperature of the drying air.

The amount of heat needed to evaporate water from the product surface. It's a key factor in determining the overall drying time and energy requirements.

The rate at which heat is transferred to the product during drying. It's determined by factors like the air temperature, product surface area, and convective heat transfer coefficient.

The ratio of the vapor pressure of water in a food to the vapor pressure of pure water at the same temperature. It represents the availability of water for microbial growth and chemical reactions.

Water that is strongly bound to molecules within a food, like a magnet holding onto a metal object. It's not easily removed and doesn't contribute to microbial growth.

Water that's free to move around within a food and can be easily removed. It impacts the food's texture, shelf life, and is available for microbes to grow.

The process of removing water from food through natural means like sunlight or wind. It's less controlled than dehydration and can have less consistent quality.

The process of removing water from food under controlled conditions using heat, vacuum, or spray methods. It results in a higher quality product than drying.

A drying method using trays placed in an oven. It's simple but less efficient than other techniques.

A drying method using a rotating drum with heated surfaces. It's suitable for liquids and allows for continuous drying.

A drying method where food is frozen and then subjected to vacuum. It's effective for preserving delicate foods.

A drying method where food is sprayed into hot air, causing rapid evaporation. It's efficient and suitable for liquids.

The process of removing water from milk to create a powdered form, extending its shelf life and making it easier to transport and store.

A crucial factor affecting the shelf life and safety of food. Low water activity makes it harder for microbes to grow and deteriorates food quality.

Water activity is a critical factor in controlling the spoilage and deterioration of food products.

Water activity may be the most important factor in controlling spoilage and deterioration of food, even more so than temperature or pH.

The drying process can be divided into three periods: the initial adjustment period, the constant drying rate period, and the falling drying rate period.

The drying rate remains constant during this period, as more water evaporates from the surface and is replaced by water diffusing from the core.

The drying rate starts to decrease during this period, as the surface water film becomes thinner and the rate of diffusion from the core slows down.

The heat energy required to vaporize liquid water from the surface of a product during drying. This energy is crucial for the evaporation process.

The difference between the temperature of the drying medium, usually air, and the product surface temperature. This difference drives the heat transfer process.

The rate at which moisture evaporates from the product surface. A higher drying rate means faster evaporation.

The effect where the outer surface of a product dries much faster than the interior, creating a hard crust and hindering further drying.

Decreasing the drying rate to prevent surface hardening and maintain a more uniform moisture distribution within the product.

The process of removing water from a food product to increase its shelf life and make it easier to store and transport.

A type of drying that uses heated air to evaporate moisture from food, often in a controlled environment like a chamber or tunnel.

Similar to cabinet drying but with a long tunnel and moving carts, constantly feeding in fresh product and removing dried product.

A large rotating drum used for drying thick liquids or slurries, by spreading a thin layer on the heated drum surface.

A drying method that involves spraying a liquid into a hot chamber, where it dries quickly in a fine mist.

A process that happens during drying of fruits and vegetables, where natural pigments like carotenoids and chlorophyll change due to heat and oxidation, causing color changes.

A browning reaction that occurs in fruits and vegetables during drying, caused by enzymes like polyphenoloxidase.

A treatment used to prevent browning in fruits and vegetables during drying. This can be accomplished by immersing the food in a solution of ascorbic acid or sulfur dioxide before drying.

A process where sulfur dioxide is used to bleach the color of fruits and vegetables during drying. However, it can have health drawbacks as it leaves residues in the final product.

The point at which water can exist as a solid (ice), liquid (water), and vapor (gas) simultaneously. It's a specific temperature and pressure.

The process where ice changes directly into vapor, bypassing the liquid state. It takes place under specific pressure and temperature conditions.

The first step in freeze-drying where food is frozen to temperatures below -50°C or -80°C, ensuring that the water becomes solid ice.

The second step, where pressure is reduced, and enough heat is applied to sublimate the ice into vapor, removing the vast majority of water from the product.

The third step, where the temperature is slightly increased to break down any remaining bonds between water molecules and the frozen material, ensuring complete dehydration.

A refrigeration system chills the condenser and shelves, ensuring the product is frozen for primary drying and vapor condensation for efficient removal of water.

A vacuum pump connected to the condenser and product chamber, creating a low-pressure environment that promotes sublimation of ice during drying.