3.4 Water management in food processing

Water management is crucial in food processing. Dehydration, freeze-drying, and osmotic dehydration remove water to extend shelf life and prevent spoilage. These methods reduce water activity, inhibiting microbial growth and creating lightweight, long-lasting products.

Water control additives like binding agents, humectants, and cryoprotectants influence water behavior in foods. Packaging techniques such as modified atmosphere, vacuum, and active packaging control the environment around food, further extending shelf life and maintaining quality.

Dehydration Methods

Removing water from foods

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Top images from around the web for Removing water from foods

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  Osmotic Dehydration of Toddy Fruit Cubes in Sugar Solution Using Response Surface Methodology View original

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• 

  IoT implemented Osmotic Dehydrator View original

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• 

  Frontiers | Advancing the Role of Food Processing for Improved Integration in Sustainable Food ... View original

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  Osmotic Dehydration of Toddy Fruit Cubes in Sugar Solution Using Response Surface Methodology View original

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  IoT implemented Osmotic Dehydrator View original

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• Dehydration removes water from foods to extend shelf life and prevent spoilage
  • Involves heating food to evaporate water and then removing the water vapor
  • Can be done using hot air, microwave, or other heating methods
  • Reduces water activity ($a_w$) of the food, inhibiting microbial growth (bacteria, molds)
  • Dehydrated foods are lightweight and have a long shelf life (raisins, beef jerky)
• Freeze-drying combines freezing and dehydration to preserve foods
  • Food is first frozen and then placed under vacuum
  • Ice sublimes directly from solid to vapor state, removing water while maintaining food structure
  • Produces high-quality dehydrated products with excellent rehydration properties (instant coffee, backpacking meals)
• Osmotic dehydration uses a hypertonic solution to remove water from foods
  • Food is immersed in a concentrated solution of sugar or salt
  • Water moves out of the food and into the solution due to osmotic pressure
  • Simultaneously infuses food with the solute, altering its flavor and texture (candied fruits, salt-cured meats)

Water Control Additives

Substances that influence water behavior in foods

• Water binding agents are added to foods to increase their water-holding capacity
  • Hydrocolloids like gums (xanthan gum, guar gum) and starches can bind and immobilize water
  • Proteins (soy protein, whey protein) also have water binding properties
  • Helps maintain food texture, reduce syneresis, and improve mouthfeel (yogurt, ice cream)
• Humectants are hygroscopic substances that attract and retain moisture in foods
  • Examples include sugars (honey, corn syrup), polyols (glycerol, sorbitol), and some salts
  • Prevent foods from drying out and maintain a soft texture
  • Used in baked goods, confections, and other moisture-sensitive products (soft cookies, marshmallows)
• Cryoprotectants protect foods from damage during freezing
  • Sugars (sucrose, trehalose) and some proteins act as cryoprotectants
  • Stabilize proteins and cell membranes during freezing, preventing denaturation
  • Improve texture and reduce drip loss in frozen foods (ice cream, frozen dough)

Packaging Techniques

Controlling the package environment to extend shelf life

• Modified atmosphere packaging (MAP) involves altering the gas composition inside the package
  • Oxygen is often removed and replaced with nitrogen or carbon dioxide
  • Low oxygen levels slow oxidation reactions and inhibit aerobic microbial growth
  • Carbon dioxide has antimicrobial properties and can dissolve into the food
  • Extends shelf life of perishable products (fresh pasta, pre-cut salads)
• Vacuum packaging removes air from the package before sealing
  • Eliminates oxygen to prevent oxidation and microbial growth
  • Tight-fitting package reduces moisture loss and protects food from external contamination
  • Commonly used for meats, cheeses, and dried goods (beef brisket, parmesan cheese)
• Active packaging incorporates additives into the packaging material itself
  • Oxygen scavengers remove residual oxygen from the package (iron powder sachets)
  • Moisture absorbers control humidity inside the package (silica gel packs)
  • Antimicrobial agents inhibit microbial growth on the food surface (silver zeolites, essential oils)
  • Extends shelf life and maintains food quality (sliced deli meats, fresh berries)