Wet pet food, commonly sold in cans, trays, or pouches, differs from dry food primarily in moisture content and preservation method. When evaluating the different types of pet food, it is crucial to understand that wet diets are preserved through thermal sterilization, a process designed to achieve shelf stability by eliminating microbial growth.

Wet pet food is defined by:

• High moisture content, typically 70–85% water

• Hermetically sealed packaging

• Preservation via retort processing rather than dehydration

These diets may be formulated as complete meals or supplemental foods and are used for both dogs and cats across all life stages.

Wet or canned pet food is preserved using retorting, a form of high-temperature thermal sterilization.

The process involves:

1. Filling sealed containers with raw ingredients

2. Heating under pressurized steam

3. Maintaining temperatures sufficient to destroy bacteria, spores, and pathogens

This process renders the product shelf-stable without refrigeration until opened. Because it operates within a sealed container under high pressure, it requires rigorous food processing technology to ensure complete commercial sterility, providing a different logistical model than commercial kibble.

Retort processing typically exposes food to temperatures exceeding 120°C (248°F) for sustained periods.

Thermal exposure results in:

• Protein denaturation

• Vitamin degradation

• Inactivation of naturally occurring enzymes

While moisture is retained, structural and biochemical changes occur prior to consumption.

Wet pet foods often contain:

• Fresh or frozen animal tissues

• Meat by-products and organs

• Additives in wet pet food (e.g., gums, carrageenan)

• Added vitamins and minerals

Because moisture content is high, nutrient density per gram is lower than dry or freeze-dried formats, requiring larger serving volumes.

Moisture Content: Key Structural Difference

The defining distinction between wet and dry pet food is water content.

Higher moisture intake:

• Reduces reliance on voluntary drinking

• Alters gastric emptying time

• Changes nutrient concentration per serving

This factor is particularly relevant for cats, which exhibit low thirst drive and evolved to obtain most water from prey. Proper moisture intake, hydration, and renal load management is a primary clinical reason owners choose wet foods.

Despite moisture retention, wet foods still experience nutrient loss during thermal processing.

As a result:

• Synthetic vitamin and mineral premixes are added

• Nutritional adequacy is achieved through reconstruction

• Food-bound nutrient complexity is not preserved

This parallels fortification practices used in extruded diets, highlighting the broader biological discussion of synthetic nutrients vs. whole foods when attempting to meet the established nutrient requirements of dogs and cats.

Wet food texture and aroma are shaped by:

• Cooking reactions during retorting

• Added fats and flavor compounds

• Gel matrices that stabilize structure

Palatability is generally higher than dry food, though acceptance varies by species, formulation, and feeding history.

Wet pet food differs structurally from dry kibble by retaining water rather than removing it. However, both formats rely on thermal processing and nutrient reconstruction to achieve shelf stability.

• Wet food provides higher moisture intake

• Retort processing alters food structure

• Nutritional adequacy is achieved post-processing

These characteristics position wet food between extruded dry diets and minimally processed alternatives.

1. Fellows, P. Food Processing Technology.

2. Rahman, M.S. Handbook of Food Preservation.

3. National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press.

4. Hand et al. Small Animal Clinical Nutrition.

5. Strohmeyer et al. "Handling of raw and processed pet foods." Veterinary Clinics.