How We are Preserving the Next Generation of Pet Food

As the pet food market has diversified away from traditional dry kibble or canned pet food options, pet parents have never had more variety in pet food product forms to choose from. Of these new forms, freeze-dried products and the fresh/frozen category have seen tremendous growth over the past few years. Both styles are marketed as minimally processed and healthier for pets than traditional dry kibble. Freeze-dried diets and treats are not extruded or subjected to extreme processing, and sometimes may be referred to as raw. Fresh and frozen diets have existed since 2006, but they have increasingly gained popularity. In recent years there has been strong growth of fresh human foods, through home delivery services with $16 billion revenue in 2022¹. This is followed by emerging growth in fresh, home delivered pet diets with an estimated value of $9 billion by 2030². Fresh and freeze-dried products represent the extremes of percent moisture, fat level, and storage temperature and provide unique challenges for preservation. The approaches to preserve each and achieve shelf-life requirements have evolved in recent years to address these challenges.

Preserving Freeze-Dried Pet Food

What freeze-dried products lack in weight, they make up for in flavor impact and texture. The high degree of palatability of freeze-dried products for cats makes them particularly appealing alone or as a topper for kibble. Making freeze-dried products for pets typically starts with a fresh meat slurry, blending in any other formula ingredients, freezing rapidly to the product’s triple point, then forcing the loss of water through sublimation under vacuum or lyophilization.

Preservation of freeze-dried products to prevent microbial contamination is simple, because the water activity is too low to support microbial growth. Raw material quality is the most important factor in oxidation and off aromas due to lipid oxidation and biogenic amines formation. Raw meat slurry has a water activity suitable for microbial growth. Microbial growth at high levels, even when the slurry is held at refrigerated temperatures, can lead to formation of biogenic amines. Biogenic amines, such as histamine, tyramine, cadaverine and putrescine, survive processing and cause negative palatability impacts. Treatment of the meat slurry with antimicrobial additives extends the shelf-life of the slurry and prevents the formation of biogenic amines. High pressure pasteurization or irradiation may be used to prevent cross contamination during processing before packaging as well. When used as a kill step or when the microbial burden is so high that it requires extensive sterilization processes, oxidation can occur (see Figure 1).

Application of antioxidants must occur prior to processing. During processing the moisture reduces, the fat percent increases and with it the antioxidant concentration increases and exceeds the sacrifice rate. This stands in contrast to all extruded or baked product types where a sacrifice in antioxidant is expected. Excessive use of tocopherols may lead to pro-oxidant impacts due to the high concentration of the antioxidant. The use of an antioxidant blend that is effective at low temperatures is recommended. When antioxidant is used properly, freeze-dried products are shelf stable for years (see Figure 2). Shelf-life testing uses similar methods to kibble. Peroxide Value along with aldehyde measurements, and antioxidant residuals are used to determine effectiveness of the antioxidant product used.

Preserving Fresh Pet Food Diets 

Shelf-life expectations differ widely for fresh pet food diets. These products can be sold by e-commerce, in a cooler at your local grocery retailer, or via a meal delivery service. Meals may be pre-made and frozen and be stored for a year. Storage in the refrigerated case at the store may be up to 14 days. In the customer’s refrigerator, a thawed, unopened diet shelf-life is 7-10 days, then perhaps another 5 days after opening. All of these storage times amount to a challenge when testing for shelf-life, especially when you consider possible temperature fluctuations during transport.

Fresh diets are considered high moisture foods with an elevated water activity of 0.9, making them highly susceptible to microbial growth. Depending on processing conditions, sterilization method, and packaging type, bacterial levels may be quite low and well-controlled during shelf-life. To reduce bacterial load, acids are typically used, but most not interfere with any gums that are providing texture. Acids can also cause an unfavorable color change, which is important to the consumer, because these products are sold in clear packaging. Under refrigerated conditions, lactic acid bacteria growth can cause package bloat when allowed to propagate.

Since fresh diets are stored in the refrigerator near human food, control of foodborne bacteria is important. High variability in bacteria recovery is typical. In Figure 4, lactic acid bacteria control in a fresh pet food diet with a natural acid product is demonstrated, while Figure 5 shows control of enteric bacteria.

Antioxidant preservatives are added to fresh diets to prevent lipid oxidation, protect the color of the product, and may act as cure enhancers. These diets are marketed as fresh and healthy, but a faded, inconsistent or off color could imply to customers that the diets are not as advertised and possibly indicate poor quality. Traditional oxidation does not occur as in dry products, so the level of antioxidant used is low and must be active at cold temperatures rather than extreme heat typical of extrusion. Aroma and pet acceptance favors dogs for these products, but the appeal to cats may be enhanced via use of natural flavors.

How We Can Help Preserve Freeze-Dried and Fresh Pet Food Diets

Despite the stark differences in product attributes, some universal quality approaches benefit both fresh and freeze-dried products. Both product types are mostly meat slurry based. The quality of the protein that goes into any pet food recipe greatly impacts shelf-life from both a microbial and an oxidation standpoint. Sterilization procedures must be accounted for when formulating a preservative system to ensure adequate product protection when out on the shelf.

As more companies enter the market for these fun and functional diet types, new products are continuously being launched. Safety and quality of both freeze-dried and fresh/frozen products remains challenging but possible.

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References

1 Meal

2 Pet

3 CLS

Meal Kit Delivery Services Market size is projected to grow at a

CAGR of 16.8% - EIN Presswire (einnews.com)

Pet meal kit delivery services to see 15% annual growth

(fooddeliverynews.com)

Kemin Internal Document CLS #13478

Kemin Internal Document CLS Study #13277

Kemin Internal Document CLS Study #28927