The Impact of Rendered Protein Meal Level of Oxidation on Shelf Life and Acceptability in Extruded Pet Foods: Determining Sensory Limits for Oxidation Values

Title: The Impact of Rendered Protein Meal Level of Oxidation on Shelf Life and Acceptability in Extruded Pet Foods: Determining Sensory Limits for Oxidation Values

Principal Investigator: Kadri Koppel, Kansas State University

Keywords: pet food, Koppel, 2014, oxidation, quality, shelf life, dog food, beef, meat and bone meal, poultry by-product meal, consumers

Year: 2014

Objective:
1. Determine the effect of incorporating increasing levels of oxidation in rendered protein meals used to produce extruded pet food on sensory properties related to oxidation in finished product.
2. Determine the effect of increasing rancid ingredients on pet owner acceptability (liking) of extruded pet foods.
3. Determine the sensory standard for rancidity that could be allowed in a rendered protein meal without negative affecting acceptability (liking) of the finish pet food.

Lay Summary/Industry Summary:
Pet owners are the ones who actually purchase pet food, so it matters if they find a particular food acceptable. Antioxidants, such as ethoxyquin or BHA/BHT, are used to minimize oxidation, but can create off-flavors and off-odors. Brokers and pet food companies often set guidelines on how much oxidation is acceptable but the limits are often can be vague and vary from company to company. In this study, a sampling of pet owners was asked to evaluate the overall likability of appearance and aroma of pet food treats made from beef meat and bone meal or poultry by-product meal that included either no antioxidants, ethoxyquin, or mixed tocopherols. All evaluated aroma attributes were significantly different across samples made with beef meat and bone meal and poultry by-product meal. Even so, changes in sensory characteristics such as oxidized oil, stale, cardboard, or rancid odors were minimal and it’s possible consumers may not be able to detect them.

Descriptive sensory analysis detected significant changes over time in pet food aroma and flavor characteristics for both the beef meal samples and the poultry byproduct meal samples. However, for poultry byproduct meal samples, the differences were more pronounced and directional. Antioxidants did improve the stability of poultry meal samples but not beef meal samples. The consumer study showed no differences in consumer likability of beef meal samples between various aromas or flavors. This may have been caused by the low levels of aromatics of the samples.

On the other hand, the noticeable increase in aroma characteristics in poultry meal samples over storage time did have an effect on consumer likability. Consumers tended to give a lower score for samples with either too low or too intense in aroma, but particularly didn’t like samples with intense negative odor. Besides aroma, appearance was another factor considered. Beef meal samples tended to have appearance characteristics (such as bone pieces and hair) that the consumers disliked. This was not as pronounced in poultry meal samples. Sensory profiles created by people could be used successfully as a powerful and predictive indicator of acceptable levels of oxidation for purchasing customers due to the strong correlation between sensory profile and consumers’ acceptability.

This study also includes considerable consumer survey data. Almost half of participants store their dry pet food in airtight containers, with another 35% storing it in the original resealed container. Almost 70% of participants said they finish a package of dry pet food in a month with only 2% taking 6 months to finish a package. Almost 87% of respondents said they spend less than $100 a month on pet food (but 13% spend more than $100/month on pet food). Most participants had a dog (58.4%) but almost 21% had both cats and dogs.

Scientific Abstract:
Pet foods are expected to have a shelf-life for 12 months or more. Sensory analysis can be
used to determine changes in products and to estimate products’ shelf-life. The objectives of this
study were to (1) investigate how increasing levels of oxidation in rendered protein meals used to
produce extruded pet food affected the sensory properties and (2) determine the effect of shelf-life
on pet owners’ acceptability of extruded pet food diet formulated without the use of preservative.
Pet food diets contained beef meat bone meal (BMBM) and chicken byproduct meal (CBPM) in
which the oxidation was retarded with ethoxyquin, mixed tocopherols, or none at all, and then
extruded into dry pet foods. These samples represented low, medium, and high oxidation levels,
respectively. Samples were stored for 0, 3, 6, 9, and 12 months at ambient temperature. Each time
point, samples were evaluated by six highly trained descriptive panelists for sensory attributes
related to oxidation. Samples without preservatives were chosen for the acceptability test, since the
differences in sensory characteristics over storage time were more distinguishable in those samples.
Pet owners evaluated samples for aroma, appearance and overall liking. Descriptive sensory analysis
detected significant changes in oxidized-related sensory characteristics over storage time. However,
the differences for CBPM samples were more pronounced and directional. The consumer study
showed no differences in pet owners’ acceptability for BMBM samples. However, the noticeable
increase in aroma characteristics (rancid aroma 0.33–4.21) in CBPM samples over storage time did
have a negative effect on consumer’s liking (overall liking 5.52–4.95).

Publications:
S. Chanadang, K. Koppel, and G. Aldrich. 2016. The Impact of Rendered Protein Meal Oxidation
Level on Shelf-Life, Sensory Characteristics, and Acceptability in Extruded Pet Food. Animals. 6(8) 44. http://www.mdpi.com/2076-2615/6/8/44