Measuring Pet Food Quality Using Rapid Loss-on-Drying Instruments

Recent developments in the pet food industry have resulted in products suitable for various stages of growth and development of pets. These developments have driven manufacturers to provide higher quality pet food products to ensure better care for pets and the stringent quality requirements drive manufacturers to implement more control in order to provide products with consistent quality.

Quality Control

Commercial pet foods have different forms and mixtures of nutrients that are determined by the pet they are designed for. 'Wet' and 'dry' foods are the two common consistencies for dog food and the moisture content for these types varies as expected. Hence, maintaining consistent moisture and mineral contents is essential for a company to achieve a high quality product.

AOAC approved methods are traditionally employed for making these measurements using ovens or furnaces. Although they yield reliable and accurate results, their longer analysis times will delay the introduction of products to the marketplace. Furthermore, these methods can only yield measurements after completion of the analysis.

The development of rapid loss-on-drying instruments facilitates yielding results in good agreement with conventional methods but more rapidly at a fraction of the analysis time of conventional methods. Moreover, these devices can provide in-test measurements, thus providing a comprehensive profile of the food being analyzed to users.

High temperature furnaces are traditionally used for determining mineral content by burning off organic materials in the food. However, high temperature analysis has many limitations, with small errors in sample handling and preparation resulting in poor analysis.

New technology involving high temperature analyzers yields more accurate measurement results. These analyzers are user friendly and yield in-situ measurements of samples.

Experimental Procedure

In the following example, the Computrac® MAX® 5000XL high temperature ash analyzer was used to test two different brands of dry dog food for moisture and ash analysis. With a linked test feature, the device enables multiple testing types and can perform both moisture and ash analysis with one sample. The reference analysis was performed utilizing a muffle furnace for ash analysis and a convection oven for moisture analysis.

The sample preparation involved processing each brand of dog food with a coffee grinder and subsequent storage in a mason jar to prevent moisture evaporation and to increase surface area. A metal sampling scoop was used to evenly transfer the sample to the sample pan.

Experimental Results

The experimental results are summarized in Tables 1 and 2, showing a good agreement in results between the Computrac® MAX® 5000XL and the conventional methods. However, the Computrac® MAX® 5000XL showed greater repeatability in three of the four sample groups when compared to conventional methods.

In addition, the Computrac® MAX® 5000X yielded the results within a fraction of the analysis time, with the values summarized being the median values for the sample groups.

Table 1. Moisture and Ash Results for Generic Pet Food

Pet Food 1
MAX® 5000XL Convection Oven
% Moisture Test Time (mm:ss) % Moisture Test Time
Average 8.280 13:38 Average 8.200 2 Hours
S.D. 0.070 S.D. 0.040
MAX® 5000XL Muffle Furnace
% Ash Test Time (mm:ss) % Ash Test Time
Average 9.350 28:55 Average 8.613 4 Hours
S.D. 0.090 S.D. 0.171

Table 2. Moisture and Ash Results for Puppy Food

Pet Food 2
MAX® 5000XL Convection Oven
% Moisture Test Time (mm:ss) % Moisture Test Time
Average 7.252 13:38 Average 7.122 2 Hours
S.D. 0.060 S.D. 0.011
MAX® 5000XL Muffle Furnace
% Ash Test Time (mm:ss) % Ash Test Time
Average 7.956 32:54 Average 7.774 4 Hours
S.D. 0.030 S.D. 0.649

As can be seen in Figures 1 and 2, the Computrac® MAX® 5000XL provides a comprehensive profile of the analysis in real time. The rate graph shows the possibility of optimizing the time for moisture analysis because very low amount of moisture is evolved off of the sample after 600s. The current testing conditions are designed for obtaining highly accurate results.

Moisture Test Results for Puppy Food.

Figure 1. Moisture Test Results for Puppy Food.

Multiple peaks can be observed in the ash profile (Figure 2) when heating the sample between 120°C and 600°C. This is because of the release of different organic components from the food at different temperatures. The residual ash is the mineral content of the food.

Ash Results for Puppy Food.

Figure 2. Ash Results for Puppy Food.


The results clearly demonstrate the advantage of using the Computrac® MAX® 5000XL over the conventional analysis methods for measuring moisture and ash content of dry pet foods. The significant reduction in the analysis time minimizes product throughput and enables manufacturers to bring products to the marketplace more rapidly. F

Furthermore, the ability of the Computrac® MAX® 5000XL to yield a complete analysis profile facilitates better analysis of food, thereby providing manufacturers more control on formulation and optimizing nutritional content.

About Arizona Instrument

Initially known as the Quintel Corporation, Arizona Instrument LLC was founded in 1981 by a group of engineers breaking away from The Motorola Corporation who were dedicated to the idea of providing precision moisture analysis instruments that were accurate, reliable, and easy to use.

The first instrument released was the MA Moisture Analyzer, but the company quickly expanded its Computrac® moisture analysis line and became an accepted leader in moisture analysis, setting a standard that has been adopted by many Fortune 500 companies. Today the Computrac® line is comprised of three technologies: rapid loss-on-drying, high temperature loss-on-ignition, and moisture specific analysis using polymer capacitance sensor, GREEN alternative to Karl Fischer.

Arizona Instrument

This information has been sourced, reviewed and adapted from materials provided by Arizona Instrument.

For more information on this source, please visit Arizona Instrument.


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