Abstract
Simple SummaryThe protein sources used for the production of dry pet food are mainly made of fresh meats (FMs) and especially meat meals (MMs). The transport and storage conditions of these raw materials, together with thermal and mechanical treatments in the case of MMs, may result in undesirable alterations of food products and their protein content. The aim of this study was to analyze the protein component of the raw materials used for dry pet food production, also testing the use of an alternative method to traditional ones, i.e., the Bradford assay. The results showed that the MMs are lower in quality compared to FMs, both in terms of protein bioavailability and digestibility. Furthermore, the Bradford assay proved to be a quick and simple method to better estimate protein bioavailability in the ingredients used for dry pet food production compared to traditional methods.The majority of dry pet food currently on the market is produced using fresh meats (FMs) and especially meat meals (MMs) as the main protein source. The transport and storage conditions of the raw materials, together with thermal and mechanical treatments in the case of MMs, may result in undesirable alterations of food products and their protein content. This study was conducted to analyze the protein component of three different kinds of raw materials used for dry pet food production, i.e., chicken, pork, and salmon. The quantitative analysis of the protein component was determined using the traditional Kjeldahl method and near-infrared (NIR) spectroscopy, and an alternative method, i.e., the Bradford assay, while the qualitative analysis was performed through SDS-PAGE, followed by Coomassie Blue staining. The amino acid (AA) profile was also evaluated by quadrupole time-of-flight liquid chromatography/mass spectrometry (Q-TOF LC/MS). In addition, the digestibility was tested through in vitro gastric and small intestine digestion simulation. Statistical analysis was performed by the Student’s t-test, and data are reported as mean ± SEM, n = 10 (p < 0.05). The results showed that the MMs are lower in quality compared to FMs, both in terms of protein bioavailability and digestibility, having a lower soluble protein (SP) content (chicken MM = 8.6 g SP/100 g dry sample; pork MM = 6.2 g SP/100 g dry sample; salmon MM = 7.9 g SP/100 g dry sample) compared to FMs (chicken FM = 14.6 g SP/100 g dry sample; pork FM = 15.1 g SP/100 g dry sample; salmon FM = 13.7 g SP/100 g dry sample). FMs appear, therefore, to be higher-quality ingredients for pet food production. Moreover, the Bradford assay proved to be a quick and simple method to better estimate protein bioavailability in the raw materials used for dry pet food production, thanks to its correlation with the in vitro digestibility.
Highlights
IntroductionAs far as the protein sources are concerned, most dry pet foods found on the market are produced using two different kinds of raw materials: fresh meats (FMs) and especially meat meals (MMs) [2,3]
The European market of dry pet food is constantly expanding, and new formulations are proposed, making it necessary to have a more accurate assessment of the ingredients used in the production process, consisting mainly of meat processing wastes [1].As far as the protein sources are concerned, most dry pet foods found on the market are produced using two different kinds of raw materials: fresh meats (FMs) and especially meat meals (MMs) [2,3]
Raw materials used in this study consisted of: chicken breast meat for human consumption (MHC), 10 batches produced by Italian farms; chicken FM and MM for companion animal food, 10 batches each produced by Italian farms; pork loin MHC, 10 batches produced by Italian farms; pork FM and MM for companion animal food, 10 batches each produced by Italian farms; salmon fillet MHC, 10 batches produced by Norwegian farms; salmon FM and MM for companion animal food, 10 batches of FMs produced by Norwegian farms and 10 batches of MMs produced by Polish farms
Summary
As far as the protein sources are concerned, most dry pet foods found on the market are produced using two different kinds of raw materials: fresh meats (FMs) and especially meat meals (MMs) [2,3]. FMs are made up of parts of animals, which are rejected as unfit for human consumption, but which did not show any signs of disease transmissible to humans, while MMs may, in addition, include animal hooves, horns, bristles, and feathers. These MMs are mainly used by pet food manufacturers to increase the amino acid (AA) content of pet kibbles in order to make complete feedstuffs. Inappropriate storage conditions could give rise to the proliferation of microorganisms, which degrade the organic component, leading to the development of harmful products, such as biogenic amines [6,7]
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