Dry Pet Food Research Articles

Mycobiota and aflatoxins in raw materials and pet food in Brazil

Commercial feedstuffs are a basic element in modern pet husbandry in the world. In dogs, the effect of mycotoxins is severe and can lead to death. Few reports on the influence of dietary mycotoxins were found in the scientific literature. The aims of this work were to isolate and identify the mycoflora and to determine the aflatoxins (AFs) natural occurrence in raw materials and ready dry pet food. Therefore, the aflatoxigenic capacity of Aspergillus flavus species was investigated. Aspergillus was the prevalent genera (65-89%) followed by Penicillium and Fusarium spp. Aspergillus flavus was the most prevalent species, followed by Aspergillus sydowii, Aspergillus fumigatus and Aspergillus versicolor. Aspergillus flavus frequencies ranged from 58% to 86% except in sorghum meal. All samples assayed (except corn grains and ready pet food) showed Fusarium spp. contamination. Corn meal and corn meal and gluten samples had 100% Fusarium verticillioides. Fusarium graminearum was isolated from sorghum meal. Aspergillus flavus strains (75%) isolated from raw materials and 57% from pet food were able to produce AFs. All samples showed AFs contamination percentages over 70%; corn and sorghum meal obtained the highest AFs levels. Ready pet food did not show quantitative levels of the tested toxins. This is the first report of the aflatoxigenic capacity by A. flavus from Brazilian pet food.

Effects of extrusion processing on nutrients in dry pet food

AbstractExtrusion cooking is commonly used to produce dry pet foods. As a process involving heat treatment, extrusion cooking can have both beneficial and detrimental effects on the nutritional quality of the product. Desirable effects of extrusion comprise increase in palatability, destruction of undesirable nutritionally active factors and improvement in digestibility and utilisation of proteins and starch. Undesirable effects of extrusion include reduction of protein quality due to e.g. the Maillard reaction, decrease in palatability and loss of heat‐labile vitamins. Effects of extrusion processing on the nutritional values of feeds for livestock have been well documented. Literature results concerning effects of extrusion on dry pet foods, however, are scarce. The present review discusses the results of studies investigating the impact of extrusion cooking on the nutritional quality of dry pet foods. Copyright © 2008 Society of Chemical Industry

Evaluation of the GeneQuence® DNA Hybridization Method in Conjunction with 24-Hour Enrichment Protocols for Detection of Salmonella spp. in Select Foods: Collaborative Study

A multilaboratory study was conducted to compare performance of the GeneQuence DNA hybridization (DNAH) method incorporating new 24 h enrichment protocols and reference culture procedures for detection of Salmonella spp. in select foods. Six food types (raw ground turkey, raw ground beef, dried whole egg, milk chocolate, walnuts, and dry pet food) were tested by the DNAH method and by the culture methods of either the U.S. Department of Agriculture-Food Safety and Inspection Service (USDA-FSIS) or the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA/BAM). Fifteen laboratories participated in the study. Four of the foods tested (raw ground turkey, dried whole egg, milk chocolate, and dry pet food), showed no statistically significant differences in performance between the DNAH method and the reference procedure as determined by Chi square analysis. Sensitivity rates for the DNAH method ranged from 92 to 100%. The DNAH method, with the specific enrichment protocol evaluated, was found to be ineffective for detection of Salmonella spp. in walnuts. For raw ground beef, results from one trial showed a statistically significant difference in performance, with more positives obtained by the reference method. However, evidence suggests that the difference in the number of positives was likely due to lack of homogeneity of the test samples rather than to DNAH method performance.

Precollaborative Study of the GeneQuence® Salmonella Assay Using 24-Hour Enrichment Protocols for Detection of Salmonella spp. in Select Foods

New enrichment protocols are described for use with a DNA hybridization (DNAH) method for detection of Salmonella spp. in select foods. GeneQuence Salmonella, in its original version, utilized a 3-stage enrichment of minimum 42 h duration. New 2-stage procedures of 24-28 h duration are described for raw poultry, raw beef, pasteurized egg products, milk chocolate, and dry pet food. In the validation study described here, a total of 345 samples were tested by the abbreviated DNAH method in parallel with either the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA/BAM) or U.S. Department of Agriculture-Food Safety and Inspection Service (USDA-FSIS) reference culture procedures. Results showed an overall sensitivity for the DNAH method of 97.1% (false-negative rate 2.9%). There were no false-positive results by the DNAH method; therefore the specificity was 100%. Overall agreement between the DNAH and reference culture methods was 98.5%. There were no significant differences in performance between the DNAH and reference methods for any of the foods tested as determined by Chi-square analysis. It is recommended that the DNAH method be subjected to AOAC collaborative study.

Anaerobic co-digestion of a simulated organic fraction of municipal solid wastes and fats of animal and vegetable origin

The potential of mesophilic anaerobic digestion for the treatment of fats of different origin through co-digestion with the organic fraction of municipal solid wastes (OFMSW) has been evaluated. Co-digestion process was conducted in a pilot plant working in semi-continuous regime in the mesophilic range (37 °C) and the hydraulic retention time (HRT) was 17 days. During the start-up period the digester was fed with increasing quantities of a simulated OFMSW (diluted dry pet food). When the designed organic loading was reached, co-digestion process was initiated. The fat used consisted of waste from the food industry (animal fat), its composition was very similar to that of the simulated OFMSW in relation to the long-chain fatty acid (LCFA) profile. Fat content in the feedstock was gradually increased up to 28%, and hence the organic loading, with stable operation of the digester. Animal fat was suddenly substituted by vegetable fat maintaining the organic loading. No accumulation of LCFA or volatile fatty acids (VFA) was detected in either case. After a short adaptation period, total fat removal throughout the experiment was over 88%, whereas biogas and methane yields were very similar to those of simulated OFMSW. In conclusion, anaerobic co-digestion of OFMSW and fat wastes appears to be a suitable technology to treat such wastes, obtaining a renewable source of energy from biogas.

A new versatile and robust mite trap for detection and monitoring of storage mites in the cereal and allied industries

Storage mites are important primary pests but present methods for trapping them are either rudimentary or have several limitations. These prevent effective early detection or reliable monitoring of mites in the food, animal feed and associated industries. The BT Trap is the first trap designed specifically for the detection and monitoring of mite infestation. This trap is made up of a mixed food base lure held in a robust adjustable housing. It is user friendly, requires an exposure period of only 4 days and can be used in a dusty environment. The performance of the BT Trap was evaluated in the laboratory and the mean minimal capture rate of mites was 62%. In a comparative field trial, this trap detected significantly more mites than the bait bag or the fishmeal trap. The trap's performance was also assessed in four different types of premises. These were premises engaged in the production of cereal based dry pet food, specialist animal feed, traditional cheese, and in the finished cereal section of a large transit storage warehouse. A total of 17 genera or species of storage and predatory mites was detected in these four premises, with at least seven species detected in each of these premises. This study confirms that the BT Trap was able to function under the rigours of use in the field. It has demonstrated its potential as a useful tool for early detection and monitoring of mites in production premises. It also provided information that was vital for improving existing mite control measures and in implementing effective management strategies.

Corn hybrid affects in vitro and in vivo measures of nutrient digestibility in dogs

Corn is a commonly used ingredient in dry pet foods because there is a stable supply and it is a relatively inexpensive source of nutrients. Corn hybrids are available that are higher in CP and amylose and lower in phytate concentration than conventional hybrids. Approximately 500 mg of high-protein (HP), high-protein, low-phytate (HPLP), and high-amylose (HA) corn were compared with conventional (CONV) corn and amylomaize starch (AM) in triplicate and exposed to pepsin/hydrochloric acid and pancreatin to simulate hydrolytic digestion. Substrate remaining after this was used to determine in vitro colonic fermentation. Organic matter disappearances as a result of hydrolytic digestion were >80% for CONV, HP, and HPLP, whereas HA (60.7%) and AM (43.7%) were lower (P < 0.05). Total digestion (TD) values after hydrolytic digestion and 8 h of fermentation using canine fecal inoculum were greater (P < 0.05) for CONV, HP, and HPLP vs. HA and AM. The residue left after hydrolytic digestion of all substrates was poorly fermented. Five ileal-cannulated dogs were fed each corn hybrid at approximately 31% of the diet in a 5 x5 Latin square design. Dogs fed diets containing HP corn had higher (P < 0.05) ileal OM digestibility (70.3%) and tended (P < 0.10) to have higher DM digestibility (64.6%). Ileal starch digestibilities were lower (P < 0.05) for dogs fed HA (64.0%) and AM (63.0%). Ileal digestibilities of essential (71.2%), nonessential (67.4%), and total (69.0%) AA tended to be higher (P < 0.10) for HP diets compared with CONV (66.4, 62.4, and 64.0%, respectively). Total-tract DM, OM, CP, and GE digestibilities (77, 82, 77, and 84%, on average, respectively) were higher (P < 0.05) for dogs fed CONV, HP, and HPLP than for those fed AM (66.9, 71.6, 72.6, and 76.5%) and HA (60.6, 65.7, 69.7, and 71.5%). Total-tract fat digestibilities were lower (P < 0.05) for dogs fed HA diets (86.6%) than for all other treatments (91.0%, on average). Total-tract starch digestibilities were higher (P < 0.05) for dogs fed CONV, HP, and HPLP (98%, on average) compared with HA (72.8%) and AM (76.5%). No differences were detected among treatments in fecal bifidobacteria, lactobacilli, or Clostridium perfringens concentrations. The experiments demonstrated that HP and HPLP corn had hydrolytic digestion and fermentation characteristics similar to those of CONV corn, whereas HA resulted in similar responses to AM, a well-established resistant starch ingredient.

CHALK CULTURE METHOD FOR PRESERVING BACTERIA CULTURES AND ITS APPLICATIONS1

A simple and efficient chalk culture method was developed to preserve bacterial cultures in this study. The stability of Bacillus cereus, Enterobacter aerogenes ATCC 13048, Escherichia coli, Escherichia coli O157:H7 ATCC 43895, Listeria monocytogenes, Pseudomonas aeruginosa ATCC 25619, Salmonella Typhimurium and Staphylococcus aureus chalk cultures at 25C and 4C was evaluated at 0, 1, 2, 3 and 9 months on Tryptic Soy Agar and a specific agar for each organism. During drying process, B. cereus, E. coli O157:H7 and S. aureus chalk cultures showed less than 1.0 log CFU/g reduction, while E. aerogenes, E. coli, L. monocytogenes, P. aeruginosa and S. Typhimurium showed between 1 to 3 log CFU/g reduction. In the shelf‐life study of chalk cultures, B. cereus and E. coli O157:H7 were stable (&lt; 1 log CFU/g reduction) at both 25C and 4C during the first 3 months. E. aerogenes, E. coli, L. monocytogenes, P. aeruginosa and S. aureus had better stability at 4C (&lt;1 log CFU/g reduction) than 25C (&lt;3 log CFU/g reduction) (P&lt;0.05) during the first 3 months. S. Typhimurium was not stable at 25C and 4C during the first three months (P&lt;0.05). From the third month to the ninth month, B. cereus, E. coli O157:H7, L. monocytogenes and S. Typhimurium were stable at both 4C and 25C (&lt;1 log CFU/g reduction), while E. aerogenes, E. coli, P. aeruginosa and S. aureus were more stable at 4C than at 25C.E. coli O157:H7, L. monocytogenes, S. Typhimurium and S. aureus chalk cultures were inoculated into milk, ground beef and dry pet food, and retained constant (&lt; 1 log CFU/mL or g reduction) after 5 days storage indicating that chalk cultures are stable in these foods. For the heat treatment (55C for 5 min) study, the counts of chalk cultures in milk and ground beef reduced approximately 2 log CFU/mL or g, and about 1 log CFU/g in pet food after heating. The difference was statistically significant compared to the unheated‐inoculated sample (P&lt;0.05). The chalk cultures are easy to prepare, stable in storage and convenient to use for challenge studies especially for dry solid food samples.

Novel method for testing the grease ­resistance of pet food packaging

AbstractFor paper‐based dry pet food packaging, one of the main requirements is a high resistance against staining from the fat in the product. For both development and quality control, rapid and reliable standardized test procedures assessing this property are needed. Although a number of tests are available, they either apply only to certain types of packaging materials and show limited correlation with field behaviour, or employ non‐standard testing substances, long testing times and complicated equipment. In response to this situation, a new testing procedure that reflects field behaviour but without the drawbacks of the existing tests has been developed. The new test shows high reproducibility and good correlation with field performance for a wide range of multiwall bag and folding box materials with different types of grease resistance treatment. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Quantification of synthetic phenolic antioxidants in dry foods by reversed-phase HPLC with photodiode array detection

Propyl gallate (PG), octyl gallate (OG), 2-and 3- tert-butyl-4-hydroxyanisole (BHA), 3,5-di- tert-butyl-4-hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) are permitted in a limited number of food products according to local legislations, with individual maximum limits in each case. This study describes an in-house validated reversed-phase HPLC method for the quantitative determination of PG and BHA in gravies and dehydrated soups, BHA in bouillons, dehydrated meat and dry pet food, and OG in dehydrated meat. Two extraction methods were developed to optimise the recovery of the phenolic antioxidants. Methanol was more suitable for the extraction of BHA and OG from dehydrated meat, PG from gravies and BHA from hard and soft bouillons while hexane/2-propanol was more suitable for the extraction of BHA from gravies and dehydrated soups, and PG in dehydrated soups. On the other hand, PG could not be quantified accurately in soft bouillons using either of these extraction methods, due to a lack of selectivity. The relative standard deviation of repeatability was between 0.9 and 5.5% and recoveries from spiked samples in the ranges 85–106% for PG, 95–104% for BHA and 83–85% for OG. The procedure allows also the detection of 2 mg/kg of TBHQ and BHT, which are not permitted in the EU for use in dehydrated soups, bouillons, gravies and dehydrated meat.

Residues of ochratoxin A in pet foods, canine and feline kidneys.

The occurrence of ochratoxin A (OTA) in canned (26 samples) as well as dry pet foods (17 samples) for cats and dogs was investigated. In addition, 26 feline kidney samples with or without kidney alterations were surveyed for OTA-residues. The separation and detection of OTA was carried out by an isocratic high-performance liquid chromatography system based on reversed phase with fluorescence detection. After homogenization and extraction steps, immuno-affinity columns were applied for sample clean up. OTA could be detected in 47% (n=40) of the pet food samples. Those found positive contained generally low amounts of OTA (0.1-0.8 microg/kg original substance). Higher levels were only detected in two pet food samples (3.2 and 13.1 microg/kg toxin, respectively). Low concentrations of ochratoxin A could also be found iIn tissue of cat kidneys, with 16 of the analysed kidneys (n=26) being positive. The concentration levels were between 0.35 and 1.5 microg/kg OTA in tissue. No relation between pathological findings and ochratoxin levels in feline kidneys could be assessed.

CONCURRENT DETECTION OF ESCHERICHIA COLI O157:H7 AND SALMONELLA FROM A SINGLE ENRICHMENT IN 24 H

ABSTRACT The objective of this study was to determine if a single assay protocol could result in the concurrent detection of Escherichia coli O157:H7 and Salmonella from a single sample grown in a single enrichment in 24 h. Twenty‐five and 375 g of ground beef nonfat dry milk, and dry pet food samples were seeded with low (10 cfu/sample) and high (100 cfu/sample) levels ofE. coli O157:H7 and Salmonella cultures and incubated at 35 and 41C for 18 h for nonselective preenrichment. Incubated samples were analyzed by immunomagnetic separation (IMS) following a 6 h incubation for selective enrichment at 37C using M‐broth and enzyme linked immumosorbent assay (ELISA). Depending on the food samples and the inoculation level, the minimum concurrent detection level of E. coli O157:H7 and Salmonella was &lt;1 cfu/g in the samples at the competitor flora level of 105 cfu/g or less in ground beef samples, but in other cases of higher competitor loads and low target inoculations E. coli O157:H7 could not be detected in the presence of the Salmonella.

Mycoflora in Commercial Pet Foods

This article reports on the identification of mycoflora of 21 dry pet foods (12 belonging to dogs and 9 to cats) that corresponded to 8 commercial brands made in Argentina and imported. The isolation frequency and relative density of the prevalent fungal genera are compared too. Ten genera and fungi classified as Mycelia sterilia were identified. The predominant genera were Aspergillus (62%), Rhizopus (48%), and Mucor (38%). The most prevalent among Aspergillus was Aspergillus flavus followed by Aspergillus niger and Aspergillus terreus. The predominant Mucor was Mucor racemosus followed by Mucor plumbeus and Mucor globosus. The moisture content of these foods ranged from 5.6 to 10.0% and from 7.2 to 9.9% for dog and cat foods, respectively. A greater moisture content in food for the senior category (9.5 ± 0.2) was observed only in comparison to adult and kitten/puppy. If the moisture content can be maintained at these levels, mold growth would be prevented or at least it would remain at an insignificant level. Some genera and species isolated and identified from the foods analyzed are potentially producing toxins, which are known as mycotoxins. This involves a risk for animal health.

Determination of Total Taurine in Pet Foods by Liquid Chromatography of the Dansyl Derivative: Collaborative Study

A liquid chromatographic (LC) method for the determination of total taurine in pet foods was evaluated in a collaborative study. Ten laboratories assayed 6 blind duplicate pairs of wet and dry pet foods. The taurine in the 6 sample pairs ranged from low (170 mg/kg) to high (2250 mg/kg) concentrations as is. Collaborators also assayed a sample of known taurine concentration for familiarization purposes. Samples were hydrolyzed to release bound taurine, which was subsequently converted to the dansyl derivative and quantitated by gradient-elution LC with fluorescence detection. Repeatability relative standard deviations, RSDr, ranged from 3.2 to 10.0%; reproducibility relative standard deviations, RSDR, ranged from 6.1 to 16.1%. The method has been adopted Official First Action status by AOAC INTERNATIONAL.

The influence of diet and other factors on owner-perceived obesity in privately owned cats from metropolitan Perth, Western Australia

A randomly selected group of cat-owning households ( n = 458) were interviewed to determine the diet of their cats ( n = 644) in the week prior to the survey and to identify dietary and other factors which were associated with obesity. All cats were categorised by their owners as underweight, correct-weight or overweight and the weight of 127 cats was also recorded. Nearly all cats were fed commercially prepared dry pet food (90.5%) or canned pet food (84.6%) in the week prior to the survey. Nineteen percent of cats were classified as overweight. Although the make-up of a cat's diet was found not to be associated with its weight or weight category, cats fed dietary supplements or those which had not received a specific kitten diet when <6 months of age were more likely to be overweight after univariable analysis. Logistic multiple regression was used to investigate the effect of putative risk factors on obesity while controlling for other factors. Overweight cats were more likely to be cross-bred (OR = 2.1), neutered (OR = 2.8), living in houses with only one or two cats (OR = 1.8), male (OR = 1.4) and predominantly confined inside a house (OR = 1.4). Obesity is influenced by a variety of factors including host, dietary and management factors and these must be considered when developing weight control programmes for cats.

EFFECTS OF LIPIDS AND PROCESSING CONDITIONS ON THE SENSORY CHARACTERISTICS OF EXTRUDED DRY PET FOOD1

ABSTRACTThe effects of fat type, fat content, and initial moisture content on the sensory attributes of extruded dry pet food were studied. A ‘Difference‐from‐Control” descriptive analysis was used to evaluate the extrudate sensory characteristics every 2 to 3 months for 14 months. There was no significant change of the intensity of attributes over time for no fat added samples and the results indicated their sensory characteristics remained stable within the studied time period. Significant correlation was found between sensory lightness and lipid oxidation of the pet food with fat addition. The instrumental L value was also found to have a high correlation with the sensory lightness. Principal Component Analysis (PCA) plots showed that the addition of fat enhanced the perceived fatty, painty, and cardboardy odors and oily surface of the pet foods; and the effects of beef tallow were more significant than poultry fat on these attributes. The highly correlated attributes of fatty, painty, and cardboardy odors indicated that the strong and characteristic aroma of beef tallow and poultry fat might interfere with the perception of painty and cardboardy odors, which represent the aroma of lipid oxidation.

Effects of lipids and processing conditions on lipid oxidation of extruded dry pet food during storage

Effects of fat type (beef tallow and poultry fat), fat content (0–0.75 g kg −1) and processing conditions (initial moisture: 1.6–2 g kg −1; screw speed: 200–400 rpm) on lipid oxidation of extruded dry pet food were studied. The results showed that the lipid oxidation rate constant of the extruded dry pet food was a function of fat types, added fat content and feed moisture content. Control (no fat) samples had the highest lipid oxidation rate, as compared to the samples with fat addition. Samples with poultry fat had a higher lipid oxidation rate than those with beef tallow addition. Samples containing a higher fat content resulted in a lower rate of lipid oxidation during storage. Feed moisture content had the same effect as the fat content; the extrudates with a higher moisture content resulted in a lower lipid oxidative rate. Pet foods extruded at 300 rpm had a significantly higher lipid oxidation rate than the ones produced at 200 and 400 rpm. Lipid oxidation of the extrudates appeared to be affected mainly by the degree of extrudate expansion. Products with a higher degree of expansion, which had larger cells and thinner cell walls, were more susceptible to oxidation.

Effects of Lipids and Processing Conditions on Degree of Starch Gelatinization of Extruded Dry Pet Food

Effect of fat type (poultry fat and beef tallow), fat content (0–75 g/kg) and processing conditions (initial water content 160–200 g/kg; screw speed 200–400 rpm) on the degree of starch gelatinization of extruded, dry pet food was investigated. Fat content had the most prominent influence on starch gelatinization of the samples. Increasing the fat content significantly decreased the degree of starch gelatinization of the extrudates. Addition of beef tallow resulted in a lower degree of starch gelatinization as compared to poultry fat. Increasing the initial moisture decreased the degree of starch gelatinization of the extrudates. However, the effect was not very significant within the range studied. Interactive effects of screw speed and fat content on starch gelatinization of dry pet foods were observed.

Low Moisture Extrusion: Effects of Cooking Moisture on Product Characteristics

ABSTRACTA commercial Creusot‐Loire BC‐105 twin‐screw expanded dry pet food extruder was operated to provide extruded moistures between 7.9% and 12.4% at constant product density. Low moisture extrusion decreased product uniformity 45% and product shape roundness by 70%. It increased air ceil size 41% and internal fissuring by 25%. After drying all samples to low moisture, the samples extruded at a low initial moisture were more fragile with 15% lower ultimate strength as measured by crushing with an Instron testing machine.