Influence of dietary fiber on macrostructure and processing traits of extruded dog foods

Abstract

Fiber is currently used in dog food formulations due to its nutritional properties. However, few studies have evaluated the influence of fiber on the extrusion traits and kibble formation. The present study evaluated the effect of fiber type and particle size on extrusion processing parameters and kibble macrostructure of dog foods. In treatment 1, guava fiber was added to a control formula (CO) at different inclusion levels: 3% (GF3), 6% (GF6), and 12% (GF12). In treatment 2, two fiber types (sugarcane and wheat bran) and two fiber particle sizes were compared to a control (CO) product. Foods were manufactured using a single screw extruder. Each food was processed on two separate days and samples were collected four times per run, for a total of eight replications per diet. The processing conditions were not changed for any treatment. Data were analyzed via analysis of variance, and compared by polynomial contrasts for treatment 1, and by defined orthogonal contrasts for treatment 2 (P < 0.05). Guava fiber inclusion resulted in a linear increase in temperature, pressure, and specific mechanical energy (SME) input (P < 0.001) during extrusion, whereas starch cooking (assessed by the amyloglucosidase method) and radial expansion decreased linearly (P < 0.001). Kibble density and cutting force increased linearly (P < 0.001) with guava fiber inclusion. In treatment 2, fiber addition also increased SME (P < 0.001) and decreased radial expansion (P = 0.008). However the latter was compensated by an increase in longitudinal expansion in the case of sugarcane fiber, resulting in no change in kibble density. Cutting force was higher (P < 0.001) for fiber supplemented foods, similar to treatment 1, but sugarcane fiber had a higher impact on hardness than wheat bran (P < 0.001). The finely ground fibers led to higher starch gelatinization (P < 0.05) and kibbles with lower piece density (P = 0.018). To summarize, insoluble fibers such as guava fiber, sugarcane and wheat bran at high inclusion rate increase the electric energy required to extrude, may reduce starch cooking and result in the production of less expanded, denser and harder kibbles. However, kibble characteristics are also significant impacted by fiber type and particle size.

Thermal energy application on extrusion and nutritional characteristics of dog foods

“…All studies in this area, however, were conducted for extruded human snacks or breakfast cereals, and none were found for dog foods. SME is more relevant for breakfast cereals and starch-based formulations than for pet food recipes, for which thermal energy assumes greater relevance due to the high protein, fat, and fiber contents (Monti et al, 2016). In the present study, the kibble bulk density was reduced by 63 g/L, or approximately 14%, and the kibble expansion increased by 23% after the greater STE application and higher preconditioner temperature.…”

“…The tested recipe was simple, based on corn and chicken by-product meal and caution is needed to extrapolate results to different formulations. Altering the protein, fiber, and fat content of the recipe the outcomes might be different, as the chemical composition of the mass have important implications on energy transferences and flowability on extruder barrel (Guy, 2001;Monti et al, 2016). The starch source used was corn, and starch from other cereals, and even from legumes or tubers shows different responses during extrusion (Guy, 2001), altering the implications of the different STE applications tested on the present study.…”

“…These transformations affect food digestibility and palatability by dogs, impacting both animal health and the commercial performance of the products. However, few published studies have evaluated methods to optimize energy input within processing conditions involved in the extrusion of dog foods (Monti et al, 2016).…”

“…Together, these two energy sources promote extensive raw material transformations that are directly linked and are dependent on the total specific energy (TSE) applied to the mass (Riaz, 2000;Van Zuilichem et al, 2011). Although very few papers have reported the application of STE in the production of dog foods (Monti et al, 2016), authors evaluations of commercial single screw extrusion systems suggests that between 60% and 75% of the TSE applied corresponds to STE, and the remainder is SME. The authors were unable to find published studies that aimed to optimize the TSE and STE:SME ratios in the production of pet foods, that would facilitate achieve the better balance between raw material transformation and efficient use of energy saving production cost.…”

Processing traits and digestibility of extruded dog foods with soy protein concentrate

“…Kibble cutting force was analysed using a texture analyzer (TA‐XT2 SMS, Stable Micro Systems, Godalming, UK) and the Texture Exponent software (Stable Micro Systems, Godalming, UK), which was equipped with 1 ½ inches diameter compression probe. Kibbles were first stabilized at the same moisture in an oven (ETS Modelo 532, Systems Eletro‐Tech, Glenside, PA, USA) at 35°C for 24 hr (Monti et al., ). Twenty extrudates from each treatment were tested with a 10‐mm penetration distance and speed of 2.0 mm/s, using a Warner‐Bratzler knife.…”