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Application of thermomechanical energy in the formation of kibbles, palatability, digestibility and nutrient retention in extruded food for dogs and cats.

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Mayara Aline Baller
Total Authors: 1
Document type: Doctoral Thesis
Press: Jaboticabal. 2020-12-07.
Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
Defense date:
Advisor: Aulus Cavalieri Carciofi

Extrusion is a versatile operation that can be applied to a variety of food processing. Extruders are used to cook, shape, sanitize, texturize and mold a homogeneous mixture of ingredients, by applying moisture, pressure, temperature and mechanical friction in a short time. These conditions increase the nutritional quality, with elevated productivity and relatively small production costs. Extrusion promotes physical and chemical changes in ingredients, altering their digestibility, energy value, the mechanic of apprehension and palatability. Undesirable effects, such as destruction of vitamins, oxidation of lipids and reduced availability of amino acids need also to be considered. The best processing conditions to optimize digestibility, palatability and nutrients stability in dog and cat formulations are not known. CHAPTER 1: Addresses a literature review on the proposed topics. CHAPTER 2: The influence of the application of different amounts of specific thermal energy (STE) on processing parameters, kibbles macrostructure, starch gelatinization, coefficients of apparent total tract digestibility (CDA), fermentation products on feces, and palatability of cat food was evaluated. A standard diet was formulated and divided into six treatments, consisted by six STE applications in the preconditioner by modulating steam input. Six cats per diet were used for the digestibility study, and 30 for palatability comparisons. The increase in STE application resulted in linear reduction on specific mechanical energy (SME) application, quadratic increase in total specific energy (TSE) implementation, improvement of kibble macrostructure with reduced density and increased expansion, and in linear increase on starch gelatinization (P<0.05). The CDA of nutrients did not differ (P>0.05), but a linear reduction on volatile fatty acids on cat feces was observed (P<0.05), suggesting higher ileal digestibility and lower fermentation on colon. CHAPTER 3: The effects of grinding, extrusion with three SME applications (respectively 10, 20 and 30 kWh/t), and drying were evaluated on the retention of vitamins A, B2 and B6 in a formulation for dogsTo vitamin A was observed that the grinding and drying steps resulted in significant losses (P<0.05), but this vitamin did not decrease at the extrusion step, regardless of the SME application amount (P>0.05). An average final retention of 40± 5.51% of vitamin A was observed. The commercial form of vitamin B2 studied proved be stable, without significant losses in any processing steps (P>0.05). The vitamin B6, on the other hand, showed loss after extrusion, without effect of grinding, drying or the different applications of SME (P>0.05). The average retention of vitamin B6 was 65± 7.57%. CHAPTER 4: The effects of the extrusion process on the retention of three selenium sources were evaluated: selenium-yeast, commercial sodium selenite for animal feed, purified anhydrous sodium selenite. The three selenium sources were added at 0 μg/kg (control), 400 μg/kg and 800 μg/kg. Selenium in the control diet was derived only from ingredients and was not affected by processing (P<0.05). A small reduction in total selenium was observed for the 800 μg/kg selenium-yeast treatment (7 ± 0.30% reduction; P<0.05), but no alteration was observed for the 400 μg/kg selenium yeast diet (P>0.05), with recovery rates ranging from 93% to 104% (comparing with the values of the ingredient mixture before extrusion). Lower total selenium concentration xvi was observed after the extrusion of the diets supplemented with both sodium selenite sources, with recovery rates ranging from 62% to 86% and an average loss of 23.4± 3.04% (P<0.01). The commercial selenium-yeast presentation studied proved be stable, without significant losses along the processing steps evaluated. Significant selenium losses can be observed for sodium selenite, what should be considered during formulation. As a general conclusion of this thesis, there was a relevant effect of the application of STE on the formation and palatability of the kibbles, with a significant increase in productivity and efficiency of extrusion. Vitamin A showed significant loss in grinding and drying, steps that exposed the compound to oxygen. Vitamin B2 was stable during the process, but vitamin B6 was degraded in the extrusion step itself. Sodium selenite showed significant loss with extrusion, a fact not verified with yeast selenium. (AU)

FAPESP's process: 18/23864-4 - Effects of different amounts of thermal energy added in the conditioner on starch cooking, the macrostructure kibbles, digestibility and palatability of extruded diets for cats
Grantee:Mayara Aline Baller
Support type: Scholarships in Brazil - Doctorate