Abstract
In the pelleting process, mash feed passes through a conditioner were it is exposed to steam under high pressure and pushed through the die to form pellets. To determine the effect of adding different amounts of water and different thermal processing parameters on the pellet conversion percentage, pellet durability index (PDI) and solubility of protein in KOH of broiler feed. The processing factors were combined in a 4x2 factorial scheme: four moisture addition levels (0%; 0.7%; 1.4%; 2.1%), and two thermal processes (conditioning-pelleting or conditioning-expanding-pelleting). Eight samples of each treatment were collected to evaluate quality parameters. The feed used in this study was a typical corn-soybean broiler diet processed in a commercial feed mill. The pellet conversion percentage and PDI responded linearly and positively in the range of 0 to 2.1% moisture addition. Positive and linear equations relating moisture addition in the conditioner with pellet conversion percentage and PDI were obtained (p<0.001). Expansion improved PDI and pellet percentage respectively by 18% and 21% when compared to simple conditioning-pelleting feed processing. However, an adverse effect on protein quality was observed when higher processing temperature was used. No particle size effect was observed for conditioned-expanded-pelleted feed. Medium particle size resulted in better PDI and higher pellet conversion percentage (p < 0.001) compared to coarse grinding (% pellets – 66.97% versus 64.96%; PDI – 77.30% versus 66.10%).
Highlights
In the pelleting process, mash feed passes through a conditioner were it is exposed to steam under high pressure and pushed through the die to form pellets
The different particle sizes were attained by changing the hammer tip speed, since the hammer mill was equipped with a variable hammer rotation control (3600 rpm for medium size grinding and 1800 rpm for coarse size grinding)
In order to evaluate the effect of different moisture addition levels (0% 0.7%; 1.4% and 2.1% water addition), thermal processing and particle size, four batches of four tons of feed were mixed in sequence for each particle size (2 x 16 tons)
Summary
Mash feed passes through a conditioner were it is exposed to steam under high pressure and pushed through the die to form pellets. Attar et al (2017) reported that the addition of 2.5% and 5.0% water in the mixer prior to pelleting increased the PDI. Kanmani et al (2018) observed improvements on pellet quality when 2% and 4% tap water were added in the mixer. Parameters such as starch gelatinization and protein solubility can be monitored in order to check the effect of thermal processing on the feed ingredients. The objective of the experiment reported here was to determine the effect of feed particle size, 2020, Vol 8, No 3 different moisture addition to the mash feed in the conditioner and two thermal processes (conditioning-pelleting or conditioning-expanding-pelleting) on the pellet quality and protein solubility of corn-soybean broiler feeds
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