The effect of addition of plant protein concentrates in animal feed on pellet quality

Suncokretova sačma ima manju zastupljenost u peletiranim smešama za ishranu životinja od sojine sačme zbog većeg udela sirovih vlakana. Sirova vlakna depresivno deluju na svarljivost obroka i proizvodne rezultate, a mogu da imaju negativan uticaj na fizički kvalitet peleta. Pri peletiranju smeša za ishranu životinja u poslednje vreme značajna pažnja se posvećuje funkcionalnim promenama makronutrijenata, jer se smatra da ove promene pozitivno utiču na fizički kvalitet peleta. Razvojem modernih analitičkih tehnika, posebno termalne analize, moguće je opisati promene na skrobu u procesu peletiranja, nastale usled uticaja toplote i vlage. Sa druge strane, promene na proteinskoj komponenti u procesu peletiranja nisu dovoljno objašnjene. Najčešće se tumačenja svode na pretpostavke, bez objašnjenja o promenama u veličini molekula proteina, kao i njihovoj koncentraciji. Inovativan pristup ove doktorske disertacije je usmeren na opisivanje uticaja dodatka sojine i suncokretovih sačmi različitog sadržaja proteina u smeše na bazi kukuruza na tehnološke parametre procesa peletiranja, funkcionalne promene makronutrijenata (želatinizaciju skroba i denaturaciju i degradaciju proteina) i fizički kvalitet peleta. U okviru svake smeše takođe je ispitivan uticaj procesnih parametara, prečnika otvora sita mlina čekićara (2, 3 i 4 mm), vremena produženog kondicioniranja parom (bez produženog kondicioniranja, 5 i 10 minuta) na fizički kvalitet peleta. Istraživanja su pokazala da temperatura peletiranja, specifična potrošnja električne energije i udeo prašine u peletama zavise od sirovinskog sastava smeša, prečnika otvora sita mlina čekićara i vremena zadržavanja u kondicioneru, pri čemu temperatura peletiranja i specifična potrošnja električne energije rastu, a udeo prašine u peletama opada sa porastom koncentracije proteina u smešama. Dokazano je i da proces peletiranja utiče na funkcionalne promene makronutrijenata, želatinizaciju skroba i strukturne promene na proteinima. Takođe je dokazano i da za optimalno vreme zadržavanja materijala u kondicioneru, smanjenje prečnika otvora sita mlina čekićara i povećanje sadržaja proteina u smešama utiču na poboljšanje fizičkog kvaliteta peleta, tj. tvrdoće peleta i stepena otiranja peleta. Optimalni uslovi procesa peletiranja određeni su metodom željene funkcije. Dat je predlog opsega procesnih parametara za dobijanje peleta minimalnog stepena otiranja uz optimalnu specifičnu potrošnju električne energije. Istraživanja u ovoj doktorskoj disartaciji dala su doprinos novim saznanjima o uticaju dodatka sačme različitog sadržaja proteina (37,3, 40,3 i 42,6 %) na fizički kvalitet peleta. Kvalitet peleta sa dodatkom suncokretove sačme je poređen sa kvalitetom peleta sa dodatom sojinom sačmom, kao i kvalitetom peleta od čistog kukuruza, u cilju objašnjenja uticaja izvora i koncentracije proteina. Ispitivanja su vršena ne samo za standardno vreme kondicioniranja, nego uz primenu najsavremenijih postupaka termičke obrade hrane za životinje, tj. uz upotrebu produženog kondicioniranja od 5 i 10 minuta. Doprinos nauci je dat i time što je pokazano da proces peletiranja utiče ne samo na denaturaciju i degradaciju proteina, nego i na njihovo povezivanje.Sunflower meal has a lesser presence in pelleted compound feed than soybean meal due to a higher proportion of raw fiber. Raw fiber has depressing effect on the digestibility and production results, and can have a negative impact on the physical quality of the pellets. Lately, considerable attention is paid to the functional changes of macronutrients in pelleting of animal feed. It is believed that these changes have a positive impact on the physical quality of the pellets. With the development of modern analytical techniques, especially the thermal analysis, it is possible to describe the changes of starch in pelleting process, caused by the impact of heat and moisture. On the other hand, changes of the protein components in the pelleting process are not sufficiently explained. The most common interpretation is reduced to the presumption, with no explanation of changes in the size of protein molecules, as well as in their concentration. The innovative approach of this dissertation is focused on describing the effect of the addition of soybean meal and sunflower meals, with different protein content, in mixtures based on corn, on the technological parameters of the pelleting process, functional changes of macronutrients (starch gelatinization, and protein denaturation and degradation), and physical quality of the pellets. Within each of the mixtures, the influence of process parameters, the diameter of the hammer mill sieve openings (2, 3 and 4 mm), duration of long term steam conditioning (without extended conditioning, 5 and 10 minutes) on the physical quality of the pellets was also investigated. Studies have shown that pelleting temperatures, the specific power consumption and the proportion of dust in pellets were dependent of composition of the mixtures, the diameter of the hammer mill sieve openings, and residence time in the conditioner. Pelleting temperature and specific power consumption increased, and the extent of fines in pellets decreased with increasing of concentration of protein in the diets. Additionally, it is proved that pelleting process affects functional changes of macronutrients, starch gelatinization and structural changes in proteins. It is also proved that for the optimal retention time of material in conditioner, decrease of diameter of the hammer mill sieve openings and increase of protein content in the diets had positive effect on the physical quality of pellets, i.e. pellet hardness and degree of abrasion of pellets. The optimum process conditions in pelleting process were determined by the method of desired function. A proposal has been made for setting the range of process parameters for obtaining the minimum degree of abrasion of pellets, with optimal specific energy consumption. The research within this Ph.D. thesis contributed to the knowledge about the effects of addition of sunflower meal with different protein content (37.3, 40.3 and 42.6 %) on the physical quality of the pellets. Quality of pelleted mixtures with sunflower meal added were compared with the quality of pelleted mixtures with soybean meal added and quality of pelleted corn, in order to explain the effects of starch concentration, protein concentration and protein source. Studies were performed not only for the standard time of conditioning, but with the use of modern techniques for heat treatment of animal feed, i.e. with the use of long term conditioning process for a 5 or 10 minutes. Additional contribution to science has been given with showing that the pelleting process causing not only the denaturation and degradation of proteins, but also synthesis of proteins