| Conventional antibiotic additives used in animal feeds have played a vital important role in accelerating the development of breeding industry. However, the potential of these agricultural antibiotics contributing to the development of antibiotic resistant, drug residue and environmental pollution is the subject of intense debate and research. Potassium diformate (KDF), a novel feed additive, has been firstly authorized by the European Union as an alternative to antibiotic growth promoters. This acid formate exhibits excellent biological effectiveness which can generate similar benefits, such as increasing growth, improving feed efficiency and reducing incidence of certain diseases, as the antibiotic growth promoters. Moreover, it is advantageous in terms of good palatability and high safety. The manufacturing techniques of KDF are currently under exploitation, especially in our country the KDF manufacture has just been at its initial stage. Consequently, studies on the synthetic technology of KDF and its extended applications are of great significance.In this thesis, three synthetic methods of KDF were evaluated, and their synthetic technologies were investigated. Moisture sorption characteristics of the KDF product were further examined. Moreover, KDF was used to prevent mildew in animal feeds. Main work and results are as follows:(1) Syntheses of KDF by HCOOH and HCOOK, HCOOH and K2CO3, and HCOOH and KOH were accomplished, respectively. The reaction conditions which influence the yield of product significantly were investigated. Orthogonal design experiments were also carried out to optimize the synthetic technologies. Furthermore, different techniques such as FT-IR spectroscopy, melting range determination and acid-base titration were adopted to characterize the products. The results showed that the optimal conditions were: molar ratio of HCOOH to HCOOK 1.3 : 1.0, reaction temperature 65℃and reaction time 30 minutes for the reaction by HCOOH and HCOOK with the yield of KDF of 94.0%, molar ratio of HCOOH to K2CO3 4.4 : 1.0, reaction temperature 85℃and reaction time 90 minutes for the reaction by HCOOH and K2CO3 with the yield of KDF of 89.9%, and molar ratio of HCOOH to KOH 2.2 : 1.0, reaction temperature 70℃and reaction time 30 minutes for the reaction by HCOOH and KOH with the yield of KDF of 98.4%. Concerned with the materials and energy consumption and the yield and quality of products, the method by HCOOH and KOH, an environmentally benign synthesis route, was the best one among the three mentioned above.(2) The moisture sorption characteristics of KDF were measured employing the static gravimetric method. It was found that the moisture sorption velocity of KDF was linearly dependent on the relative humidity at 30℃during the first 12-hour period, and the moisture sorption velocity could be predicted successfully by using a linear equation. Besides, the equilibrium moisture content was significantly influenced by relative humidity, and it could be also predicted successfully by employing a polynomial equation. The critical relative humidity of KDF was 46.2%, below which the equilibrium moisture content was less than 0.11 g/g dry KDF. The equilibrium moisture content increased with an increase of relative humidity and especially a sharp increase emerged, which could finally exceed 2.0 g/g dry KDF, while the relative humidity was greater than 46.2%.(3) Efforts were also made to explore the anti-mold performance of KDF in feeds. KDF could prolong storage period of feeds up to 35 d with an addition of 0.1 wt % or 0.3 wt %, and preserve feeds from going moldy within 2 months. While it exhibited more remarkable anti-mold performance by prolonging storage period of feeds over 60 d with an addition ranging from 0.6 wt % to 2.4 wt %, and preserve feeds from going moldy over 3 months. KDF exhibited excellent anti-mold performance, and it was superior to sodium diacetate which has been accepted as a good mold inhibitor, and thus could be used as an alternative to both antibiotic growth promoters and mold inhibitors of feeds. |
