Preparation, Characterization Of Citral Microcapsules And Its Application In Necrotic Enteritis Control Of Poultry

The current global migratioin towards the prudent use of antibiotics in food animal production has highlighted an urgent need to develop viable alternatives to in-feed antibiotics. Citral is an important essential oil with antibacterial activities, but its use as an antibiotic alternative is limited due to its physical and chemical instability during processing and inbiological systems such as the gastrointestinal tract of animals. The objective of this study is to encapsulate citral to maintain its stability during feed processing and transition through upper gastrointestinal tract, and thus to target the delivery to the lower intestines of animals where most pathogenic bacteria harbor. A Maillard reaction product(SPPMP) from soy protein isolate(SPI) and soy soluble polysaccharide(SSPS) was used as emulsifier and stabilizer in emulsions for citral protection in this study. Citral was successfully encapsulated in SPPMP with high encapsulation efficiency by spray drying technology, which is readily adapted by industry scale production. Encapsulation in SPPMP provided good protection to citral during feed pelleting which allowed its easy delivery in feed. MPPC-encapsulation effectively increased the amount of citral that was delivered to the lower intestines when it was tested in vitro and in experimental chickens. This study provided a theoretical basis and practical experience for development of antibiotic alternative with essential oils.1. The processing parameters for making a Maillard reaction product(SPPMP) from soy protein isolate(SPI) and soy soluble polysaccharide(SSPS) were studied against the yield of the product and its emulsification capacity in an oil-in-water emulsion. The optimized SPPMP was produced by dry-heating the SPI-SSPS mixture(SPP) at a ratio of 3:5, temperature of 60 °C and 75% relative humidity for 3 days. The formation of SPI-SSPS conjugates was confirmed by gel electrophoresis, FTIR spectroscopy and highperformance size exclusion chromatography. The citral(10 wt %) oil-in-water emulsionsstabilized by SPPMP exhibited superior physical stability than those stabilized by SPI or SPP during prolonged storage, after thermal treatment or under simulated gastrointestinalconditions. At p H 7.0, all the emulsions studied exhibited monomodal particle size distribution initially, however, only those stabilized by SPPMP remained monomodaldistribution for up to 70 days during storage at 25 oC. The SPPMP-stabilized emulsionmaintained its physical stability to the thermal treatment at 95°C for 30 minutes or undersimulated gastric conditions for 2 h; while the emulsions stabilized by SPI or SPP exhibited various degrees of instability. The retention rates of citral in the emulsions during long time storage, upon heating and under simulated gastrointestinal conditions were determined. The results showed that SPPMP-stabilized emulsions demonstrated outstanding ability to stabilize citral under all challenge conditions.2. The mass yield(MY), encapsulation efficiency(EE), release rate of citral after incubation in simulated gastric fluid were investigated for evaluating the effect of formulation on citral encapsulation. Formulation comprising 10.4% SPPMP and 13% citral provided a better preservation of citral during spray drying and in simulated gastric conditions, compared with other formulations. The retention rate of SPPMP-encapsulated citral was higher than 80% after 6 month storage at 25oC away from light. More than 80% of citral could be entrapped inside SPPMP from being released during incubation in simulated gastric fluid, which could be slowly released in the followed incubation in simulated intestinal fluid. Microencapsulation of citral with SPPMP contributed to more than two-times increase of citral amount to be delivered to the small intestine when tested in the experimental chickens, compared with un-encapsulated citral.3. The encapsulation showed no adverse effect on the antimicrobial activity of citral. In addition, encapsulated citral was superior to the un-encapsulated form in retaining its antimicrobial activity after treatment with simulated gastrointestinal fluids and in the presence of chicken intestinal digesta. The higher antimicrobial activity of encapsulated citral was also confirmed in digesta samples from the broilers that had been gavaged with encapsulated or un-encapsulated citral.4. When tested on broilers infected with C. perfringens, the diets supplemented with encapsualted citral at both 250 and 650 μg/g significantly reduced Necrotic Enteritis(NE) lesions in the chicken intestine, which was comparable to the effect of antibiotics-containing conventional diets. However, the supplement with encapsulated citral appeared to have no significant impact on the intestinal burden of C. perfringens and Lactobacillus. These data indicate that citral can be used to control NE disease in chickens after proper protection by encapsulation.