| 高含量乳清粉的仔猪配合饲料热特性及调质温度控制 |
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| 引用本文： | 孔丹丹,方鹏,王红英,陈啸,岳岩,吕芳,金楠.高含量乳清粉的仔猪配合饲料热特性及调质温度控制[J].农业工程学报,2017,33(16):299-307. |
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| 作者姓名： | 孔丹丹 方鹏 王红英 陈啸 岳岩 吕芳 金楠 |
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| 作者单位： | 中国农业大学工学院,国家农产品加工技术装备研发分中心,北京100083 |
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| 基金项目： | 公益性行业（农业）科研专项（201203015）；中央高校基本科研业务费专项（2017GX001） |
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| 摘 要： | 为探究热敏性饲料原料乳清粉及不同含量乳清粉的仔猪配合饲料的热物理特性,该文以仔猪料配方中的4种主要饲料原料玉米、豆粕、乳清粉和鱼粉为研究对象,采用混料设计的方法得到33种不同含量(0～30％)乳清粉的仔猪配合饲料,并利用差示扫描量热法(differential scanning calorimetry,DSC)测定了4种单一原料在25～120℃范围内以及33种仔猪配合饲料在25～110℃范围内的比热,分析了乳清粉及高含量乳清粉(质量分数≥14.548％)的仔猪配合饲料的热变性过程.结果显示:玉米、豆粕和鱼粉的比热分别与温度(25～120℃)呈线性、对数和二次关系,而乳清粉的比热与温度(25～110℃)遵循三次多项式的关系;当配合饲料中含有≥6.25％的乳清粉时,其比热与温度遵循三次多项式的关系;配合饲料的比热显著受温度、原料配比以及二者交互作用的影响(P＜0.001),其中,温度的影响最为显著,而乳清粉含量的影响次之.DSC热焓曲线上,乳清粉在109.79℃会出现吸热峰,为乳清蛋白的热变性导致;而随着温度由20℃升高到110℃,乳清粉颗粒由存在许多凸起与微孔的粗糙表面结构逐渐过渡为光滑、粘结的状态.与乳清粉相似,高含量乳清粉的配合饲料也会在77.95～87.69℃出现吸热峰.在仔猪配合颗粒饲料的加工过程中,为降低乳清蛋白的变性程度、减少环模制粒机的堵机现象,应将调质温度降低至70℃以下为宜.研究结果为高含量乳清粉的仔猪配合饲料的调质、制粒等热处理过程的工艺优化提供理论指导.
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| 关 键 词： | 比热 温度 物理特性 乳清粉 配合饲料 热变性 差示扫描量热法 |
| 收稿时间： | 2017/3/30 0:00:00 |
| 修稿时间： | 2017/7/28 0:00:00 |
Thermal properties and conditioning temperature control of formula feeds containing high content of whey powder for weanling pigs |
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| Kong Dandan,Fang Peng,Wang Hongying,Chen Xiao,Yue Yan,Lü Fang,Jin Nan.Thermal properties and conditioning temperature control of formula feeds containing high content of whey powder for weanling pigs[J].Transactions of the Chinese Society of Agricultural Engineering,2017,33(16):299-307. |
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| Authors: | Kong Dandan Fang Peng Wang Hongying Chen Xiao Yue Yan Lü Fang Jin Nan |
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| Institution: | National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China,National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China,National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China,National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China,National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China,National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China and National R&D Center for Agro-processing Equipment, College of Engineering, China Agricultural University, Beijing 100083, China |
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| Abstract: | Whey powder is a kind of thermosensitive feedstuff,which is particularly prone to pyrogenation and protein denaturation in conditioning and pelleting processing of pellet feed for weanling pigs.Pellet mill can be blocked easily when the feed formulation is designed with high level of whey powder.Studies on thermal proprieties of whey powder and formula feed containing different levels of whey powder are required for parameter optimization in thermo processing of formula feed.As corn meal,soybean meal,whey powder and fish meal are the most common and important ingredients in the diet of weanling pigs,33 kinds of formula feeds consisting of different levels of corn meal (22.6％-70％),soybean meal (13.7％-46％),whey powder (0-30％) and fish meal (0-10％) were obtained by D-optimal mixture design method in this work.Proximate composition of 4 ingredients including moisture,crude protein,crude fat,crude ash,crude fiber,starch,lactose contents was determined.The specific heat of these 4 ingredients at the temperature range of 25-120 ℃C and 33 kinds of formula feeds at 25-110 ℃C were measured by DSC (differential scanning calorimetry) at a programmed heating rate of 10℃/min,and the prediction models of specific heat as a function of temperature were established.Thermal denaturation of whey powder and formula feeds containing high levels of whey powder was also analyzed by DSC.The moisture contents of corn meal,soybean meal,whey powder and fish meal were 12.01％,10.96％,3.84％ and 7.28％ (wet basis) respectively,and the crude protein contents were 8.08％,47.26％,11.24％ and 65.73％ (wet basis) respectively.The specific heat of corn meal ranged from 1.614 to 2.705 kJ/(kg·K),soybean meal from 1.844 to 2.529 kJ/(kg·K),whey powder from 1.355 to 2.911 kJ/(kg·K),and fish meal from 1.592 to 2.464 kJ/(kg·K).Whey powder showed significantly lower values of specific heat at 25-100 ℃ compared to the other 3 ingredients,but significantly higher value at 120 ℃ (P＜0.05).The specific heat of corn meal increased linearly with the increase in temperature,and that of soybean meal increased logarithmically with the increase in temperature.The specific heat of whey powder followed a cubic polynomial relationship with temperature,and fish meal displayed a quadratic polynomial relationship with temperature.The specific heat of formula feeds containing no less than 6.25％ whey powder followed a cubic polynomial relationship with temperature,which was the same as that of whey powder.However,the specific heat of formula feeds containing no whey powder displayed a logarithmical relationship with temperature,similar with that of soybean meal.Analysis of variance showed that the specific heat of formula feeds was significantly dependent on temperature,ingredient proportion and the interaction of the 2 factors (P＜0.001).Temperature had the most significant effect on specific heat,followed by the level of whey powder.An endothermic peak with an enthalpy of 4.14 J/g was observed on the DSC thermogram of whey powder,which may be caused by the denaturation of whey protein.The onset temperature,peak temperature,and termination temperature were 90.23,109.79,and 115.25 ℃,respectively.During this thermal denaturation process,the specific heat of whey powder raised from 1.745 kJ/(kg·K) at onset temperature to 2.798 kJ/(kg·K) at peak temperature,and then declined to 2.662 kJ/(kg·K) at termination temperature.Whey powder particles exhibited a spherical shape with numerous bulges and micro pores on the surface after the thermal treatments of 20-90 ℃,but an irregular shape with smooth surface and agglutinate status after the thermal treatments of 110-115 ℃ based on micrographs obtained from the scanning electron microscope.Similarly,20 kinds of formula feeds containing high levels (≥ 14.548％) of whey powder also displayed endothermic peaks on the DSC thermograms,but the onset temperatures (67.46-74.99 ℃),peak temperatures (77.95-87.69℃),termination temperatures (81.47-91.72℃) and enthalpy (0.38-1.00 J/g) were lower than that of whey powder.Mixture with corn meal,soybean meal and fish meal could decrease the thermal stability of whey powder and facilitate the denaturation of whey protein obviously.Consequently,in order to reduce the denaturation of whey protein and the blocking of pellet mill,the conditioning temperature of formula feed containing high level of whey powder for weanling pigs should be lower than 70 ℃.In addition,the onset temperature,peak temperature,termination temperature and enthalpy of formula feed were significantly positively correlated with whey powder content (r=0.697,0.905,0.903,and 0.946,respectively,P＜0.001).This investigation provides fundamental theory and data for process optimizations of thermo processing such as conditioning,and pelleting of formula feed containing high level of whey powder for weanling pigs. |
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| Keywords: | specific heat temperature physical properties whey powder formula feed thermal denaturation DSC(differential scanning calorimetry) |
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