油茶籽干燥_储藏及压榨制油工艺研究
油茶籽作为我国特有的木本植物油料，主要用于制取油茶籽油。近年来，在国家政策扶持下油茶产业逐年升温，油茶籽产量逐渐提高，对油茶籽加工厂的加工能力和技术要求更高，但现有的油茶籽预处理、制油技术仍然是适合小型加工的，与新背景下的大生产不匹配，因此本文以新鲜普通油茶籽为原料，主要研究内容如下：首先，研究测定了带壳和去壳油茶籽在不同温度不同水分活度下的水分吸附数据，以绘制油茶籽的水分吸附等温线；选择7种数学模型对油茶籽水分吸附数据进行非线性回归拟合并预测了油茶籽的单层水分含量值。结果表明，Peleg模型具有最佳的拟合效果，在不同温度下的Adj-R2值都达到了0.99以上；通过GAB模型计算出了带壳和去壳油茶籽的单层水分含量值。利用油茶籽吸附数据和模型拟合结果分析计算了油茶籽水分吸附过程的热力学性质。结果表明：随着水分含量的增加，微分焓迅速下降，当水分含量超过7%（干基）后，微分焓值趋向于0；微分熵表现出类似变化趋势；扩张压力随着水分活度的增加而增加，但相同水分活度下温度越高扩张压力越低；随着水分含量的逐渐增加，净余积分焓值先逐渐增加到一最大值然后再逐渐减小；积分熵值先是逐渐减小到一最小值然后再逐渐增大。在此基础上，研究了不同水分活度条件下油茶籽的储藏稳定性，结果表明：相对湿度低于75.5%、水分含量9.8%以下储藏7个月后，油茶籽未发
生霉变虫害现象，油茶籽中所含油脂的氧化程度较低，但抗氧化能力有所下降；相对湿度超过80%、水分含量高于11.4%时，油茶籽储藏5个月后开始发生霉变，霉变率为20%，7个月后几乎完全霉变，油茶籽油品质较差，个别品质指标已超过国标规定值，储藏期不宜超过5个月。
其次，研究比较了4种干燥方式对油茶籽中油脂储藏稳定性的影响，并利用扫描电镜观察了不同干燥方式对油茶籽微观结构的影响，考察了温度对油茶籽干燥特性的影响规律，并采用4种数学模型拟合描述油茶籽的热风干燥过程。电镜观察结果表明微波干燥和90 °C热风干燥具有最宽敞的水分转移通道，在50 °C、70 °C、90 °C下热风干燥处理油茶籽至目标水分含量9%（干基）时，分别需20 h、7.5 h、5 h，干燥后的油茶籽储藏稳定性好；非线性回归分析表明，Page模型能很好的表征油茶籽的热风干燥过程，预测油茶籽干燥过程中水分含量的变化。
最后，通过对蒸炒温度、蒸炒时间、压榨压力和仁中含壳率等因素的优化，确定了液压榨油机制取油茶籽的热榨工艺，结果表明，蒸炒温度为140 °C，蒸炒时间50 min，压榨压力10 Mpa，仁中含壳率为10%时，经过一次压榨的油茶籽具有最低的饼粕残油率9.15%。
通过以上研究，了解了油茶籽的水分吸附特性为油茶籽储藏过程中水分含量的控制提供了依据，同时对油茶籽干燥预处理过程及热榨工艺提供理论指导。
关键词：油茶籽；水分吸附；水分活度；干燥；储藏稳定性；热榨
Camellia oleifera, as Chine endemic woody plants oiled, was mainly ud in producing Camellia oleifera oil. In recent years, the Camellia oleifera industry is heating up year by year under the national policy support, and the ed output improved gradually. So, the requirements for technical and processing capacity were higher for Camellia oleifera processing plants. However, the existing pretreatment and squeezing technology was only suitable for small lot processing. The main contents of this paper were listed as follows: Moisture sorption isotherms of shelled and unshelled Camellia oleifera were determined by using a gravimetric static method at 20, 30 and 40 °C with water activity ranging from 0.111 to 0.976. Estimated parameters and fitting ability of ven models were evaluated, and the Peleg model provided the best description of the experimental sorption behaviour. The experimental data and the models were also ud t
o obtain thermodynamic functions. The differential enthalpy decread rapidly as the moisture content incread, when the moisture content exceeded 7% (dry basis) the value of differential enthalpy approached to zero. The differential entropy showed similar trends. Spreading pressure incread with increasing water activity and decread with increasing temperature at a given water activity. Net integral enthalpy incread slightly with moisture content to a maximum value, and thereafter decread with increasing moisture content. However, net integral entropy decread gradually with increasing moisture content to a minimum value, and then incread slightly with further increas in moisture content.
The storage stability of Camellia oleifera was studied by being stored at different water activity conditions, and then determined the Camellia oleifera oil quality to evaluate the effect. The results showed that: the Camellia oleifera didn’t appear mildew pest phenomenon after 7 months stored under a relative humidity lower than 75.5%, and the contained oil showed a low degree of oxidation, but declined in antioxidant capacity; when the relative humidity was over than 80%, the Camellia oleifera appear mildew phen
omenon, and the oil quality became bad, so the storage period should not exceed 5 months under this condition.
Four drying methods were lected and compared, and then the effect on the storage stability of the contained Camellia oleifera oil was evaluated. We obrved the microstructure of Camellia oleifera procesd by four drying methods. In order to establish the hot-air dying model, we cho four mathematic models to fitting the experimental data of hot-air drying at 50, 70, 90 °C. The results showed that: it’s best to adopt the hot-air drying method to process the Camellia olrifera, and the time needed to reach the goal moisture content 9% was 20, 7.5, 5 h at 50, 70, 90 °C, respectively. It’s proved that the Camellia oleifera procesd by hot-air drying had good storage stability. The obrving results of SEM showed that microwave drying and 90 °C hot-air drying method generated the vastest moisture transfer channel. The result of non-lineal regression analysis proved that the Page model provided the best fitting results and description of the hot-air drying procedure of Camellia oleifera.
Keywords: Camellia oleifera; moisture sorption; water activity; drying; storage stability; oiled squeezing
摘要.........................................................................................................................................II 1 绪论. (1)
1.1油茶籽及油茶籽油简介 (1)
1.1.1 油茶籽概况 (1)
1.1.2 油茶籽油简介 (1)
1.1.3 油茶籽油制取技术综述 (2)
1.2 水分吸附等温线在食品加工和储藏中的实际意义 (3)
1.3干燥技术在农产品加工中研究进展 (5)
1.3.1 自然干燥 (5)
1.3.2 热风干燥技术 (5)
1.3.3 微波干燥技术 (5)
1.3.4 真空干燥技术 (6)
1.4 立题意义及主要研究内容 (6)
2 材料与方法 (7)
2.1 材料与仪器 (7)
2.1.1主要试剂 (7)
2.1.2主要仪器 (7)
2.2实验方法 (7)
2.2.1油茶籽水分吸附等温线测定 (7)
2.2.2油茶籽水分吸附热力学性质分析 (8)
2.2.3 油茶籽的四种干燥方法 (9)
2.2.4干燥油茶籽微观结构的扫描电镜观察 (10)
2.2.5干燥油茶籽储藏后提取油脂的评价 (10)
2.2.6 新鲜油茶籽储藏稳定性研究 (10)
