控温包装在莴笋尖常温物流过程中的保鲜机理及优化研究

发布时间：2018-02-01 07:41

本文关键词： 控温包装莴笋尖常温物流保鲜机理优化　出处：《西南大学》2017年硕士论文　论文类型：学位论文

【摘要】：我国冷链物流供给能力不足,且大部分蔬菜的附加价值较低,使用冷链也存在成本过高的问题,生鲜蔬菜在流通过程中缺乏有效的保鲜手段,损耗严重。控温包装通过蓄冷剂吸收热量来控制箱内温度,保持蔬菜在物流过程中的品质,作为冷链系统的补充,是目前市场上使用最广泛,也是最经济和实用的蔬菜物流保鲜方式之一。莴笋尖主要指莴笋的可食嫩叶部分,俗称凤尾,与莴笋茎相比,其营养更丰富,保健功效更好,食用价值更高。莴笋尖是一种高呼吸速率叶菜,有组织脆嫩,易脱水萎蔫黄化,常温物流难度大等特点,同时获取容易,价格便宜,对CO2有一定的耐受性,作为试验材料研究蔬菜采后生理及常温物流保鲜技术具有较强的代表性。本文以莴笋尖为研究对象,研究控温包装在莴笋尖常温物流过程中的保鲜机理,并通过协同预处理技术、改进结构、建立控温时间估算模型,提升控温包装保鲜效果,节约物流成本。文章首先使用不同重量的蓄冷剂,分析箱内的环境变化以及莴笋尖生理活动、营养品质变化,探究控温包装的保鲜机理及其保鲜效果的主要制约因素。然后,通过复合预冷、热处理,弥补单一控温包装的不足,研究控温包装复合前处理对莴笋尖常温物流保鲜品质的影响。再次,对箱盖做微小的开孔处理,使控温包装具备一定的气体交换能力,能长时间形成自发气调环境,研究其保鲜效果。最后,通过分析控温包装箱内外的传热过程,依据蓄冷剂用量建立物流控温时间估算模型并试验验证。全文主要得出如下结论:1、本章通过加入不同重量的蓄冷剂,研究控温包装在莴笋尖常温物流下的保鲜机理。结果表明,控温包装对莴笋尖生理活动、营养品质的影响具有明显的阶段性。在物流过程前期,箱内温度较低,莴笋尖呼吸作用自然降氧形成自发气调环境,各处理组均能维持较低的失重,保持较好的色泽(ΔE、h)及营养品质(叶绿素、Vc含量)。但在物流过程后期,呼吸作用消耗O2产生CO2形成超低氧环境,使莴笋尖进行无氧呼吸,产生乙醇等次级代谢产物,生理代谢失调,加速腐烂。提高控温包装蓄冷剂的用量,在物流过程前期有利于维持莴笋尖的品质,但对其保鲜期的延长效果有限,箱内气体成分变化导致的无氧呼吸是制约控温包装保鲜效果的主要因素。2、本章使用预冷复合热处理对莴笋尖进行保鲜处理,研究在密闭控温包装条件下复合前处理对莴笋尖常温物流保鲜品质的影响。结果表明,预冷处理有利于延长控温包装的控温时间,在物流过程前期保持莴笋尖较好的色泽和营养品质,但在物流过程后期会加速衰老,与对照组差异不大甚至更差(P0.05)。热处理会加剧果蔬表面原有角质层、蜡质层的破坏,在物流前期促进莴笋尖的蒸腾作用,短暂的提高其呼吸作用,导致失重率增加;同时,热处理能维持莴笋尖细胞膜稳定性,降低超氧阴离子产生速率、提高PPO及POD活性,抑制莴笋尖在物流过程后期遭受低O2高CO2胁迫时的腐烂。预冷复合热处理能结合两种处理方式的优势,保鲜效果优于单独预冷处理或热处理,能有效延缓莴笋尖的生理代谢,延缓莴笋尖无氧呼吸的发生和呼吸高峰的到来,提升控温包装对莴笋尖的保鲜效果,延长保鲜期。3、本章使用海绵-MA及微孔-MA两种自发气调方式改进控温包装结构,研究其对莴笋尖常温物流保鲜品质的影响。结果表明,海绵-MA及微孔-MA处理均能有效的调节控温包装箱内气体成分,防止CO2过多积累,保证莴笋尖正常的呼吸代谢,避免无氧呼吸的发生。但气体交换会伴随着水分的散失和热量交换,海绵-MA及微孔-MA处理也会提高莴笋尖的失重率,同时,略微削弱控温包装的控温效果。海绵-MA处理在维持相对电导率,降低超氧阴离子产生速率,提高PPO及POD活性等方面,与微孔-MA处理差异不大(P0.05),但能维持较低的失重率及较高的Vc、叶绿素含量,保持较好的颜色、质地、形态,整体保鲜效果更好。4、本章以瓦楞纸箱内套泡沫箱的典型双层控温包装形式为研究对象,通过计算控温包装系统热阻,综合考虑果蔬自身吸热以及蓄冷剂相变后的升温过程,运用传热学基本理论分别对蓄冷剂相变的稳态传热过程及之后箱内升温的非稳态传热过程进行了分析,建立了控温包装的控温时间估算模型。同时,加入不同重量的蓄冷剂模拟常温下莴笋尖的物流保鲜试验,监测其箱内温度变化,验证建立的估算模型。试验结果表明,在不同的蓄冷剂用量下该模型的估算值与实际控温时间的相对偏差在-9.68%~6.45%,偏差因子(Bf)为1.021,准确性因子(Af)为1.06,均接近1,在实际应用中属于可接受范围。所提出的估算模型能准确预测环境温度基本恒定的常温物流条件下控温包装的控温时间。综上所述,在常温物流过程中,控温包装对莴笋尖的生理活动、营养品质的影响有着明显的阶段性,在物流过程后期,箱内的O2消耗、CO2积累导致的气体损伤是制约其保鲜效果的主要因素。协同预处理技术及自发气调的改进方式对莴笋尖在常温物流下的保鲜均有较好提升效果。预冷复合热处理结合两种预处理方式的优势,保鲜效果优于单独预冷处理或热处理,能有效延缓莴笋尖的生理代谢,推迟但不能避免箱内无氧呼吸的发生。自发气调方式能有效的调节控温包装箱内的气体成分,保证莴笋尖正常的呼吸代谢,同时避免无氧呼吸的发生,但也会略微削弱控温包装的控温效果,提高莴笋尖的失重率,开孔填充纳米海绵的海绵-MA方式整体保鲜效果更好。基于典型双层控温包装形式建立的控温时间估算模型,能较准确的估算常温物流过程中控温包装的控温时间。这三种改进方式均具有一定的应用价值,在其他叶菜或高呼吸速率农产品的物流保鲜方面也有一定的借鉴意义。
[Abstract]:The ability of cold chain logistics supply in China is insufficient, and the added value of most of the vegetable is low, there is the problem of high cost in the use of cold chain, lack of fresh vegetables preservation methods, effective in severe loss circulation process. The temperature control package coolant absorbs heat to control the temperature, keep the vegetables in the process of logistics quality. As a supplement to the cold chain system, is currently on the market the most widely used, and it is also one of the most economical and practical way. Lettuce fresh vegetable logistics mainly refers to the edible part of lettuce leaves, commonly known as the Phoenix, compared with the lettuce stem, it is more nutritious, better health, higher edible value is lettuce. A high respiration rate of vegetables, organized crisp, easy to dehydration wilt chlorosis, characteristics of normal logistics. It also is easy to obtain, the price is cheap, there is resistance to CO2, as the experimental material production of vegetables After physiological and normal temperature fresh-keeping technology has a strong representation. In this paper, lettuce as the research object, preservation mechanism research of temperature controlling packaging in lettuce at room temperature in the process of logistics, and through collaborative pretreatment technology, improving the structure, establish the control time estimation model, enhance the preservation effect of temperature control package, save the cost of logistics. Firstly, the use of the weight of different coolant tank, analysis of changes in the environment and physiological activities of lettuce, nutrition quality change, the main restricting factors on the preservation mechanism of temperature control package and its preservation effect. Then, through the combined cooling, heat treatment, make up the deficiency of single temperature control package, study on temperature control packaging composite pretreatment on lettuce in normal logistics the quality of preservation effect. Thirdly, the box cover do small hole processing, the temperature control has certain ability of gas exchange packaging, can long time spontaneous gas ring Study on the preservation effect of the environment. Finally, through the analysis of the heat transfer process of the temperature control box inside and outside, according to the coolant temperature control amount to establish logistics time estimation model and experimental verification. The main conclusions are as follows: 1, this chapter by adding different weight of coolant, fresh mechanism of temperature control in lettuce under normal logistics packaging. The results show that the temperature control packaging on lettuce physiological activity, effects of nutritional quality has obvious stage. In the logistics process, the temperature is low, lettuce natural respiration and oxygen reduction spontaneous formation of atmosphere environment, each treatment group could maintain low weightlessness, maintain good color (E, H) and nutritional quality (chlorophyll Vc content). But in the logistics process of the late respiration consumption O2 formation of ultra low oxygen environment CO2, the lettuce in anaerobic respiration, ethanol and other secondary metabolites, physiological and metabolic loss Adjustable, accelerated decay. Improve the amount of coolant temperature control package, early in the logistics process is conducive to the maintenance of lettuce in quality, but the preservation period of the extension effect is limited, leading to anaerobic respiration box gas composition changes are the main factors restricting the preservation effect of temperature control package of.2, this chapter uses the pre cooling composite heat treatment tip the preservation of lettuce, study in a closed temperature control package condition composite pretreatment on lettuce quality preservation effects of logistics at room temperature. The results show that pre cooling treatment is beneficial to prolong the time of temperature control temperature control package, keep the lettuce better color and nutritional quality in the logistics process, but in the logistics process of the latter will accelerate aging, compared with control group (P0.05) is even worse. Heat treatment will increase the cuticle surface of fruits and vegetables, destruction of wax layer, promote early in the logistics transpiration of lettuce, short. The respiration, resulting in weight loss rate increased; at the same time, the heat treatment can maintain cell membrane stability of lettuce, reduce the production rate of superoxide anion, increase PPO and POD activity, inhibited lettuce in the logistics process later suffered decay of low O2 and high CO2 stress. With two kinds of treatment methods of the advantages of pre cooling combined heat treatment, preservation effect is better than that of pre cooling or heat treatment, can effectively delay the physiological metabolism of lettuce, lettuce in delaying anaerobic respiration and respiration peak arrival, enhance the temperature control package on preservation of lettuce, prolong the storage period of.3, this chapter uses -MA and -MA two kinds of microporous sponge modified atmosphere method temperature control packaging structure, on the preservation quality of lettuce in normal logistics effect. The results showed that -MA and -MA are microporous sponge packing box can control the gas regulating components effectively, prevent the excessive accumulation of CO2, Paul Certificate of lettuce in normal respiration, avoid anaerobic respiration. But the gas exchange will be accompanied by the loss of water and heat exchange, sponge -MA and microporous -MA treatment will improve lettuce weight loss rate, at the same time, slightly weaken the effect of temperature control temperature control package. -MA treatment in maintaining the relative conductivity of sponge, reducing superoxide production the rate of increase of PPO and POD activity, and microporous -MA treatments were the same (P0.05), but it can maintain the low rate of weight loss and higher Vc, chlorophyll content, good color, texture, shape, overall preservation effect is better.4, this chapter takes the typical double temperature control packaging corrugated box set foam box as the research object, through the calculation of temperature control packaging system resistance, considering its heat and coolant phase change and after the heating process, the heat transfer for steady-state coolant phase change theory The unsteady heat transfer process of heat transfer process and after heating box are analyzed, established time temperature control temperature control package estimation model. At the same time, adding the weight of different coolant simulation under normal temperature fresh-keeping test pointed lettuce, monitor the temperature change in the box, verify the estimation model. The experimental results show that in different cold storage the amount of estimated value of the model and the actual temperature time relative deviation of the -9.68%~6.45% deviation factor (Bf) was 1.021, the accuracy factor (Af) was 1.06, are close to 1, is within the acceptable range in practical application. The temperature time temperature control package at room temperature logistics condition to estimate the proposed model can accurately predict the environment under constant temperature. To sum up, in the normal logistics process, temperature control package on physiological activities of lettuce, affect the nutritional quality has obvious phase, late in the logistics process, The O2 gas consumption, accumulation of CO2 damage is the main factor restricting its preservation effect. Synergistic pretreatment technology and modified atmosphere to improve the way of lettuce in the preservation of normal logistics has a better enhancement effect. The advantage of the pre cooling composite heat treatment combined with two kinds of pretreatment, the preservation effect is better than that of pre cold or heat treatment, can effectively delay the physiological metabolism of lettuce, but can not avoid the delay of anaerobic respiration. The gas composition of modified atmosphere method can effectively adjust the temperature control box, ensure the lettuce normal respiration, while avoiding the occurrence of anaerobic respiration, but also slightly weakened the effect of temperature control temperature control packaging, improve the weight loss rate of lettuce tip, better preservation effect of hole filled with nano sponge sponge -MA. The overall estimate time to establish a typical double temperature control temperature control package based on form The model can accurately estimate the temperature control time of temperature control packaging in normal temperature logistics process. These three improved methods have certain application value, and also have some reference significance in other leafy vegetables or high breathing rate agricultural products logistics preservation.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TS255.3;TS206

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