干制对淀粉特性及其制品品质的影响

干制是淀粉原料及其制品加工的常用手段。淀粉原料（块根、块茎、籽粒等）通过干制预处理,不仅便于安全保藏和后续加工,而且显著提高了淀粉提取率和加工适性。在淀粉基食品（粉条、粉丝、虾味片等）生产中,干燥是必要环节,对产品品质有决定性作用。干制过程复杂,涉及水分迁移、热量传递以及其他物理化学变化（如淀粉分子链重结晶、淀粉与其他共存成分相互作用）,这使生产中干制的经验性仍多于科学性。因此,作者全面总结和分析了干制对原料中淀粉特性以及淀粉基食品品质的影响及规律,为通过选择干制方式及干制条件来改善淀粉原料加工适性及干制淀粉基食品的品质提供参考。     

Effect of hydrocolloid addition and microwave-assisted freeze drying on the characteristics of foamed raspberry puree

Foamed fruit purees can be dried and consumed as snacks. This study compares the characteristics of foamed raspberry puree dried via microwave-assisted freeze drying and conventional freeze drying. The effect of potato protein (PP) (as a foaming agent), maltodextrin (MD) (as a foam stabilizer), and microwave power on the product characteristics was investigated. The puree contained 18%–20% higher content of anthocyanins and ascorbic acid than unprocessed raspberries. The retention of ascorbic acid and anthocyanins increased with increasing concentrations of MD and PP. Both drying methods resulted in 66%–81% retention of ascorbic acid and 53%–84% retention of total anthocyanins. The higher drying rates obtained at higher maltodextrin concentrations resulted in higher ascorbic acid and anthocyanin retention. The total color difference was significantly higher for the foam with 30% MD (w/w) at 2.0 W g⁻¹, accounting for the formation of hot spots. Protein concentration did not have a considerable effect on product color. Increasing the maltodextrin concentration yielded a harder foam structure, while increasing the protein concentration had the opposite effect. Overall, microwave-assisted freeze drying was found to be a promising alternative to conventional freeze drying, as it offers a more efficient drying process with comparable product quality.     

Food structure: Its formation and relationships with other properties

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food.     

Performance of Drying Technologies to Ensure Microbial Safety of Dried Fruits and Vegetables

Dried fruits, vegetables, herbs, and spices are produced in and sourced from many countries worldwide, but they have been increasingly reported to be involved in outbreaks and alerts due to the presence of foodborne pathogens such as Salmonella. These dried products are mainly produced by solar drying and conventional air drying, but a wide range of drying technologies are available. From a technological point of view the general trend is to optimize and standardize the drying process to ensure high‐quality products to be offered. Drying technologies are mainly evaluated for their performance to reduce water activity at low energy cost while maintaining good sensorial quality of the dried product. However, as low water activity foods are increasingly recognized to support microbial survival and dried products are often consumed as they are, or are used as ingredients in many ready‐to‐eat foods, there is increasing attention to the microbiological quality and safety aspects of these products. This review presents traditional and emerging technologies to dry fruits, vegetables, herbs, and spices and discusses their potential to inactivate bacteria and viruses throughout the drying process. Overall, the microbial inactivation effect of the presented technologies has not yet been thoroughly assessed, even for traditional methods like solar drying, conventional air drying, or freeze‐drying. Emerging technologies such as dielectric (assisted) drying and low‐pressure superheated steam drying have been shown to reduce microbial populations; however, the number of studies is still low. Very few studies have focused on viral inactivation during drying processes.     

挂面干燥工艺过程研究进展及展望

干燥是挂面生产中较难控制的工序,干燥工艺不合理易造成产品质量问题和能源浪费。目前,挂面生产装备水平已有很大提高,已具备现代食品工业的雏形。但是在干燥环节依然存在控制粗放、热能消耗偏高、产品质量不稳定的现象。针对目前挂面干燥生产面临的技术需求,本文综述了挂面干燥原理、干燥工艺、影响因素、过程控制及节能技术的研究现状及面临的问题,探究挂面干燥可能的发展模式和面临的技术难题,提炼存在的学术和工程问题,理清进一步研究的思路,以期为挂面生产管理、节能控制、工艺升级提供指导。     

哈密瓜切片热风干燥特性及数学模型

目的:提高规模化生产的哈密瓜品质,缩短干燥周期。方法:以不同漂烫时间(0.5,1.0,1.5,2.0,2.5 min)、浸渍液(0.1%,0.2%,0.3%,0.4%,0.5%柠檬酸溶液)预处理哈密瓜切片,并分别研究不同热风温度(35,45,55,65,75℃)、热风速度(0.5,1.0,1.5,2.0,2.5 m/s)和切片厚度(2,4,6,8,10 mm)条件下的哈密瓜切片热风干燥特性和水分扩散系数,拟合不同薄层干燥数学模型。结果:0.4%柠檬酸预处理后得到品质最优的干制产品,热风温度和切片厚度对切片干燥影响较为显著,哈密瓜切片无恒速干燥阶段,有效水分扩散系数为1.1348×10^-7~4.9080×10^-7 m²/s,活化能为28.15 kJ/mol。结论:哈密瓜切片的最佳热风干燥工艺为热风温度55℃、热风速度2.0 m/s、切片厚度6 mm,Page模型具有最高的R²值和最小的均方根误差,更适于评估和预测哈密瓜热风干燥的水分去除规律。     

热风-远红外联合干燥肉脯的工艺优化及其品质研究

为提高肉脯品质,本文研究了不同干燥技术对肉脯品质的影响,以水分含量、剪切力、色差和质构为指标,通过单因素和正交试验优化热风-远红外联合干燥肉脯的工艺条件,确定干燥模型,并对比分析微波、热风、远红外干燥技术对肉脯品质的影响。结果表明:热风-远红外联合干燥肉脯的最佳工艺为:第一段热风干燥温度Ⅰ170℃,第二段热风干燥温度Ⅱ 250℃,第三段红外烤制温度Ⅲ 260℃,干燥100 s,制得肉脯的水分含量低(13.54±0.48) g/100 g,嫩度高,易咀嚼,符合Modified Henderson and Pabis干燥模型(R²=0.9976);与微波干燥、热风干燥和远红外干燥相比,热风-远红外联合干燥的肉脯品质最佳,改善了产品的感官质量,水分含量、剪切力、硬度、咀嚼性、L^*值和a^*值分别是热风干燥的92%、55%、60%、46%、109%和121%,胶粘性和b^*值无显著差异。该研究为肉脯的干燥加工提供了理论依据。     

A novel infrared freeze drying (IRFD) technology to lower the energy consumption and keep the quality of Cordyceps militaris

A novel laboratory scale apparatus using infrared lamps replacing the electric heating plate for the freeze drying of Cordyceps militaris was developed in this study. The drying time, energy consumption, nutritional properties, antioxidant activities and main volatile compounds of Cordyceps militaris dried by infrared freeze drying (IRFD) and traditional freeze drying (TFD) at different drying temperatures (40, 50, 60 and 70 °C) were compared. Results indicated that drying at 40, 50 and 60 °C resulted in higher retention of cordycepin, total phenolics, hydroxyl radical scavenging activity, reducing power, 3-octanone, 3-octanol and 1,3-octadiene when compared with those dried at 70 °C. IRFD could reduce 7.21–17.78% of the drying time and 11.88–18.37% of the energy consumption at a constant drying temperature in comparison of TFD. In terms of quality, IRFD and TFD had similar retention effects on cordycepin, adenosine, hydroxyl radical scavenging activity and reducing power. Consequently, the results suggest that IRFD should be a promising approach for achieving high-quality dried products.Industrial relevance.IRFD could reduce 7.21–17.78% of the drying time and 11.88–18.37% of the energy consumption at a constant drying temperature in comparison of TFD without compromising the quality of the dried product. This study can help food processing industries to produce high quality freeze dried Cordyceps militaris and many other foods with an energy efficient freeze drying process.     

不同香菇干燥方式的干燥特性和干品品质对比研究

干制香菇是延长香菇保质期的有效方式之一,采取三种单一干燥方法和两种组合干燥方法对香菇进行干燥处理,研究了香菇干燥过程中的干燥动力学特性和干制品品质的变化。实验结果表明:从干燥效率和失水速率来看,三种干燥方法从优到次依次为热风干燥、普通烘箱干燥、真空干燥;从干制品外形品质来评价,从优到次依次为真空干燥、热风干燥、普通烘箱干燥。而真空与热风联合干燥香菇是有应用价值的,联合干燥后的干香菇产品品质远优于热风干燥,且比单一的真空干燥缩短干燥时间。      

基于Weibull分布函数的双孢菇热泵干燥特性研究

为提升双孢菇干制品品质,采用热泵式冷风干燥对双孢菇进行脱水处理,以双孢菇热风干燥和冷冻干燥为参照实验,对不同热泵式冷风干燥条件下(进口风速、干燥温度)双孢菇的干燥耗时、干燥能耗、产品硬度以及产品白度进行研究;利用Weibull分布函数对双孢菇热泵式冷风干燥过程中的水分扩散机制进行分析;基于干燥效率指标和产品品质指标,采用加权综合评分法对双孢菇热泵式冷风干燥过程进行评价。实验表明:加快进口风速干燥耗时最小值比最大值降低9.09%,提升干燥温度干燥耗时最小值比最大值降低27.27%;干燥温度对双孢菇热泵式冷风干燥能耗、产品硬度和产品白度影响更为显著(p<0.05);Weibull分布函数能够准确描述(R²>0.99)双孢菇热泵式冷风干燥过程,不同干燥条件下双孢菇冷风干燥的形状参数均小于1,整个干燥主要受内部水分扩散控制;相对于冷冻干燥,双孢菇热泵式冷风干燥耗时及能耗分别降低了50%和26.35%;而相对于热风干燥,冷风干燥技术将双孢菇干制品的产品硬度降低13.44%,同时干制品产品白度提升了59.92%;实验操作条件范围,双孢菇冷风干燥最佳干燥条件为25 ℃干燥温度和2 m/s进口风速。结论:热泵式冷风干燥技术能够提升双孢菇干制品品质同时降低干燥耗时和能耗。     

Fruit snacks from raspberries: influence of drying parameters on colour degradation and bioactive potential

Raspberries were dehydrated using air and freeze‐drying with wet and dry sugar infusion pretreatments. Product quality factors such as colour, bioactive compounds, antioxidant capacity and sensorial characteristics were analysed. Special emphasis was placed on the analysis of anthocyanin degradation and its relationship with colour deterioration and with polymeric compounds development and browning. Freeze‐dried raspberries presented a higher retention of bioactive compounds and a lower content of polymeric compounds than air‐dried ones. Dried samples without pretreatment (control) showed the highest retention of total phenolic content (freeze‐dried ≈82% and air‐dried ≈37% retention), but the lowest sensory acceptability. Although sugar infusion pretreatments caused an important loss of bioactive compounds (9–18% of TPC retention), a higher sensorial acceptability was obtained. Pretreatments with bisulphite and acid allowed obtaining the best quality attributes in terms of anthocyanin and polyphenol content, antiradical activity and colour retention. Polyphenol intake through pretreated dried raspberries (115–299 mg gallic ac./100 g intake) would be higher in some cases than that of usually consumed foods as vegetables, cereals and several fresh fruits.     

High power airborne ultrasound assist in combined drying of raspberries

A new approach to fruit drying with the application of ultrasound to enhance convective and combined convective–microwave drying is presented. High-power ultrasound was used in the experimental studies, in which the acoustic energy significantly affected the drying of sensitive biological material like raspberries. The raspberries were first subjected to pure convective drying as a reference process and then to hybrid drying as a combination of convective, microwave and ultrasound drying methods. The combined hybrid processes significantly improved the drying kinetics as well as the energy utilization, however, not in each case given the acceptable product quality in comparison with the pure convective drying. The global model of drying was used to compare the theoretical drying kinetics with the experimental one. Moreover, the effectiveness of ultrasound-assisted convective drying was evaluated in terms of drying rate and such ultrasound phenomena as “heating effect”, “vibration effect” and “synergistic effect” were analyzed.Industrial relevance1. Research objectivesProduct quality is a very important indicator that enables to assess the effectiveness of the drying process. For biological materials such as vegetables and fruits, that are characterized by instability and a delicate and sensitive internal structure to temperature, quality is a priority because it determines the functional value of these products. The traditional drying techniques, eg. convective drying, affect negatively on the final quality of dried biomaterials. Due to long exposure to a relatively high temperature and a high content of harmful oxygen in the drying agent, there is a change in the internal structure, deterioration of the sensory properties (color, aroma, texture) and changes in chemical composition (loss of bioactive components). One of the recommended modes to minimize these adverse changes is to carry out the drying process in non-stationary conditions. This method is based on the periodical changes in the process parameters such as temperature, humidity or flow rate. As a result, product quality is definitely better, at approximately the same drying time. Alternatively, drying may be carried out by hybrid method, providing the energy by a combination of several mechanisms, such as convection with microwave radiation, or with ultrasounds, which also leads to a significant improvement in quality of dried fruits and vegetables.The purpose of this article is a deep analysis of the effect of variable hybrid drying conditions, ie. cyclic supply of microwave and ultrasound energy during convective drying on a variety of properties of dried biomaterials. The research assumes that if drying results in changes of the biological material properties, a modification of the process parameters should minimize its negative effects and gain better quality products. The authors believe that a proper and skillful combination of different drying techniques will develop an optimal and effective drying method of thermo-labile materials, which retains their high quality, with reduced time and lower power consumption. Therefore, it is necessary to optimize the convective drying with microwave and ultrasound enhancement, in order to select the best process parameters for the established objective functions.2. Research project impactThe experimental results will contribute to the development of modern drying technologies of biological materials, characterized by, eg.:

• •much better and more controlled product quality (low level of processing),
• •much shorter process time resulting from the intensification of heat and mass processes due to additional sources of energy (microwaves and ultrasounds),
• •lower energy consumption resulting from the possibility of carrying out the drying process at much lower temperatures of the drying agent.

The expected results of the drying tests relate to the development of research activities in this field and to link a cooperation between science and industry. The effective transfer of new solutions in the field of chemical engineering and technology between science and industry is a hope of improving the quality of dried products, as well as the rational use of raw biomaterials (to prevent their losses from reaching about 50% of produced foods). The proposed drying method will also have a positive value for consumers and contribute to the reduction in influence of that branch of industry on the environment. In the consideration of the increasing demands of product quality, the need for better control of unit processes and minimization of its energy intensity, this new technique would be extremely competitive with currently used, expensive and environmentally damaging drying methods.     

气调与热风干燥对毛竹笋干燥速度与干制品品质的影响

以提高毛竹笋干燥速度与干制品品质为目的,采用QTM实验设备进行气调与热风干燥对比试验,分析表明:脱水过程中的干燥速度及干制品品质的一系列变化,气体的含氧量是一重要影响因素。采用气调方式,降低干燥过程中的气体含氧量可明显提高竹笋干燥速度及干制品品质。在干燥室气体的氧气含量相同状态下,毛竹笋采用充二氧化碳降氧干燥更为理想。     

黎豆荚高温高湿干燥工艺的研究

采用高温高湿干燥技术生产干制黎豆荚,研究干燥条件对干制黎豆荚品质的影响,确定适宜的干燥条件,为干制黎豆荚的工业化生产提供实验依据。结果表明,适宜的相对湿度可以改善干制黎豆荚的色泽、形状和复水率。黎豆荚干燥的最佳工艺条件为:采用三段式干燥工艺,前期干燥温度80℃,相对湿度55%,干燥时间30min;中期干燥温度80℃,相对湿度35%,干燥时间30min;后期干燥温度80℃,相对湿度25%,干燥时间155min,用此条件生产的干制黎豆荚产品褐变小,收缩率低(约48%),最终含水量约为7.4%,复水后色泽鲜艳,口感脆嫩。      

Microwave‐Osmotic/Microwave‐Vacuum Drying of Whole Cranberries: Comparison with Other Methods

A novel drying method for frozen‐thawed whole cranberries was developed by combining microwave osmotic dehydration under continuous flow medium spray (MWODS) conditions with microwave vacuum finish‐drying. A central composite rotatable design was used to vary temperature (33 to 67 °C), osmotic solution concentration (33 to 67 °B), contact time (5 to 55 min), and flow rate (2.1 to 4.1 L/min) in order to the determine the effects of MWODS input parameters on quality of the dried berry. Quality indices monitored included colorimetric and textural data in addition to anthocyanin retention and cellular structure. Overall it was found that the MWODS‐MWV process was able to produce dried cranberries with quality comparable to freeze dried samples in much shorter time. Additionally, cranberries dried via the novel process exhibited much higher quality than those dried via either vacuum or convective air drying in terms of color, anthocyanin content, and cellular structure.     

Catalytic Infrared Dehydration of Onions

ABSTRACT:  Dehydrated onions are commonly dried with convection heating, which is inefficient and costly. This study compared the drying and quality characteristics of onion dried with catalytic infrared (CIR) heating and forced air convection (FAC) heating. Sliced high-solids onions were dehydrated under 9 conditions: CIR heating with and without air recirculation, and FAC each operated at 60, 70, and 80 °C. In general, CIR both with and without air recirculation had higher maximum drying rates, shorter drying times, and greater drying constants than FAC at moisture contents greater than 50% (d.b.). Dried onion quality, measured as pungency degradation, was similar for both the drying methods at 60 and 70 °C. The color analysis showed better product color (whiter and less yellow) at lower temperatures for CIR and higher temperatures for FAC. The browning could have been caused by the higher surface heat flux of the CIR heating and longer process times of FAC drying. Aerobic plate counts and coliform counts were not significantly different for either product from the CIR or FAC drying. However, samples dried by the CIR had significantly lower yeast and mold counts than those dried by the FAC. It is recommended that CIR be used in the early stages of onion drying.     

Effects of vacuum and microwave freeze drying on microstructure and quality of potato slices

Potato slices immersed in 0.5% CaCl₂ solution for 10 min were examined using light microscopy for their microstructure in frozen state before drying, during the sublimation drying stage, in the desorption drying stage and in the final dried form. Additionally, the final dried product was also tested for vitamin C content, color, starch content, texture and sugar content. Experiments were carried out using conventional vacuum freeze dryer as well as a microwave freeze dryer. Results for both unblanched and blanched potato tissues, crystal growth during sublimation drying stage was observed to cause structural damage to the cell walls. Blanched tissue suffered more damage during the freezing process. Interestingly, microwave freeze drying yielded product similar in quality to that obtained in vacuum freeze drying with conductive heating.     

冰温真空干燥压力对猕猴桃切片干燥品质的影响

以去皮的猕猴桃切片为试材,利用冰温真空干燥技术对其进行脱水处理,研究不同干燥压力(150、350、550 Pa)对猕猴桃切片的干燥速率及干燥后品质的影响。结果表明,冰温真空干燥技术可以最大限度的降低营养物质的损失。干燥压力为350 Pa时的干制品品质最好,猕猴桃切片的失水率和糖度分别为70.6%和24.5%,而复水比、V_C含量、色差值分别为4.75、110 mg/(100 g)和20.35。表明冰温真空干燥技术具有良好的应用前景。      

不同干燥方式对铁棍山药品质的影响

以外观、营养成分、复水性及超微结构为指标,比较4种不同的干燥方式对铁棍山药品质的影响。冻干(FD)对铁棍山药品质的保留最好,冻干真空微波联合干燥(FD-MVD)对产品品质的保留接近于FD,且能够使干燥时间缩短31%。微波真空干燥时间最短,但品质不如前两种干燥方式。热风干燥(AD)对感官品质和维生素C破坏较多,但对于多糖含量的保持与其它方法无异。超微结构的结果表明,MVD和AD对结构破坏较多,而FD和FD-MVD很好的保持了原有的细胞结构。     

不同干燥方式对双孢蘑菇干制品质量的影响

对双孢蘑菇进行热风、真空和真空冷冻干燥的对比实验,建立了3种干燥方式下物料的干燥曲线,测定干制品Vc含量、复水比和感官质量。结果表明:从干燥效率和干制品Vc含量看,真空干燥>真空冷冻干燥>热风干燥;从复水比看,真空冷冻干燥>真空干燥>热风干燥,其中真空冷冻干燥的干制品感官质量最好。对干制品进行护色和复水实验,结果显示干制品护色质量好于不护色,复水时间直接影响复水程度,最佳复水时间为40min。