Concentration of apple and pear juices in a multi-plate freeze concentrator

In this article we will examine the process for concentration of apple and pear juices as well as concentration of sugar solutions modelling pear juice (simulation fluid) using a descending film multi-plate freeze concentrator. It has been determined in advance the freezing point of those fluids in the working concentration and temperature intervals. In addition, different parameters were studied to allow tracking of the process of freeze concentration, such as ice accumulation, variation of the content of soluble solids in the solution and in the ice removed, ice production and energy consumption. The apple and pear juices tested showed similar behaviour, while the mixture of sugars used for simulation showed better behaviour, due perhaps to the absence of foam in the process and to the quicker formation of ice. It has been obtained concentrations of 30.2 and 30.8 °Bx with the apple and pear juices, respectively, and up to 32.7 °Bx with the simulation fluid.Industrial relevanceThe clarified juices usually are concentrated on an evaporation stage. In this stage the juice is subjected to high temperatures that cause undesirable reactions, such as non enzymatic browning and destruction of nutritive compounds. The freeze concentration is a technology that allows eliminating water from the juices at temperatures below the water’s freezing point, what allows obtaining products of better quality. In this work has been applied this technology to concentrate apple and pear juices, obtaining promissory results.     

Calculation method for designing a multi-plate freeze-concentrator for concentration of fruit juices

The aim of this work is to establish a calculation method for designing and sizing of equipment for film freeze-concentration of fruit juices. The various steps are outlined of an algorithm that uses the characteristics of the juice as inputs.The calculation method assumes that the amount of fruit juice, its concentration (^°Brix), and its sugar composition (% of fructose, glucose and sucrose) are known. Using pre-set (constant) values for the flow of concentrated juice and for the heat flow, the algorithm predicts the values of the main unknowns: the concentration of impurities in the ice, the concentration of sugars in the final concentrate, the heat-exchange surface needed, the amount of ice obtained, and the duration of the concentration step.Using this calculation method, one can estimate the size of the equipment and its operational costs, which can be used to analyse the economic viability compared to alternative processes.     

果汁冷冻浓缩中生物冰核的成冰作用及初步应用

介绍了冰核细菌促进成冰的机制,并结合国外有关报道和我们的研究结果,论述了冰核细菌在食品冷冻浓缩中导致冰晶形成的结构、冷冻效率、应用前的预处理及食用级冰核细菌在果汁中的应用情况,最后展望了未来的研究方向。     

冷冻(冰晶)浓缩法在谷氨酸发酵液提取中的应用与研究

用冷冻浓缩工艺对谷氨酸发酵液进行浓缩实验,准确分析温度、pH值、结晶时间、搅拌操作等因素对冰结晶浓缩分离效果的影响,由此确定最适合于谷氨酸的冷冻浓缩等电点的条件.     

Improving tomato juice concentration process through a novel ultrasound-thermal concentrator under vacuum condition: A bioactive compound investigation and optimization

We investigated the simultaneous effects of temperature, ultrasound, and vacuum pressure in the tomato juice concentration process. To this end, a novel ultrasound-thermal concentrator under vacuum conditions was fabricated. The process was performed at three levels of ultrasound power (48, 84, and 120 W), three vacuum pressures (10, 20, and 30 kPa), and three temperatures (50, 60, and 70 °C). Also, ultrasound effects were investigated using other experimental setups without ultrasound. We obtained the optimal conditions for the tomato juice concentration process through the ultrasound-thermal method with ultrasound power of 120 W, the vacuum pressure of 10 kPa, and at 64 °C also by the thermal method were obtained at 65.5 °C and a vacuum pressure of 10 kPa. Overall, applying ultrasound in tomato juice concentrating had positive effects such as reducing the concentration time (28.42%) and total energy consumption (4.94%), as well as increasing the lycopene (49.20%) and vitamin C contents (22.10%).     

一种连续冷冻浓缩装置及其应用分析

介绍了一种基于界面渐进原理的新型连续式冷冻浓缩装置。该装置通过将制冷过程和浓缩过程有机结合,具有结构简单、调控性强、适用料液广、能源效率高等优点。初步分析表明该装置从料液中除去1t水的电能消耗低于5kW·h,在果蔬汁浓缩、海水淡化等领域均具较强的市场竞争力。     

Progressive freeze concentration of orange juice in a pilot plant falling film

In the present study the cryoconcentration of orange juice was investigated, using a pilot plant unit for cryconcentration of liquids using a cold surface. The evolution in time of the concentration of solids in the juice and in the ice was analyzed during the process. It was found that the concentration of solids in the juice showed a linear increase in time at a rate of 0.75 °Brix/h until a final concentration of 28.8 °Brix. The concentration of solutes in the ice showed an exponential increase.Industrial relevanceThe freeze concentration allows dewatering orange juice at temperatures below the water's freezing point, which allows obtaining products of better quality. The freeze concentration is a technology that allows eliminating water from the juices at temperatures below the water's freezing point, which allows obtaining products of better quality. This work has applied this technology to concentrate orange juice, obtaining promissory results.     

国内外冷冻浓缩的应用及研究进展

简要地介绍了冷冻浓缩的原理,对国内外应用现状及研究进展进行了阐述,并展望了未来的发展趋势.     

Estimation of the freezing point of concentrated fruit juices for application in freeze concentration

In freeze concentration operations the fluids remain at temperatures below 0 °C. For a good study of this concentration operation is very important to know the values of freezing point. The aim of this work was to establish a model that predicts the freezing point of fruit juices at various concentrations within the range of interest for freeze concentration (10-40 °Brix). The model proposed relates the freezing point of a juice with the concentrations of main sugars present in the juice: sucrose, glucose and fructose. The freezing point of apple juice, pear juice and peach juice was determined experimentally at various concentrations, and experimental results were well correlated with model calculations.     

基于体积增量表征的冷冻浓缩进程的数学模型及试验验证

建立了基于物料容积变化所关联的溶液结晶率、用于表征冷冻浓缩进程的数学模型。在一台多级冷冻浓缩试验装置上通过溶液冷冻浓缩试验和海水脱盐试验,测量了液柱高度与溶液浓度和溶液结晶率的对应关系,并与模型预测值作了比较和验证且吻合度较高,溶液结晶率误差在5%以内。     

Improving the nutritional and phytochemical compounds of a plant-based milk of sapucaia nut cake using block freeze concentration

The nutrient profile and the phytochemical composition of the sapucaia nut cake milk (SNCM) were evaluated after applying five consecutive stages of block freeze concentration (C1, C2, C3, C4 and C5). The profile of phenolic compounds by LC-ESI-MS/MS and the antioxidant activity (ABTS and FRAP) of SNCM were also determined. The freeze concentration increased proteins, lipids, carbohydrates, ash, soluble solids (°Brix) and total phenolic compounds (TPC) in all stages and in the ice fractions obtained from C1, C2 and C3 stages. The antioxidant activity (ABTS) in C3, C4 and C5 fractions was highly significant (P < 0.05). The antioxidant activity (FRAP) and the phenolic compounds (gallic, vanillic, ferulic, sinapic and salicylic acids, catechin, taxifolin and sinapaldehyde) increased significantly (P < 0.05) for all five fractions. The freeze concentration was successfully used for enriching the SNCM, generating a promising ingredient for the food industry.     

真空冷冻喷雾干燥下川藏高原冰酒发酵菌剂复合保护剂的配方优化

将冰葡萄渣中分离得到的酿酒酵母,经真空冷冻喷雾干燥制成菌剂,通过单因素和正交实验优化保护剂配方,并对该菌剂进行性能分析。结果表明:复合保护剂最佳配方为甘油5%,蔗糖7%,脱脂乳粉11%,麦芽糊精15%,菌剂产品活菌数和活菌率分别为10.34 CFU/g和78.25%。在此最佳配方条件下,该冰酒发酵菌剂各项性能较优,其颗粒表面光滑平整,具有较强的耐热性和低温稳定性,在10 ℃下能发酵产气,其发酵性能优于市售酿酒酵母。     

苇浆碱回收工艺及设备的优化

介绍了岳阳丰利纸业有限公司苇浆碱回收工艺及设备优化情况。     

Beeswax organogels: Influence of gelator concentration and oil type in the gelation process

This work focused on how different types of oil phase, MCT (medium chain triglycerides) and LCT (long chain triglycerides), exert influence on the gelation process of beeswax and thus properties of the organogel produced thereof. Organogels were produced at different temperatures and qualitative phase diagrams were constructed to identify and classify the type of structure formed at various compositions. The microstructure of gelator crystals was studied by polarized light microscopy. Melting and crystallization were characterized by differential scanning calorimetry and rheology (flow and small amplitude oscillatory measurements) to understand organogels' behaviour under different mechanical and thermal conditions. Fourier transform infrared spectroscopy (FTIR) analysis was employed for a further understanding of oil-gelator chemical interactions. Results showed that the increase of beeswax concentration led to higher values of storage and loss moduli (G′, G″) and complex modulus (G*) of organogels, which is associated to the strong network formed between the crystalline gelator structure and the oil phase. Crystallization occurred in two steps (well evidenced for higher concentrations of gelator) during temperature decreasing. Thermal analysis showed the occurrence of hysteresis between melting and crystallization. Small angle X-ray scattering (SAXS) analysis allowed a better understanding in terms of how crystal conformations were disposed for each type of organogel. The structuring process supported by medium or long-chain triglycerides oils was an important exploit to apprehend the impact of different carbon chain-size on the gelation process and on gels' properties.     

Control of ice crystal nucleation and growth during the food freezing process

Freezing can maintain a low-temperature environment inside food, reducing water activity and preventing microorganism growth. However, when ice crystals are large, present in high amounts, and/or irregularly distributed, irreversible damage to food can occur. Therefore, ice growth is a vital parameter that needs to be controlled during frozen food processing and storage. In this review, ice growth theory and control are described. Macroscopic heat and mass transfer processes, the relationship between the growth of ice crystals and macroscopic heat transfer factors, and nucleation theory are reviewed based on the reported theoretical and experimental approaches. The issues addressed include how heat transfer occurs inside samples, variations in thermal properties with temperature, boundary conditions, and the functional relationship between ice crystal growth and freezing parameters. Quick freezing (e.g., cryogenic freezing) and unavoidable temperature fluctuations (e.g., multiple freeze–thaw cycles) are both taken into consideration. The approaches for controlling ice crystal growth based on the ice morphology and content are discussed. The characteristics and initial mechanisms of ice growth inhibitors (e.g., antifreeze proteins (AFPs), polysaccharides, and phenols) and ice nucleation agents (INAs) are complex, especially when considering their molecular structures, the ice-binding interface, and the dose. Although the market share for nonthermal processing technology is low, there will be more work on freezing technologies and their theoretical basis. Superchilling technology (partial freezing) is also mentioned here.     

食品真空冻干技术市场前景广阔

本文介绍了真空冷冻干燥食品的发展现状、特点及其工艺流程,着重讨论了发展冻干食品工业的广阔前景.     

The effect of resuscitation and the incubation-temperature on recovery of uninjured, heat injured and freeze injured enterococci.

Five strains of enterococci were inoculated on the Slanetz and Bartley enterococcus agar (EA), and incubated at 37 degrees C and 44 degrees C following: no injury, heat-injury and freeze-injury. The experiments were repeated introducing a 2 h resuscitation step in Tryptic Soy Agar (TSA) at 37 degrees C and subsequent overlay with EA (TSA/EA) followed by incubation at both 37 degrees C and 44 degrees C. The TSA/EA method gave a significantly better recovery (1% confidence level) than the EA method at both 37 degrees C and 44 degrees C. The effect of incubation-temperature was only significant for two strains of Enterococcus durans, as one strain showed no growth at 44 degrees C and the other strain was recovered significantly (5% confidence level) better at 37 degrees C that at 44 degrees C when employing the EA method. Interpretation of the results using TSA/EA method was easier than that of the EA. Different lactic streptococci and lactobacilli commonly employed in the dairy industry did not develop false positive colonies in TSA/EA incubated at 37 degrees C.