Recent developments in high-quality drying of vegetables,fruits, and aquatic products

Fresh foods like vegetables, fruits, and aquatic products have high water activity and they are highly heat-sensitive and easily degradable. Dehydration is one of the most common methods used to improve food shelf-life. However, drying methods used for food dehydration must not only be efficient and economic but also yield high-quality products based on flavor, nutrients, color, rehydration, uniformity, appearance, and texture. This paper reviews some new drying technologies developed for dehydration of vegetables, fruits, and aquatic products. These include: infrared drying, microwave drying, radio frequency drying, electrohydrodynamic drying, etc., as well as hybrid drying methods combining two or more different drying techniques. A comprehensive review of recent developments in high-quality drying of vegetables, fruits and aquatic products is presented and recommendations are made for future research.     

Encapsulation for preservation of functionality and targeted delivery of bioactive food components

There has been a tremendous increase in the number of food products containing bioactive components with a health promoting or disease preventing effect. Bioactive food components can be divided into bioactive molecules and bioactive living cells (probiotics). Both bioactive molecules and bioactive living cells may benefit from encapsulation since many report low survival of bioactivity due to adverse effects of (i) processing and storage in the products that serve as vehicles and due to (ii) deleterious circumstances during transport through the gastrointestinal tract. For probiotics, it may even be mandatory to apply protection by encapsulation as the survival of probiotics in traditional products such as in dairy foods and powdered formulas is low. Encapsulation promotes not only viability but more importantly also protects the functionality, and may facilitate targeted release in specific parts of the gut. Different encapsulation approaches qualify for protection of bioactive food components. The most commonly applied technologies are emulsification, coacervation, spray drying, spray cooling, freeze drying, fluid bed coating and extrusion technologies, but also more expensive techniques such as liposome encapsulation, and cyclodextrin encapsulation are used. When targeted release is desired in combination with adequate protection in the product, it is essential to realize which processes in the human gut can be applied to facilitate targeted release. The majority of systems that have been used in the past were either sensitive to mechanical stress, pH, or transport time variations in the gut. More recent systems take advantages of the different enzyme concentrations associated with variations in the composition of the microbiota in different parts of the gut. The latter system should receive more attention in the food industry as it allows for precise release of bioactive food components. The principle of targeted release by enzymatic activity of the microbiota is compatible with many carbohydrates that are generally regarded as safe (GRAS).     

Impact of varying hydrocolloid proportions on encapsulation of ascorbic acid by spray drying

There has been considerable research into ascorbic acid (AA) as a food component in the human diet and disease prevention. Microencapsulation technology has a promising strategy for enhancing the stability of AA towards the carrier food. The effects of varying hydrocolloid proportions on encapsulation of AA by spray drying have been evaluated. Spray drying pilot plant scale was used to produce the microcapsules, and capillary electrophoresis has been applied to analyse the retention of AA during bread making process. To investigate the characteristics of microstructure of encapsulated AA after processing, the environmental scanning electron microscope was used to investigate the structure of microcapsules. In addition to that to measure the particle size and distribution of microcapsules, the laser beam scattering was used. The impact of varying hydrocolloids proportion on encapsulation of AA by spray drying was studied.     

Survival of Microencapsulated Probiotic Bacteria after Processing and during Storage: A Review

The use of live probiotic bacteria as food supplement has become popular. Capability of probiotic bacteria to be kept at room temperature becomes necessary for customer's convenience and manufacturer's cost reduction. Hence, production of dried form of probiotic bacteria is important. Two common drying methods commonly used for microencapsulation are freeze drying and spray drying. In spite of their benefits, both methods have adverse effects on cell membrane integrity and protein structures resulting in decrease in bacterial viability. Microencapsulation of probiotic bacteria has been a promising technology to ensure bacterial stability during the drying process and to preserve their viability during storage without significantly losing their functional properties such acid tolerance, bile tolerance, surface hydrophobicity, and enzyme activities. Storage at room temperatures instead of freezing or low temperature storage is preferable for minimizing costs of handling, transportation, and storage. Concepts of water activity and glass transition become important in terms of determination of bacterial survival during the storage. The effectiveness of microencapsulation is also affected by microcapsule materials. Carbohydrate- and protein-based microencapsulants and their combination are discussed in terms of their protecting effect on probiotic bacteria during dehydration, during exposure to harsh gastrointestinal transit and small intestine transit and during storage.     

Spray‐drying for the production of dried cultures

This review emphasises the importance of spray‐drying as an under‐used but promising technique to preserve viable and active starter cultures and also, potentially, probiotic cultures. The knowledge concerning the production of spray‐dried starter cultures is discussed. Different drying techniques and micro‐organisms have been investigated for their survival through the drying process. During drying and subsequent storage in the dried state, bacteria are subjected to several stresses, which have already been described as causing damage to cells, leading to the loss of cellular viability and activity. Some studies found that several factors/strategies can confer improved cellular viability.     

Advances in micro and nano-encapsulation of bioactive compounds using biopolymer and lipid-based transporters

BackgroundBioactive compounds possess plenty of health benefits, but they are chemically unstable and susceptible to oxidative degradation. The application of pure bioactive compounds is also very limited in food and drug formulations due to their fast release, low solubility, and poor bioavailability. Encapsulation can preserve the bioactive compounds from environmental stresses, improve physicochemical functionalities, and enhance their health-promoting and anti-disease activities.Scope and approachMicro and nano-encapsulation based techniques and systems have great importance in food and pharmaceutical industries. This review highlights the recent advances in micro and nano-encapsulation of bioactive compounds. We comprehensively discussed the importance of encapsulation, the application of biopolymer-based carrier agents and lipid-based transporters with their functionalities, suitability of encapsulation techniques in micro and nano-encapsulation, as well as different forms of improved and novel micro and nano-encapsulate systems.Key findings and conclusionsBoth micro and nano-encapsulation have an extensive application, but nano-encapsulation can be a promising approach for encapsulation purposes. Maltodextrin in combination with gums or other polysaccharides or proteins can offer an advantageous formulation for the encapsulation of bioactive compounds by using encapsulation techniques. Electro-spinning and electro-spraying are promising technologies in micro and nano-encapsulation, while solid lipid nanoparticles and nanostructure lipid carriers are exposing themselves as the promising and new generation of lipid nano-carriers for bioactive compounds. Moreover, phytosome, nano-hydrogel, and nano-fiber are also efficient and novel nano-vehicles for bioactive compounds. Further studies are required for the improvement of existing encapsulate systems and exploring their application in food and gastrointestinal systems for industrial application.     

益生菌微胶囊的制备及其在食品中应用的研究进展

益生菌对人体健康有益而被广泛应用于食品领域,但其易受温度、氧气、湿度、压力、胃酸和胆汁盐等不良环境因素影响。为使益生菌在加工、储藏、消化过程中保持高存活率,人们利用不同的微胶囊技术对益生菌进行包埋和保护。益生菌微胶囊技术通过创建一种物理屏障来提高益生菌对不良环境的抗性力,减少保护基质中益生菌的损伤,从而使其到达目标部位顺利释放并发挥作用。文章概述了益生菌的起源、种类及益生功效,重点总结了益生菌微胶囊常用制备方法的基本原理及优缺点,包括挤压法、乳化法、喷雾干燥法、冷冻干燥法、喷雾冷却法、复凝聚法、静电纺丝、电喷雾和撞击气溶胶法,进而重点讨论了益生菌微胶囊技术在乳制品、肉制品、非乳饮料及焙烤制品等食品中的应用优势和可能性。虽然众多研究进行体外模拟消化,但仍存在一定局限性,对于现有的问题,未来仍然需要通过扩大包埋方法、开展体内实验、建立系统性数据库等方法来满足益生菌食品的工业化生产需求,以为开发新型益生菌食品提供理论借鉴和参考。     

复凝聚法鼠李糖乳杆菌微胶囊工艺优化及储藏稳定性

为提高鼠李糖乳杆菌在贮藏过程中的稳定性,以明胶、阿拉伯胶为壁材,采用复凝聚法制备鼠李糖乳杆菌微胶囊。研究以湿态微胶囊的包埋率为指标,考察pH、壁材浓度、转速和菌添加量对复凝聚法微胶囊制备的影响,在单因素试验的基础上进行正交试验,优化最佳工艺。将最优条件下的湿微胶囊进行喷雾干燥和真空冷冻干燥,并在不同水分活度和不同温度条件下研究了喷雾干燥和真空冷冻干燥鼠李糖乳杆菌微胶囊的储藏稳定性。结果表明,pH 3.75、壁材浓度1.5%、转速200 r/min、菌添加量109 CFU,此条件下制备的鼠李糖乳杆菌微胶囊包埋率最高,为93.21%;复凝聚法制备的鼠李糖乳杆菌湿微胶囊干燥后,每克真空冷冻干燥微胶囊的活菌数比喷雾干燥微胶囊高1.9个对数值;储藏时水分活度越低,温度越低,鼠李糖乳杆菌微胶囊的储藏性越好;与喷雾干燥微胶囊相比,储藏时真空冷冻干燥微胶囊在高水分活度下较稳定,且在不同水分活度、不同温度条件下的活性均高于喷雾干燥微胶囊。因此复凝聚法制备的鼠李糖乳杆菌微胶囊真空冷冻干燥后能更好的保护鼠李糖乳杆菌,延长其储藏期。     

Nanoencapsulation Techniques for Food Bioactive Components: A Review

The protection and controlled release of bioactive compounds at the right time and the right place can be implemented by encapsulation. Nanoencapsulation remains to be the one of the most promising technologies having the feasibility to entrap bioactive compounds. Nanoencapsulation of bioactive compounds has versatile advantages for targeted site-specific delivery and efficient absorption through cells. However, researches in the application of nanotechnology in the food industry have been very limited and there are only a few review articles that explored the nanoencapsulation technology. This review focuses on the various nanoencapsulation techniques such as emulsification, coacervation, inclusion, complexation nanoprecipitation, emulsification–solvent evaporation, and supercritical fluid for food ingredients. Drying techniques such as spray drying and freeze drying for stabilization of nanoparticles are also discussed. Current state of knowledge, limitations of these techniques, and recent trends are also discussed. Finally, safety and regulatory issues in the nanoencapsulation of bioactive compounds are also highlighted.     

超声在食品干燥领域中的研究进展

如何快速而经济地干燥物料并获得高品质的产品,是干燥领域需要解决的核心问题。目前传统单一的干燥技术在一些方面已无法满足实际需求,探索各种干燥技术的组合成为近年来的研究热点。功率超声(声强大于1 W/cm_²)作为一种绿色、无污染的物理加工方法,在干燥过程中强化水分的传热和传质方面已显示出独特的优越性,在食品干燥领域方面具有广阔的应用前景。本论文主要介绍了超声在食品干燥前预处理、超声强化渗透脱水、超声耦合热风干燥、超声耦合喷雾干燥、超声耦合冷冻干燥、超声耦合热泵干燥、超声耦合太阳能干燥等方面的研究进展,分析了超声干燥的作用效应及机理,总结了超声干燥的优点并指出目前存在的问题及今后的研究方向。     

Ascorbic Acid: Microencapsulation Techniques and Trends—A Review

Developments in nutritional sciences have increased the functional significance of ascorbic acid (vitamin C) as a food component in the human diet for health promotion and disease prevention. This has motivated food researchers to develop ascorbic acid–fortified food products to deliver appropriate levels of this vital food ingredient. Unfortunately, the highly unstable nature of ascorbic acid has posed technological challenges for its incorporation into different food systems. Microencapsulation is a promising approach to ensure the stability of ascorbic acid and to improve consumer acceptability towards the carrier food. The most commonly used techniques for ascorbic acid (water soluble) encapsulation, including spray drying, spray cooling, spray chilling, fluidized bed coating, liposomes, and extrusion, are reviewed and discussed with respect to technical hurdles and potential benefits.     

Application of Modified Atmosphere Packaging and Active/Smart Technologies to Red Meat and Poultry: A Review

This paper reviews the current advances in modified atmosphere packaging (MAP) of red meat and poultry products. This type of packaging results in shelf-life prolongation by inhibiting microbial growth and promoting oxidative stability, compared to those packaged aerobically. High O₂ modified atmosphere packaging results in the desirable red colour, but it also enhances both lipid and pigment oxidation and promotes the growth of aerobic spoilage microorganisms. The presence of high levels of CO₂ in modified atmosphere packages inhibits microbial growth but can also cause meat discoloration through oxidation. Low O₂ MAP atmospheres limit microbial growth but change the colour of meat to purple. The use of CO gives promising results due to its positive effects on colour and microorganism growth inhibitions which result in shelf-life prolongation during wider distribution of case-ready products. The use of MAP can lead to an effective growth reduction of pathogenic microorganisms like Listeria sp. and Salmonella sp. The combination of MAP and vacuum with other treatments can be an effective tool in delivering safe minimally processed foodstuffs. In response to the changes in consumer demand and market trends, the area of active and intelligent/smart packaging is becoming more and more important. These relatively new technologies are capable of providing better results regarding product safety and shelf-life prolongation as well as communicating information on several quality characteristics of packaged food during transportation and storage.     

Encapsulation of mangosteen pericarp anthocyanin-rich extract by spray drying

Mangosteen pericarp anthocyanin-rich extract (MPA) was encapsulated by maltodextrin dextrose equivalent 20 (MD20) combined with gum arabic (GA), inulin (IN) or pectin (PEC) using spray drying. The highest encapsulation efficiency and anthocyanin content exhibited MD20:PEC and MD20:IN combinations. The MPA-encapsulated powders had a crystalline-mixed amorphous structure. Scanning electron microscopy (SEM) analysis showed smooth, round, fine particles. Fourier transform infrared spectroscopy (FTIR) analysis confirmed entrapment of anthocyanins by carrier agents. Thermogravimetric analysis (TGA) revealed a high thermal stability of encapsulated powders at temperatures <200°C and found that encapsulation reduced thermal degradation of anthocyanins. Incorporation of MPA-encapsulated powders into natural yoghurt produced shelf-stable naturally coloured product but slightly suppressed the multiplication of Lactobacillus bulgaricus. Encapsulation of anthocyanin-rich mangosteen pericarp extract using spray drying presents a viable opportunity for food technologists to utilise this source in the development of functional food products.     

Challenges associated with spray drying of lactic acid bacteria: Understanding cell viability loss

Lactic acid bacteria (LAB) cultures used in food fermentation are often dried to reduce transportation costs and facilitate handling during use. Dried LAB ferments are generally lyophilized to ensure high cell viability. Spray drying has come to the forefront as a promising technique due to its versatility and lower associated energy costs. Adverse conditions during spray drying, such as mechanical stress, dehydration, heating, and oxygen exposure, can lead to low LAB cell viability. This reduced viability has limited spray drying's industrial applications thus far. This review aims to demonstrate the operations and thermodynamic principles that govern spray drying, then correlate them to the damage suffered by LAB cells during the spray-drying process. The particularities of spray drying that might cause LAB cell death are detailed in this review, and the conclusion may enhance future studies on ways to improve cell viability.     

Principles and recent applications of novel non-thermal processing technologies for the fish industry—a review

Thermal treatment is a traditional method for food processing, which can kill microorganisms but also lead to physicochemical and sensory quality damage, especially to temperature-sensitive foods. Nowadays consumers’ increasing interest in microbial safety products with premium appearance, flavor, great nutritional value and extended shelf-life has promoted the development of emerging non-thermal food processing technologies as alternative or substitution to traditional thermal methods. Fish is an important and world-favored food but has a short shelf-life due to its extremely perishable characteristic, and the microbial spoilage and oxidative process happen rapidly just from the moment of capture, making it dependent heavily on post-harvest preservation. The applications of novel non-thermal food processing technologies, including high pressure processing (HPP), ultrasound (US), pulsed electric fields (PEF), pulsed light (PL), cold plasma (CP) and ozone can extend the shelf-life by microbial inactivation and also keep good sensory quality attributes of fish, which is of high interest for the fish industry. This review presents the principles, developments of emerging non-thermal food processing technologies, and also their applications in fish industry, with the main focus on microbial inactivation and sensory quality. The promising results showed great potential to keep microbial safety while maintaining organoleptic attributes of fish products. What’s more, the strengths and weaknesses of these technologies are also discussed. The combination of different food processing technologies or with advanced packaging methods can improve antimicrobial efficacy while not significantly affect other quality properties under optimized treatment.     

New Trends in the Microencapsulation of Functional Fatty Acid‐Rich Oils Using Transglutaminase Catalyzed Crosslinking

Preparing stable protein‐based microcapsules containing functional fatty acids and oils for food applications has been a big challenge. However, recent advances with transglutaminase (TGase) enzyme as an effective protein cross‐linker could provide workable solutions for the encapsulation of omega‐3 and omega‐6 fatty acids without compromising their targeted release and their biological and physicochemical characteristics. The recent and available literature related to the microencapsulation techniques, physical and oxidative properties, and core retention and release mechanisms of TGase‐crosslinked microcapsules entrapping edible oils were reviewed. The effects of factors involved in microencapsulation processes, on the efficiency and quality of the produced innovative microcapsules were also discussed and highlighted. A brief focus has been finally addressed to new insights and additional knowledge on micro‐ and nanoencapsulation of lipophilic food‐grade ingredients by TGase‐induced gelation. Two dominant microencapsulation methods for fish, vegetable, and essential oils by TGase‐crosslinking are complex coacervation and emulsion‐based spray drying. The developed spherical particles (<100 μm) with some wrinkles and smooth surfaces showed an excellent encapsulation efficiency and yield. A negligible release rate and a substantial retention level can result for different lipid‐based cores covered by TGase‐crosslinked proteins during the oral digestion and storage. A significant structural, thermal and oxidative stability for edible oils‐loaded microcapsules in the presence of TGase can be also obtained.     

Effect of microencapsulation on morphology,physicochemical properties and flavour profiles of solid yoghurt-flavoured bases

Yoghurt-flavoured bases have many applications in food industry, but the poor stability in the volatile compounds limits their applications. In this study, the morphology and physicochemical properties of yoghurt-flavoured base microcapsules were evaluated with four different wall materials including chitosan, β-cyclodextrin, octenyl succinate anhydride and maltodextrin solution by spray drying. The encapsulation efficiencies of these four microcapsule formulations exceeded 93%. Microcapsules produced by chitosan possessed the best physical properties with improved encapsulation efficiency and smooth microstructure, so chitosan was selected as the encapsulating material of yoghurt-flavoured bases. Compared with those without chitosan, the encapsulated yoghurt-flavoured bases with chitosan had smaller particle size, better water solubility and moisture resistance as well as better stability. Furthermore, microencapsulation and spray drying technology can preserve many volatile compounds and the proportion of ketones, aldehydes, alcohols and other compounds increased. Hence, chitosan is a microcapsule material suitable for outputting solid yoghurt-flavoured bases.     

Influences of different carbohydrates as wall material on powder characteristics,encapsulation efficiency,stability and degradation kinetics of microencapsulated lutein by spray drying

In the present study, seven carbohydrates were selected as encapsulant for preparing lutein microencapsulated powders (LMPs). The surface morphology, physical properties, encapsulation efficiency, and thermo- and storage stability of LMPs were studied to determine the protective effects of different carbohydrates on microencapsulated lutein during spray drying and storage. Results on powder characteristics indicated that the crystal inhibition of wall material in spray drying was necessary for decent encapsulation efficiency, and higher glass transition temperature of wall material could cause high product yield. In stability assessment, degradation kinetics of different LMPs at two different temperature conditions were analysed, revealing that inulin could provide more effective protection compared with the other carbohydrate. Our results suggested that the different carbohydrates had great influence on the quality of LMPs, and inulin could be considered as an alternative for the generation of LMPs to enhance storage stability and extend shelf life of this bioactive product.     

Characterisation of Aronia powders obtained by different drying processes

Nowadays, food industry is facing challenges connected with the preservation of the highest possible quality of fruit products obtained after processing. Attention has been drawn to Aronia fruits due to numerous health promoting properties of their products. However, processing of Aronia, like other berries, leads to difficulties that stem from the preparation process, as well as changes in the composition of bioactive compounds. Consequently, in this study, Aronia commercial juice was subjected to different drying techniques: spray drying, freeze drying and vacuum drying with the temperature range of 40–80 °C. All powders obtained had a high content of total polyphenols. Powders gained by spray drying had the highest values which corresponded to a high content of total flavonoids, total monomeric anthocyanins, cyaniding-3-glucoside and total proanthocyanidins. Analysis of the results exhibited a correlation between selected bioactive compounds and their antioxidant capacity. In conclusion, drying techniques have an impact on selected quality parameters, and different drying techniques cause changes in the content of bioactives analysed. Spray drying can be recommended for preservation of bioactives in Aronia products. Powder quality depends mainly on the process applied and parameters chosen. Therefore, Aronia powders production should be adapted to the requirements and design of the final product.     

Electrohydrodynamic drying: Can we scale-up the technology to make dried fruits and vegetables more nutritious and appealing?

Electrohydrodynamic (EHD) drying is a promising technology to better preserve the nutritional content and sensory appeal of dried fruits and vegetables. To successfully scale up this technology, we need to rethink the current EHD dryer designs. There is also a significant potential to further enhance the nutritional content and sensory quality of the dried products by optimizing EHD process parameters. This study particularly highlights the current bottlenecks in scaling up the technology and improving nutrient retention and sensory appeal of the dried products. We discuss plausible future pathways to further develop the technology to produce highly nutritious dried products. Particular emphasis has been given to quantifying the residual nutritional and sensory properties of EHD dried products, and possible EHD dryer configurations for farmers and the industry. Concerning the nutritional content, EHD drying preserves vitamins, carotenes, and antioxidants significantly better than convective air drying. From the sensory perspective, EHD drying enhances the color of dried products, as well as their general appearance. With respect to scalability, placing the fruit on a grounded mesh electrode dries the fruit much faster and more uniformly than the grounded plate electrode. Future research should be directed toward simultaneous measurements of multiple food nutrients and sensory properties during EHD drying with a grounded mesh collector. Quantifying the impact of the food loading density on drying kinetics and energy consumption of the EHD drying process should also be a future research goal. Research comparing EHD drying with commercially available drying methods such as freeze-drying, microwave-drying, and infrared drying should also be carried out. This study gives promising insight toward developing a scalable novel thermal drying technology tailored to the requirements of the current and future society.