FOAM-MAT FREEZE-DRYING OF APPLE JUICE�PART 1: EXPERIMENTAL DATA AND ANN SIMULATIONS

Exploring conventional and emerging dehydration technologies for slurry/liquid food matrices and their impact on porosity of powders: A comprehensive review

The contribution of dehydration to the growing market of food powders from slurry/liquid matrices is inevitable. To overcome the challenges posed by conventional drying technologies, several innovative approaches have emerged. However, industrial implementation is limited due to insufficient information on the best-suited drying technologies for targeted products. Therefore, this review aimed to compare various conventional and emerging dehydration technologies (such as active freeze, supercritical, agitated thin-film, and vortex chamber drying) based on their fundamental principles, potential applications, and limitations. Additionally, this article reviewed the effects of drying technologies on porosity, which greatly influence the solubility, rehydration, and stability of powder. The comparison between different drying technologies enables informed decision-making in selecting the appropriate one. It was found that active freeze drying is effective in producing free-flowing powders, unlike conventional freeze drying. Vortex chamber drying could be considered a viable alternative to spray drying, requiring a compact chamber than the large tower needed for spray drying. Freeze-dried, spray freeze-dried, and foam mat-dried powders exhibit higher porosity than spray-dried ones, whereas supercritical drying produces nano-porous interconnected powders. Notably, several factors like glass transition temperature, drying technologies, particle aggregation, agglomeration, and sintering impact powder porosity. However, some binders, such as maltodextrin, sucrose, and lactose, could be applied in controlled agglomeration to enhance powder porosity. Further investigation on the effect of emerging technologies on powder properties and their commercial feasibility is required to discover their potential in liquid drying. Moreover, utilizing clean-label drying ingredients like dietary fibers, derived from agricultural waste, presents promising opportunities.

Optimization of foaming process for development of modified aloe polysaccharide (MAP) juice and powder using foam-mat drying

The present study was performed to optimize the modified aloe polysaccharide (MAP) foaming process and to determine the effect of drying process parameters on the quality of obtained MAP powder. The studied process parameters were glycerol monostearate (GMS), carboxymethyl cellulose (CMC), and whipping time (WT) which was varied between 1 and 4% w/v, 0.1-0.5% w/v, and 1-5 min, respectively. The optimized values of foaming process parameters were 3.87% GMS, 0.39% CMC, and 4.89 min WT with a desirability of 0.889. The optimized foamed MAP juice was dried at different foam thicknesses (FT) (1, 3, and 5 mm) and drying temperatures (DT) (50, 60, and 70 °C) to develop MAP powder and compared with non-foamed aloe powder developed under the same drying condition. Based on functional properties, the best GMS foamed MAP powder was achieved at 50 °C DT and 1 mm FT, recording powder yield (16%), solubility (20.85%), and polysaccharide content (282 mg/L).

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01354-6.

Foam mat drying: Recent advances on foam dynamics, mechanistic modeling and hybrid drying approach

Drying is one of the oldest and most widely used methods for food preservation. It reduces the availability of moisture and inhibits microbial and enzymatic spoilage in food products. Foam mat drying is a mild drying technique used for semiliquid and liquid foodstuff. It is useful for heat-sensitive and sticky liquid food products. In this process, liquid food is converted into foam using surfactant additives, which can be a foaming agent or foam stabilizer. These additives are surface-active compounds of vegetative and animal origins. The foamed material is then convectively dried using hot air. The foam mat drying is an efficient and economical technique. With the emergence of different hybrid techniques such as foam mat freeze drying, foamed spray drying, foamed vacuum drying, and microwave assisted foam mat drying, the powders' physical, chemical, and functional properties have enhanced many folds. These strategies have shown very promising results in terms of cost and time efficiency in almost all the cases barring a few exceptions. This review article attempts to comprehensively summarize the mechanisms dictating the foam mat drying process, novel technological tools for modeling, mathematical and computational modeling, effects of various foaming additives, and various hybrid techniques employed to foam mat drying.

Impact of the Freeze-Drying Conditions Applied to Obtain an Orange Snack on Energy Consumption

Nowadays, the consumer is looking for healthier, more attractive, ready-to-eat, and safer foodstuffs than fresh products. Despite freeze drying being known for providing high added value products, it is a slow process which is conducted at low pressures, so, in terms of energy consumption, it turns out to be quite costly for the food industry. With the purpose of obtaining a freeze-dried orange puree, previously formulated with gum Arabic and bamboo fiber, which can be offered to consumers as a snack at a low economic cost, the impact of the process conditions on energy consumption has been considered. The product temperature evolution and the energy consumption were registered during the drying of frozen samples at different combinations of chamber pressures (5 and 100 Pa) and shelf temperatures (30, 40 and 50 °C). In each case, the time processing was adapted in order to obtain a product with a water content under 5 g water/100 g product. In this study, the secondary drying stage was considered to start when the product reached the shelf temperature and both the pressure and the temperature affected the duration of primary and secondary drying stages. The results obtained led to the conclusion that the shorter duration of the process when working at 50 °C results in significant energy saving. Working at a lower pressure also contributes to a shortening of the drying time, thus reducing the energy consumption: the lower the temperature, the more marked the effect of the pressure.

Freeze-Drying of Plant-Based Foods

Vacuum freeze-drying of biological materials is one of the best methods of water removal, with final products of highest quality. The solid state of water during freeze-drying protects the primary structure and the shape of the products with minimal volume reduction. In addition, the lower temperatures in the process allow maximal nutrient and bioactive compound retention. This technique has been successfully applied to diverse biological materials, such as meats, coffee, juices, dairy products, cells, and bacteria, and is standard practice for penicillin, hormones, blood plasma, vitamin preparations, etc. Despite its many advantages, having four to ten times more energy requirements than regular hot air drying, freeze-drying has always been recognized as the most expensive process for manufacturing a dehydrated product. The application of the freeze-drying process to plant-based foods has been traditionally dedicated to the production of space shuttle goods, military or extreme-sport foodstuffs, and specialty foods such as coffee or spices. Recently, the market for 'natural' and 'organic' products is, however, strongly growing as well as the consumer's demand for foods with minimal processing and high quality. From this perspective, the market for freeze-dried plant-based foods is not only increasing but also diversifying. Freeze-dried fruits and vegetables chunks, pieces, or slices are nowadays majorly used in a wide range of food products such as confectionaries, morning cereals, soups, bakeries, meal boxes, etc. Instant drinks are prepared out of freeze-dried tea, coffee, or even from maple syrup enriched with polyphenol concentrated extracts from trees. The possibilities are endless. In this review, the application of freeze-drying to transform plant-based foods was analyzed, based on the recent research publications on the subject and personal unpublished data. The review is structured around the following related topics: latest applications of freeze-drying to plant-based foods, specific technological problems that could be found when freeze-drying such products (i.e., presence of cuticle; high sugar or lipid concentration), pretreatments and intensification technologies employed in freeze-drying of plant-based foods, and quality issues of these freeze-dried products.

Trends in foam mat drying of foods: Special emphasis on hybrid foam mat drying technology

Dehydration of foods is not simply a preservation technique in the present era, rather an important food processing operation which has many benefits in addition to enhancement of shelf life of foods. There are various methods of drying foods and most of them are unique in their own way. Liquid foods can be dried in many ways and foam mat drying is one such method which is being researched frequently for its potential use at commercial level. Foam mat drying has got almost all the features to be a commercially successful method of drying. It is a simple technique and has shown good results in drying of liquid foods with low glass transition temperature. Hybridization of this method has shown the results that make this technology look even more promising than the conventional one. Studies on freeze drying, vacuum drying and microwave drying of foam have indicated encouraging results with respect to drying kinetics and product quality. This review presents an overview of foam mat drying of foods. The procedure and technology of this method of drying have been summarized with an intention to make them easy to understand. The emphasis is, however, on the hybrid foam mat drying technology.

Comparison of blueberry powder produced via foam-mat freeze-drying versus spray-drying: evaluation of foam and powder properties

BACKGROUND

Blueberry juice powder was developed via foam-mat freeze-drying (FMFD) and spray-drying (SD) via addition of maltodextrin (MD) and whey protein isolate (WPI) at weight ratios of MD/WPI = 0.4 to 3.2 (with a fixed solids content of 5 wt% for FMFD and 10 wt% for SD). Feed rates of 180 and 360 mL h^-1 were tested in SD. The objective was to evaluate the effect of the drying methods and carrier agents on the physical properties of the corresponding blueberry powders and reconstituted products.

RESULTS

Ratios of MD/WPI = 0.4, 1.0 and 1.6 produced highly stable foams most suitable for FMFD. FMFD gave high yields and low bulk density powders with flake-like particles of large size that were also dark purple with high red values. SD gave low powder recoveries. The powders had higher bulk density and faster rehydration times, consisting of smooth, spherical and smaller particles than in FMFD powders. The SD powders were bright purple but less red than FMFD powders. Solubility was greater than 95% for both FMFD and SD powders.

CONCLUSION

The FMFD method is a feasible method of producing blueberry juice powder and gives products retaining more characteristics of the original juice than SD. © 2017 Society of Chemical Industry.