Cryogenic Pretreatment Enhances Drying Rates in Whole Berries.

The impact of cryogenic pretreatments on drying performance was studied in blueberries, seabuckthorn fruits and green grapes. The fruits were immersed in liquid nitrogen in 2 min freezing/thawing cycles (one to five). Untreated samples were used as the control. Drying experiments were carried out on treated and non-treated berries at 50 °C and 1 m/s (hot-air-drying), 50 °C and 25″ Hg vacuum (vacuum-drying), 30 mTorr total pressure and 25 °C shelf temperature (freeze-drying). The weight loss evolution of the foodstuffs was measured as a function of time. Microscopic (SEM and optical) determinations of the epicarp were performed. A visual inspection was performed and color changes and volume reductions were assessed before and after dehydration. The thickness of the berries' epicarp decreased between 20 and 50% (depending on the fruit) after 3-5 immersions in liquid N2. The drying kinetics was accelerated significantly for the three tested drying processes (i.e., drying time decreased from 48 to 16 h for blueberry freeze-drying). The best quality of dried berries was observed for pretreated blueberries after freeze-drying, keeping their volume, shape and color after the process. This work shows that "tailor-made" dried berry products with desired properties can be achieved and drying performance can be improved by the application of ultra-low temperature pretreatments.

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.

Sugar profiles modulation of mangoes during osmotic dehydration in agave syrup solutions.

Chemical interaction and multicompound competition were investigated on solids gain and carbohydrate profiles evolution during osmotic dehydration of mangoes. Tommy Atkins mango slices (0.4 cm and 1.5 cm thickness) were osmotically processed at 40°C for up to 4 h and 8 h, respectively. Osmotic solutions (60 °Brix) were separated in two categories: single solute (sucrose, glucose, fructose) and multisolute (agave syrup, alone or with additions of 5% inulin or 0.1-0.3% xanthan gum) solutions. High performance liquid chromatography (HPLC) analysis was carried out on treated mango to determine sugar profiles evolution during osmotic dehydration and final product concentrations. Findings pointed out that composition of osmotic solution may modulate mango sugar profiles by triggering uptake or loss of sugar according to different phenomena: chemical potential gradient, lixiviation, prevailing mass transfer, formation of carbohydrate barrier, and solution viscosity. Mango was enriched with the solute present in the single solute osmotic solution, while it lost its own native sugars, which were absent in the osmotic solution. Increasing sample thickness reduces individual sugar uptake or loss in mango treated with both single and multisolute solutions. Significant differences in mono solute solution behavior were found for sucrose due to its capability to form a sugar layer outside the surface of thicker samples, which was shown by scanning electron microscopy (SEM) images, a barrier markedly hindering the sucrose uptake or loss. Addition of polysaccharides (particularly xanthan gum) was found to have an impact of lowering mango individual sugar uptake (18-30%). Practical Application These results will help in understanding the mechanisms by which gain of individual sugars could be reduced and composition could be modulated during osmotic dehydration of fruits. Thus, the findings in this work could lead to production of low-sugar content, osmotically processed mango snacks, enriched with inulin, enhancing their dietary and marketable value.

A mapping approach to assess the evolution of pores during dehydration.

Shrinkage and collapse phenomena are the two mechanisms involved in the evolution of pores within food products during dehydration. These phenomena can be mathematically represented by shrinkage and collapse functions, which can be derived from theoretical models of porosity, bulk density, or volume reduction coefficient. In this contribution, these two functions were simplified to capture four extreme scenarios of dehydration, which consist in the combination of total or no shrinkage with total or no collapse. The four simplified equations were used to generate theoretical maps characterized by three distinct zones that are associated with pore evolution. Each of these zones represents a key dehydration situation. By superimposing experimental data of porosity, bulk density, or volume reduction coefficient on these theoretical maps, it is possible to assess dehydration processes, i.e., drying technologies and/or dehydration conditions, in terms of pore formation and evolution over time. These theoretical maps can be constructed for each food product before starting the dehydration processes. Therefore, when the experimental data is available, the suggested mapping approach is a simple, fast, and reliable tool to: (i) assess the performance of a given dehydration process versus specific cases of pore formation, and (ii) compare different dehydration processes in terms of their ability to promote pore formation. This practical tool can be used by the industry and academia to quantitatively evaluate how far a drying technology and/or its dehydration conditions are from the ideal scenario in terms of pore formation. This gap quantification will provide a basis for converging towards the ideal scenario by fine-tuning the dehydration conditions or choosing the appropriate drying technology.

Pulsed Electric Field and Freeze-Thawing Pretreatments for Sugar Uptake Modulation during Osmotic Dehydration of Mango.

Osmotic dehydration kinetics depends on food tissue microstructure; thus, modulation of mango porosity could help selectively enhance water removal over sugar gain. In this present study, pretreatments of freeze-thawing (freezing at -36 °C for 2 weeks and thawing at 4 °C for 24 h) and pulsed electric field (1 kV/cm, 10 and 30 pulse numbers), were applied to mango 1 cm-thickness slices prior to osmotic dehydration conducted at 40 °C for 4 h. Three different 60 °Brix agave syrup solutions with or without added polysaccharides (inulin or xanthan gum) were used in the osmotic dehydration operation. Water loss (WL), sugar gain (SG) and microstructure images were used to compare the effects of pretreatments on mango osmotic dehydration efficiency. Results indicated that pulsed electric field (PEF) pretreatment increased slightly WL during osmotic dehydration, contrary to freeze-thawing (F-T), which for most cases led to a decrease. As for solids uptake, due to higher damage induced by F-T to mango tissue, SG was higher than for fresh and PEF pretreated mangoes. Using xanthan gum as additive to agave syrup solution, helped to decrease sugar uptake in frozen-thawed mango due to an increase in solution viscosity. A similar WL/SG ratio was obtained with frozen-thawed mango in solution with xanthan gum. Therefore, in the case of frozen-thawed mango, it is recommended to use an osmotic solution with high viscosity to obtain low sugar uptake in the final product. The novelty of this contribution is twofold: (i) using pretreatments (F-T or PEF) to minimize sugar uptake during osmotic dehydration, and (ii) using agave syrup with added polysaccharides to enrich final product with inulin.

Fate of Residual Pesticides in Fruit and Vegetable Waste (FVW) Processing.

Plants need to be protected against pests and diseases, so as to assure an adequate production, and therefore to contribute to food security. However, some of the used pesticides are harmful compounds, and thus the right balance between the need to increase food production with the need to ensure the safety of people, food and the environment must be struck. In particular, when dealing with fruit and vegetable wastes, their content in agrochemicals should be monitored, especially in peel and skins, and eventually minimized before or during further processing to separate or concentrate bioactive compounds from it. The general objective of this review is to investigate initial levels of pesticide residues and their potential reduction through further processing for some of the most contaminated fruit and vegetable wastes. Focus will be placed on extraction and drying processes being amid the main processing steps used in the recuperation of bioactive compounds from fruit and vegetable wastes.

Ultrasound-Assisted Aqueous Extraction of Biocompounds from Orange Byproduct: Experimental Kinetics and Modeling.

Orange byproduct (flavedo and albedo) from juice extraction, was used as raw material for this study. Kinetics of total phenolic and total flavonoid contents and antioxidant activity was experimentally determined during both conventional (agitation at 80 rpm) and ultrasound assisted (at 520 and 790 W/L) aqueous extraction from orange byproduct at 5, 15, and 25 °C. An extraction mathematical model was also developed. Significant increase of biocompounds extraction yields was observed as temperature and acoustic power density increased. Ultrasound assistance allowed higher yields at lower temperatures and shorter times. Yields of total phenolic and total flavonoid contents and antioxidant activity obtained with ultrasound extraction (790 W/L, 25 °C, 3 min) were 29%, 39%, and 197% higher, respectively, than those obtained by conventional extraction. The extraction kinetics curves were properly represented by the Weibull model for both conventional and acoustic extraction (mean relative error lower than 5%). Naringin, neohesperidin, and hesperidin were the main phenolic compounds found in the extracts, followed by ferulic, sinapic, and cuomaric acids. Neohesperidin, hesperidin, coumaric acid, and sinapic acid presented the highest yields, especially when extraction was assisted by ultrasound. Meanwhile, naringin and ferulic acid were extracted in a lesser extent, most likely due to their lipophilic character.

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.

Nutrients, Antioxidant Capacity and Safety of Hot Water Extract from Sugar Maple (Acer saccharum M.) and Red Maple (Acer rubrum L.) Bark.

Sugar maple (Acer saccharum M.) and red maple (Acer rubrum L.) barks were treated with hot water to extract nutrients in order to explore, for the first time, its potential as safe dietary antioxidants. The organic and inorganic nutrients of these extracts, as well as their safety on human PLB-985 cells differentiated into neutrophils-like cells, were determined. Proximate analysis showed that both bark extracts were low in moisture and fat. Sugar maple bark extract (SM-BX) showed crude protein and ash content higher than those found in red maple bark extract (RM-BX). In addition, SM-BX had total sugars higher than those evaluated in RM-BX, while complex sugars (oligo- and/or poly-saccharides) were similarly abundant in both bark extracts. Furthermore, SM-BX demonstrated a wide array of vital minerals (K, Ca, Mg, P, Na, Fe and Cu) in quantity larger than that evaluated in RM-BX, whereas RM-BX have Zn and Mn levels higher than those found in SM-BX. Phytochemical analyses showed that RM-BX exhibited total phenolic and flavonoid contents higher than those measured in SM-BX. Consequently, RM-BX presented an antioxidant activity higher than that of SM-BX: 2.85-fold ABTS radical cation scavenging capacity and 1.9-fold oxygen radical absorbance capacity. Finally, RM-BX and SM-BX were greatly safe since, at concentration up to 100 µg/ml, they did not modify the viability of neutrophils as determined by flow-cytometry assay using Annexin V-FITC/Propidum Iodide as markers. In conclusion, our in vitro studies indicate that both red and sugar maple bark extracts have a real potential as food additives.

Shrinkage and porosity evolution during air-drying of non-cellular food systems: Experimental data versus mathematical modelling.

In the present work, the impact of glass transition on shrinkage of non-cellular food systems (NCFS) during air-drying will be assessed from experimental data and the interpretation of a 'shrinkage' function involved in a mathematical model. Two NCFS made from a mixture of water/maltodextrin/agar (w/w/w: 1/0.15/0.015) were created out of maltodextrins with dextrose equivalent 19 (MD19) or 36 (MD36). The NCFS made with MD19 had 30°C higher Tg than those with MD36. This information indicated that, during drying, the NCFS with MD19 would pass from rubbery to glassy state sooner than NCFS MD36, for which glass transition only happens close to the end of drying. For the two NCFS, porosity and volume reduction as a function of moisture content were captured with high accuracy when represented by the mathematical models previously developed. No significant differences in porosity and in maximum shrinkage between both samples during drying were observed. As well, no change in the slope of the shrinkage curve as a function of moisture content was perceived. These results indicate that glass transition alone is not a determinant factor in changes of porosity or volume during air-drying.

Foam-Mat Freeze-Drying of Bifidobacterium longum RO175: Viability and Refrigerated Storage Stability.

Foaming as a pretreatment was used prior to freeze-drying of Bifidobacterium longum RO175 to investigate the potential acceleration of the drying rate and increase in microorganism viability after the process. A study on storage of foamed and nonfoamed freeze-dried products at 4 °C completed this study. B. longum RO175 in foamed medium could be freeze-dried in 1/7 to 1/4 of the time required for nonfoamed suspensions. In addition, foamed suspensions presented higher viability immediately after freeze-drying (13.6% compared to 12.81 % or 11.46%, depending on the cryoprotective media). Refrigerated storage led to a reduction in B. longum RO175 viability for all tested protective agents (foamed and nonfoamed). No correlation between glass transition temperature and stability of probiotic powders was observed during storage. In addition, lower viability after 56 d of storage was observed for foamed materials, probably due to foam porous structure and higher hygroscopicity, and oxygen presence and moisture pickup during storage.

Osmotic dehydration of tomato in sucrose solutions: Fick's law classical modeling.

Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 degrees Brix and at 35, 45, and 55 degrees C. Other experiments were done in a 70 degrees Brix sucrose solution at 35 degrees C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and degrees Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh(s) = 1.3 Re(0.5)Sc(s) (0.15) and Sh(w) = 0.11 Re(0.5)Sc(w) (0.5), respectively. The effective diffusion coefficients of water (4.97 10(-11)- 2.10 10(-10) m(2)/s) and sucrose (3.18 10(-11)- 1.69 10(-10) m(2)/s) depended only on temperature through an Arrhenius-type relationship.

Effect of protective agents on the viability of geotrichum candidum during freeze-drying and storage.

The effect of 3 cryoprotective agents (trehalose, sucrose, and maltose) on the survival of concentrated cultures of Geotrichum candidum was studied. Initially, the effect of the carbohydrates at 9% and 23% concentrations or combined with skim milk (16%) was compared to the control (skim milk alone) immediately after freeze-drying. Two freeze-drying shelf temperatures, 25 degrees C and 35 degrees C, were investigated. Afterwards, the survival of G. candidum freeze-dried with carbohydrates at 23% concentration (alone or combined with skim milk 16%) was studied during 12 wk of storage at 4 degrees C, in the darkness, under vacuum, and at 0% relative humidity. The glass transition temperature (T(g)) of the dehydrated protective agents was measured by differential scanning calorimetry. The results showed that the survival after freeze-drying was proportional to the concentration of the protective agents, with skim milk alone giving poor survival of G. candidum. However, when skim milk was combined with disaccharides, a clear improvement was noted. No general tendency of shelf temperature on the survival of G. candidum was noted immediately after freeze-drying. However, changes in the viability were observed during storage. Glass transition temperature (T(g)) of protective agents linked to their moisture may contribute to predict the stability of lyophilized G. candidum during freeze-drying and storage.