Vacuum impregnation and osmotic dehydration in matrix engineering

Review of osmotic dehydration: Promising technologies for enhancing products' attributes, opportunities, and challenges for the food industries

Osmotic dehydration (OD) is an efficient preservation technology in that water is removed by immersing the food in a solution with a higher concentration of solutes. The application of OD in food processing offers more benefits than conventional drying technologies. Notably, OD can effectively remove a significant amount of water without a phase change, which reduces the energy demand associated with latent heat and high temperatures. A specific feature of OD is its ability to introduce solutes from the hypertonic solution into the food matrix, thereby influencing the attributes of the final product. This review comprehensively discusses the fundamental principles governing OD, emphasizing the role of chemical potential differences as the driving force behind the molecular diffusion occurring between the food and the osmotic solution. The kinetics of OD are described using mathematical models and the Biot number. The critical factors essential for optimizing OD efficiency are discussed, including product characteristics, osmotic solution properties, and process conditions. In addition, several promising technologies are introduced to enhance OD performance, such as coating, skin treatments, freeze-thawing, ultrasound, high hydrostatic pressure, centrifugation, and pulsed electric field. Reusing osmotic solutions to produce innovative products offers an opportunity to reduce food wastes. This review explores the prospects of valorizing food wastes from various food industries when formulating osmotic solutions for enhancing the quality and nutritional value of osmotically dehydrated foods while mitigating environmental impacts.

Effect of the Pulsed Electric Field Treatment on Physical, Chemical and Structural Changes of Vacuum Impregnated Apple Tissue in Aloe Vera Juices

Vacuum impregnation (VI) stands as a diffusion-driven food processing method that has found recent application within the food industry, particularly for the cold formulation of fortified food products. Pulsed electric field (PEF) treatment can affect the food structure, influencing therefore the mass transfer phenomena during the further processing. Thus, the study aimed at investigating the effect of PEF treatment on selected physicochemical properties of vacuum-impregnated apples. Apple slices were vacuum impregnated with aloe vera juice solution with or PEF treatment at different intensities (125, 212.5 or 300 V/cm). The PEF was applied as a pretreatment-applied before the VI process as well as posttreatment-applied after the VI process. The VI process with aloe vera juice resulted in a sample weight increase of over 24% as well as structural changes, partial cell viability loss and color alteration. In addition, the decrease of bioactive compounds was observed, while antioxidant activity remained at a similar level as in raw material. PEF treatment adversely affected vacuum impregnation efficiency, causing microstructural changes and cell viability loss. Additionally, chemical composition modifications were evident through thermogravimetric analysis (TGA) and Fourier Infrared Spectroscopy (FTIR) analyses. Tissue hardness decreased significantly due to structural damage and caused high leakage from plant tissue, which resulted in hindering saturation with aloe vera juice during the VI process. Additionally, reduced bioactive substance content after PEF treatment was observed and the VI process did not restore apple samples of the bioactive compounds from aloe vera juice.

Enhancing bioaccessibility of resveratrol by loading in natural porous starch microparticles

Resveratrol (RSV) is a lipophilic polyphenol susceptible to photo- and thermal degradation, and strategies are to be studied to enable its distribution in food matrices, prevent its degradation during storage, and increase its bioaccessibility during digestion. In this study, the porous matrix of natural starch, in the form of milled freeze-dried potato microparticles (FDPMs), was studied as an absorbent to load RSV. The binary solvent of ethanol and polyethylene glycol 400 (40:60 v/v) was used to dissolve 30% w/v RSV for diffusion into FDPMs. After ethanol was evaporated, the loading capacity was 112 mg RSV/g FDPMs and was maintained at 104 mg RSV/g FDPMs (92.9% retention) after 110-day ambient storage. The RSV stability under UV irradiation at 253 nm was improved by 32% due to shielding effect of FDPMs, and the ferric reducing power was 25% higher than the pristine RSV. The release of RSV in FDPMs was significantly higher than pristine RSV during simulated gastric and intestinal digestions (82.3% vs 51.4% bioaccessibility). The increased reducing power and bioaccessibility were supported by the amorphous state of RSV in FDPMs. The present study illustrates the potential of porous vegetable microparticles as natural matrices to load lipophilic bioactive compounds in functional foods.

Antioxidants Bioaccessibility and Lactobacillus salivarius (CECT 4063) Survival Following the In Vitro Digestion of Vacuum Impregnated Apple Slices: Effect of the Drying Technique, the Addition of Trehalose, and High-Pressure Homogenization

To benefit the health of consumers, bioactive compounds must reach an adequate concentration at the end of the digestive process. This involves both an effective release from the food matrix where they are contained and a high resistance to exposure to gastrointestinal conditions. Accordingly, this study evaluates the impact of trehalose addition (10% w/w) and homogenization (100 MPa), together with the structural changes induced in vacuum impregnated apple slices (VI) by air-drying (AD) and freeze-drying (FD), on Lactobacillus salivarius spp. salivarius (CECT 4063) survival and the bioaccessibility of antioxidants during in vitro digestion. Vacuum impregnated apple slices conferred maximum protection to the lactobacillus strain during its passage through the gastrointestinal tract, whereas drying with air reduced the final content of the living cells to values below 10 cfu/g. The bioaccessibility of antioxidants also reached the highest values in the VI samples, in which the release of both the total phenols and total flavonoids to the liquid phase increased with in vitro digestion. The addition of trehalose and homogenization at 100 MPa increased the total bioaccessibility of antioxidants in FD and AD apples and the total bioaccessibility of flavonoids in the VI samples. Homogenizing at 100 MPa also increased the survival of L. salivarius during in vitro digestion in FD samples.

Impact of Various Vacuum Impregnation Methods on Viability of Cereal Grains

Grain viability is of key importance in the production of malt. This paper presents the results of research on the influence of vacuum impregnation of grains of various cereals on theirservice life. One malting barley cultivar, two wheat cultivars, and a rye cultivar mix were tested. The grain was subjected to wet vacuum impregnation and wet vacuum impregnation carried out cyclically under the pressure of 5 kPa. Then, samples of the impregnated grain were sown and its germination capacity was tested every 24 h to 120 h. The control sample was grain soaked under atmospheric pressure. Vacuum impregnation did not cause any significant changes in the germination capacity of the examined cereal varieties. The vacuum-impregnated grain displayed a higher initial water content and germinated faster. It was found that the impregnation did not disturb the internal structure of the grain, indicated by the fact that the most delicate part of the grain, i.e., the embryo, retained its vital functions in every examined case.

Survival of Lactobacillus salivarius CECT 4063 and Stability of Antioxidant Compounds in Dried Apple Snacks as Affected by the Water Activity, the Addition of Trehalose and High Pressure Homogenization

Survival of probiotic microorganisms in dried foods is optimal for water activity (a_w) values between 0.1 and 0.3. Encapsulating and adding low-molecular weight additives can enhance probiotic viability in intermediate a_w food products, but the effectiveness of sub-lethal homogenization is still not proven. This study evaluates the effect of 10% (w/w) trehalose addition and/or 100 MPa homogenization on Lactobacillussalivarius CECT 4063 counts and antioxidant properties of apple slices dried to different water activity values (freeze-drying to a a_w of 0.25 and air-drying at 40 °C to a a_w of 0.35 and 0.45) during four-week storage. Optical and mechanical properties of dried samples were also analyzed. Freeze-drying had the least effect on the microbial counts and air drying at 40 °C to a a_w of 0.35 had the greatest effect. Antioxidant properties improved with drying, especially with convective drying. Decreases in both microbial and antioxidant content during storage were favored in samples with higher water activity values. Adding trehalose improved cell survival during storage in samples with a water activity of 0.35, but 100 MPa homogenization increased the loss of viability in all cases. Air-dried samples became more translucent and reddish, rather rubbery and less crispy than freeze-dried ones.

Impact of Processing Factors on Quality of Frozen Vegetables and Fruits

In this paper I review the production of frozen vegetables and fruits from a chain perspective. I argue that the final quality of the frozen product still can be improved via (a) optimization of the complete existing production chain towards quality, and/or (b) introduction of some promising novel processing technology. For this optimization, knowledge is required how all processing steps impact the final quality. Hence, first I review physicochemical and biochemical processes underlying the final quality, such as water holding capacity, ice crystal growth and mechanical damage. Subsequently, I review how each individual processing step impacts the final quality via these fundamental physicochemical and biochemical processes. In this review of processing steps, I also review the potential of novel processing technologies. The results of our literature review are summarized via a causal network, linking processing steps, fundamental physicochemical and biochemical processes, and their correlation with final product quality. I conclude that there is room for optimization of the current production chains via matching processing times with time scales of the fundamental physicochemical and biochemical processes. Regarding novel processing technology, it is concluded in general that they are difficult to implement in the context of existing production chains. I do see the potential for novel processing technology combined with process intensification, incorporating the blanching pretreatment—but which involves quite a change of the production chain.

Influence of Selected Parameters and Different Methods of Implementing Vacuum Impregnation of Apple Tissue on Its Effectiveness

The study provides comprehensive information on the vacuum impregnation process applied to plant materials. It aims (in traditional applications) to ensure impermeability and elimination of porosity of various materials. The process substantially accelerates mass transfer in the liquid–solid system. The study describes the course of the process and accompanying phenomena as well its effects on plant tissues. The aim of the investigations was to determine the impact of some impregnation parameters (pressure, pressure change rate, vacuum maintenance time, relaxation time, and the coefficient of impregnating liquid viscosity) and the mode of impregnation (wet, dry, cyclic wet) on the degree of filling the plant tissue with the impregnating solution. Jonagold apples were used as the study material. The investigations have revealed that changes in the vacuum impregnation parameters (vacuum maintenance time, relaxation time, pressure change rate in the system) and the impregnation method do not exert a significant impact on the effectiveness of the process as expressed by the degree of permeation of the impregnating solution into the tissue. The pressure value and the viscosity coefficient were the only parameters that had a significant effect on the impregnation yield.

Functional exploration of free and encapsulated probiotic bacteria in yogurt and simulated gastrointestinal conditions

The core objective of the current study was to evaluate the effect of microencapsulation on the viability and stability of probiotic bacteria in yogurt and simulated gastrointestinal conditions. For this purpose, probiotic bacteria were encapsulated with sodium alginate and carrageenan by encapsulator. Yogurt was prepared with the incorporation of free and encapsulated probiotic bacteria and was analyzed for physicochemical, microbiological, and sensorial attributes. Encapsulation and storage exhibited a significant (p < .05) effect on different parameters of yogurt. An increasing trend in syneresis and acidity while a decreasing trend in viscosity, pH, viability, and stability were observed. The value of syneresis increased from 2.27 ± 0.17 to 2.9 ± 0.14 and acidity from 0.48 ± 0.04 to 0.64 ± 0.01 during 4 weeks of storage. The value of viscosity decreased from 3.68 ± 0.21 to 2.42 ± 0.09 and pH from 4.88 ± 0.31to 4.43 ± 0.36 during 28 days of storage. Unencapsulated (free) cells exhibited poor survival. The viable cell count of probiotic bacteria in the free-state in yogurt was 9.97 logs CFU/ml at zero-day that decreased to 6.12 log CFU/ml after 28 days. However, encapsulation improved the viability of the probiotics in the prepared yogurt and GIT. The cell count of probiotics encapsulated with sodium alginate and carrageenan was 9.91 logs CFU/ml and 9.89 logs CFU/ml, respectively, at zero-day that decreased to 8.74 logs CFU/ml and 8.39 log CFU/ml, respectively. Free cells (unencapsulated) showed very poor survival. Similarly, during in vitro gastrointestinal assay, the survival rate of encapsulated probiotic bacteria in simulated gastric solution and intestinal solutions was higher than that of free cells. In the case of encapsulated bacteria, only 3 logs while for free cells, 7 log reduction was recorded. Sodium alginate microcapsules exhibited better release profile than carrageenan. Conclusively, microencapsulation improved the survival of probiotic bacteria in carrier food as well as in simulated gastrointestinal condition.

Incorporation of microencapsulated hydrophilic and lipophilic nutrients into foods by using ultrasound as a pre-treatment for drying: A prospective study

The present work proposes using the ultrasound technology to incorporate microencapsulated nutrients during pre-treatments for drying of food products. Both hydrophilic and lipophilic nutrients were evaluated: incorporation of microcapsules of iron (obtained by spray drying using maltodextrin as wall material) and carotenoids (obtained by hot emulsification and solidification using hydrogenated palm oil as wall material). The ultrasound pre-treatment was applied in water and ethanol, where the microcapsules were dispersed, and food samples were immersed. Pumpkin and apple were selected as suitable food material to perform the iron and carotenoid incorporation, respectively. Ultrasound allowed more homogeneous iron incorporation in pumpkin. The iron content increased more than 1000% in pre-treated samples compared to control. In the same manner, carotenoid content increased in about 430% when ultrasound was applied. After drying, the carotenoid content decreased by 65% in control samples. However, better carotenoid retention was obtained after drying in ultrasound processed samples. The results show that pre-treatment with ultrasound can be used to incorporate nutrients into the food matrix, increasing not only the incorporated quantity but also promoting their preservation. Nevertheless, future studies must be performed to determine the nutrient bioavailability and bioaccessibility.

Mass transfer characteristics during ultrasound-assisted osmotic dehydration of button mushroom (Agaricus bisporus)

Button mushroom (Agaricus bisporus) slices were dehydrated using ultrasound-assisted osmotic dehydration (UOD), and three osmotic agents including sucrose, glucose and sodium chloride were investigated for their effects on the mass transfer characteristics, average density and microstructure. Different mathematical models were selected to describe the osmotic behaviours, and the effective moisture (D _m) as well as solid diffusivities (D _s) during UOD were also calculated. The results showed that, during UOD, button mushrooms had the highest D _m values in the sodium chloride solutions, and they had the highest D _s values in the glucose solutions, which indicated that faster moisture and solid transfers could occur in these two osmotic solutions, respectively. Moreover, the Weibull model provided the best fit for the UOD curves of button mushrooms under the study's operating conditions, which showed good predictability for the moisture and solid contents of the button mushrooms during UOD. In addition, sucrose agents were suggested for use in the UOD of button mushrooms due to the better microstructure of the products as well as the appropriate rates of effective moisture and solid diffusivities during UOD. This study provides a theoretical basis for the deep processing of mushrooms and other food products.

Increased Phenolic Compounds in Potato Chips Vacuum Impregnated with Green Tea

This studied tested the feasibility of producing vacuum fried potato chips enriched with antioxidants by introducing green tea extract using vacuum impregnation (VI) technology. Total phenolic content (TPC) was used to find the optimal VI parameters. Sliced potatoes were fried under vacuum at 110, 120, or 140 °C from 20 to 720 s to test the thermal degradability of the TPC. Three frying systems were also compared: vacuum frying (VF), dual-step (DS) frying, and atmospheric frying (AF). Green tea concentration of 5%, vacuum time of 10 min, and a pressure of 80 kPa gave the maximum TPC of 196.11 ± 15.41 mg GAE/100 g of dry matter. Samples fried at 120 °C showed an overall greater phenolic retention capacity compared to the chips fried at 140 and 110 °C. Using the optimal VI and VF parameters (140 °C, 100 s), the three frying systems were then compared. Samples fried using the AF system contained twice as much the oil content as those fried using the VF or DS systems. VF chips had the highest percentage in TPC increase (209%) while AF chips had the lowest (163%). A consumer panel found the samples fried under AF more acceptable and were given the highest scores for all quality. VI had a negative effect on the color scoring of the participants (they were dark). Overall, VI is a suitable precursor of VF to create potato chips with a high phenolic content. PRACTICAL APPLICATION: Vacuum impregnated potato chips with green tea extract have potential for manufacture of functional snacks that may influence the public into consuming phenol-rich fruit and vegetable snack.

Manufacturing personalized food for people uniqueness. An overview from traditional to emerging technologies

Personalized nutrition means that we are unique in the way to absorb and to metabolize nutrients as a consequence of our genetic profile and the microbiome that we host in the gut. With the terminology of Personalized Food Manufacturing we want not only to stress the idea of the capability to manufacture food meeting our unique nutritional needs but - based on the idea that eating is a global experience - also to broad this to meet additional personal requirements and expectations, i.e. taste, texture, color, aspect, etc. To address this aim, traditional and advances technologies will have to be employed in new ways and new technological solutions will have to be implemented. All these considerations motivated our paper by which we want to explore and to discuss the technological options having the potential to produce personalized food. After pointing out the main diet styles, firstly we have analyzed the modern approaches of agricultural and animal nutrition in use to manufacture food for narrow group of consumers. Secondly, we have explored emerging technologies at disposal employable to manufacture customized food that meet our uniqueness. Finally the most important market products belonging in the sector of personalized food production have been considered.

Enrichment of Apple Slices with Bioactive Compounds from Pomegranate Cryoconcentrated Juice as an Osmodehydration Agent

Pomegranate juice is an important source of bioactive compounds, and cryoconcentrated juice is an interesting osmodehydration agent to enrich a vegetal matrix. This investigation aimed to incorporate bioactive compounds from pomegranate cryoconcentrated juice into apple slices using osmodehydration (OD) assisted by pulse vacuum (PV) and ohmic heating (OH). The apple slices (3 × 4 × 0.5 cm) were osmodehydrated using a 47 °Brix pomegranate cryoconcentrated juice at 30, 40, or 50°C for 180 min with an electric field of 6.66 V/cm (50 V) and a 5 min pulsed vacuum. Over the time, all of the treatments applied to the apple slices increased the soluble solids and bioactive compounds compared with the fresh sample. PVOD/OH at 50°C had the highest content of total anthocyanin during processing, and the best results for the total flavonoids were obtained with OD/OH at 50°C and 40°C. The osmodehydration assisted by pulse vacuum and ohmic heating using a cryoconcentrated juice is a useful combined technique to acquire enriched vegetal samples with bioactive compounds.

Effect of Dipping and Vacuum Impregnation Coating Techniques with Alginate Based Coating on Physical Quality Parameters of Cantaloupe Melon

Edible coating based on sodium alginate solution was applied to fresh-cut cantaloupe melon by dipping and vacuum impregnation coating methods. One aim of this work is to produce more technical information concerning these conventional and novel coating processes. For this purpose, the effect of various coating parameters (dipping time, draining time, time length of the vacuum period, vacuum pressure, atmospheric restoration time) with several levels on physical quality parameters (percentage of weight gain, color, and texture) of noncoated and coated samples were determined in order to define adequate coating process parameters to achieve a successful coating application. Additionally, the effects of dipping and vacuum impregnation processes were compared. Both processes improved the firmness of the melon pieces. However, vacuum impregnation application had higher firmness and weight gain results, and had significant effect (P < 0.05) on color (lower luminosity, higher redness, yellowness, and chroma values). Experimental results affirm that vacuum impregnation method can be used successively to improve mechanical and structural properties of food products.

PRACTICAL APPLICATION

Type of edible coating technique and the parameters used significantly affect the physical quality characteristics of coated food products. The work presented produced more technical information concerning dipping and vacuum impregnation coating techniques, along with evaluating the effects of various coating parameters with several levels. The results revealed that vacuum impregnation technique is a successful coating method; however the effects should be carefully assessed for each product.

Functional Dehydrated Foods for Health Preservation

The market of functional foods has experienced a huge growth in the last decades due to the increased consumers’ awareness in a healthy lifestyle. Dried fruits constitute good snacks, in alternative to salty or sweet ones, and food ingredients due to their taste and nutritional/health benefits. Bioactive molecules are interesting sources to develop functional foods, as they play a major role in improving the health status and minimizing disease risks. The bioactive compounds most widely discussed in literature are presented in this review, for example, polyphenols, phytosterols, and prebiotics. Different technologies to dry bioproducts for producing functional foods or ingredients are presented. New drying techniques for the preservation of bioactive compounds are proposed, focusing more specifically on dielectric drying. A discussion on the techniques that can be used to optimize drying processes is performed. An overview on dehydrated plant based foods with probiotics is provided. The microorganisms used, impregnation procedures, drying methods, and evaluated parameters are presented and discussed. The principal bioactive compounds responsible for nutritional and health benefits of plant derived dried food products—fruits and vegetables, fruits and vegetables by-products, grains, nuts, and algae—are presented. Phytochemical losses occurring during pretreatments and/or drying processes are also discussed.

Apple snack enriched with L-arginine using vacuum impregnation/ohmic heating technology

Modern life has created a high demand for functional food, and in this context, emerging technologies such as vacuum impregnation and ohmic heating have been applied to generate functional foods. The aim of this research was to enrich the content of the semi-essential amino acid L-arginine in apple cubes using vacuum impregnation, conventional heating, and ohmic heating. Additionally, combined vacuum impregnation/conventional heating and vacuum impregnation/ohmic heating treatments were evaluated. The above treatments were applied at 30, 40 and 50  ℃ and combined with air-drying at 40 ℃ in order to obtain an apple snack rich in L-arginine. Both the impregnation kinetics of L-arginine and sample color were evaluated. The impregnated samples created using vacuum impregnation/ohmic heating at 50 ℃ presented a high content of L-arginine, an effect attributed primarily to electropermeabilization. Overall, vacuum impregnation/ohmic heating treatment at 50 ℃, followed by drying at 40 ℃, was the best process for obtaining an apple snack rich in L-arginine.

Uptake Kinetics and Absorption of Calcium in Apple Matrices

The purpose of this paper was to study the kinetics of calcium uptake of blanched and not blanched apple tissue during impregnation treatments under vacuum or/and at atmospheric pressure. The relative absorption of calcium in rats, regarding calcium carbonate as reference substance, was also analyzed as a first approach. Apple impregnation is conducted (with and without previous blanching in saturated vapor) in isotonic glucose aqueous solutions containing calcium gluconate and lactate. A 50 mm Hg vacuum pressure is applied for a time t1 (0—180 min) or atmospheric pressure is used for a process time t2 (0—7.5 h). Calcium uptake by apple tissue is influenced by system pressure, blanching, and impregnation time, reaching 500—4600 μg Ca/g according to process variables. Preliminary data of true calcium absorption ranges between 74 and 86% regarding calcium carbonate.

Food Matrix Engineering: The Use of the Water-Structure-Functionality Ensemble in Dried Food Product Development

The structured food systems (i.e. cellular tissues) are dissipative structures whose functionality mainly concerns their properties (physico-chemical properties, chemical and biochemical reactions), external interactions with surroundings (interactions with micro-organisms, heat and mass transport pathway) and especially, their interactions with consumers (nutritional value, quality, taste and flavour, texture, appearance: size, shape, colour). Dehydration or rehydration processes concern heat and mass transport phenomena (water, solutes) coupled with micro and macrostructure changes both producing important effects on food functionality. Control of these changes is the major concern in food product development. This control must be applied not only to the changes in physico-chemical properties but also to those related with consumers' issues. Food matrixengineering is a branch of food engineering which aims to apply the knowledge of the food matrixcomposition, structure and properties to promote and control adequate changes which can improve some sensorial and/or functional properties in the food. These changes, which are caused by some basic operations, are related to the phenomena of heat and mass transfer, vaporization-condensation, internal gas or liquid release, structure deformation-relaxation and phase transitions in matrixcomponents, and are usually coupled throughout the operation's progress. The final product may be a new product with improved composition and sensorial properties and/or more stability. All these concepts are discussed in this paper using several examples related to the application of combined food dehydration techniques.

Effect of Combined Air-Drying-Osmotic Dehydration on Kinetics of Techno-functional Properties, Color and Total Phenol Contents of Lemon (Citrus limon. v. lunari) Peels

Combined osmotic dehydration (sucrose solution: 50–70 % w/w, 30–50 °C for 2 h followed by air drying at 40 and 60 °C) is an appropriate process for preservation of oil retention capacity, lightness and yellowness of lemon peels (Citrus limon. v. lunari). Incorporation of sugars to lemon cuboids pieces increased drying rate during the first falling rate phase of the air dehydration step and improved their color stability. Osmotic dehydration process allows protective effect against further total phenol loss during air drying: significant loss of total phenol content (70–80 %) was recorded during osmotic dehydration and then it remains constant during air drying at 40 and 60 °C. For the investigated temperature of osmotic pre-treatment (30–50 °C), water retention capacities were reduced by up to 70 % and were maintained constant during air drying.