Microwave vacuum drying of dairy cream: Processing, reconstitution, and whipping properties of a novel dairy product

Traditional ways to preserve cream involve processing it into butter, butter oil, or frozen storage. These technologies do not preserve the unique functionality of cream with respect to whipping or processing into butter. In this work, microwave vacuum drying (MVD) was investigated as a method to manufacture dehydrated cream. Dehydrated cream microstructure, color, and free fat were evaluated using scanning electron microscopy, colorimetry, and solvent extraction, respectively. Effects of homogenization on reconstituted cream microstructure and functionality were investigated using confocal laser scanning microscopy, color, particle sizing, and texture analysis of whipped cream. Reconstituted MVD cream whipped faster, and the whipped cream was more cohesive and firmer when 2-step homogenization at 3.5/7 MPa was used. Fat globules in reconstituted MVD cream were covered by phospholipids, explaining MVD cream's similar functionality compared with pasteurized cream. These results may foster the development of novel shelf stable and highly functional dairy products using MVD.

[Application of microwave vacuum drying with process management in extract drying of personalized traditional Chinese medicine preparations]

Extracts are important intermediates in the production of traditional Chinese medicines preparations. The drying effect of extracts will directly affect the subsequent production process and the quality of the preparation. To meet the requirements of high drug loading, short time consumption, and simple production process of personalized traditional Chinese medicine preparations, this study explored the application of multi-program microwave vacuum drying process in the extract drying of personalized traditional Chinese medicine preparations. The influencing factors of microwave vacuum drying process were investigated for 5 excipients and 40 prescriptions. Taking the feasibility of drying, drying rate, drying time, and dried extract status as indicators, this study investigated the feeding requirements of microwave vacuum drying. With the dried extract status as the evaluation indicator, the three drying programs(A, B, and C) were compared to obtain the optimal drying condition. The experimental results showed that the optimal feeding conditions for microwave vacuum drying were material layer thickness of 2 cm and C program(a total of 7 drying processes), which solved the problem of easy scorching in microwave drying with process management. Furthermore, the preset moisture content of the dried extract in microwave drying should be 4%-5%, so that the dried extract of traditional Chinese medicine preparation had uniform quality, complete drying, and no scorching. This study lays a foundation for the application of microwave drying in the production of traditional Chinese medicine preparations, promoting the high-quality development of personalized traditional Chinese medicine preparations.

Insight into the Effects of Drying Methods on Lanzhou Lily Rehydration

This study investigated the effects of drying methods (hot air drying (HAD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD)) on the rehydration performance (RP) of dried Lanzhou lily scales (LLS). Rehydration rate and water migration showed that MVD had the best RP, followed by VFD, while HAD had the worst. The results of additional morphology observation using scanning electron microscopy (SEM) and micro X-ray computed tomography (CT) imaging showed that both MVD and VFD created more channels in more porous structures, which facilitated their better RP than that by HAD. The results also revealed the spatial structure diversity (including pores, channels size, and internal network) of each dried Lanzhou lily scale group. In addition, studies analyzed how drying techniques affected the physiochemical properties of lily starch, including its water solubility, pasting profiles, and starch particle morphology. The findings indicated that when MVD was in operation, partial gelatinization in lily starch was brought about by thermal effects, allowing MVDS crystals to change from B-type to V-type and causing MVDS to have better water absorption ability. Consequently, despite the fact that MVD's desiccated lilies have a lower porous structure and thinner channels than VFD's, MVD has a higher RP than VFD.

A process optimization approach for microwave vacuum drying of concentrated skim milk

Microwave vacuum drying (MVD) of concentrated skim milk and its resulting powder properties have been studied to a very limited extent. To explore the potential of this technology for the manufacture of milk powder, MVD of concentrated skim milk (37.5% total solids) was evaluated with respect to product properties and drying efficiency. A custom factorial design was used to optimize drying parameters, which enabled us to find optimal drying conditions with a minimal number of drying experiments (16). Vacuum level (3.3-13.3 kPa), specific power input (0.86-1.72 W·g^-1), and product layer thickness (1-4 mm) were studied as factors. Total drying time, product foaming at the beginning of the process, product temperature in the last drying interval, browning, insolubility index, and calculated product yield were used as responses to identify optimal MVD processing parameters. Optimal drying of concentrated skim milk that maximized yield and minimized drying time while maintaining good product quality was achieved at a layer thickness of 2 mm, pressure of 6.0 kPa, and a specific power input of 1.29 W·g^-1. Under constant power output, layer thickness was found to be the most important processing parameter to control product temperature during the final drying stage. Maximum product temperatures below 55°C yielded powder with good solubility. The findings of this exploratory study for MVD of concentrated skim milk yield important information and guidelines for production of good quality milk powders or preservation of starter cultures in a dairy matrix such as infant formula.

Effect of different drying technologies on the characteristics and quality of lemon slices

This experiment aimed to investigate the effects of four drying methods, namely, hot air drying (HAD), microwave drying (MD), vacuum drying (VD), and microwave vacuum drying (MVD), on the quality of lemon slices. The relevant indicators, including total phenolic content, ascorbic acid content, browning, color, reducing sugar content, volatile component measurements, and principal component analysis of 0 and 30 days storage, were compared after exposure to the four drying methods. The shortest time of 64 min was used to treat the lemon slices via MVD at 1 KW. These samples displayed the least damage after drying and the highest rehydration ratio of 4.12. The contents of VC, reducing sugars, and total phenols of MVD samples were significantly higher than those in the HAD, VD, and MD groups, retaining 105.94 mg/100 g, 21.35 g/100 g, and 77.81 mg GAE/g, respectively, while their color difference values were also the smallest, with a browning degree of 3.55, significantly lower than those in the other treatment groups (p < 0.05), and the degree of browning of the samples in the HAD treatment group was the most serious; in terms of volatile flavor substances, the lemon slice samples in the MVD and HAD treatment groups were more diverse and of better quality. The order of product sensory evaluation was: MVD > VD > HAD > MD. The final scores after comprehensive analysis revealed the order of the four drying methods as MVD, HAD, VD, and MD. Therefore, MVD had a better effect on the sensory perception and nutritional properties of the lemon slices, providing a useful alternative to the conventional drying method. PRACTICAL APPLICATION: Lemon slices during drying are affected by various aspects, leading to changes in its color, aroma substances, and nutrient composition. The results of this work will not only provide a technical reference for the future production of high-quality dried lemon slices, but also have important implications for fresh-cut lemons in processing and storage. It also generates important implications for fresh-cut lemons in processing and storage.

Modern Methods of Pre-Treatment of Plant Material for the Extraction of Bioactive Compounds

In this review, recent advances in the methods of pre-treatment of plant material for the extraction of secondary metabolites with high biological activity are presented. The correct preparation of the material for extraction is as important as the selection of the extraction method. This step should prevent the degradation of bioactive compounds as well as the development of fungi and bacteria. Currently, the methods of preparation are expected to modify the particles of the plant material in such a way that will contribute to the release of bioactive compounds loosely bonded to cell wall polymers. This review presents a wide range of methods of preparing plant material, including drying, freeze-drying, convection drying, microwave vacuum drying, enzymatic processes, and fermentation. The influence of the particular methods on the structure of plant material particles, the level of preserved bioactive compounds, and the possibility of their release during the extraction were highlighted. The plant material pre-treatment techniques used were discussed with respect to the amount of compounds released during extraction as well their application in various industries interested in products with a high content of biologically active compounds, such as the pharmaceutical, cosmetics, and food industries.

Effects of microwave vacuum drying on the moisture migration, microstructure, and rehydration of sea cucumber

Effectsof microwave vacuum drying (MVD) on moisture migration, microstructure, and rehydration of sea cucumber were investigated in this paper. Vacuum condition avoided the exposure of sea cucumber to high temperature. Low-field nuclear magnetic resonance relaxation results revealed that the peaks of three water components in sea cucumber shifted to short relaxation time during MVD process, and the peak area of major water component-immobilized water-decreased significantly due to water evaporation. Magnetic resonance imaging found that the water in the internal layer of sea cucumber body wall was first removed due to the internal heating of microwave, and then the water in the outer layer. Higher microwave power could promote the moisture transfer motion during drying process, and shorten the drying time. Porous microstructure was observed by Cryo scanning electronic microscope images in sea cucumber dried with microwave power of 200 and 250 W, which might be responsible for high values of rehydration ratio and water holding capacity. High microwave power caused the increase of amino acids content, but had no significant effect on the change of saponins content. In addition, excellent prediction models of moisture ratio have been developed by partial least squares regression analysis based on transverse relaxation data, which proved the feasibility of low-field nuclear magnetic resonance to monitor moisture changes of sea cucumber during MVD process. PRACTICAL APPLICATION: Effects of microwave vacuum drying (MVD) on moisture migration, microstructure, and rehydration of sea cucumber were investigated. Understanding the impacts of MVD drying on water status, texture, and nutritional characteristics of sea cucumber is important to improve the processing quality of dried sea cucumber.

Evaluation of Microwave Vacuum Drying as an Alternative to Freeze-Drying of Biologics and Vaccines: the Power of Simple Modeling to Identify a Mechanism for Faster Drying Times Achieved with Microwave

Vial-based lyophilization for biopharmaceuticals has been an indispensable cornerstone process for over 50 years. However, the process is not without significant challenges. Capital costs to realize a lyophilized drug product facility, for example, are very high. Similarly, heat and mass transfer limitations inherent in lyophilization result in drying cycle on the order of several days while putting practical constraints on available formulation space, such as solute mass percentage or fill volume in a vial. Through collaboration with an external partner, we are exploring microwave vacuum drying (MVD) as a faster drying process to vial lyophilization wherein the heat transfer process occurs by microwave radiation instead of pure conduction from the vial. Drying using this radiative process demonstrates greater than 80% reduction in drying time over traditional freeze-drying times while maintaining product activity and stability. Such reduction in freeze-drying process times from days to several hours is a welcome change as it enables flexible manufacturing by being able to better react to changes either in terms of product volume for on-demand manufacturing scenarios or facilities for production (e.g., scale-out over scale-up). Additionally, by utilizing first-principle modeling coupled with experimental verification, a mechanism for faster drying times associated with MVD is proposed in this article. This research, to the best of our knowledge, forms the very first report of utilizing microwave vacuum drying for vaccines while utilizing the power of simplified models to understand drying principles associated with MVD.

Functional group changes and chemical bond-dependent dielectric properties of lotus seed flour with microwave vacuum drying

Microwave vacuum drying (MVD) was applied to dehydrate lotus (Nelumbo nucifera Gaertn.) seeds. This paper evaluated the changes of molecular, crystalline, and morphological structural properties of lotus seeds after MVD. The results showed the frequency of δ(CH) bending, β(CH), ν(OH), and carbon-oxygen double bonds (C = O) increased with increasing microwave power density. Moreover, as microwave power density increased, the transition enthalpy of crystallinity gradually increased, which was related to the formation of crystalline starch, re-crystallization, and complexes of starch-lipid structure depending on the hydrogen bonds formed. The MVD process resulted molecular polarity of lotus seeds, whereas the dielectric properties also changed. The dielectric properties interacted with the changes of molecules and crystalline structure. The morphology of lotus seed flour changed because the shape of starch granules was disrupted and the granules became aggregated with nonstarch components as the microwave power density increased. All these results explain the interactions among polymer molecules in lotus seeds dried by MVD.

Effects of microwave vacuum drying and conventional drying methods on the physicochemical and microstructural properties of squid shreds

BACKGROUND

Microwave vacuum drying is an innovative technology for drying fruits and vegetables. However, this technology has not been well explored for drying seafood. In the present study, the effects of microwave vacuum drying (MVD), hot air drying (HAD) and sun drying (SD) on the proximate composition, texture, rehydration, color and microstructure of squid shreds were investigated.

RESULTS

Proximate components of the samples dried by different methods were not significantly different, but the drying time was markedly lower for the MVD technique. The rehydration rate and water absorption index followed the order MVD > HAD > SD. The extent of browning as indicated by the b* value was significantly lower in MVD samples (14.38) compared with HAD (19.47) and SD (21.94) samples. MVD resulted in the lowest values for hardness, springiness and chewiness of both dried and rehydrated squid shreds, while SD recorded the highest values for the same. Scanning electron microscopy (SEM) images of the muscle fiber indicated muscle shrinkage and more toughness in SD samples, whereas Fourier transform infrared (FTIR) spectra revealed a small extent of protein degradation in MVD samples.

CONCLUSION

The study revealed that higher-quality dried squid shreds can be prepared by microwave vacuum drying in a shorter time compared with the traditional methods of sun drying and hot air drying. Hence microwave vacuum drying can be used as an energy-efficient and time-saving technology to make dried seafood of superior quality. © 2019 Society of Chemical Industry.

Effect of Non-Conventional Drying Methods on In Vitro Starch Digestibility Assessment of Cooked Potato Genotypes

Potatoes (Solanum tuberosum L.) are a good dietary source of carbohydrates in the form of digestible starch (DS) and resistant starch (RS). As increased RS content consumption can be associated with decreased chronic disease risk, breeding efforts have focused on identifying potato varieties with higher RS content, which requires high-throughput analysis of starch profiles. For this purpose, freeze drying of potatoes has been used but this approach leads to inaccurate RS values. The present study objective was to assess the starch content (RS, DS and total starch (TS)) of three cooked potato genotypes that were dried using freeze drying and innovative drying techniques (microwave vacuum drying, instant controlled pressure drop drying and conductive hydro-drying) relative to freshly cooked potato samples. Depending on the genotype, all drying methods showed one or more starch measures that were significantly different from freshly cooked values. The combination of ultrasound and infrared assisted conductive hydro-drying was the only method identified to be associated with accurate assessment of DS and TS content relative to fresh samples. The drying treatments were all generally associated with highly variable RS content relative to fresh controls. We conclude that freshly cooked samples must be used for selecting varieties with a high proportion of RS starch as drying of cooked potatoes leads to unreliable RS measurements.

The Concept of Microwave Foam Drying Under Vacuum: A Gentle Preservation Method for Sensitive Biological Material

Microwave vacuum drying as compared to conventional vacuum drying has evinced advantages regarding drying time, while comparable product characteristics were achieved when drying sensitive biological material. Due to the volumetric microwave input, a time reduction of up to 90% is possible. When drying viscous liquids, a foamed structure that remains stable during drying exhibits further advantages as the diffusion-limited third drying step is enhanced by the porous structure. As foams not only have to be thermally resistant during microwave vacuum processing, but also withstand the vacuum, a specific process for foam drying by microwaves under low pressure conditions was developed. Foam formation and stabilization was achieved by using a synergistic mixture of proteins and carbohydrates; Lactobacillus paracasei ssp. paracasei F19 (L. paracasei) served as a model sensitive substance. Investigation of surface activity and foaming properties as a function of L. paracasei concentration revealed a significant positive contribution of the bacterial cells. It was shown that L. paracasei directly adsorbed at the air-water interface. Besides, a structuring of the liquid lamellae was assumed. Moreover, drying time was reduced to at least 50% compared to microwave vacuum drying without foaming. It was further observed that the slight loss in survival was mainly due to the relatively high moisture content and high vacuum levels at the beginning of the process. However, foaming, vacuum application, and final drying, respectively, did not affect viability of the bacterial cells. Thus, by incorporation of lactic acid bacteria into foam structures, drying can be carried out in a fraction of time, and further results in high-product quality. PRACTICAL APPLICATION: The application of continuous foam drying offers an efficient and energy-saving alternative to the currently applied techniques for the processing of sensitive material. The process could be applied for the preservation of starter cultures and probiotics as well as in the pharmaceutical industry, when sensitive material such as therapeutic proteins is dried. This process is especially suitable for freezing-sensitive and thermolabile substances.

Effect of Microwave Vacuum Drying on the Drying Characteristics, Color, Microstructure, and Antioxidant Activity of Green Coffee Beans

The aim of this study is to investigate the effect of microwave vacuum drying (MVD) on the drying characteristics and quality attributes of green coffee beans. We specifically focused on the effective moisture diffusion coefficient (D_eff), surface temperature, glass transition temperature (T_g), water state, and microstructure. The kinetics of color changes during drying, total phenolic content (TPC), and antioxidant activity (DPPH, FRAP, and ABTS) were also characterized. Microwave power during MVD affected the porosity of coffee beans, their color, TPC, and antioxidant activity. The Allometric 1 model was the most suitable for simulating surface temperature rise kinetics. Thermal processing of green coffee beans resulted in increased b*, L*, ΔE, and TPC values, and greater antioxidant capacity. These findings may provide a theoretical reference for the technical improvement, mechanisms of flavor compound formation, and quality control of dried green coffee beans.