Foam mat drying of fig fruit: Optimization of foam composition and physicochemical properties of fig powder

Preserving nutrient content in red cabbage juice powder via foam-mat hybrid microwave drying: Application in fortified functional pancakes

Red cabbage, a highly nutritious cool-season cruciferous vegetable, is rich in anthocyanins; however, the instability of anthocyanins during processing and storage poses challenges. This study aimed to optimize the foam-mat drying process of red cabbage juice (RCJ) with a high anthocyanin content using a hybrid microwave hot air-drying system (MW-HAD) as a dehydration method compared to conventional techniques (HAD) using response surface methodology (RSM). Additionally, the produced red cabbage juice powder (RCJP) was used to enrich the pancake formulation. The developed model exhibited a high degree of reliability with optimal conditions and was determined for microwave power, temperature, foaming agent carboxymethylcellulose (CMC), and egg white protein (EWP) as 360 W, 60°C, 0.3%, and 1.2%, respectively. Moisture content (%) was decreased from 93.47 to 8.62 at optimum process conditions. In comparison to the control (60°C), foam mat drying with the MW-HAD hybrid system reduced the drying time (DT) by more than 90.9% due to the higher drying rate, while many physicochemical properties, especially total anthocyanin content (TAC), were better preserved. Utilization of RCJP in the production of anthocyanin-rich functional pancakes resulted in enhanced nutritional qualities compared to control pancakes with increased protein (35.07%), total phenolic (75.8%), dietary fiber (82.9%), and anthocyanin content (100%). In conclusion, MW-HAD demonstrates significant potential as a promising drying method to reduce the DT and preserve the physicochemical properties of RCJP. Furthermore, the application of the optimized RCJP in anthocyanin-rich functional pancakes highlights improved nutritional qualities, making a substantial contribution to the advancement of functional foods.

Tropical Red Fruit Blend Foam Mat Drying: Effect of Combination of Additives and Drying Temperatures

Foam mat drying is a widely used technique for liquid products because it has a number of advantages; however, for an efficient process, the choice of additives and temperatures is extremely important. The objective of this study was to evaluate the effect of additives and drying temperatures on the powders obtained from the blend of tropical red fruits, such as acerola, guava, and pitanga. The foam formulations were prepared by mixing the pulps of the three fruits in equal proportions (1:1:1), all added with 6% albumin and 1% stabilizing agent: E1, gum Arabic; E2, guar gum; E3, gelatin. The combinations were subjected to beating, and subsequently, they were dried in an oven with forced air circulation at four temperatures (50 to 80 °C), with a mat thickness of 0.5 cm. The obtained powders showed low levels of water and water activity and high levels of bioactive compounds, colors with a predominance of yellow, intermediate cohesiveness, poor fluidity, and solubility above 50%. The best temperature for obtaining the powders was 60 °C. The formulation that produced the best results for the production of the tropical red fruit blend powder was the combination of albumin and gelatin.

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.

Optimization of foaming process: drying behaviour, physicochemical, and powder properties of hot air-assisted foam-mat dried nectarine

Nectarine powder is widely used in the industries of baking and confectionery. The production of nectarine powder can be made by several drying techniques such as spray, tray, drum, freeze, and foam mat. This study was aimed to optimize the parameters of the nectarine foaming process. Besides, hot air-assisted foam-mat drying of nectarine was carried out to evaluate the effect of different temperatures (50, 60, and 70 °C) on drying kinetics, physicochemical and powder properties of nectarine powder. Factors studied were egg albumin concentration, carboxymethyl cellulose concentration, and whipping time that varied between 10 and 30% (by weight), 0.2–0.8% (by weight), and 3–5 min, respectively. Optimum conditions were determined as 30% of egg albumin, 0.8% carboxymethyl cellulose, and a whipping time of 5 min to get maximum foam expansion, high foam stability, and minimum foam density. The drying rate and effective moisture diffusivity of nectarine foam powder increased with increasing drying temperature. Carr Index and Hauser Ratio values were in the range of 32.31–47.00 and 1.48–2.00, respectively. Foamed nectarine powder dried at 70 °C had the lowest hygroscopicity value and the highest wettability value. No significant difference was found between the powders’ porosity (p > 0.05). The powders produced at 50 °C resulted in higher total phenolic, vitamin C, and carotenoid content.

Development of yoghurt powder using microwave-assisted foam-mat drying

Yoghurt powder is widely used in industries of confectionery and baking. The production of yoghurt powder can be made by several drying methods, including freeze, spray, microwave vacuum, convective and foam-mat. In this study, the effect of varying concentrations of egg albumin (EA) on foam and powder characteristics of yoghurt were determined. Besides, microwave-assisted foam-mat drying of yoghurt was carried out to examine the effects of three microwave output powers (100, 180 and 300 W) on powder properties of yoghurt. Increased in EA concentration resulted in an increase in foam expansion and decrease in foam density. Higher foam stability (after 120 min.) was observed for foams containing 10 and 15% EA (both found as 88.24%). As powder properties, wettability and solubility times were significantly decreased with the addition of EA, while water holding capacity was increased. Change in EA concentration was significantly (p ≤ 0.05) effective on all powder properties dried at 100 W. Carr Index and Hausner Ratio values were in the range of 0.99-13.89 and 1.01-1.17, respectively. Microwave powers were significantly (p ≤ 0.05) effective on the flowability of powders containing 0, 5 and 10% EA. Yoghurt powders showed mostly excellent flow characteristics (for all concentrations of EA and microwave output powers).

Impact of Foam-Mat Drying on Plant-Based Foods Bioactive Compounds: a Review

Plant-based foods are recognized by their remarkable content of bioactive compounds. In an attempt to increase plant-based foods shelf-life, technologies like drying can be used. Foam-mat drying is a mild drying technology that removes water, usually by using hot air, from a foam obtained by the whipping of a liquid or semi-liquid food added with a foaming agent. There are several reports on the use of foam-mat drying for extending plant-based foods shelf-life, including reports on the effect of drying on their bioactive compounds. Therefore, this study aimed at reviewing the literature on the impact of foam-mat drying on plant-based foods bioactive compounds published in the last 10 years. Results show that short foam-mat drying time is beneficial to bioactive compounds retention. In addition, hot air temperature between 40-65 °C, foam thickness between 0.2 and 1 cm and the use of egg white as one of the foaming agents leads to high bioactive retention. Egg white is also the most used foaming agent. Regarding the mathematical models used for fitting the foam-mat drying kinetics, the Page model was shown as the most proper model. Foaming agent concentration is a delicate parameter, as its increase in foam formulation may beneficially enhance drying rates but, at the same time, it dilutes bioactive compounds and may cause their loss by oxidation. In conclusion, foam-mat drying stands out as a suitable technology for producing food powders with high bioactive retention.

Usability of soapwort and horse chestnut saponin extracts as foaming agents in foam mat drying of pomegranate juice

BACKGROUND

This study evaluated the usability of saponin-rich extracts (soapwort and horse chestnut) as a foaming agent for foam mat drying of pomegranate juice.

RESULTS

According to the foaming and stabilization studies, the optimum conditions were determined as 0.4% of soapwort extract, 0.03% of carboxymethyl cellulose as a stabilizer, and 3 min of whipping time. The foams produced using these conditions were dried at different spreading thicknesses and drying temperatures. The results showed that the thicker spreading thicknesses provided a higher antioxidant activity. On the other hand, drying temperature had a significant effect on all measured parameters except moisture content and water activity. The higher drying temperature caused a greater colour change and a lower content of total phenolics, total monomeric anthocyanins, cyanidin-3-glucoside, and delphinidin-3-glucoside. On the other hand, a higher content of ascorbic acid and better antioxidant activity was determined in the samples dried at 70 °C.

CONCLUSION

According to the results obtained, spreading thickness of 2 mm and drying temperature of 70 °C were suggested for pomegranate juice powder production by foam mat drying. Overall, it was demonstrated that saponin-rich extracts are a good foaming agent alternative that provides foaming at very low concentrations and a product with high quality. © 2020 Society of Chemical Industry.

Processing of raspberries to dried fruit foam: impact on major odorants

Application of an aroma extract dilution analysis (AEDA) to the volatiles isolated from raspberry fruits by solvent extraction and solvent-assisted flavour evaporation (SAFE) resulted in 40 odour-active compounds with flavour dilution (FD) factors between 1 and 4096. Among the most potent odorants were violet-like smelling β-ionone (FD factor 4096), fruity smelling methyl 3-methylbutanoate (1024), baked-apple-like smelling β-damascenone (1024), raspberry-like smelling raspberry ketone (128), and floral, raspberry-like smelling α-ionone (64). These five odorants were subsequently monitored during processing of raspberry fruits to freeze-dried fruit foam. Major losses occurred during separation of the pulp from the seeds and during the final freeze-drying step. It was shown that the pulp fraction directly adherent to the seeds contained higher odorant concentrations than the outer parts of the pulp, thus losses associated with the removal of the seeds can be minimised by increasing the efficiency of the separation. Losses associated with the freeze-drying process could be reduced using microwave-assisted freeze drying instead of conventional freeze drying. Higher amounts of potato protein and maltodextrin used as foaming agent and foam stabiliser, respectively, reduced the odorant recoveries in the dried foams. Only a small part of the odorants not recovered in the dried fruit foams was found in the condensate.