Effect of operating parameters on the surface and physico-chemical properties of spray-dried camel milk powders

Camel milk whey powder formulated using thermal (spray-drying process) and non-thermal (ultrasonication) processing methods: Effect on physicochemical, technological, and functional properties

Whey protein concentrates (WPCs) are gaining importance as a functional ingredient due to their high technological and functional properties and their diverse application in the food industry. In this study, Camel milk whey (CW) was separated from skimmed camel milk, then either spray-dried (SD) at 170, 185 and 200 °C, or treated by ultrasonication (US) (20 kHz) for 5, 10 and 15 min followed by freeze-drying to obtain camel milk whey powder (CWP). The structural analysis of CWP was carried out by Fourier-Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) which showed no significant difference in the functional groups profile of US samples compared to control and SD samples. US samples showed some degree of crystallinity that was comparable to the control samples, while SD samples exhibited very low degree of crystallinity. The surface morphology, particle size, and surface charge of CWP were evaluated using scanning electron microscopy (SEM) and Zetasizer. The lowest particle size of 215.1 nm with surface charge of -21.6 mv was observed in SD-185 WPC. Moreover, SD samples revealed whiter color compared to the US-treated samples which were having lower L* values (P < 0.05). US-15 sample exhibited high protein solubility (100 %), whereas the SD-200 sample showed reduced solubility (92.7 %). Improvement in the emulsifying activity of CWP samples was observed after SD and US, with highest emulsifying activity index (EAI) values of 143.75 m2/g and 143.11 m2/g were reported for SD-185 and US-15 CWP samples, respectively. To conclude, SD and US were found to improve the physico-chemical, technological, and functional properties of CWP, and thus can be utilized as a promising strategy to preserve and enhance the technofunctional properties of CWP.

Spray-drying and ultrasonication processing of camel whey protein concentrate: Characterization and impact on bioactive properties

The production of whey protein concentrates (WPC) from camel milk whey represents an effective approach to valorize this processing byproduct. These concentrates harbor active ingredients with significant bioactive properties. Camel WPC were spray-dried at inlet temperature of 170, 185 and 200°C, or ultrasonicated (US) for 5, 10, and 15 min, then freeze-dried to obtain fine powder. The effect of both treatments on protein degradation was studied by sodium dodecyl sulfate-PAGE and reverse-phase ultraperformance liquid chromatography techniques. Significantly Substantially enhanced protein degradation was observed after US treatment when compared with spray-drying (SPD). Both SPD and US treatments slightly enhanced the WPC samples' antioxidant activities. The US exposure for 15 min exhibited the highest 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) scavenging activity (12.12 mmol Trolox equivalent per gram). Moreover, US treatment for 10 min exhibited the highest in vitro antidiabetic properties (α-amylase and α-glucosidase inhibition), and dipeptidyl peptidase-IV inhibitory activity among all samples. In addition, the US for 10 min and SPD at 170°C showed the lowest median inhibitory concentration (IC50) values for in vitro antihypercholesterolemic activities in terms of pancreatic lipase and cholesteryl esterase inhibition. Conclusively, these green techniques can be adapted in the preservation and processing of camel milk whey into active ingredients with high bioactive properties.

Camel milk products: innovations, limitations and opportunities

Camel milk is the mainstay for millions of people in arid and semi-arid environments. In these areas, it is mainly consumed raw or after it spontaneously turns sour. Although some attempts have been made to produce dairy products from camel milk, processing of camel milk is generally considered to be difficult and the quality of the final products made from camel milk do not correspond to their bovine milk counterparts. This paper reports a comprehensive analysis of the literature on camel milk products and presents synthesis of the latest developments, limitations pertaining processing and opportunities for development of new and improved camel milk products. The protein composition and colloidal structure of camel milk differs from cow milk. It is characterized by absence of β-lactoglobulin, low κ-casein content, high proportion of β-casein, larger casein micelles and smaller fat globules. These differences lead to the difficulty of making dairy products from camel milk using the same technologies as for bovine milk. Some of the challenges of camel milk processing include poor stability of the milk during UHT treatment, impaired rennetability, formation of weak and fragile curd during coagulation, longer fermentation time, and low thermal stability of the milk during drying. Despite these difficulties, it has now become possible to produce a range of commercial and traditional dairy products from camel milk. Some of the strategies that could be applied to improve the quality and characteristics of camel milk products are discussed.

Graphical Abstract

Physicochemical Properties and Whey Proteomes of Camel Milk Powders Produced by Different Concentration and Dehydration Processes

Camel milk powder production is an alternative to preserve the perishable milk for later-date consumption. However, the impacts of dehydration processes on bioactive compounds in camel milk are largely unknown. Hence, the present study attempted to compare the physicochemical properties and protein profiles of camel milk powders produced by different concentration and dehydration processes. Six camel milk powders were produced by freeze- and spray-drying methods in conjunction with two liquid concentration techniques, namely spray dewatering and reverse osmosis. The results of proteomic analysis showed that direct freeze-dried camel milk powder had the least changes in protein profile, followed by direct spray-dried powder. The camel milk powders that underwent concentration processes had more profound changes in their protein profiles. Among the bioactive proteins identified, lactotransferrin and oxidase/peroxidase had the most significant decreases in concentration following processing. On the contrary, glycosylation-dependent cell adhesion molecule 1, peptidoglycan recognition protein 1, and osteopontin increased in concentration. The results revealed that direct freeze drying was the most ideal method for preserving the bioactive proteins during camel milk powder production. However, the freeze-drying technique has cost and scalability constraints, and the current spray-drying technique needs improvement to better retain the bioactivity of camel milk during powder processing.

Changes in surface chemical composition relating to rehydration properties of spray-dried camel milk powder during accelerated storage

Alterations in surface chemical composition relating to rehydration properties of spray-dried camel milk powders during accelerated storage (11-33% RH, 37 °C) over 18 weeks were investigated. The results showed that the surface of the fresh spray-dried camel milk powder (t = 0) was dominated by lipids (78%), followed by proteins (16%) and lactose (6%). During storage, the surface protein and lactose content decreased while the surface lipid content increased, resulting in an increase in surface hydrophobicity and slight agglomeration of the powder, especially for powder kept at 33% RH. Although fresh camel milk powder had very poor wettability, it displayed very high dispersibility and solubility (99%). During storage, dispersibility and solubility declined with increasing storage time and increasing RH levels, which correlated with an increase in surface lipid content. However, at the end of the storage period, camel milk powder still retained very high solubility (>93%).

Physicochemical, techno-functional, and fat melting properties of spray-dried camel and bovine milk powders

In this study, three skimmed and one whole-fat spray-dried camel milk powders were produced and their characteristics were compared to those of bovine milk powders. The physicochemical analysis of the produced powders indicated that camel milk powders (whether skimmed or not) presented higher ash and whey protein contents as compared to those of bovine milk powders. Our results indicated that the investigated camel and bovine milk powders exhibited a high solubility index (>99%) with poor dispersibility and wettability indexes due to their small particles size (d₅₀ ≤ 12 µm) and their narrow size distribution (span ≤ 2). In addition, although camel and bovine milk powders presented the same total fat content, lower free fat content was measured for camel milk powders. Besides, the whey protein nitrogen index and the SDS-PAGE electrophoresis underlined that camel and bovine milk proteins remained intact after drying with low denaturation extent. It is worth noticed that camel milk proteins were less denaturized due to the absence of the heat-sensitive β-lactoglobulin in camel milk. Moreover, the low denaturation extent participated in the enhancing of the foaming capacity and stability of camel and bovine milk powders. Finally, the calorimetric analysis showed that higher fat melting temperatures were recorded in whole-fat camel milk powder and in their anhydrous form as compared to those of bovine milk. PRACTICAL APPLICATION: Camel milk powder is an emerging non-bovine dairy product. Understanding its rehydration ability and evaluating the impact of spray drying on its protein quality are promising approaches to obtain high-quality camel milk powder with high reconstitution ability. Findings of this study indicated that spray drying is a suitable technique to produce highly soluble camel milk powders with low denaturation extent. These results will benefit the research and development department of food industry (especially those producing camel milk powder) as well as the direct consumers.

Spray drying and storage of probiotic-enriched almond milk: probiotic survival and physicochemical properties

BACKGROUND

The combination of the nutritional profile of almond milk with the benefits of probiotic bacteria is an interesting development to meet the demand for sustainable and health-promoting food. Almond milk inoculated with probiotic Lactobacillus plantarum (ATCC8014) was spray dried and the almond, its milk, and powders were characterized physicochemically. Samples were characterized in terms of bacterial survival before and after atomization. Bacterial viability and total fatty acid changes were studied during 8 months' storage at 4 and 22 °C.

RESULTS

Results showed adequate physicochemical properties and an optimal bacterial survival rate, maintaining almost the same values before and after the spray-drying operation. A decrease was observed in the cell viability for samples stored at 4 °C. However, the cell count was maintained above the minimum level suggested (10⁷ living cells) to allow potential probiotic functionality for 8 months. On the other hand, the count cell of powders stored at 22 °C was below the minimum level required after 6 months. The fatty acids profile was not significantly (P > 0.05) affected by storage time and temperature.

CONCLUSION

A new almond-based-product with probiotics was developed to meet consumer demands. Almond nutrients were recovered from almond milk powder and were found to be a good source of K and high in Mg and in monounsaturated fat. The viability of bacteria was assured during 8 months of storage at 4 °C and up to 6 months for samples stored at 22 °C. © 2020 Society of Chemical Industry.

Stability of bifidobacteria entrapped in goat's whey freeze concentrate and inulin as wall materials and powder properties

Goat's whey was submitted to two cycles of block freeze concentration process, resulting in concentrate 1 and concentrate 2. Concentrate 1 was added with 5 g of inulin and both concentrates were inoculated with Bifidobacterium animalis ssp. lactis BB-12, the concentrates were then denoted as feed solutions 1 and 2, respectively. Feed solutions were spray-dried, resulting in powder 1 and 2. The stability of the bifidobacteria entrapped within the powders was evaluated for both spray-dried powders stored at 4 °C and 25 °C for 60 days. The spray-dried powders were also evaluated in relation to their physical and thermal properties. It was noted that Bifidobacteria displayed increased stability at refrigeration temperature. Analysis of physical properties indicated that the addition of inulin resulted in increased water solubility. However, both spray-dried powders displayed less flowability, as well as a yellow-greenish color. By evaluating the spray-dried powders thermal properties, it was possible to confirm that goat whey concentrates behave as excellent wall materials.