Changes in physicochemical properties of spray-dried camel milk powder over accelerated storage

Stability and expression of K-ras mimotopes in freeze-dried recombinant Lactococcus lactis NZ3900-fermented milk powder during storage in vacuum packaging

AIMS

This study aims to evaluate the storage stability of the freeze-dried recombinant Lactococcus lactis NZ3900-fermented milk powder expressing K-ras (Kristen rat sarcoma viral oncogene homolog) mimotopes targeting colorectal cancer in vacuum packaging.

METHODS AND RESULTS

The freeze-dried L. lactis-fermented milk powder stored in 4-ply retortable polypropylene (RCPP)-polyamide (PA)-aluminium (AL)-polyethylene terephthalate (PET) and aluminium polyethylene (ALPE) was evaluated throughout 49 days of accelerated storage (38°C and 90% relative humidity). The fermented milk powder stored in 4-ply packaging remained above 6 log10 CFU g-1 viability, displayed lower moisture content (6.1%), higher flowability (43° angle of repose), water solubility (62%), and survivability of L. lactis after simulated gastric and intestinal digestion (>82%) than ALPE packaging after 42 days of accelerated storage. K-ras mimotope expression was detected intracellularly and extracellularly in the freeze-dried L. lactis-fermented milk powder upon storage.

CONCLUSIONS

This suggests that fermented milk powder is a suitable food carrier for this live oral vaccine.

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

The production of whey protein concentrates (WPCs) from camel milk whey represents an effective approach to valorize this processing by-product. These concentrates harbor active ingredients with significant bioactive properties. Camel WPCs were spray-dried (SD) 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 impact of both treatments on protein degradation was studied by sodium dodecyl sulfate-PAGE and reverse-phase ultraperformance liquid chromatography (RP-UPLC) techniques. Significantly enhanced protein degradation was observed after US treatment when compared with SD. Both SD and US treatments slightly enhanced the WPCs samples' antioxidant activities. The US exposure for 15 min exhibited highest 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) scavenging activity (12.12 mmol TE/g). Moreover, US treatment for 10 min exhibited the highest in vitro anti-diabetic properties (α-amylase and α-glucosidase inhibition), and dipeptidyl-peptidase-IV inhibitory activity among all samples. In addition, the ultrasonication for 10 min and SD at 170°C showed the lowest IC50 values for in vitro anti-hypercholesterolemic 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.

Crystal size, a key character of lactose crystallization affecting microstructure, surface chemistry and reconstitution of milk powder

Lactose crystallization during storage deteriorates reconstitution performance of milk powders, but the relationship between lactose crystallization and reconstitution is inexplicit. The objective of this study is to characterize crystalline lactose in the context of formulation and elucidate the complex relationship between lactose crystallization and powder functionality. Lactose in Skim Milk Powder (SMP), Whole Milk Powder (WMP) and Fat-Filled Milk Powder (FFMP) stored under 23 %, 53 % and 75 % Relative Humidity (RH) at 25  ℃ for four months was compared. Lactose, surface chemistry and microstructure of FFMP stored at 25 ℃ and 40 ℃ at 23 % to 75 % RH for four months were also analyzed and interpreted. At the same RH, FFMP crystallized in the same pattern as WMP. At 53 % RH, FFMP and WMP differentiated from SMP in terms of lactose morphology as well as the ratio between anhydrous α-lactose and anhydrous β-lactose. Lactose remained amorphous at 23 % RH, crystallized predominantly to α/β-lactose (1:4) at 40 to 58 % RH and to α-lactose monohydrate at 75 % RH. The crystallinity index was similar for all powders containing crystalline lactose. The estimated crystallite size increased from approx. 0.1 to 20 µm with increasing RH and temperature. When amorphous lactose crystallized into crystals below approx. 0.1 µm at 25 °C and 43 % RH, the microstructure and surface lipid were comparable to that of the reference powder. This powder reconstituted into a stable suspension system comparable to that of reference (well performing) powders. These results demonstrate that crystallite size is the key property linking lactose crystallization and reconstitution. Our finding thus indicates limiting crystallite size is important for maintaining desired product quality.

Storage of spinach juice agglomerates: Physical, flow, structural, and thermal properties

The objective of this study was to investigate how the various storage temperatures affected the physical properties, flow characteristics, microstructure, and glass transition temperature of spinach juice agglomerates. For this purpose, spray-dried spinach juice powders were processed to agglomerates by using a modified fluidized bed dryer (1.6 m/s airflow rate, 60°C drying air temperature, 20 min processing time, and with different binder solutions containing agents as maltodextrin, gum Arabic, and whey powder isolate). The analyses were carried out every month throughout 6 months while the spinach juice agglomerates were stored at temperatures of 4, 20, and 35°C. The results revealed that over the storage time, the moisture content and water activity values of the agglomerates were generally under 11% and 0.6, respectively. The color values generally showed a decreasing trend depending on the storage time. The solubility times of the samples stored at 4°C were longer than those of stored at other storage temperatures. The SJA-GA had the lowest HR and CI values and thus the best flowability properties during all storage times. There was no detectable change in the structures of SJA stored at 20°C according to the storage time. Throughout the storage time, it was discovered that the glass transition temperature of all spinach juice agglomerates was remarkably similar. Overall, the investigation revealed that storage at 35°C for 6 months might be suitable because it delivered the intended outcomes such as greater flowability and cohesiveness, and shorter wettability and solubility times.

Effects of storage conditions on milk powder properties

Studies on the storage stability of milk powder are currently fragmented and mainly affect only the area of above-zero temperatures. At the same time, there are no studies that consider the load factor when milk powder is stored in bags on a pallet. The purpose of this study was to identify the influence of various factors of industrial storage (temperature, height or layer number, and time) on the change in quality and technological properties of powdered dairy products. We placed skim milk powder (SMP) and whole milk powder (WMP) in 10 × 14 × 2 cm resealable plastic bags on a model stand simulating an industrial layout on pallets. The samples were stored for 18 mo at temperatures -30 ± 1°C, 6 ± 1°C, and 25 ± 3°C and 40 to 80% relative humidity. Samples from the control (0), 5, and 10 (lower) layers of pallets were selected for analysis on 0, 3, 6, 9, 12, 15, and 18 mo of storage for each of the temperatures. As a result, we did not detect any changes in the storage process for water activity and mass fraction of moisture. The particle size distribution of all the SMP and WMP samples changed over time. The greatest changes were observed in the WMP samples placed on the 10th layer of pallets at 25 ± 3°C, from 0 to 18 mo of storage, the mean particle size (D[4,3]) increased from 120 to 258 μm (90% of all sample particle sizes ranging from 209 to 559 μm). We found significant clumping in the WMP samples (lumps up to 5 cm), correlating with the layer and storage time. The contact angle of the samples increased from 17° (SMP) and 53° (WMP) to 40° and 71°, respectively. The insolubility index and titratable acidity did not change only in the SMP samples stored with no load applied at -30 ± 1°C and 6 ± 1°C. The heat stability of all samples stored at 25 ± 3°C showed the lowest values. The data obtained allowed us to rank the factors as "layer - time - temperature." Only the temperature of 25 ± 3°C caused critical changes in the product properties. Thus, the possibility of industrial storage of the product for up to 15 mo over the entire temperature range is confirmed.

Freeze-dried human milk microcapsules using gum arabic and maltodextrin: An approach to improving solubility

Human milk (HM) is essential for newborns' food, but its low storage stability is a limiting factor so that microencapsulation may stabilize and protect compounds sensitive to degradation. This study investigated the action of maltodextrin and gum arabic on freeze-dried HM concerning its quality and solubility. Microencapsulation was evidenced by morphology, and all samples presented high encapsulation efficiency (>85 %), proving to be an efficient process. Furthermore, specific signals in the Fourier-Transform Infrared (FTIR) spectra indicate the interactions between the coating materials and the HM matrix. Gum arabic improved the reconstitution properties of freeze-dried HM (higher solubility, 3 % on average, and lower dissolution time, around 80 %), elucidating its high stabilization capacity, even at low concentrations (5 and 10 %). Despite the best results reached by gum arabic, the addition of maltodextrin proved effective; in other words, its low stabilization capacity enables combinations with gum arabic. A lower polidispersibility (difference of 20 % between samples: control and containing gum arabic) was also observed, which means that the encapsulated samples were more homogeneous. Therefore, through the analysis performed, we recommend using gum arabic alone or with maltodextrin to obtain HM microcapsules with a good quality of reconstitution.

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.

Effects of Pasteurization and High-Pressure Processing of Camel and Bovine Cheese Quality, and Proteolysis Contribution to Camel Cheese Softness

The effects of high-pressure processing (HPP) compared to thermal treatments on the quality of camel vs. bovine cheeses were studied. The study showed that camel milk has a lower microbial load compared to bovine milk, which is maintained during 7 days' storage of the processed milk. The effect of three HPP treatments (350, 450, and 550 MPa for 5 min at 4°C) and two pasteurization treatments (65°C for 30 min and 75°C for 30 s) on the quality of soft unripened camel and bovine milk cheeses were accessed. The cheeses were evaluated for pH, yield, proximate composition, textural and rheological properties, microstructure, and protein profile by SDS-PAGE electrophoresis. The effects of the treatments on cheese's hardness were different between the camel and bovine cheeses; while heat treatment at 65°C for 30 min gave the hardest bovine milk cheese (1,253 ± 20), HPP treatment at 350 MPa for 5 min gave the highest value for camel milk cheese (519 ± 5) (p < 0.05). The hardness of the cheeses was associated with low yield and moisture content. SDS-PAGE electrophoresis revealed that extensive proteolysis might have contributed to the softness of camel cheeses compared to bovine and suggested the involvement of some residual enzyme activities.

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%).

The variability of physico-chemical properties of brewery spent grain from 8 different breweries

This research aimed to identify the differences in brewer's spent grains, which were collected from eight breweries for their physicochemical properties. The spent grains were dried until they reached stable weights, grounded to pass through a 385-μm sieve, vacuum-packed in nontransparent packaging, and kept in room temperature conditions for further analysis. The physicochemical properties, including proximate, color, water activity, water-holding capacity, oil-holding capacity, and density were evaluated. The results showed some differences in all measured quality parameters between all eight different spent barley grain samples. A similar pattern was noted in some properties studied. Hence, mathematical modeling of these studied properties should be undertaken with further qualities, such as fiber composition, mechanical properties, and thermal stability.

Recent Advances in Camel Milk Processing

Simple Summary

The camel milk market was limited for a long time by its almost exclusive self-consumption use in nomadic camps. Significant development has been observed for the past two or three decades, including internationally, boosted by its reputation regarding its health effects for regular consumers. Such emergence has led the stakeholders in the sector to offer diversified products corresponding to the tastes of increasingly urbanized consumers, more sensitive to “modern” products. Thus, traditionally drunk in raw or naturally fermented form, camel milk has undergone unprecedented transformations such as pasteurization, directed fermentation, cheese or yoghurt processing, and manufacture of milk powder for the export market. However, the specific characteristics of this milk (composition, physical properties) mean that the technologies applied (copied from technologies used for cow milk) must be adapted. In this review, some technological innovations are presented, enabling stakeholders of the camel milk sector to satisfy the demand of manufacturers and consumers.

Abstract

Camel milk is a newcomer to domestic markets and especially to the international milk market. This recent emergence has been accompanied by a diversification of processed products, based on the technologies developed for milk from other dairy species. However, technical innovations had to be adapted to a product with specific behavior and composition. The transformation of camel milk into pasteurized milk, fermented milk, cheese, powder, or other products was supported, under the pressure of commercial development, by technological innovations made possible by a basic and applied research set. Some of these innovations regarding one of the less studied milk sources are presented here, as well as their limitations. Technical investigations for an optimal pasteurization, development of controlled fermentation at industrial scale, control of cheese technology suitable for standardized production, and improvements in processes for the supply of a high-quality milk powder are among the challenges of research regarding camel milk.

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.

Using recombinant camel chymosin to make white soft cheese from camel milk

Bovine derived chymosin in rennet cannot coagulate camel milk (CAM). The study aimed at producing cheese curd from CAM using a recombinant camel chymosin. Pasteurized CAM was prepared for curdling using a recombinant camel chymosin (50 IMCU/ kg). CAM (pH 6.65) contained 2.83% Fat, 3.34% proteins and 9.11% non-fat solids. Physicochemical properties of soft cheese from cultured CAM were 51.89%, 15.62%, 20.21% and 2.47% for moisture, protein, fat and ash, respectively. Cultured CAM afforded higher cheese yield (8.75%) than non-cultured CAM (3.34%). CAM cheese whey had 48.94% and 76.80% of the fat and proteins, respectively, of their corresponding concentrations in CAM. The study is the first report on soft cheeses from CAM (cultured and non-cultured) using a recombinant camel chymosin, with reference to whey constituents. CAM cheese and whey could be added-value products.

Encapsulation of Lactobacillus spp. using bovine and buffalo cheese whey and their application in orange juice

The aim of this study was to evaluate and compare the efficiency of bovine (CW) and buffalo cheese whey (BCW) as encapsulating agents for the spray-drying (SD) of endogenous Lactobacillus pentosus ML 82 and the reference strain Lactobacillus plantarum ATCC 8014. Their protective features were also tested for resistance to storage (90 days, 25 °C), simulated gastrointestinal tract (GIT) conditions, and for their application in orange juice. Survival rates after SD were approximately 95% in all samples tested, meaning both CW and BCW performed satisfactorily. After 90 days of storage, both species remained above 7 log Colony Forming Units (CFU)/g. However, CW generally enabled higher bacterial viability throughout this period. CW microcapsule characteristics were also more stable, which is indicated by the fact that BCW had higher moist content. Under GIT conditions, encapsulated lactobacilli had higher survival rates than free cells regardless of encapsulating agent. Even so, results indicate that CW and BCW perform better under gastric conditions than intestinal conditions. Regarding their use in orange juice, coating materials were probably dissolved due to low pH, and both free and encapsulated bacteria had similar survival rates. Overall, CW and BCW are suitable encapsulating agents for lactic acid bacteria, as they provided protection during storage and against harmful GIT conditions.

Formation of heterocyclic aromatic amines with the structure of aminoimidazoazarenes in food products

Thermal food processing has many beneficial consequences, although it also produces some unintentional undesired effects, such as the formation of potentially mutagenic and carcinogenic substances. Among them, the formation of heterocyclic aromatic amines (HAAs) has been related to the declared carcinogenicity of processed meats. In spite of this importance, HAA formation pathways remain mostly unknown, which avoids the design of targeted procedures to inhibit HAA appearance. The objective of this review is to collect information recently appeared that allow advancing in the understanding of how these compounds are produced. Particularly, the possibility that aminoimidazoazarenes are produced similarly to PhIP is discussed, including their formation by cyclizations and oligomerizations of aldehydes and creatinine under usual cooking conditions. Present data suggest that HAA formation might be related to the pool of carbonyl compounds existing in foods, the food carbonylome, which can be controlled by carbonyl-trapping agents, such as amine and phenolic compounds.