Skim Milk Powder Research Articles

Survivability of Salmonella and Escherichia coli O157:H7 Pathogens and Food Safety Concerns on Commercial Powder Milk Products

Milk and dairy products are susceptible to the incidence of foodborne illnesses by numerous pathogens, including Listeria monocytogenes, Salmonella spp., Escherichia coli, enteropathogenic Campylobacter jejuni, Yersinia enterocolitica, Cronobacter (Enterobacter sakazakii) and Staphylococcus aureus. Annually Salmonella infections cause approximately 93.8 million cases of gastroenteritis and 155,000 deaths worldwide. Including meat and poultry, dairy products are the most commonly contaminated foods by Salmonella. Studies show that Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes are among the top 5 pathogens causing hospitalization and life-threatening foodborne illnesses. The U.S. Centers for Disease Control and Prevention (CDC) estimated that annually around 1.2 million foodborne illnesses with more than 23,000 hospitalizations, 450 deaths and 130 outbreaks were attributed to Salmonella infection in the U.S. The Salmonella enteric in skim milk powder survived at three months storage, with water activity as low as 0.33. With respect to Escherichia coli O157:H7, it is capable of causing disease at a low dosage, ranging from 5–50 cells. Viable cells of Escherichia coli O157:H7 reportedly survive in infant formula powder for one year at 5 °C. The survivability of Escherichia coli in powder milk was significantly reduced with the synergistic effects of storage time and temperature. The U.S. Dairy Export Council recommends that milk powder should be stored in a cool and dry place, at a temperature not to exceed 27 °C, and a relative humidity not to exceed 65%. Reports have recommended that milk powder products need to be stored in light, oxygen, and moisture-proof containers. In this article, the survival of the major foodborne pathogens including Salmonella and Escherichia coli O157:H7 in powdered milk products from common dairy species such as cow and goats are reviewed.

Continuous microwave heating to inactivate thermophilic spores in heating-sensitive skim milk concentrate

Skim milk powders often contain high spore counts, originating from persistent thermophilic bacilli in the processing plants. Through germination and enzymatic spoilage, product defects in the reconstituted product formulation may result. Heating of skim milk concentrate prior to drying may inactivate these spores. Within this study, a new method to grow thermophilic spores isolated from dairy processing plants (Anoxybacillus flavithermus and Geobacillus stearothermophilus; N0 = 6 log10 cfu mL−1) was developed, followed by heat-inactivation experiments in reconstituted skim milk concentrate using a continuous pilot-scale microwave plant. Spore reductions were counted on tryptic-soy agar (55 °C) and formal reaction kinetics were calculated. Reductions of 1–3 log10 units while applying temperatures of 110–125 °C with heat holding times of 5–270 s were achieved, depending on the strain, whereby G. stearothermophilus 1978 spores were more heat resistant than the ones of A. flavithermus 1958.

Partial substitution of 40 g/100 g fresh milk with reconstituted low heat skim milk powder in high-moisture mozzarella cheese production: Rheological and water-related properties

Skim milk powders may be used as a convenient alternative to fresh milk in high moisture Mozzarella cheese manufacturing. The effects of a blend of 40 g/100 g of reconstituted low heat skim milk powder and 60 g/100 g fresh milk on processing and quality of Mozzarella cheese (experimental) were evaluated, in comparison with cheeses produced only with fresh milk (control). The ability of experimental curd to retain fat during stretching was lower than control, as showed by the fat content in stretching water (2.85 ± 0.45 g/100 g and 2.01 ± 0.31 g/100 g for experimental and control curds, respectively). However, cheeses showed a similar composition. Cheese rheological properties were affected, as experimental Mozzarella showed a more organized casein network with tanδ and n’ values lower than control cheeses. The use of powder milk also increased the fraction of solvation water measured with low field NMR when compared with control cheeses. This study demonstrated the applicability of a blend with 40 g/100 g of reconstituted milk to obtain Mozzarella cheese without major changes in product quality.

Effect of Whey Protein Concentrate on Physicochemical, Sensory and Antioxidative Properties of High-Protein Fat-Free Dairy Desserts

This study evaluates a new formula for high-protein fat-free dairy desserts. The rheological, textural, organoleptic and antioxidative properties of this product have been examined. They were prepared in laboratory conditions using a magnetic stirrer and then mixed in a water bath at 80 °C for 10 min. The composition included skimmed-milk powder, different concentrations of whey proteins (WPC80) (5, 7, 9, 11 or 13%), sucrose and ĸ-carrageenan. Samples were stored at 4 °C. The use of different amounts of whey proteins significantly influenced the texture, rheological properties and appearance of dairy desserts. With the increase of WPC80 content, the hardness (5–11%), adhesiveness (5–13%), cohesiveness (513%), springiness (5–11%) and viscosity (5–13%) of the high-protein fat-free dairy desserts increased. Elastic (gel) properties were exhibited throughout the process (G’ > G”). This result was confirmed by the measurements of tan(δ) (tan(δ) < 1). Water activity decreased with an increase in WPC80 content. Health-promoting features using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) measurements were evaluated. Both methods showed that the samples have antioxidant properties. Panelists described desserts with 9% WPC80 as the most favorable according to sensory properties. This research promotes the reduction of production waste using high-protein whey powder, a by-product of whey from cheese manufacturing, as a main component during food production, and it also promotes fat-free food.

Impact of spray-drying conditions on physicochemical properties and rehydration ability of skim dromedary and cow's milk powders

The aim of this study was to evaluate the effect of air outlet temperature (75 and 85 °C) and milk type on proximate composition, water activity, particle size distribution, color, and rehydration ability of spray-dried skim dromedary and cow’s milk powders. While the water activity of powders was close to 0.4 when spray-dried at 75 °C air outlet temperature, it ranged from 0.2 to 0.3 for a production at 85 °C air outlet temperature. Skim dromedary milk powder had a lower water activity than skim cow’s milk powder after spray-drying at 85 °C air outlet temperature. Spray-drying yields were greater at the higher air outlet temperature (85 °C) for both skim milk powders. The particle size distributions of spray-dried skim milk powders were centered around 14–20 µm. The particles of skim dromedary milk powders were smaller than those of skim cow’s milk powders as skim dromedary milk was less viscous, leading to smaller sprayed droplets. No significant influence of spray-drying conditions on particle size distribution was observed for dromedary milk powders. Regardless of the spray-drying conditions and the milk type, the produced powders were very bright and had a low color saturation. Scanning electron microscopy images showed that spray-dried powders appeared as agglomerates of small particles with angular shapes rather than individual particles. All investigated spray-dried powders were considered non-wettable, hardly dispersible, and fairly soluble. Skim dromedary milk powder produced at 85 °C air outlet temperature showed a significantly higher solubility index than the same formulation spray-dried at 75 °C outlet air temperature. The opposite was obtained for skim cow’s milk powder. These results demonstrated that the outlet drying air temperature significantly influenced water activity, spray-drying yield and solubility of spray-dried dairy powders.

EFFECT OF PROTEIN TYPE AND SUGAR TYPE ON CHOCHOLATE PROPERTIES

This research aimed to investigate the effect of protein types (soy milk powder and skim milk powder) and sugar types (stevia and sucrose) on sensory properties of chocolate candy. The appropriate level of protein and sugar were also expected. The research performed using factorial randomized block design (RBD) with three replications. Factors namely ratio of protein type (soy milk powder, skim milk powder) and the ratio of sugar type (sucrose, stevia) were applied. Organoleptic response variables included taste, flavor, texture, and aftertaste were conducted using a hedonic test on 30 panelists. The results indicated that chocolate candy made from the ratio of soy milk with skim milk 0:1 and the ratio of sucrose and stevia of 1:1 gave the highest value of the organoleptic test. Proximate analysis showed the chocolate candy 11.05% fat, 13.44% protein, 25.28% carbohydrate, and water content of 1.17% and has a toughness test value of 1.23 mm/sec/100gram. This study revealed that alternative sugar (stevia) can be used in chocolate candy making and is expected to reduce calories contained on chocolate candy.

Pectin co-functionalized dual layered solid lipid nanoparticle made by soluble curcumin for the targeted potential treatment of colorectal cancer

The investigation is to increase the cytotoxicity of soluble curcumin (SC) by loading it onto pectin and skimmed milk powder (SMP) dual layered solid lipid nanoparticles (DL-SLN). The DL-SLN exhibited significantly higher encapsulation efficiency (83.94 ± 6.16), better stability (90 days), and sustained the drug release in different gastro intestional (GI) environments upto 72 h. Molecular docking revealed that the Vander Waals (57420.669 Kcal-mol−1) and electrostatic (-197.533) bonds were involved in the DL-SLN complex formation. The in vivo toxicity of DL-SLN was performed by the zebrafish model, the cell cycle arrest at G2/M phase (64.34 %) by flow cytometry, and western blot investigation was recognized molecular level cell death using SW480 cells. Pharmacokinetic (PK) evaluation (Cmax-5.78 ± 3.26 μg/mL; Tmax-24 h) and organ distribution studies confirmed that the co-functionalized pectin based SLN could efficiently improve the oral bioavailability (up to 72 h) of curcumin (CMN) on colon-targeted release.

Skim milk powder used as a non-permeable cryoprotectant reduces oxidative and DNA damage in cryopreserved zebrafish sperm

Cryoprotectants play a vital role in the cryopreservation process, protecting biological samples from freezing damage. Here, we evaluate the effects of the combination and interaction of different extenders with permeable and non-permeable cryoprotectants, on the cryopreservation of Danio rerio sperm, analyzing the effects of cryopreservation through a broad approach to variables. Two extenders were used, Hank's balanced salt solution (HBSS) and Ginsburg's solution. Eight cryoprotective solutions (CS) were used: CS1 (HBSS + Me2SO 8%), CS2 (HBSS + Methanol 8%), CS3 (HBSS + Me2SO 8% + Skim milk powder 15%), CS4 (HBSS + Methanol 8% + Skim milk powder 15%), CS5 (Ginsburg + Me2SO 8%), CS6 (Ginsburg + Methanol 8%), CS7 (Ginsburg + Me2SO 8% + Skim milk powder 15%) and CS8 (Ginsburg + Methanol 8% + Skim milk powder 15%). The samples were cryopreserved in cryovials for 20 min on dry ice, stored in liquid nitrogen, thawed at 38 °C for 10 s, and analyzed. In addition to increasing viability, we show that powdered milk also allows for better preservation of the membrane and normal cell morphology, and protects the sperm cells from DNA damage and oxidative stress caused by cryopreservation.

Preparation of Functional Ice Milk from Sweet Lupine flour

This study was proposed to investigate the possibility of utilization of sweet lupine (lupines albus) flour for producing functional ice milk for human consumption. Lupine consider a rich source of protein, minerals, antioxidant, and anti-microbial materials. Sweet lupine flour (SLF) was incorporated with skim milk powder at levels 5%, 15% and 25% respectively to produce healthy ice milk. Effect of replacement on chemical, physical, viscosity, meltdown, rheological, microbial quality and sensory evaluation. Protein, fat, ash, TS contents as well as pH values and overrun were increased in all samples which reconstituted with SLF compared to control. The acidity was decreased by increasing SLF compared to control. Also, the viscosity of mixes increased by increasing SLF compared to control. As well as melting down value decreased by increasing SLF. Texture profile was affected by replacement with SLF, the hardness increased by increasing the amount of SLF from 2049.49gf in control to 2347.98, 2937.19 and 3100.05 gf for 5, 15 and 25% SLF, respectively. The microbiological aspect was improved specially the sample contained 25% SLF which had the lowest total bacterial count. The sensory properties of ice milk especially sample contained 5% SLF had the highest overall acceptability compared with other samples.

Manufacture of functional Kareish cheese fortified with Oat, Talbina, Lima bean and Sweet Lupin

Recently, fortification of kareish cheese with functional foods has gained momentum in response to the variable health status of developed countries, especially in Egypt. Functional foods such as oat, talbina, lima bean and sweet lupin were used in fortification of kareish cheese. Besides, determination of the chemical composition, microbiological counts, and rheological, organoleptic analysis. In this study, kareish cheese was made using reconstituted skim milk powder at a rate of 10% which was divided into 12 equal portions, one for the control and eleven were fortified with different concentrations 1%, 2% and 3% of the functional foods under study excepting for the ratio 3% of oat addition. The addition of those functional foods had an observed increasing effect on the content of cheese moisture, also a noticeable increase in fat, ash, fiber content, and slight increase in total protein. High acidity of kareish cheese remarkable by the addition. Total bacterial counts and lactic acid bacteria slightly decreased at zero time then started to increase significantly by the increase of the storage period until reached the maximum count at 21 days then the count began to decrease. Molds and yeasts increased by the increasing of storage period. The test results of Coliform and staphylococcus sp. Counts were negative. Rheological properties of kareish cheese were affected significantly by the addition of the functional foods under study. All treatments were sensually acceptable, but the most acceptable treatments were control and those fortified treatments with functional foods under study at ratio of 1%.

Enzymatically cross-linked skim milk powder: Enhanced rheological and functional properties

Enzymatically cross-linking milk proteins by microbial transglutaminase (MTGase) is a promising strategy in developing and promoting desired multi-functional properties of dairy foods. This study evaluated the effect of MTGase treatments (0.5, 1, 2 and 4 U g−1 milk protein) of skim milk at two different incubation conditions (20 min at 38 °C, 12 h at 4 °C) on rheological and structural characteristics of spray dried skim milk powders (SMP). SMP samples treated with MTGase showed significantly increased particle size. Cross-linking milk proteins by MTGase revealed significant improvements in powder flowability characteristics by means of lower aeration and basic flow energies, and higher bulk density and compressibility properties compared with the control SMP. Overall, cross-linked SMP offers a promising option as a multi-functional ingredient for the dairy and/or composite food producers, and appearing to be an efficient option in improving powder rheological properties for dairy powder manufacturers.

Colorimetry of dairy products

Reflectance colorimetry was investigated to measure the colour of whole (WMP) and skim milk (SKMP) powders, infant formulas (IF), an adult nutritional product (ANP), unsalted (USB) and salted (SB) butters. The colorimeter gave precise results and was cost effective, illustrating the benefits of the adoption of a colorimeter rather than the current practice of using reference charts and powders. New Zealand dairy products are yellower compared with other dairy products because of their relatively high naturally occurring β-carotene content.

RESEARCH OF RHEOLOGICAL PROPERTIES OF COMPONENTS OF THE DEVELOPED MILK-CONTAINING THERMOSTABLE FILLINGS

The research is devoted to the determination of the properties of the components of the developed milk-containing thermostable fillings and the establishment of the dependence of the effective viscosity on the temperature of the model system. In the work, studies are carried out for a model system containing xanthan gum; a model system containing tara gum; model system containing gelatin; a model system containing xanthan gum and tara gum; a model system containing xanthan gum, tara gum and gelatin; a model system containing xanthan gum, tara gum and sugar; model system containing xanthan gum, tara gum, skimmed milk powder; a model system containing xanthan gum, tara gum and maltodextrin. In this work, the dependence of the effective viscosity on the temperature of the model system is established. To achieve the aim, the following objectives are set: - determination of the dependence of the effective viscosity on the temperature of model systems with xanthan gum, tara gum, gelatin, sugar, skimmed milk powder and maltodextrin with different concentrations of these components; - establishment of the temperature range in which a sharp increase in the effective viscosity of the investigated model systems begins. An increase in the temperature of the system prevents gelation due to an increase in the intensity of Brownian motion and a decrease through it in the duration of the existence of bonds that arise between macromolecules. At the same time, a decrease in temperature promotes gelation, since this increases the number of contacts between macromolecules, which contributes to an increase in the strength of the so-called spatial network. In the article, the dependences of the effective viscosity on the temperature of model systems with xanthan gum, tara gum, gelatin, sugar, skimmed milk powder and maltodextrin with different concentrations of these components are obtained. Based on the obtained dependences, the established temperature ranges in which a sharp increase in the effective viscosity of the studied model systems begins

Development and evaluation of a processing sector model for butter manufacture using a mass balance technique at two dairy processing sites

The butter manufacturing process at two different commercial dairy processing sites in Ireland was evaluated using a mass balance approach to develop, evaluate and validate a processing sector model of the flow of milk fat from intake to final product. The mass balance was represented as a function of fat intake = fat in products + fat losses + recycled fat. Representative samples of all products, namely whole milk, cream, skim milk, butter, buttermilk and cleaning‐in‐place streams (cream silo flush, butter churn residue and sludge), were collected from two different sites. Milk fat levels and product quantities were measured to obtain the fat outputs. Total fat losses at the end of butter production ranged between 1.90% and 2.25% of the total fat input for both sites. Three different scenarios were examined to evaluate the model: S1 (Animal Breed) high genetic merit (Elite) and national average (NA) Holstein Friesian (HF) cows were evaluated, for their effect on the net value of milk; S2 (Product Portfolio) a mixed product portfolio of cheese, butter and skim milk powder (SMP) was compared to a product portfolio comprised of butter alone; and S3 (Process Efficiency) the impact of varying process losses on net values of milk and the quantities of products produced was simulated. The value per 1000 L of milk for S1 was €410.69 and €393.20 for Elite and NA cow’s milk, respectively. For S2, the butter‐only product portfolio returned €355.10, whereas the mixed‐products portfolio returned €369.60. Lastly, S3 corresponding returns for 1%, 2.2% and 5% losses was €365.90, €361.47 and €351.12, respectively.

A cross-cultural sensory analysis of skim powdered milk produced from pasture and non-pasture diets

Understanding potential cross-cultural sensory differences in the perception of Irish dairy products is important for key markets such as the USA and China. As most Irish dairy products are produced from pasture derived milk, this study investigated the impact of pasture and non-pasture diets on the cross cultural sensory perception of skim milk powder (SMP) in Ireland, USA and China. SMP was produced from cows fed outdoors on ryegrass (GRS), ryegrass/white clover (CLV), and indoors on trial mixed rations (TMR). SMP samples were evaluated by Irish (n = 78), USA (n = 100) and Chinese (n = 106) consumers using an identical hedonic sensory acceptance test in Ireland, USA and China. Optimized Descriptive Profiling (ODP) was performed using trained assessors familiar with dairy products in Ireland (n = 25) and China (n = 22), and traditional descriptive analysis was undertaken by a trained panel (n = 7) in the USA. Volatile analysis was undertaken on each SMP sample. Hedonic assessment found that USA consumers preferred SMP derived from TMR, and Irish consumers preferred SMP from either GRS or CLV. Chinese consumers perceived SMP samples differently to the USA and Irish consumers, but preference was not influenced by diet. Both Irish and Chinese trained assessors found it more difficult to discern differences between GRS or CLV SMP, but could differentiate TMR SMP. Irish assessors preferred GRS and CLV SMP. Chinese and Irish assessors had different preferences for many attributes. Trained USA panelists found significant differences, exclusively associating pasture based diets with “cowy/barny” and “cardboard/wet paper” attributes and more intense “grassy/hay” attributes than in TMR SMP. The abundance of ten volatile compounds differed significantly based on diet with acetoin derived from carbohydrate metabolism at much greater abundance in TMR SMP. This study found that sensory perception and volatile profiles of SMP were influenced by diet and differences in sensory perception existed between the three cultural groups. Irish and USA sensory responses aligned with familiarity of dairy products derived from pasture and non-pasture diets, respectively, and Chinese sensory responses differed to Irish and USA responses likely reflecting their lack of familiarity with dairy products.

Effect on cell membrane structural integrity of xylitol‐coated probiotics when stabilised with milk solids – A FTIR study

Vacuum drying of sorbitol or xylitol‐coated Lactobacillus reuteri LR6 cells and fluidised bed drying with different excipients were compared for the cell viability post‐drying. L. reuteri cells coated with xylitol and desiccated in unsupported form or together with skim milk powder as an excipient were found to be better protected at high drying temperatures. Examination of the protein and polypeptide components of the cell envelopes via Fourier transform infrared spectroscopy revealed different degrees of structural deformation in individual samples, indicating milk solids as supporting excipient and fluidised bed drying helps in retaining high cell viability.

A comparison of analytical test methods in dairy processing

Dairy quality strategies start at the beginning of a raw milk supply chain at farm level, but it is the obligation of the manufacturer at a dairy processing plant to ensure quality is upheld from intake to finished product. This is achieved by implementing robust quality systems, measured through sampling plans and analytical test methods. Influences on product quality and composition, and analytical test results within a dairy plant are multi-factorial including: seasonality; the quality of incoming milk and herd health; the level of skilled laboratory technicians; the level of production and the availability of equipment; and finally milk harvesting, transportation and handling. These factors, along with customer and regulatory requirements will determine the level and type of analytical testing required. In the dairy industry, manufacturers oftentimes pay little attention to the need for optimising analytical test strategies or improving laboratory operations, if it is not broken why fix it? The focus of this qualitative research was to differentiate the core current analytical test methods in use at three dairy manufacturing plants for the production of raw milk, skim milk and cream and skim milk powder (SMP). The main objective being to inform and educate each producer on best practice methods. Results displayed similarities across testing categories but demonstrated a range of traditional testing methods in the microbiological analysis compared to advanced instrumentation use in the chemical and compositional analytical category. The dairy industry needs to adapt to a modern, process focused quality system using industry 4.0 analytical processing regimes.

Dry heat treatment of skim milk powder greatly improves the heat stability of recombined evaporated milk emulsions

In this study, skim milk powder (SMP) was subjected to a controlled dry heat treatment at 60 °C and relative humidity of 74% to improve the heat stability of recombined evaporated milk (REM) emulsions. Free amino group determination and SDS-PAGE analysis confirmed that the glycation of both whey proteins (WP) and caseins with lactose mainly occurred in the early period (<8 h). An increase in surface hydrophobicity and changes in the structure of the SMP proteins by circular dichroism (CD) and FT-IR were found after a long time of incubation (>16 h). The non-sedimentable protein analysis indicated that WP-casein interaction and casein micelle dissociation happened during (prolonged) dry heating. The heat stability of REM emulsions stabilized by dry-heated SMP was greatly improved: dry-heated SMP-stabilized REM emulsions could withstand at least 30 min of heating at 120 °C without significant increase in particle size and viscosity (P > 0.05). However, excessive dry heating (>20 h) adversely affected the reconstitution ability of SMP as well as the heat stability of REM emulsions.

Milk fortified with calcium: Changes in the physicochemical and rheological characteristics that affect the stability

The objective of this work was to analyze the changes in the physicochemical and rheological characteristics of milk fortified with different calcium salts. Reconstituted milk samples using skim milk powder with different concentrations of calcium chloride and calcium lactate (0, 5 and 30 mmol kg−1) were obtained. Several physicochemical and rheometric techniques were used to analyze the effect of milk fortification. According to the results, all the applied techniques indicated that some of the added calcium migrates into the casein micelle forming colloidal calcium phosphate, and that the calcium added as lactate enters the micelles to a greater extent. A part of whey proteins would also be integrated into the micellar structure. An addition of 5 mmol kg−1 of calcium chloride and calcium lactate would be practically feasible, due to the mineral balance and the thermal stability that were not significantly affected at that concentration level. In conclusion, the results obtained with physicochemical techniques commonly used in literature are in agreement with those obtained in this study by rheometry, demonstrating that this simple and rapid technique allows inferring about the changes in mineral balance and effects on thermal stability when different salts are used for milk fortification.

High counts of thermophilic spore formers in dairy powders originate from persisting strains in processing lines

During the last decades, thermophilic spore counts became a very important quality parameter for manufacturers with regard to powdered dairy products. Low-spore count powders are highly demanded but challenging to produce when high production volume and long process times are intended. In this study a detailed monitoring of microbial levels in three skim milk powder plants was conducted. Anoxybacillus flavithermus was found to be primarily responsible for increased spore levels with increasing spore numbers being detected after 6–8 h already during initial processing steps. Simultaneously, the species composition shifted from a diverse bulk tank milk microbiota where different Bacillus species represented around 90% of the thermophilic bacteria to a dominance of A. flavithermus in the end product. The analysis of A. flavithermus isolates from different powder batches with RAPD PCR revealed recurring patterns in each of the eight German manufacturers sampled over several months. The high relatedness of isolates exhibiting identical RAPD patterns was exemplified by cgMLST based on whole genome sequences. We assume that A. flavithermus strains persisted in production plants and were not eliminated by cleaning. It is concluded that such persisting strains recurrently recontaminated subsequent powder productions. The data highlight that a targeted optimization of cleaning and disinfection procedures is the most promising measure to effectively reduce thermophilic spore counts in German dairy powders.