Insolubility Index Research Articles

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.

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.

Preparation of skim milk powder tablet and finite element analysis of its pressing die

AbstractThe skim milk powder (SMP) has problems of quantification and handling during milk reconstitution for tea and coffee making. To address these issues, a novel product, “SMP tablet,” was made by varying moisture content (3, 5, 10, and 15% wet basis) of SMP and compression force (625, 750, 875, 1,000, and 1,125 N) during tableting. A die containing upper, lower, and grooved punches was designed, fabricated, and analyzed with finite element method. The tetrahedral type of mesh with 1.9078–2.356 mm element size, 0.095–0.118 mm tolerance, 80,420–85,107 nodes, and 53,041–57,252 elements resulted in 40.53–68.60 MPa maximum stress and 1.9–4 minimum factor of safety advocating acceptability of design. The SMP was pressed inside die through universal testing machine in controlled manner and disintegration time (DT), tensile strength (TS), and insolubility index (ISi) of SMP tablets were evaluated. Response surface methodology showed cubic model as best fit (p < .0001 and R2 > .97) for all the responses. The numerical optimization showed 4.6% wb moisture and 1,125 N compression force favorable for good quality attributes (103.8 kPa TS; 318 s DT; 40.5 mg ISi). Further, sugar addition (10%), as a disintegrating agent, improved DT (178 s) and TS (159 kPa). The SMP tablet with sugar had 14.90 ± 0.05 mm average diameter, 5.04 ± 0.18 mm thickness, 625 ± 6 mg weight, and 3.45% weight variation with similar total soluble solids (5%) at 60°C compared with SMP. The direct consumable, no artificial additives/binders and ease in quantification are tablets' novelty comparing SMP.Practical applicationsPoor quantification and handling are the two major issues with SMP. This can be easily combated by pressing the powder and converted into tablet form. The quantity of required number of SMP tablets for milk reconstitution can be easily remembered like sugar cubes. The SMP tablets can be marketed as novel dairy products and taken directly or used in coffee and tea making. Moreover, this study will provide an insightful information to dairy industry for commercial application of SMP tablets.

Development of instant phirni mix (a traditional dairy dessert) from high amylose rice, skim milk powder and carboxymethyl cellulose-resistant starch, predicted glycemic index and stability during storage

High amylose rice (HAR) and carboxymethyl cellulose (CMC) are ideal choices to enhance the resistant starch and reduce the glycemic index of dairy desserts. Therefore, the effect of ingredient composition (i.e., skim milk powder: high amylose rice flour -SMP: HAR, and carboxymethyl cellulose- CMC) on physical characteristics of phirni dry mix were investigated in the present study. Variation in SMP: HAR flour and CMC concentration significantly (p < 0.05) affected the insolubility index, wettability, Hausner ratio, luminosity (L*), and yellowness (b*) of different phirni dry mix samples. Design expert predicted SMP (70%), HAR (30%) and CMC concentration of 0.85% as desirable conditions for preparation of phirni dry mix. A typical A-type diffraction pattern and absorption bands representative of proteins, lactose and starch were detected in optimized phirni dry-mix (OPDM). Irrespective of packaging material and storage condition, resistant starch (RS) increased significantly (p < 0.05) while predicted glycemic index (pGI) showed significant (p < 0.05) decrease during storage. However, maximum RS content (7.57%) and minimum pGI (44.95) were recorded in LDPE packed samples (LDPE-PS) on 90th day of storage under accelerated conditions. At the same time, moisture content, water activity, free fatty acids, and peroxide value increased significantly (p < 0.05), while overall acceptability showed a significant (p < 0.05) decrease in LDPE-PS. The inference drawn from the present study was that irrespective of packaging material and storage condition, the OPDM was safe to consume up to 90 days, however, aluminum laminated package and ambient storage condition could be better options to retain the quality of OPDM with better consumer acceptability.

Surface fat and insolubility of whole camel milk powders as affected by spray drying operating parameters

Face centered central composite design was used to investigate the effect of spray drying process parameters (inlet temperature, atomization pressure and feed flow rate) on selected quality parameters of whole camel milk. During storage by freezing, the integrity of camel milk fat globules is maintained with observed aggregation. Whole camel milk contains 12.18% total solids, 3.5% protein and 3.99% [w/w] lactose whereas for the powders, the total solids content was in the range of 94–97%, protein 22–29% and lactose 27–31% [w/w]. By combining response surface methodology with desirability function, the spray drying process of whole camel milk was optimized with objectives of maximizing the yield and minimizing undesired quality degradation parameters. Consequently, it was possible to recover 62% of total solids without affecting the desired aspects of the final physico-chemical properties of powders (minimum insolubility index of 0.1 mL and surface fat content of 4.2% [w/w]) with targeted final moisture content of 4.5% [w/w]. These properties would make the powders safe during extended period of storage.

Prediction of dairy powder functionality attributes using diffuse reflectance in the visible and near infrared (Vis-NIR) region

The potential of Vis-NIR for the non-invasive determination of physicochemical attributes of dairy powders was investigated for fast assessment of dairy powder quality. Three scanning techniques were compared for the collection of Vis-NIR data, including a portable, a benchtop and a hyperspectral imaging device. Models were developed with commercial dairy powders varying in batch, brand, type and length of storage and tested in a completely independent dataset. Moderate to good performance was achieved for tapped density, insolubility index, surface free fat, moisture content and bulk density (RP2: 0.65–0.88, 0.80–0.85, 0.77–0.87, 0.71–0.86 and 0.71–0.72, respectively). Analysis using variable of importance in projection and selectivity ratio show the uniqueness of each prediction model for the different physicochemical attributes. Three scanning techniques investigated present different opportunities for on-line implementation of this system.

Insolubility and denaturation of whey proteins of skimmed camel milk as affected by spray drying operating parameters

ABSTRACT The effect of spray drying process parameters (i.e., inlet temperature, atomization pressure, and feed flow rate) on the denaturation of whey proteins of skimmed camel milk was studied using a face-centered central composite design. Spray drying of skimmed camel milk (i.e., total solids of 8.4% [w/w]) produced powders with a total solids content of 94–97% (w/w), protein 22–29% (w/w) and lactose 27–31% (w/w). The process was optimized using response surface methodology in combination with desirability function. A maximum recovery of 61% of the total solids was achieved while still maintaining denaturation of whey protein and insolubility index levels at their minimum possible value of 39% and 0.1 mL, respectively. The final moisture content of the powder at these conditions was 3.3% (w/w). This implies that, as denaturation was the primary mechanism by which camel milk lose its protective proteins, minimizing denaturation would make it possible to produce skimmed camel milk powders with good nutritional and therapeutic values. The morphology of spray-dried skimmed camel milk processed at 140°C showed greater spherical intact particles than their cow milk powder counterparts.

Encapsulation of isoflavone with milk, maltodextrin and gum acacia improves its stability

This study was carried out for extraction of soy isoflavones and entrapment of the isoflavones so obtained into whole milk via encapsulation techniques. Three different solvent (ethanol, methanol and acetonitrile) were used for the extraction of isoflavone using three stage of extraction. The extracted isoflavone was encapsulated into 200 ml of whole milk by spray drying using different concentrations of gum acacia (4, 6 and 8% w/v) and 10% w/v maltodextrin DE 18. The ratio between cores to coating materials was 1:10. Though acetonitrile extracted higher amount of isoflavone, ethanol was selected for subsequent studies of extraction of isoflavone, as per the legislations regarding use of Food-grade solvents. There was no significant difference (p > 0.5) among all three samples 4% gum acacia+10% maltodextrin (A), 6% gum acacia+10% maltodextrin (B) and 8% gum acacia+10% maltodextrin (C) in terms of moisture content and hygroscopicity. However, insolubility index showed that sample A possessed a higher solubility index. Encapsulation techniques suggested that sample A showed higher encapsulation efficiency than others. Statistical analysis suggested that there was no significant difference among samples A, B and C during storage at 4°C for the time period (30 days) studied, in terms of isoflavone retention rate. However, samples stored at 25 and 37°C showed significant difference in the retention rate. Among all the three samples, sample B showed significantly lower isoflavone degradation rate of 3.80, 4.07 and 4.70 × 10−3/day at 4, 25 and 37°C, respectively. The highest amount of isoflavone degradation was observed at 37°C. Results indicate that isoflavone can be encapsulated using a combination of gum acacia either 4 or 6% w/v and 10% maltodextrin along with milk proteins at 4°C for longer shelf life.

Storage related changes in spray dried colostrum preparations

Colostrum, bioactive rich mammary secretion obtained immediately after parturition, is endowed with immunity boosting compounds such as immunoglobulins, lactoferrin, lysozyme, growth factors, etc. The colostrum feeding is recommended for imparting passive immunity to children with poor immune status. However, immunoprophylactic and therapeutic properties of colostrum are best preserved in dried form. Immunoglobulin rich spray dried colostrum protein concentrate (CPC) and colostrum whey protein isolates (CWPI) were evaluated for their storage stability at 4 and 25 °C in the HDPE jar and laminates. There was significant (p < 0.05) effects of storage time and temperature on the immunoglobulin (Ig) levels in powders. However, the reduction in activity of Ig of CPC powder was significantly higher at 25 °C and for HDPE jar as compared to one stored at 4 °C and laminates. The pH and acidity of the spray dried CPC and CWPI powders indicated absence of microbiological spoilage during storage, however, their total plate counts increased significantly (p < 0.05) with progression of storage period. The insolubility index of both powders increased progressively. Moisture sorption isotherm indicated sigmoid curve for both powders. Findings suggested that lower storage temperature coupled with use of laminates could be employed to prolong the shelf-life of colostrum powders.

Shelf‐life study of spray‐dried groundnut milk powder

AbstractShelflife study of spray‐dried groundnut milk powder was conducted in metal tin can and aluminum foil package. The observations were recorded at 0th, 1st, 2nd, 4th, 8th, 12th, and 16th week of storage. There was an increasing trend in the values of moisture content (3.69–7.56% w.b. and 3.69–7.08% w.b.), water activity (0.44–0.68 and 0.44–0.64), and free fatty acid (0.48–2.02% and 0.48–1.87%) in aluminum foil package and metal tins can, respectively. Dispersibility of powder varied between 96.10–90.22% and 96.10–91.78% while insolubility index varied between 0.75–3.88 ml and 0.75–3.56 ml in aluminum foil package and metal tin can, respectively. Results indicated that groundnut milk powder can be safely stored in both the packaging materials for 3 months and metal tin can packaging is better than aluminum foil packaging. A significant difference in the values of the above parameters was observed in commercially available milk powder during the same storage period.Practical ApplicationsGroundnut is widely used for oil extraction or consumed as roasted nuts. Considering its wide acceptability and nutritional value, groundnut processing needs more diversification in order to utilize its potential. Groundnut can be used for the preparation of imitation milk for lactose intolerant population of the country. However, groundnut milk has a very limited shelf life (5–7 days under refrigerated condition) and adds to the increased transportation cost of carrying liquid milk from one place to another. The conversion of groundnut milk into powder using spray drying will reduce product perishability as well as storage and transportation costs. Further, the shelf life study of the groundnut milk powder in different packaging material will be useful in determining the safe storage period as well as the type of packaging material to be used for storing the powder considering the quality as well as sensory attributes of the powder during the duration of storage.

Optimization of spray drying process parameters for production of groundnut milk powder

In India, groundnut is mainly used for oil extraction or consumed in roasted form prompting a need for diversification to further increase its value and utility. In the present study, spray drying of groundnut milk was carried out using three variables of spray dryer i.e., inlet air temperature (180–220 °C), atomization air pressure (2–3 bar), feed pump speed (24–36 rpm) using Box-Behnken design of Response Surface methodology. The moisture content of powder decreased with an increase in inlet air temperature and atomization air pressure. The bulk density increased with increase in atomization air pressure. Maximum dispersibility (98.48%) was observed at an atomization air pressure of 2.57 bar. The insolubility index of the powder increased and lightness value (L*) decreased with an increase in inlet air temperature. The optimized conditions for spray drying of groundnut milk were inlet air temperature: 186 °C, atomizing air pressure: 2.5 bar and feed pump speed: 27 rpm.

Optimisation of foam‐mat drying of yoghurt and properties of powdered yoghurt

Foam‐mat drying was optimised by studying the effects of different concentrations of soy lecithin on foam density and foam expansion of yoghurt. Sample thickness was studied by drawing drying and moisture ratio curves during drying in electric tray dehydrator at 58–63 °C. Prepared powder was analysed to study the impact of foaming agent on yoghurt powder. Evaluation of bulk properties was done to reduce storage and transportation volume. Wettability, water absorption capacity and insolubility index were determined to study effects on functional properties. Scanning electron microscope was performed for studying surface properties. No significant changes were observed in bulk properties, but treatment significantly affected functional and surface properties.

Physical characterization of whole and skim dried milk powders.

The lack of updated knowledge about the physical properties of milk powders aimed us to evaluate selected physical properties (water activity, particle size, density, flowability, solubility and colour) of eleven skim and whole milk powders produced in Europe. These physical properties are crucial both for the management of milk powder during the final steps of the drying process, and for their use as food ingredients. In general, except for the values of water activity, the physical properties of skim and whole milk powders are very different. Particle sizes of the spray-dried skim milk powders, measured as volume and surface mean diameter were significantly lower than that of the whole milk powders, while the roller dried sample showed the largest particle size. For all the samples the size distribution was quite narrow, with a span value less than 2. The loose density of skim milk powders was significantly higher than whole milk powders (541.36 vs 449.75kg/m3). Flowability, measured by Hausner ratio and Carr's index indicators, ranged from passable to poor when evaluated according to pharmaceutical criteria. The insolubility index of the spray-dried skim and whole milk powders, measured as weight of the sediment (from 0.5 to 34.8mg), allowed a good discrimination of the samples. Colour analysis underlined the relevant contribution of fat content and particle size, resulted in higher lightness (L*) for skim milk powder than whole milk powder, which, on the other hand, showed higher yellowness (b*) and lower greenness (-a*). In conclusion a detailed knowledge of functional properties of milk powders may allow the dairy to tailor the products to the user and help the food processor to perform a targeted choice according to the intended use.

Changes in the Shelf Life Parameters of Dietary Supplement During Storage

A dietary supplement containing multifunctional ingredient sources was formulated and optimized for management of diabetes. The formulated dietary supplement comprised of milk fat and groundnut oil (90:10), whey protein concentrate, skim milk powder and sodium caseinate (50:25:25) and resistant starch and maltodextrin (70:30). The feasibility of the formulated dietary supplement in terms of physico-chemical, microbiological and sensory attributes was evaluated during storage period. The formulated supplement was found to have 4.37, 15.93, 10.15, 3.39 and 66.15 percent moisture, protein, fat, ash and carbohydrate respectively. It was observed that there was slight increase in moisture, free fatty acid, thiobarbituric acid and insolubility index while a decrease in dispersibility and sensory attributes (color and appearance, flavor, overall acceptability) during the storage period. However, the dietary supplement stored at room temperature indicated non-significant changes in all physico-chemical, microbiological and sensory parameters throughout the storage period of 180 days. Thus, dietary supplement prepared had better acceptability for a period of six months.

Solubility and structure of milk powders manufactured with the addition of disodium phosphate and tetrasodium pyrophosphate mixtures

ABSTRACTThis study aimed to investigate the effect of adding binary mixtures of disodium phosphate and tetrasodium pyrophosphate during milk powder production. Overall, the addition of disodium phosphate–tetrasodium pyrophosphate caused an increase in pH and a decrease in the acidity and turbidity of reconstituted milk samples. The decrease in turbidity was attributed to either dispersion or swelling of the casein micelles. The addition of mixtures containing the lowest amounts of tetrasodium pyrophosphate considerably reduced the insolubility index, whereas mixtures containing higher levels of tetrasodium pyrophosphate exerted a detrimental effect on solubility. Interestingly, microscopic observations showed large agglomerated particles in mixtures with the highest level of tetrasodium pyrophosphate. We hypothesized that the formation of casein calcium–pyrophosphate complexes led to the higher insolubility index in this mixture.

Bifidus milk powder: processing parameter standardization and shelf stability evaluation.

Spray dried bifidus milk powder was prepared by supplementing cow milk with different level of additives to obtain slurry of desired concentration. The slurry was pasteurized, cooled and inoculated with Bifidobacterium bifidum, incubated and dried to produce a bifidus milk powder. Among the various bifidus milk powder prepared, the slurry of mention the level total soluble solids exhibited good organoleptic characteristics and it has been standardized for further analysis. Moisture content, bulk density, insolubility index, hydroxymethyl furfural and thiobarbituric acid value of bifidus milk powder significantly increased, while the reflectance value significantly decreased during storage. The B. bifidum count significantly reduced and the bacterium were not detected at the end of the mention storage duration. As such the sentence is not acceptable in the abstract. The reconstituted bifidus milk powder was considered acceptable with an overall acceptability score of 6.97 on a nine-point Hedonic scale and showed a shelf stability of 120days at ambient temperature condition (27±2°C).

Short communication: Effects of nanofiltration and evaporation on the physiochemical properties of milk protein during processing of milk protein concentrate

The aim of this work was to evaluate the effects of nanofiltration and evaporation concentration technologies on the physiochemical properties of milk protein concentrate (MPC) during processing. Skim milk, ultrafiltered milk, evaporated milk, nanofiltered milk, evaporated MPC, and nanofiltered MPC samples were collected at different processing stages. Chemical composition, microstructure of casein micelles, free sulfhydryl content, and surface hydrophobicity of the samples were determined. The insolubility index of MPC was also determined. Casein micelles aggregated compactly after evaporation while surface hydrophobicity increased and free sulfhydryl content decreased in evaporated milk compared with skim milk. However, the microstructure of the casein micelles was relatively undisturbed after nanofiltration, with reduced surface hydrophobicity and free sulfhydryl content. No significant difference was found in chemical composition between the 2 MPC preparations: approximately 61.40% protein and 28.49% lactose. In addition, the particulate microstructures of both MPC were similar. However, the insolubility index of evaporated MPC was significantly (0.58mL) higher than that of nanofiltered MPC. Nanofiltration may be an effective way to improve the solubility of MPC products.

Index for linear systems of differential-algebraic equations with partial derivatives

We investigate time-varying linear differential algebraic equations with partial derivatives. We introduce concept of insolubility index as the least possible order of the differential operator which transforms the initial system into a structural form with separated the “algebraic” and “differential” subsystems. The approach does not assume the existence of differential indexes with respect to independent variables.

Energy use for alternative full-cream milk powder manufacturing processes

The process of manufacturing full-cream milk powder usually involves heating the full-cream milk, concentration and spray drying. Homogenization of milk is desirable for good quality powder with low insolubility index and low solvent extractable fat (free-fat). Energy savings can be obtained using an alternative process where only a high solids cream fraction (∼45% total solids) is homogenized prior to mixing with the skim milk, concentration and drying. Homogenization of cream at high solids is made possible with the use of citrate as a processing aid. The quality of the powder and energy calculations for the various unit processes used for the alternative process (only cream homogenized) were compared with traditional full-cream milk powder production processes. The homogenization of the cream fraction only is an alternative to the homogenization of the whole of the milk for production of good quality powder, while saving energy for the homogenization step.

The influence of trehalose–maltodextrin and lactose–maltodextrin matrices on thermal and sorption properties of spray-dried β-lactoglobulin–vitamin D3 complexes

In the study, the effect of lactose–maltodextrin and trehalose–maltodextrin matrices on the glass transition temperatures and moisture sorption characteristics of spray-dried β-lactoglobulin–vitamin D3 complexes was investigated. Incorporation of sugars into complexes can influence the thermal properties and moisture sorption characteristics of powders. The glass transition temperature as an important physiochemical parameter that determines the processing conditions, product quality and stability of the final product was studied with the use of modulated differential scanning calorimetry method. Moisture sorption isotherms, water activity and moisture content as parameters related to sorption properties, were also investigated. Additionally, particle size, wettability and insolubility index were studied to characterise newly synthesized products. For the samples tested, two well-separated glass transitions were found. The dominant effect of maltodextrin on the glass transition temperatures was observed. An increase in the percentage of maltodextrin added resulted in increasing T g value of studied complexes. At low water activity all powdered complexes showed typical sorption behaviour of food systems. Trehalose as a carbohydrate component of powdered complexes, in comparison to lactose, delayed the occurrence of crystallization.