Supercritical Fluid Extrusion Research Articles

Orally self-disintegrating milk protein puffs enriched with food by-products for the elderly

Supercritical fluid extrusion (SCFX) processing was used to develop milk protein-based orally self-disintegrating puffs enriched with fruit and dairy by-products, designed specifically to cater to the needs of elderly population having swallowing issues and lactose intolerance. Lactose hydrolyzed skim milk powder (LHSMP) was also added in the formulation to mitigate lactose intolerance while LHSMP was also exploited as a precursor for the polymerization of galactose and lactose to generate galacto-oligosaccharides (GOS) in the puffs. This study for the first time took advantage of the unique features of SCFX processing for in-process GOS formation and enrichment of puffs, achieving GOS contents up to 0.48 g/30 g serving of puffs, thereby making them nutritionally superior and functionally attractive snacks. The estimated nutritional profile revealed that SCFX puffs contained higher levels of protein (16.3 g/30 g), fiber (1.6 g/30 g), phenolics and other valuable nutrients compared to the starch-rich, disintegrating Market Baby puffs.

Supercritical fluid extrusion of dairy and fruit products to generate GOS-enriched and nutritionally superior snack puffs

The consumption of ultra-processed snacks is often considered unhealthy because such foods generally are energy-dense with low nutritive value. They contain high levels of starch, fat, and sugar and low levels of essential nutrients such as fiber, protein, and bioactive compounds. Nutritionally balanced snack foods that cater to today’s on-the-go lifestyles and do not get in the way of better eating are in high demand. The present study aims to create nutritionally attractive extruded puffs by valorizing food manufacturing byproducts and to elucidate the uniqueness of hybrid extrusion processing and its effect on product quality parameters. Supercritical fluid extrusion (SCFX) was used to transform apple pomace, starch or dairy ingredient-based formulations into value-added products in a zero-waste system. Acid whey, a byproduct of yogurt and cheese manufacturing, was used in lieu of water in the extruder to mitigate environmental issues related to its disposal. The SCFX system was also used for in-process polymerization of galactose, sourced from lactose hydrolyzed skim milk powder (LHSMP), with lactose from milk protein concentrate (MPC) and acid whey sources to produce galacto-oligosaccharides (GOS), a prebiotic associated with various health benefits and making the product acceptable to lactose intolerant consumers. Analysis of the extruded puffs showed that a combination of pomace and dairy ingredients significantly improved the nutritional profile of the product, notably increasing the fiber (5.0 g/30 g serving), protein (13.6 g/30 g serving), bioactive compounds (phenolics 21.4 mg GAE/30 g and vitamin C 0.3 mg/30 g serving), minerals, and GOS (0.4 g/30 g serving) contents. A sensory acceptance test (n=91) showed that incorporation of fruit and dairy by-products in snacks either improved or maintained Just About Right (JAR) scores compared to Market Keto puffs. Overall, utilizing fruit pomace and acid whey in extruded products made by SCFX is not only able to generate nutritious and functional snacks with balanced nutrients profile, derived from inexpensive agro-food by-products feedstock, but also can help mitigate environmental and waste issues.

Orally self-disintegrating milk protein-based puffs enriched with in-process generated short chain galacto-oligosaccharides by supercritical fluid extrusion

This study aimed to design and evaluate orally self-disintegrating puffs that are nutritionally enhanced via in-process polymerization of galactose into galacto-oligosaccharides (GOS). Lactose hydrolyzed (LHSMP) or unhydrolyzed skim milk powder (SMP) was combined with 80% protein milk protein concentrate (MPC) powder and a calcium chelator, then processed using supercritical fluid extrusion (SCFX) with carbon dioxide (CO2) to produce protein-rich orally self-disintegrating puffs. Disintegration results indicate the MPC90 and MPC70-SMP20 puffs had faster disintegration rates (3.20 and 3.84%/sec) than the commercial puffs (3.12%/sec). Galactose in LHSMP as a precursor to formation of polymeric GOS during extrusion was also investigated. The low pH and controlled temperature minimize Maillard browning and enhanced the polymerization of galactose into GOS. The MPC60-LHSMP30 puffs had the highest content of short chain GOS (2.3 wt%). The current study provides first valuable insights for the utilization of LHSMP to produce orally self-disintegrating GOS enriched protein puffs.

Techno-economic feasibility & environmental sustainability of producing nutritionally enhanced snack foods from agro-food byproducts using supercritical CO2-based extrusion

This study evaluated the economic feasibility and environmental sustainability of producing nutritionally superior snacks on an industrial scale by supercritical fluid extrusion (SCFX) using milk protein concentrate (MPC81-AP) or starch (Starch-AP)-based formulations enriched with apple pomace powder. Selected nutrient contents and antioxidant attributes were also studied to highlight the nutritional qualities of the final products. For large-scale implementation using a low-temperature (85°C) and low-shear SCFX system, capital budgeting, breakeven point, and profitability ratios were determined. During a standard 12-hour production run, a substantial margin of safety of 29.03% and a breakeven point of 0.71 years were estimated, indicating resilience against potential losses and a swift return on investment. The projected prices for MPC81-AP and Starch-AP-based products were $30.13/kg (Similar market snacks, $32-65/kg) and $26.29/kg, respectively. In summary, both formulations exhibited superior nutritional qualities, better gross profit margins and return on investment with environmentally sustainability, compared with the conventional extrudate snack foods available in the market today.

Nutritionally enhanced milk protein and starch-based extrudates made from agro-food byproducts using supercritical fluid extrusion

This study aimed to develop nutritionally enhanced snacks through the synergistic combination of two diverse nutrient sources: milk protein concentrate containing >81% milk protein (MPC81), and a composite source of fiber (>70 wt%) and bioactive compounds (total phenolics, flavonoids, antioxidants, and vitamin C) in the form of agro-industrial byproducts such as apple pomace. Starch and MPC81-based formulations containing 30% (w/w) apple pomace powder were extruded into puffs using supercritical fluid extrusion (SCFX). The effect of SCFX on the retention of bioactive compounds along with the physical, textural, and morphological properties of starch and protein-based extrudates were investigated and compared. Additionally, changes in inter-and intra-molecular interactions among biopolymers during extrusion, and their role in the expansion characteristics of extrudates were also quantified. The resulting MPC81-based extrudates were found to have lighter (0.12 g/cm3 piece density) and softer texture (3.16 kg hardness) compared to starch-based extrudates (0.23 g/cm3 piece density, 12.06 kg hardness), indicating that MPC81-based extrudates containing 30% apple pomace powder offer better functional and sensory-related physical properties. Because of low-temperature (∼25 °C barrel temperature, ∼85 °C product temperature), and low-shear (100 rpm screw speed) along with the use of SC-CO2 as a blowing agent, the resulting extrudates were observed to retain up to 80% total phenolics, 75% antioxidants and 62% vitamin C, which are significantly higher than those reported previously using high-temperature, steam-based cooking extrusion. The FTIR spectra of starch-based formulations indicated a loss of crystallinity and decreased cellulose-lignin interactions, which contributed to the improved extrudate expansion. On the other hand, the expanded protein network was presumably stabilized by an increase in protein aggregation, mainly composed of an elevated β-structure, as confirmed by the FTIR analysis of the protein-based extrudates. The nutritional profile showed that milk protein-based puffs were nutritionally far superior, having significantly higher levels of protein, ash, and fat, as compared to the starch-based puffs. Overall, this study highlights the potential of SCFX to produce milk protein-based extruded products that are nutritionally enriched with agro-industry byproducts such as fruit and vegetable pomace, thereby, adding value to the industrial byproducts streams and lowering the cost of more expensive protein-based products.

Cell Nucleation Dynamic and Expansion Characteristics of Milk Protein Puffs Containing Fruit Pomace Made by Supercritical Fluid Extrusion

Cell Nucleation Dynamic and Expansion Characteristics of Milk Protein Puffs Containing Fruit Pomace Made by Supercritical Fluid Extrusion

In‐mouth, self‐disintegrating milk protein puffs‐I: Process development

AbstractThis study elucidated the reactive role of the supercritical fluid extrusion (SCFX) process along with calcium chelation by added sodium hexametaphosphate (SHMP) in altering the physicochemical properties of milk protein concentrate (MPC) with added sucrose (MPC‐S) to make expanded extrudates of defined microstructure that self‐disintegrate in the mouth. Calcium chelation by SHMP and temporarily induced acidity (pH 4.75) due to the formation of carbonic acid via SC‐CO2 incorporation during SCFX prevented protein–protein interactions involving calcium bridging and disulfide bonding in MPC‐S extrudates. The electrophoretic patterns demonstrated increased solubility of caseins in MPC‐S‐SHMP extrudates when compared to MPC‐S‐control. MPC‐S‐SHMP extrudates absorbed three times more water than MPC‐S‐control extrudates after 30 s of hydration. Textural analysis demonstrated that the compression strength of MPC‐S‐SHMP extrudates reduced by 93% on hydration as compared to 31% for MPC‐S‐control samples. During hydration, increased water absorption by MPC‐S‐SHMP extrudates resulted in weakened extrudate structure and decreased mechanical strength contributing to self‐disintegration in less than 30 s in the mouth which was confirmed by sensory evaluation.Practical ApplicationsThe developed and demonstrated process led to the manufacture of nutritious, milk protein‐based convenient and quick in‐mouth disintegrating puffs that can be used as a valuable replacement for starch‐based first finger foods intended for toddlers. They also provide the opportunity to practice baby led weaning along with being rich in protein and essential amino acids. Additionally, the developed product should be suitable for consumption by elderly as well as for patients with other conditions such as dysphagia.

Oleogelation using modified milk protein concentrate produced by supercritical fluid extrusion

In this work, we report on making oleogels based on functionalized milk protein concentrate. A protein-based oleogel was constructed and examined for the effect of lecithin and water addition on protein network formation in canola oil. To create oleogels, milk protein concentrate was modified by supercritical fluid extrusion (SCFX) into higher hydrophobicity extrudate (functionalized MPC). It was subsequently suspended in oil after the addition of lecithin and water in various concentrations. Compared to control (unextruded) MPC (CMPC), functionalized MPC (FMPC) exhibited interesting functionality as an oil-structuring ingredient. The incorporation of FMPC, water, and lecithin into canola oil formed gel by self-assembling, which differed from the oleogels made by a single gelator. It was water-induced self-assembly of protein that led to the formation of oleogels. It was further observed that the presence of lecithin in FMPC-stabilized oleogels altered the gel properties and strength. Microscopic images revealed that incorporation of lecithin led to the formation of smaller protein aggregates leading to higher strength. Non-covalent interactions between lecithin, protein, and water were also evaluated using FTIR spectroscopy, confirming the role of water and lecithin in gel formation of the mixed system.

Physicochemical Properties of Milk Protein Concentrate Extrudates Generated Using Supercritical Carbon Dioxide

This study elucidated the comparative effects of steam extrusion (SX, 115 °C) and supercritical fluid extrusion (SCFX, 85 °C) on the physicochemical properties of extruded milk protein concentrate. SCFX with SC–CO2 injection at 2.5 (SC-2.5) and 5 (SC-5) wt % feed moisture temporarily lowered the pH of melt to 4.90 and 4.75, respectively, while the pH of 6.2 was maintained during SX. Acidic conditions during SCFX prevented temperature and shear-induced protein aggregation of calcium bridging and disulfide type. Compared to unextruded samples, the free sulfhydryl content was reduced by 12.6% in SC-5 and 75.9% in SX extrudates, indicating decreased sulfhydryl interactions in SCFX extrudates. The water-soluble protein fractions in SC-5 exhibited mean particle size and zeta potential of 166 nm and −28 mV, respectively, compared to 566 nm and −12.8 mV for SX. Thus, temporarily induced acidity and lower operating temperature of SCFX prevented protein aggregation and contributed to improving the physicochemical properties of milk protein extrudates.

Quality attributes and rheological properties of novel high milk protein‐based extrudates made by supercritical fluid extrusion

SummarySupercritical fluid extrusion (SCFX) process has opened up a new way of extruding heat‐sensitive materials such as milk protein concentrate (MPC) into novel nutritional porous extrudates. Three formulations (30%:66.5%, 60%:36.5% and 90%:6.5% of MPC: rice flour, w/w) with 1% Dimodan, 1% lecithin and 1.5% salt were extruded by using SCFX. The physical, rheological and thermal properties of the extrudates were evaluated. The results showed that the increased MPC contents decreased gelatinisation enthalpy and increased the viscosity of the extrudates, which contributed to develop stable porous extrudates; and the increased MPC contents also helped to form a stronger gel network existed in dispersion of the extrudate samples, which resulted in a higher stress to break the gel and flow. The radial and overall expansions, crispness, porosity, rehydration ratio, moisture content and water activity increased while the axial expansion, hardness, piece density, apparent density, bulk density, decreased with higher amounts of MPC contents in extrudates. The overall results indicated that 90% MPC‐containing extrudate was very suitable for developing highly nutritional and healthy cereals/snacks.

In‐process flow behavior and structure formation during supercritical fluid extrusion of milk protein concentrate

The in-line flow behavior of milk protein concentrate (MPC) and MPC-sucrose (MPC-S) blends with and without added supercritical CO2 (SC-CO2) during extrusion was quantified using a slit die rheometer and related to the expansion characteristics of extrudates. The apparent viscosity of the melt was in order: MPC > MPC + SC-CO2 > MPC-S > MPC-S + SC-CO2. A lower viscosity reduction factor due to SC-CO2 incorporation was observed for MPC-S (1.3–1.1) compared to MPC (1.5–1.2) owing to decreased volume fraction of protein in MPC-S. Increase in the apparent viscosity increased the expansion ratio for both MPC and MPC-S extrudates from 2.2 to 4.3 and 1.9 to 4 and decreased the average cell size from 924 to 392 and 936 to 354 µm, respectively. Thus, expansion and cellular architecture of MPC-based extrudates can be improved by controlling the melt viscosity. The findings of this study could have significant utility in designing novel milk protein-based products. Practical applications Milk protein concentrates are highly valuable and nutritionally attractive products and their conversion into expanded and texturally designed foods will be a valuable addition to the market. The cellular architecture of such foods is one of the primary indicators of the consumer-acceptable quality and depends upon the melt rheology, which in turn is related to the feed composition and processing conditions within the extruder. Relating the in-line rheological properties to extrudate characteristics can provide better decision-making ability for the selection of feed ingredients, diluents, and inert ingredients for the development of expanded milk protein puffs of commercial utility.

Supercritical fluid extrusion: Die design and physicochemical properties of milk protein extrudates

Extrusion processing has been used to modify the functional properties of proteins. The protein-protein interactions, surface hydrophobicity, and rheological properties of milk protein concentrate extruded using dies of different geometries (circular, annular and slit) were quantified. With the same extrusion treatment history prior to the die, extrudates generated using dies with higher wall shear (slit 1.4 × 104 s−1 > annular 1.1 × 104 s−1 > circular 2.9 × 103 s−1) showed greater protein extractability, higher index of surface hydrophobicity, and enhanced water solubility index indicating significant breakdown of protein aggregates. Higher viscoelastic moduli (G' and G") and apparent viscosity were observed for slit die extrudate dispersions. However, low flow behavior indices (0.04–0.23(−)) and a high viscous activation energy (43 kJ/mol) of slit die extrudate dispersions implied their shear and temperature sensitivity, respectively. Thus, extrudate functionality can be optimized by selection of the appropriate die design.

Modeling of product temperature in a supercritical fluid extrusion process through dimensional analysis

AbstractA correlation model for predicting the maximum product temperature reached during a supercritical fluid extrusion (SCFX) process was developed using the Buckingham Pi method. Two dimensionless groups, Dref (ratio of screw diameter to screw length) and Eref (ratio of energy added to energy removed), were developed to model the maximum temperature of an SCFX process using dimensional analysis. The model was validated by comparing predicted and experimental values. Experiments were conducted using two feed formulations: 1. Milk protein concentrate (MPC) with rice flour (30%), and 2. MPC with grape pomace (15%). The average percent error was 2.57% for rice flour extrudate and 1.02% for grape pomace extrudate. Based on the results, the model could be used for prediction of maximum temperature in SCFX systems.Practical ApplicationsMaintaining the extruder temperature below 100°C remains a major challenge during the supercritical fluid extrusion (SCFX) process. The model developed determines the maximum temperature of a given SCFX system based on key extrusion parameters. Hence, the developed model can be used by manufacturers for determining the optimal operating conditions while scaling up an SCFX process.

Emulsifying properties of milk protein concentrate functionalized by supercritical fluid extrusion

Emulsifying properties of milk protein concentrate functionalized by supercritical fluid extrusion

Heat stability of emulsions using functionalized milk protein concentrate generated by supercritical fluid extrusion.

In this study, thermostable oil-in-water emulsions containing high protein contents were developed using milk protein concentrate (MPC) that was functionalized by supercritical fluid extrusion (SCFX) processing at low temperature and shear. Functionalized MPC (f-MPC) emulsions (3% protein-80% oil and 10% protein-50% oil) were compared with emulsions stabilized by commercial MPC (c-MPC), sodium caseinate (NaCas), and a commercial mayonnaise for their emulsifying properties and heat stability at 70 and 90 °C for 30 min, and 121 °C for 15 min. Zeta-potentials and interfacial protein concentrations of f-MPC emulsions were higher than that of c-MPC emulsions. f-MPC emulsions remained stable against creaming for at least 8 weeks at room temperature (23 °C), while their c-MPC counterparts showed significant creaming at the same conditions. Even after heating at 121 °C for 15 min, f-MPC emulsions retained their structural integrity as observed from their confocal images, droplet size distributions, and viscosities. In contrast, c-MPC emulsions and mayonnaise disintegrated upon heating at 121 °C for 15 min, and oil droplets of mayonnaise partially coalesced during heating at 90 °C for 30 min. f-MPC emulsions revealed higher viscosities compared to c-MPC emulsions, providing them improved stability. Viscosities of f-MPC emulsions were not significantly affected by heating at 90 °C for 30 min, while other emulsions exhibited a substantial increase in their viscosities due to protein denaturation and aggregation. Thus, f-MPC emulsions can be utilized in the development of protein-enriched functional foods (e.g., spreads) that are stable against high heat treatments.

Nutritionally improved third generation snacks produced by supercritical CO2 extrusion I. Physical and sensory properties

AbstractThis study was aimed at investigating the possible application of defatted hazelnut, camelina, pumpkin, and hemp cakes (by‐products of edible oil production) in the production of corn snack products, and to use supercritical CO2 as a blowing agent in indirectly expanded snack products. Cakes were added in 3, 6, and 9% proportions. Extrusion was performed in a laboratory single screw extruder and expanded by microwave. The obtained extrudates were evaluated for their physical and sensory properties. For comparison, directly expanded products without supercritical CO2, were produced with the same raw materials. The addition of the by‐product had a significant influence on the expansion ratio, bulk density, fracturability, and crispiness, and all four by‐products were successfully incorporated in the production of sensory acceptable, indirectly expanded snack products, produced by supercritical fluid extrusion. This type of products is interesting for consumers since it can be home‐made and produced without additives or any chemical substances.Practical applicationsBy‐products of oil production (defatted press cake from pumpkin seeds, hazelnuts, camelina seeds, and hemp seeds), known as high‐fiber and high‐protein ingredients, were added in the corn grits with the aim to increase nutritional value of the product and to reduce the waste of the food industry.For production of indirectly expanded corn snacks, supercritical CO2 is used as blowing agent, and pellets are expanded by microwave heating in few seconds. This is a good example of new products, which is interesting for consumers since it can be home‐made and it is without additives or any chemical substances.

Physical properties of supercritical fluid extrusion products composed of milk protein concentrate with carbohydrates

SummarySupercritical fluid extrusion (SCFX) is a novel process combining traditional extrusion and supercritical fluid technologies. The objective of this study was (i) to assess the effect of sugar, maltodextrin and cornstarch on the physical properties of milk protein concentrate (MPC) puffed extrudates and (ii) to compare the physical and textural properties of SCFX puffed MPC products with commercially puffed cereal products. Results showed that the nutritious MPC puffed products with carbohydrates can be made with textural properties (hardness, brittleness and crispness) resembling those of the commercial samples. The porosity of F2 (0.573) was assessed to the commercial product C1 (0.543) and C2 (0.595), the specific length of F3 (50.41) was assessed to C1 (45.51) and F4 (80.14) was assessed to C2 (78.12). The hardness of extrudate F3 (435.49 KPa) was assessed to C2 (482.7 KPa). The Young's modulus of F5 (87.03) was assessed to C2 (80.57). The starches affected the crispness of the extrudates, and sugar affected the hardness and brittleness significantly.

Preparation of Micronutrients Fortified Spirulina Supplemented Rice‐Soy Crisps Processed Through Novel Supercritical Fluid Extrusion

Micronutrients fortified spirulina supplemented rice-soy crisps (SRSC) were manufactured using novel supercritical fluid extrusion. A low-shear, twin screw, co-rotating extruder operated at lower temperatures (∼100C) was used to produce crisps supplemented with various levels (2–8%) of spirulina and fortified with four micronutrients (iron, zinc, vitamin A, C) at the recommended daily values in 100 g product. The SRSC were analyzed for proximate composition, dietary fiber, added nutrients, texture and morphological characteristics. The extrusion process retained minerals (87–100%), vitamin A (45–50%) and vitamin C (52–47%), respectively. Rice-soy crisps supplemented with 6% spirulina got the highest score (8.50) from the sensory judges due to appealing color, smooth surface, better crispiness and pleasant flavor and overall acceptability followed by rice soy spirulina crisp supplemented with 4% spirulina (7.80). The developed SRSC can successfully be incorporated in school nutrition programs due to shelf stability, palatability, economic feasibility and fulfilling nutrient requirements of children. Practical Applications SC-CO2-assisted extrusion is an innovative process-based approach to produce shelf stable nutritious crispy products which can be further be converted into food bars for school nutrition programs to reduce the menace of malnutrition. Spirulina and spirulina protein isolates can efficiently be utilized in various food formulations to alleviate the nutrient deficient among the masses. Furthermore, information derived from the present investigation can be helpful for the researchers to understand compositional, functional and nutritional attributes of spirulina and its application in array of foods.

Agro-food industry byproducts into value-added extruded foods

Food industry co-products, fruit pomace and liquid whey, were converted into shelf-stable, puffed products by using low-shear, low-temperature supercritical fluid extrusion. Co-products were utilized as a source of dietary fiber, phytochemicals, and milk nutrients in extruded products. Liquid whey was concentrated and pumped directly into extruder barrel in lieu of water while processing cereal formulations fortified with finely ground fruit pomace. The resulting extruded products were very light in weight with 0.21–0.35g/cm3 density and contain14g dietary fiber, 93mg gallic acid equivalent polyphenols, and 652mg vitamin C equivalent antioxidants in 100g products. The natural fruit color is retained in the final product, indicating the preservation of color pigments and the associated bioactive compounds. About 84% of the total phenolics and 74% of the antioxidants of apple pomace were preserved in the final extrudates. The utilization of the agro-industry waste streams offers effective preservation and utilization of the nutritionally attractive byproducts as a source of functional ingredients in extruded products while adding value to the industrial waste streams.

Enhancing Nanofiller Dispersion Through Prefoaming and Its Effect on the Microstructure of Microcellular Injection Molded Polylactic Acid/Clay Nanocomposites

Promoting better dispersion of nanofillers is crucial in producing high performance nanocomposite foams. For the effects of nanofillers on controlling foam structures and mechanical properties to be enhanced, prefoamed pellets were produced via supercritical fluid (SCF) extrusion foaming and subsequently microcellular injection molded. Structural, thermal, and mechanical properties of the prefoamed pellets and resultant polylactic acid (PLA)/clay nanocomposite foams were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy, and tensile testing. The diffraction peaks in the XRD plots of extruded prefoamed pellets were observed to shift to lower angles, indicating that prefoaming improved the intercalation of clay platelets. The driving forces behind the intercalation and dispersion of clay were (i) enhanced diffusion via the plasticizing effect of SCF and (ii) the phase change of SCF from the supercritical to th...