Functional properties and Angiotensin-I converting enzyme inhibitory activity of soy–whey proteins and fractions

Soy proteins when prepared to high purity can confer good functional properties and the whey by-product is a potential source for bioactivity. In this study, we determined the protein, moisture, fiber, solubility, foaming, emulsion properties, as well as Angiotensin-I converting enzyme (ACE-I) inhibitory activity of prepared soy–whey proteins and its fractions. The soy–whey proteins were fractionated into < 5, > 5, > 10, and > 50 kDa using ultrafiltration. The expanded AACC methods were used to determine protein, moisture, and fiber analyses of the whey and its fractions. Solubility method was conducted to determine the protein solubility profile of the soy–whey and its fractions at varying pHs. Turbidimetric method was used to evaluate emulsifying activity (EA) and emulsion stability (ES). There were significant differences observed in moisture, protein and salt contents between unfractionated, > 50 kDa and smaller sized fractions. No significant differences were observed with phytic acid and total dietary fiber contents among all samples. The unfractionated whey protein and > 50 kDa fraction showed better solubility than other fractions. Unfractionated whey protein had the highest foam capacity (42.7 mL) while the fraction > 5 kDa showed the greatest foaming stability (46 min). The highest emulsion activity (0.33 ± 0.1) and stability (825.1 ± 45.1) was obtained with the > 50 kDa fraction while the unfractionated whey protein had the highest ACE-I inhibition activity. The findings indicate that soy–whey protein fraction (> 50 kDa) had good solubility, emulsion activity and stability, while the unfractionated whey protein exhibited the strongest ACE-I inhibition percentage (19%).     

Impact of cryoconcentration on casein micelle size distribution,micelles inter-distance,and flow behavior of skim milk during refrigerated storage

Cryoconcentration combined with a cascade effect was used to concentrate skim milk up to 25.12% total dry matter. Size, shape, and inter-micellar distance of casein micelles were characterized by ZetasizerNano-ZS, transmission electron microscopy, and ImageJ analyses. Flow properties of the cryoconcentrated skim milk were evaluated during 5 weeks of storage under refrigerated condition at 4 °C. Milk color was also evaluated according to the L*, a*, and b* system. The cryoconcentrated skim milk obtained after three cryoconcentration cycles was characterized by a monomodal distribution of its micelles with a tendency to smaller casein micelles. Approximately 60% of the total micellar volume was occupied by the casein micelles with a size of 100–200 nm, less than 18% of the volume with a size of 50–100 nm and only less than 1% was occupied by micelles with a size > 350 nm. This result shows that cryoconcentration changed the distribution of the mean size of the casein micelles to smaller units. No significant difference was observed on the inter-micellar distance. Cryoconcentration significantly improved the color of skim milk by increasing the L* value up to 67 which was similar to that of whole milk. Transition from a Newtonian to a non-Newtonian behavior was observed from the fourth week storage with a slight increase of casein micelle size.Industrial relevanceA concentration procedure of skim milk based on a complete block cryoconcentration technique was proposed. Application of this sub-zero technology permitted the concentration of skim milk total dry matter up to 25%. The casein micelle size was positively affected by moving the major part of the micelles toward the smaller size, whereas the inter-micellar distance was not affected. This new knowledge can be exploited in milk-based products to enhance the product stability. The cryoconcentrated skim milk color was positively affected since its L* value, which represents the milk whiteness, was significantly improved. The flow behavior of the cryoconcentrated milk was of Newtonian type up to 4 weeks of storage at 4 °C. The generated knowledge in this study can be easily used by the milk processing industry in order to make stable milk product with high dry matter content without adding milk powder, which negatively affects the product sensory properties (floury consistency).     

Encapsulation of Lactobacillus rhamnosus in double emulsions formulated with sweet whey as emulsifier and survival in simulated gastrointestinal conditions

Lactobacillus rhamnosus cultured in sweet whey and harvested in the late log phase was entrapped in the inner aqueous phase of a double water-in-oil-in-water emulsion using concentrated sweet whey as emulsifier. The primary and double emulsion droplets showed practically no changes in their morphology and droplet size with aging time. The viability of the entrapped L. rhamnosus in the double emulsion was compared to that of non-entrapped control cells exposed to low pH and bile salt conditions. The viability of the control cells (initial number = 6.57 ± 0.3 log cfu ml^?1) decreased significantly under low pH and bile salt conditions, and their survival was 71% and 89%, respectively. The survival of the entrapped cells (initial number = 6.74 ± 0.2 log cfu ml^?1) increased significantly under low pH and bile salt conditions, and their survival was 108% and 128%, respectively. It is concluded that the double emulsion protected L. rhamnosus against simulated gastrointestinal tract conditions.     

Skim Milk Whey Cryoconcentration and Impact on the Composition of the Concentrated and Ice Fractions

The present work is a continuation of our previous study on the cryoconcentration of whole milk whey. The aim of the present work was to study a cryoconcentration procedure of skim milk whey and to compare the results with those obtained using whole milk whey. In the present study, skim whey was cryoconcentrated at four stages. It was found that by increasing the cryoconcentration stage, total dry matter content of the concentrated fraction increased, while it decreased in the ice fraction only until the third stage. Total dry matter content in the concentrated fraction reached an average value of 35% (w/v) at the fourth stage. The ratio of total protein to total dry matter remained constant in both fractions independently of the cryoconcentration stage. Results showed that the fat matter is an important factor for protein and lactose distribution between the concentrated and the ice fractions. Mathematical equations were developed to help the optimization of the process. Results showed that three cryoconcentration stages are optimal.     

Production of gluconic acid from whey by free and immobilized Aspergillus niger

Deproteinized whey has been used as a fermentation medium for the production of gluconic acid by Aspergillus niger immobilized in polyurethane foam or free cells. Addition of a small amount of glucose (0.5%, w/v) in the whey medium enhanced the production of gluconic acid by 140% over the unsupplemented medium. Immobilized mycelia produced 92 g of gluconic acid from 1 L of whey medium containing 9.5% lactose and 0.5% glucose against 69 g by free mycelia. Immobilized mycelia can be reused.     

Chewing activities and particle size of rumen digesta and feces of precision-fed dairy heifers fed different forage levels with increasing levels of distillers grains

The objective of this study was to determine the effects of 2 differing forage to concentrate ratios (F:C) and various levels of corn dry distillers grain with solubles (DDGS) replacing canola meal in precision-fed dairy heifer rations on chewing behavior, rumen pH and fill, and particle size of rumen contents and feces. A split plot design with F:C as whole plot and DDGS inclusion level as subplot was administered in a 4-period 4 × 4 Latin square. Eight rumen-cannulated Holstein heifers (12.5 ± 0.5 mo of age and 344 ± 15 kg of body weight, respectively) housed in individual stalls were allocated to F:C 50:50 (low forage) or 75:25 [high forage (HF); dry matter basis] and to a sequence of DDGS level (0, 7, 14, and 21%; dry matter basis). Forage was a mix of 50% corn silage and 50% grass hay (dry matter basis). Diets were fed once daily and formulated to provide equal amounts of nutrients and body weight gain. No differences were found for rumen pH between dietary treatments. Time spent eating tended to be longer for HF and was not affected by DDGS inclusion rate. Ruminating time did not differ by F:C, but linearly increased as DDGS increased (422 to 450 ± 21 min/d). Total chewing time tended to be longer for HF and to increase linearly as DDGS increased (553 to 579 ± 33 min/d). Wet rumen digesta weight and volume were greater for HF. Geometric mean particle length of rumen contents was greater for HF 2 h prefeeding when analyzed with solubles (particles <0.15 mm). Proportion of rumen solubles decreased as DDGS increased 5 h postfeeding. Fecal geometric mean particle length and proportion of particles >1.18 mm increased with increasing levels of DDGS and did not change with F:C. Total chewing time increased by the addition of DDGS and higher F:C. Heifers can compensate for lower physically effective neutral detergent fiber by modifying their chewing behavior. Rumen pH was never at a level that could induce acidosis, and lower eating time at lower F:C was somewhat compensated by time spent ruminating per unit of physically effective neutral detergent fiber intake. Dry distillers grains with solubles, when used in dairy heifer rations as a replacement for canola meal, yielded similar rumen digestion traits.     

Factors affecting the rheological properties of a structured cellular solid used as a fat mimetic

The effects of water content, monoglyceride chain length and concentration, oil type, and the addition of oil-phase and water-phase additives on the elastic modulus and yield stress of a structured oil in water were evaluated. The goal was to increase the elastic modulus of the original emulsion from 8.42 × 10³ ± 11.3 Pa to 1.55 × 10⁶ ± 2.1 × 10⁵ Pa, and the yield stress from 112 ± 2.31 Pa to 835 ± 227 Pa. The addition of wax at greater than 10% (w/w), the use of palm oil or the gelation of the liquid oil phase with 5–7.5% rice bran wax, the use of C-18 saturated monoglyceride at 6%(w/w), and 4% (w/w) for C-22 saturated monoglyceride molecules were effective modifications capable of improving the mechanical behavior of the emulsion so that it can be used as a zero trans and reduced saturated fat laminating shortening substitute for puff pastry products.     

Stability of flocculated particles in concentrated and high hydrophilic solid layer-by-layer (LBL) emulsions formed using whey proteins and gum Arabic

The objective of the present study was to investigate flocculation in layer-by-layer (LBL) emulsion systems with high total solids content and deflocculation at various pH conditions, and the effects of whey protein isolate (WPI) concentration and total solids content on the stability of LBL emulsions. WPI (1.96% (1WPI) or 10.71% (10WPI), w/w in water) was prepared in water and high-pressure homogenized with sunflower oil (10%, w/w, of total emulsion). Gum Arabic (0.15%, w/w, in total emulsion) was added to assemble electrostatically on WPI at oil particle interfaces at pH 3.5 using aqueous citric acid (10% w/w) forming LBL emulsion. The ζ-potential measurements showed charge reversal upon addition of gum Arabic solution into single layer (SL) emulsion confirming the formation of LBL interface. Trehalose:maltodextrin mixture (1:1, w/w, total emulsion, 28.57% (28) or 57.14% (57), w/w, in water) was used in the continuous phase. The high total solids content of the system results in depletion flocculation of the particles leading to bridging flocculation without coalescence as deflocculation into individual particles occurred with increasing pH from pH 3.5 to pH 6.5 in 10WPI systems. Deflocculation was evident in 10WPI-28 and 10WPI-57 as found from a decreased ζ-average diameter and visually under microscope. Coalescence was observed in 1WPI systems. Viscosity of the systems was significantly (P < 0.05) increased with higher total solids content. Accelerated destabilization test showed that systems at higher WPI and total solids contents exhibited the highest stability against creaming. Deflocculation in LBL systems can be controlled by pH while high solids in the aqueous phase provide stability against creaming.     

Influence of emulsifier type on in vitro digestibility of lipid droplets by pancreatic lipase

The objective of this study was to investigate the influence of interfacial composition on the in vitro digestion of emulsified lipids coated by various emulsifiers by pancreatic lipase. Sodium caseinate, whey protein isolate (WPI), lecithin and Tween 20 were used to prepare corn oil-in-water emulsions (3 wt% oil). Pancreatic lipase (1.6 mg/mL) and/or bile extract (5.0 mg/mL) were added to each emulsion and the particle charge, droplet aggregation, microstructure and free fatty acids released were measured. In the absence of bile extract, the amount of free fatty acids released per unit volume of emulsion was much lower for lipid droplets coated by Tween 20 (13 ± 16 μmol ml⁻¹) than those coated by lecithin (75 ± 20 μmol ml⁻¹), sodium caseinate (220 ± 24 μmol ml⁻¹) or WPI (212 ± 6 μmol ml⁻¹). In the presence of bile extract, there was an appreciable increase in the amount of free fatty acids released in all the emulsions, with the most appreciable effects being observed in the Tween 20-stabilized emulsions. The stability of the emulsions to droplet flocculation and coalescence during hydrolysis was also strongly dependent on emulsifier type, with the WPI emulsions being the least stable and the Tween 20 emulsions being the most stable. Our results suggest that the access of pancreatic lipase to emulsified fats decreases in the following order: proteins (caseinate and WPI) > phospholipids (lecithin) > non-ionic surfactants (Tween 20). These results may have important consequences for the design of foods with either increased or decreased lipid bioavailability.     

The effect of Yucca schidigera extract on the physical structure and on the oxidative stability of sugar-candy foam products

The influence of water extract of yucca (Yucca schidigera Roezl.) powder on foaming potential, structure of sugar-candy foam and its stability during the shelf-life was researched. Water extract of yucca powder (1:7 w/v) contained 0.102 mg/ml of steroidal saponins. This was added to sugar-candy foam in concentration equivalent of 50 and 100 ppm saponins. In parallel, similar sugar-candy foam was prepared by adding 200 ppm of α-tocopherol or in a traditional way but without any additives. It was shown that yucca extract had beneficial influence on the structure (dry matter content, hardness, density and porosity) of sugar-candy foam products both in newly prepared as well as in candies stored over two months period. Moreover, antioxidant properties of yucca extract were much stronger than those shown by α-tocopherol and allowed to maintain freshness of candies for 2-months period. This indicates that yucca water extract might be a beneficial natural ingredient improving both quality and stability of sugar-candy foam products.     

Effect of static electric field on ice crystal size reduction during freezing of pork meat

The objective of this research was to evaluate the influence of static electric field (SEF) on the freezing of pork meat (pork tenderloin muscle) with respect to the size of ice crystal formulation. The results showed that by increasing the strength of the static electric field, the degree of supercooling was reduced. The measured degree of supercooling varied from 3.93 ± 1.3 °C to 1.92 ± 1.45 °C for the control and the frozen sample under 12 kV SEF, respectively. Meat microstructure was investigated after Carnoy fixation of the frozen tissues. The overall relative surface of the ice crystals was unchanged. The average equivalent circular diameter of the ice crystals was significantly reduced with increasing SEF; values from 32.79 ± 4.04 μm for the control to 14.55 ± 8.20 μm for the sample frozen at the maximum magnitude electric field which was tested were observed respectively. These findings demonstrate clearly the advantage of freezing under SEF which appears as a promising and innovative freezing process for food systems.Industrial relevanceThe reduction of freeze damage exerted to any tissue undergoing freezing remains a challenge. The mechanical and biochemical stress caused by the ice crystals to the cellular membranes results in irreversible tissue damage. Freezing under static electric field (SEF) has been identified as a possible means to reduce the size of ice crystals during freezing of biological tissues. In the present study SEF was applied during freezing of pork meat. Our results indicate that the size of the formed ice crystals was significantly reduced under SEF freezing leading to a lower damage on the microstructure of meat. This paper describes an innovative freezing process that could be used in order for higher quality frozen products to be produced.     

Skim milk cryoconcentration as affected by the thawing mode: gravitational vs. microwave‐assisted

In the present study, skim milk was successfully cryoconcentrated up to 43.72 ± 0.69% (w/w) total dry matter after four cryoconcentration cycles. Total proteins were concentrated up to 22.49 ± 0.31% (w/w). It was found that the cryoconcentrated skim milk fraction was rich in potassium ions. The effect of the cryoconcentration cycle and thawing mode on process efficiency was studied. The obtained data showed that the cryoconcentration cycle effect was significant (P < 0.001). The thawing mode (gravitational and microwave assisted thawing) had no effect on process efficiency. However, the microwave assisted thawing mode was more efficient regarding to the time needed to obtain the desired thawed fraction. To achieve high process efficiency, three cryoconcentration cycles were sufficient since the process efficiency drastically decreased after this cycle. The concentration of the dry mater entrapped in the ice fraction was the highest at the fourth cryoconcentration cycle.     

Fluidized bed microencapsulation of Lactobacillus reuteri with sweet whey and shellac for improved acid resistance and in-vitro gastro-intestinal survival

This study aimed at developing a micro-encapsulation process for Lactobacillus reuteri DSM 20016 with sweet whey powder and dietary shellac by a two-step fluidized bed granulation and top spray coating technique to enhance resistance to acid conditions and to increase bacterial survival under gastro-intestinal conditions. L. reuteri DSM 20016 was a top-spray fluid bed granulated at 50 °C with sweet whey and different thermo-protectants followed by top spray coating with an aqueous shellac solution. Moisture content and particle size of granules measured by infrared moisture balance and laser diffraction were appropriate for the encapsulation of the bacteria. Bacterial survival rates were evaluated by pour plate counting. Viabilities after granulation were 43 ± 4.5%, after 15 min shellac coating 22.69 ± 2.41% and 14.86 ± 1.29% after 30 min coating time. Endpoint bacterial count after 28 d storage at 4 °C remained equal for coated and uncoated bacteria. After incubation in gastric acid and intestinal conditions the final survival rate of coated L. reuteri DSM 20016 with 76.74 ± 24.36% was higher compared to free cells with 17.74 ± 10.51% (p = 0.0388).To conclude fluidized bed technology with a combination of sweet whey and shellac as encapsulation material offers distinct acid resistance for L. reuteri DSM 20016 and enables improved survival during gastro-intestinal transit. Hence the usage of shellac and sweet whey powder as encapsulation material improves the effectiveness of probiotic food applications.     

Effect of Adding Dried Whey to Starter Diet of Early and Late Weaned Calves

Forty-four Holstein calves, 20 males and 24 females, were randomly assigned to one of four treatments in a 2 × 2 factorial designed experiment. Treatments consisted of early (35 d) versus late (70 d) weaning and the feeding of a pelleted starter diet containing either 0 or 24.5% dried sweet whey. Calves were housed in individual, elevated, shaded pens. Whole milk was fed at 10% of body weight adjusted weekly. The assigned starter diet and water were provided free choice beginning on the 8th d of the trial. Intakes of milk and starter diet were recorded daily. Body weight, heart girth, and wither height measurements were recorded weekly during the 14-wk trial. Calves fed the starter diet containing whey consumed less dry matter (119.2 vs. 150.7 kg) and had a lower rate of gain (.63 vs. .72 kg/d) than those fed the control starter ration. Late weaned calves consumed less starter (115.8 vs. 145.0 kg) and gained more rapidly (.74 vs. .61 kg/d) than early weaned calves. Bull calves were more efficient converters of dietary dry matter into body weight gain than heifer calves, and late weaned calves were more efficient than early weaned calves. Inclusion of whey in the starter ration did not influence feed conversion. It was concluded that the addition of whey at 24% of a pelleted starter diet depressed intake and rate of gain of calves.     

Water absorption as an evaluation method of cooking quality for yam (Dioscorea alata) and cassava (Manihot esculenta crantz)

Water absorption as a new method of cooking quality (hard cooking or mealy cooking) of yam and cassava cultivars determination was studied by cooking eight (08) cultivars. 30 g of each were boiled in 500 ml of water during 20 minutes and dried at 70 °C for 15 hours and 103 °C for 3 hours in a vacuum oven. Results showed that cassava and yam have different cooking quality. Dry matter content does not influence the cooking quality of yam and cassava. Mealy cooking quality of yam absorbs less water (6.6%) during cooking but looses more soluble dry matter (9.5%) during the same process. Hard cooking quality of yam absorbs much water (23.5%), but looses less soluble dry matter (3.9%). The soluble dry matter is the main parameter to determine the quality of D. alata. It stands at 9.5% ± 2.9 for mealy cooking quality and 3.9 ± 0.73 for hard cooking quality cultivars of D. alata. Water absorbed by mealy cooking cassava (27.6%) is significantly (p < 0.05) higher compared to water absorbed of hard cooking cassava (12.4%). Water absorbed during cooking is the main parameter in determining the quality of cassava cultivars. Water absorbed stands at 27.6% ± 8.8 for mealy cooked quality and 12.4% ± 1.9, for hard cooked quality of cassava cultivars. A close relation between water absorption and cooking quality was revealed to contribute to a better selection procedure for cultivars in the frame of food security.     

Highly-porous mannitol particle production using a new templating approach

A new method has been successfully developed to create highly-porous powder templates through the spray drying of mannitol, using citric acid as the templating agent and then removing the citric acid by ethanol washing of the spray-dried powders. It has been demonstrated that textural properties, such as the surface area and the pore volume of the resultant mannitol, can be tuned by varying the concentrations of citric acid, whey protein isolate (WPI), and Gum Arabic. The resulting powder structure is a mannitol network with significant porosity and high surface area of 8.0 ± 0.4 m²/g and total pore volume of 0.075 ml/g. The scanning electron microscope micrographs were consistent with the Brunauer–Emmett–Teller (BET) surface area measurements. It has been found that higher concentrations of WPI, more than 0.5% w/w, have a detrimental effect on the porosity of the spray-dried powders from the solutions of mannitol/WPI with 2% (w/w) citric acid. For Gum Arabic, more than 1% (w/w) Gum Arabic causes lower porosities due to the lower citric acid removal by ethanol washing. The results of this study allow excipient powders to be produced with high specific surface areas.     

Characterization and acid-induced gelation of butter oil emulsions produced from heated whey protein dispersions

Whey protein isolate was dispersed at 4% or 8% (w/v) and heated at neutral pH to produce protein polymers. Butter oil, up to 20%, was homogenized in heated whey protein dispersions at pressure ranging from 10 to 120 MPa. Emulsion gelation was induced by acidification with glucono-δ-lactone. Whey protein polymers produced finely dispersed emulsions with fat droplet diameter ranging from 340 to 900 nm. Homogenization pressure was the main factor influencing droplet size. At low fat volume fraction, the emulsions exhibited Newtonian behaviour. As fat content increased, shear thinning behaviour developed as a result of depletion flocculation. Emulsion consistency index increased with protein and fat concentrations. Increasing homogenization pressure had no effect on Newtonian emulsions but promoted flocculation and significantly increased the consistency of high fat emulsions. Protein concentration was the main factor explaining emulsion gel hardness and syneresis. Syneresis decreased with increasing fat content in the gel.     

Emulsifying properties of lactose-amines in oil-in-water emulsions

Lactose-amines were synthesized with hexadecyl-amide and lactose via the Maillard reaction and their emulsion stabilization properties were investigated. Lactose-amines were synthesized using two different constant heating (4 and 8 h) and two different heating/cooling cycles (12 and 24 h). Each lactose-amine sample was used as an emulsifier in 20:80 ratio oil-in-water emulsions at four different concentrations (0.01%, 0.05%, 0.1%, and 1%). Emulsion stability was monitored by measuring the oil droplet sizes and the extent of destabilization via clarification over 5 days. At 1% concentrations, emulsions prepared with lactose-amines synthesized for 4, 12, and 24 h were as stable as the whey protein positive control emulsion. The 8 h lactose-amine sample resulted in a less stable emulsion. We assume the difference is related to the amount of heat this sample was exposed to during synthesis, with extensive heat leading to advanced Maillard products, which possessed reduced emulsification properties.     

Nanoencapsulation of date palm pit extract in whey protein particles generated via desolvation method

An alkaline solution of whey protein isolate was charged with absolute ethanol resulting in precipitation of whey protein particles. The vacuum-dried particles were then dispersed either in water or aqueous ethanol. Heat-treatment of whey proteins before desolvation process decreased the mean size of particles when dispersed in aqueous ethanol from 280 nm to 183 nm. The range and mean size of particles prepared from heat-treated protein solution when dispersed in water were 41–212 nm and 103 nm, respectively. Date palm pit aqueous extract was encapsulated inside the particulating heat-treated whey proteins during the desolvation stage with encapsulation efficiency of ~ 78%. Extract-loaded particles had mean size of 163 nm in alcoholic dispersion and 92 nm in water dispersion. Scanning electron microscopy imaging showed spherical nanoparticles aggregated in dry state. Fourier transform infrared spectroscopy suggested that extract and whey proteins did not covalently bind. Heat-treatment of whey proteins before desolvation resulted in the absence of denaturation endotherm in differential scanning calorimetry curve of extract-free particles. Extract loading in particles interrupted the continuity of protein matrix causing the occurrence of mild glass transition phenomenon in extract-loaded particles when heated.