Laminar flow continuous settling crystalliser. Part 2. Modifications

This paper (Part 2 of 2) revises and expands on the original model for the laminar flow continuous settling crystalliser presented in Part 1 in an effort to understand why the original model over-predicted product particle d₁₀ and d₅₀ and under-predicted the span and d₉₀. Because agglomerates were observed experimentally, an agglomeration term was added to the initial theoretical model resulting in no significant particle size distribution prediction changes. On further analysing potential flow conditions a region of high flow and a subsequent area of low flow explained the d₅₀ and span deviations found experimentally. It was concluded that the difference between the ideal predicted spans and the experimental spans was due to non-ideal laminar flow conditions existing in the column. Although not achieved experimentally, it is postulated that an ideal parabolic laminar column flow profile would result in a narrow particle size distribution.     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.     

High-pressure homogenisation of raw bovine milk. Effects on fat globule size distribution and microbial inactivation

Whole raw milk was processed using a 15 L h⁻¹ homogeniser with a high-pressure (HP) valve immediately followed by a cooling heat exchanger. The influence of homogenisation pressure (100–300 MPa) and milk inlet temperature T_in (4°C, 14°C or 24°C) on milk temperature T₂ at the HP valve outlet, on fat globule size distribution and on the reduction of the endogenous flora were investigated. The T_in values of 4–24°C led to milk temperatures of 14–33°C before the HP valve, mainly because of compression heating. High T_in and/or homogenisation pressure decreased the fat globule size. At 200 MPa, the d_4.3 diameter of fat globules decreased from 3.8±0.2 (control milk) to 0.80±0.08 μm, 0.65±0.10 or 0.37±0.07 μm at T_in=4, 14°C or 24°C, respectively. A second homogenisation pass at 200 MPa (T_in=4°C, 14°C or 24°C) further decreased d_4.3 diameters to about 0.2 μm and narrowed the size distribution. At all T_in tested, an homogenisation pressure of 300 MPa induced clusters of fat globules, easily dissociated with SDS, and probably formed by sharing protein constituents adsorbed at the fat globule surface. The total endogenous flora of raw milk was reduced by more than 1 log cycle, provided homogenisation pressure was ⩾200 MPa at T_in=24°C (T₂∼60°C), 250 MPa at T_in=14°C (T₂∼62°C), or 300 MPa at T_in=4°C (T₂∼65°C). At all T_in tested, a second pass through the HP valve (200 MPa) doubled the inactivation ratio of the total flora. Microbial patterns of raw milk were also affected; Gram-negative bacteria were less resistant than Gram-positive bacteria.     

X-ray diffraction analysis of lactose crystallization in freeze-dried lactose–whey protein systems

Water sorption, time-dependent crystallization and XRD patterns of lactose and lactose–WPI mixtures were studied with glass transition data. The results indicated that the sorbed water of lactose–WPI mixtures was fractional and water content of individual amorphous components in lactose–WPI mixtures at each a_w from 25 °C to 45 °C could be calculated. Crystallization occurred in pure lactose whereas partial crystallization was typical of lactose–WPI mixtures (protein content ≤ 50%) at intermediate and high a_w (> 0.44 a_w) from 25 °C to 45 °C. The extents of crystallization were significantly delayed by WPI. The T_g values of lactose–WPI systems showed the composition-dependent property in systems and might indicate the occurrence of phase separation phenomena during 240 h storage. XRD showed no anhydrous β-lactose and mixed α-/β-lactose with molar ratios of 4:1 crystals in crystallized lactose–WPI systems (70:30 and 50:50 solids ratios). Reduced crystallization in the presence of WPI was more pronounced possibly because of reduced nucleation and diffusion during crystal-growth. The present study showed that WPI could present an important role in preventing sugar crystallization.     

Major triterpenes,cycloeucalenone and 31-norcyclolaudenone as inhibitors against both α-glucosidase and α-amylase in banana peel

The inhibitory activities of banana peel extract against carbohydrate digestive enzymes were investigated. Cycloeucalenone and 31-norcyclolaudenone were obtained by bioassay-guided fractionation as effective inhibitors of α-glucosidase and α-amylase. The structure–activity relationships of four triterpenes isolated from banana peel, cycloeucalenone, 31-norcyclolaudenone and cycloeucalenol and its isomer were investigated. The IC₅₀ values of cycloeucalenone and 31-norcyclolaudenone against α-glucosidase were 31.83 ± 2.46 μm and 38.85 ± 1.54 μm , respectively, and their IC₅₀ values against α-amylase were 20.33 ± 0.59 μm and 27.63 ± 0.83 μm , respectively. In contrast, cycloeucalenol and its isomer had insufficient inhibitory activity against either enzyme. The primary active sites of cycloeucalenone and 31-norcyclolaudenone are the carbonyl group at C-3 and the double bond in the side chain. Cycloeucalenone induced a parabolic mixed-type inhibition with a K_i value of 73.86 μm in the α-glucosidase inhibitory assay. This study provides new evidence for the potential use of banana peel triterpenes as antidiabetic agents.     

High-pressure homogenization. Part I. Liquid-liquid dispersion in turbulence fields of high energy density

On the basis of the author's own measurements and data given in the literature, the present paper shows that disperision in turbulence fields of high energy density under conditions of high-pressure homogenization takes place in two stages.Primary dispersion is affected by large eddies of high energy content. The isotropy of these eddies is influenced by the size of the turbulence chamber. Secondary dispersion takes place as a results of pressure fluctuations of the smallest energy-dissipating eddies if the particle diameter is much larger than the dimensions of these eddies (10 < d_PS < 1000 μm. In the case of very high energy densities, secondary dispersion takes place by viscous shearing between two convergent small energy-dissipating eddies if the particle diameter is roughly equal to the dimensions of these eddies 0·2 < d_PS < 10 μm).     

Physical and mechanical properties of lactose/WPI mixtures: Effect of pre-crystallisation

This study investigated the physical and mechanical properties of spray-dried lactose/whey protein isolate (WPI) (4:1) mixtures with different contents of α-lactose monohydrate (1.0%, 11.2%, 29.2%, and 46.8%, w/w). Particle size of samples with 11.2%, 29.2%, and 46.8% crystallinity was significantly (P < 0.05) larger compared with the sample with 1.0% crystallinity. The presence of less than 46.8% crystalline lactose in lactose/WPI mixtures had only a minor effect on water sorption behaviour at a_w 0.11–0.44, whereas samples with higher crystallinity had higher stable water content after showing lactose crystallisation. Moreover, samples with lower crystallinity showed higher initial sorption rates. Increasing the amount of crystalline lactose had no significant influence on the glass transition temperature and the initial crystallisation temperatures at a_w 0.11–0.44. Furthermore, dairy powders with higher crystallinity had higher stiffness and water plasticisation showed a stronger effect on the structural relaxation of dairy powders with lower crystallinity.     

Novel β-casein derived antioxidant and ACE-inhibitory active peptide from camel milk fermented by Leuconostoc lactis PTCC1899: Identification and molecular docking

Antioxidant and angiotensin-I converting enzyme inhibitory (ACE-I) activities of bioactive peptide fractions from camel milk fermented by Leuconostoc lactis PTCC 1899 were assessed. The fraction <3 kDa obtained from ultrafiltration showed ACE-I (IC₅₀ = 1.61 ± 0.18 mg mL⁻¹) and ABTS radical scavenging (1883.39 μm TE mg⁻¹ protein) activities and was purified through RP-HPLC. The active peptide, MVPYPQR, with antioxidant (8933.05 μm TE mg⁻¹ peptide) and ACE-I (IC₅₀ = 30 μm) activities was identified. To investigate the ACE-I mechanism of the purified peptide the docking study was performed. The presence of hydrogen bond between Gln 162 (S'1 pocket of ACE) and Arg in the C terminal of the peptide was identified and the peptide could distort the Zn²⁺ tetrahedral geometry of the enzyme. This study showed the ability of Leuc. lactis to produce a novel and safe functional food by hydrolysing the milk proteins during the fermentation.     

Influence of bulk and interfacial properties and operating conditions on continuous foaming operation applied to model media

Continuous foaming operation was investigated on model food as a function of rotation speed N and of the gas-to-liquid flow ratio G/L. Newtonian glucose syrup solutions exhibiting various viscosities were studied using additives in order to modify their elasticity and interfacial properties. Without surfactant, gas dispersion experiments showed that a total incorporation of the gas phase could not be achieved at constant liquid flow rate (L = 30 mL/min) for G/L higher than 5/30; the Sauter diameter d₃₂ of the bubbles could not be predicted using a simple approach based on a constant critical value of the laminar Weber number We = We_C. The addition of whey proteins gave abundant foams with total gas incorporation. d₃₂ could be predicted using We = 0.3 when We was defined using the process viscosity measured during foaming. Gelatin increased We_C, while gelatin–whey proteins mixtures decreased We_C by reinforcing the rigidity of the interfacial film; PAA–whey protein mixtures exhibited similar trends, but We_C decreased when G increased. Conversely, We_C varied significantly with operating conditions when emulsifiers or proteins/emulsifiers mixtures were used as foaming agents.     

Laccase mediated conjugation of sugar beet pectin and the effect on emulsion stability

Laccase catalyzes intermolecular cross-links between ferulic acid of sugar beet pectin (SBP). Conjugation of SBP by laccase was confirmed by increased molecular weight, monitored by size exclusion chromatography, combined with multi-angle laser light scattering (SEC–MALLS), by reduced ferulic acid concentration detected at UV 325 nm, as well as by increased particle size. In addition, cross-linked SBP developed a more compact, branched structure as verified by a smaller root mean square (RMS) when molecular weight increased. Emulsions prepared with conjugated SBP had significantly smaller d_4,3 diameter and uniform droplet size, with more negative ζ-potential than non-treated SBP, during 30 days storage at 37 °C. The d_4,3 diameter was 5.3 μm and 3.8 μm for SBP and conjugated SBP, respectively. Covalently conjugated SBP has increased functionality and improved emulsion stability, most likely attributable to development of thick layer at the oil interface.     

Angiotensin I-converting enzyme inhibitory activity of chickpea and pea protein hydrolysates

ACE inhibitory activity was studied for different hydrolysates obtained from protein concentrates of chickpea (kabuli and desi) and yellow pea (Golden) using in vitro gastrointestinal simulation, alcalase/flavourzyme, and papain. Protein/peptide profiles studied by SDS–PAGE and SE-HPLC, showed a rich composition of the hydrolysates in small peptides having MWs under 4 kDa. Papain hydrolysed yellow pea proteins showed the highest ACE inhibitory activity. In addition, chickpea desi proteins hydrolysed by in vitro gastrointestinal simulation showed higher ACE inhibition (IC₅₀ of 140 ± 1 μg/ml) compared to its digests obtained by alcalase/flavourzyme (IC₅₀ of 228 ± 3 μg/ml) or papain (IC₅₀ of 180 ± 1 μg/ml) and to chickpea kabuli hydrolysed by gastrointestinal simulation (IC₅₀ of 229 ± 1 μg/ml). The results demonstrate that enzymatic hydrolysates of chickpea and pea proteins contain bioactive ACE inhibitory peptides; furthermore, the type of enzyme used for hydrolysis affects the ACE inhibitory activity.     

Purification and characterization of angiotensin I-converting enzyme inhibitory peptides of small red bean (Phaseolus vulgaris) hydrolysates

Angiotensin I-converting enzyme (ACE) inhibitory activity was investigated for small red bean (Phaseolus vulgaris) protein hydrolysate produced by sequential digestion of Alcalase, papain followed by in vitro gastrointestinal simulation. The hydrolysate had ACE inhibitory activity with IC₅₀ of 67.2 ± 1.8 μg protein/mL. Peptides responsible for potent ACE inhibitory activity were isolated by a three-step purification process, including ultrafiltration, gel filtration and preparative reverse phase high performance chromatography (RP-HPLC). The fraction obtained after RP-HPLC fractionation with the highest activity yielded an IC₅₀ of 19.3 ± 1.4 μg protein/mL. Enzymatic kinetic studies using this fraction demonstrated competitive inhibition with K_i of 11.6 ± 1.7 μg protein/mL. Mass spectrometric characterization identified for the first time the octapeptide PVNNPQIH which demonstrated an IC₅₀ value of 206.7 ± 3.9 μM. The results expand the knowledge base of ACE inhibitory properties of small red bean protein hydrolysate and should be useful in further identification of specific ACE inhibitory peptides in beans.     

Synthesis of galactooligosaccharides using sweet and acid whey as a substrate

Two commercial available lactases from Aspergillus oryzae and Kluyveromyces lactis were used to study the synthesis of galactooligosaccharides (GOS) in sweet and acid whey. At 38 g L⁻¹ initial lactose concentration, the A. oryzae enzyme gave a GOS yield of 10.91 ± 0.01% in lactose solution, 10.93 ± 0.18% in sweet whey and 11.32 ± 0.59% in acid whey. Thus, the components in whey did not influence the enzymes transgalactolytic activity. On the other hand, the K. lactis enzyme showed a strong dependence on whey type and whey concentration. At 38 g L⁻¹ initial lactose concentration, GOS yields were 10.93 ± 0.26% in lactose solution, 4.30 ± 0.17% in sweet whey and 10.56 ± 0.41% in acid whey. However, with increasing initial lactose concentration, the inhibitory effect of sweet whey was decreasing, which resulted in even higher yields than in lactose solution.     

Amorphous lactose crystallisation kinetics

Amorphous lactose crystallisation kinetics were investigated at different relative humidity and temperature combinations. Amorphous lactose was equilibrated to a water activity of 33%, then placed in sealed pans with a saturated magnesium chloride solution to maintain a constant relative humidity (33%). The temperature was raised to 10–40 °C above the glass transition temperature (T_g). The degree of crystallisation was measured using isothermal microcalorimetry. Crystallisation was shown to be an all-or-nothing event, such that direct measurement of the kinetics was not possible. This was not expected from the Avrami model. The rapid crystallisation could be an autocatalytic effect, as moisture is released during crystallisation, or a showering event as seen in highly supersaturated lactose solutions. Experiments using a blend of crystalline and amorphous lactose, produced by spray drying a lactose crystal slurry, showed crystallisation occurring at lower T_g conditions than was required for the crystallisation of 100% amorphous lactose.     

Influence of protein concentration on surface composition and physico-chemical properties of spray-dried milk protein concentrate powders

Surface composition, moisture sorption behaviour and glass–rubber transition temperature (T_gr) were determined for spray-dried milk protein concentrate (MPC) powders over a range of protein contents (35–86 g 100 g⁻¹). Surface characterisation of MPC powders indicated that fat and protein were preferentially located on the surface of the powder particles, whereas lactose was located predominantly in the bulk. Moisture sorption analysis at 25 °C showed that MPC35 exhibited lactose crystallisation, whereas powders with higher protein contents did not and continually absorbed moisture upon humidification up to 90% RH. The GAB equation, fitted to sorption isotherms of MPCs, gave increases in monolayer moisture value (m_m) with protein content. T_gr, measured with a rheometer, decreased significantly (P < 0.05) with increasing water content and increased with increasing protein content (P < 0.05). In conclusion, increasing protein concentration of MPCs resulted in altered surface composition and increased m_m value and T_gr values.     

Flavor release from spray-dried amorphous matrix: Effect of lactose content and water plasticization

Glass-forming carbohydrates are widely used as matrix for encapsulation of nutrients and bioactive compounds. In this study, encapsulation systems with lactose/whey protein isolate (WPI) mixtures (4:1, 1:1, and 1:4), or WPI as wall materials and ethyl butyrate as core material were prepared by spray drying. The effects of lactose content and water plasticization on encapsulation efficiency and flavor release were investigated. Wall material consisting of lactose/WPI (4:1) mixture had significantly (P < 0.05) higher encapsulation efficiency. The flavor retention in powders did not have significant decrease with equilibration at 0.33 a_w, while it was dramatically decreased at 0.54 a_w and 0.65 a_w as a result of lactose crystallisation. Mechanical property study showed that the molecular mobility and free volume of encapsulation systems with higher lactose content increased more significantly with increasing water content, which accelerated the diffusion of flavor molecules. Those results may use in the assessment of protection and release characteristics of flavor components in formulated systems.     

Sugar beet pectin as a natural carrier for curcumin,a water-insoluble bioactive for food and beverage enrichment: Formation and characterization

Food and beverages enrichment with water-insoluble health-promoting nutraceuticals is important, but technologically challenging. Sugar beet pectin (SBP) is a natural dietary fiber with high emulsifying capacity. However, its potential as a natural encapsulator of hydrophobic nutraceuticals for beverage enrichment, has hardly been explored. Curcumin is a potent antioxidant with numerous attributed health benefits, but very low aqueous-solubility. We herein explored SBP as a carrier for solubilization and protection of curcumin (CUR). Using spectrofluorimetry, the CUR-SBP binding constant determined was (6.74 ± 0.5) ∙ 10⁵M⁻¹. As CUR:SBP molar ratio increased from 14:1 to 140:1, CUR encapsulation capacity increased from 14.5 ± 0.8 to 127.4 ± 0.4 mg _{CUR/g SBP}, and encapsulation efficiency moderately decreased from ~100% to 86 ± 7%. The encapsulation in SBP dramatically decreased CUR particle size, from >17 μm to <0.5 μm, in average, and conferred substantial protection to CUR during simulated shelf-life, decreasing the decay rate constant ~7 fold. Therefore, SBP is a potent natural encapsulator for hydrophobic nutraceuticals for food and even clear beverage enrichment.     

Bovine ossein powder: effect of particle size on its physicochemical and functional characteristics and its application in emulsion-type sausage

Ossein (OS) powder was prepared from bovine bone, ground and sieved through mesh screens to obtain two different particle sizes of 50 (OS₅₀) and 200 mesh (OS₂₀₀). Regarding OS property determination, average particle diameters of the OS₅₀ and the OS₂₀₀ were 260.08 ± 6.48 μm and 51.79 ± 0.39 μm, respectively. Based on non-reducing electrophoresis, both OS samples consisted of α1- and α2-chain of type I collagen. Fourier transform infrared spectra revealed the presence of triple helical structure with partial unfolding of which the OS₂₀₀ showed the greater denaturation extent. The OS₂₀₀ also showed higher emulsion activity but lower oil absorption than those of the OS₅₀. The emulsion-type sausages containing OS powders (0.5% w/w) exhibited significantly lower total fluid, water, and fat releases than those of the sausages without OS. The OS₂₀₀-containing sausages exhibited the lowest expressible water and received the highest hedonic scores in texture and overall acceptance from consumer panel.