Maize processing waste water arabinoxylans: Gelling capability and cross-linking content

Water-soluble feruloylated arabinoxylans were extracted from maize processing waste water (nejayote) generated from tortilla-making industries. Nejayote arabinoxylans (NAX) presented a ferulic acid content of 0.23 μg/mg, an arabinose to xylose ratio (A/X) of 0.65, an intrinsic viscosity, [η], of 183 ml/g and a molecular weight (Mw) of 60 kDa. Laccase-induced gels were obtained from 4% (w/v) NAX solution while, at lower concentrations, no gelation was observed. Laccase covalent cross-linking of NAX led to the formation of diferulic (di-FA) and triferulic (tri-FA) acid structures. 4% (w/v) NAX gel presented di-FA and tri-FA contents of 0.02 and 0.01 μg/mg NAX, respectively, and a G′ value of 2 Pa. Recuperation of this gum from a low-value maize by-product could represent a commercial advantage over other gums commonly used in the food industry.     

Sequential preheating and transglutaminase pretreatments improve stability of whey protein isolate at pH 7.0 during thermal sterilization

Whey protein isolate (WPI) is a potential ingredient to manufacture shelf-stable transparent beverages if proteins are heat stable, i.e., without causing turbidity, precipitation and gelation after the required thermal processing to obtain commercial sterility (138 °C for 8 s or longer). However, information is lacking about stability of WPI during heating at 138 °C. Furthermore, novel technology and mechanistic understanding on how to produce clear products after heating systems with >5% WPI, particularly with salt, is needed. In this work, 5% w/v WPI was pretreated by microbial transglutaminase (mTGase) at three levels for 1–15 h at 50 °C, with and without prior preheating at 80 °C for 15 min. Heat stability of the pretreated samples at pH 7.0 and 0, 50, and 100 mM NaCl was evaluated at 138 °C. Samples pretreated by mTGase for a greater extent demonstrated improved heat stability. Samples subjected to sequential preheating and mTGase pretreatments produced clear dispersions even after heating at 138 °C for 30 min in the presence of 0 and 50 mM NaCl at pH 7. All pretreatments increased the magnitude of zeta-potential and resistance against thermal denaturation. The sequentially-pretreated WPI was the most heat-resistant, having decreased hydrodynamic diameter (<36 nm) during extended heating at 138 °C and 50 mM NaCl. The present study demonstrates the feasibility of using sequential preheating and mTGase pretreatments to develop sterilized beverage products with a high content (5% w/v) of whey protein and yet of transparent appearance at ambient temperatures.     

Effects of variation in the palm stearin: Palm olein ratio on the crystallisation of a low-trans shortening

Changes in the rheological properties during crystallisation and in the crystal size and morphology of blends containing rapeseed oil with varying percentages of palm stearin (POs) and palm olein (POf) have been studied. The crystals formed from all three blends were studied by confocal laser scanning microscopy, light microscopy and environmental scanning electron microscopy, which revealed the development of clusters of 3–5 individual elementary “spherulites” in the early stages of crystallisation. The saturated triacylglycerol content of the solid crystals separated at the onset of crystallisation was much greater than that in the total fat. Fat blends with a higher content of palm stearin had a more rapid nucleation rate when observed by light microscopy, and this caused an earlier change in the rheological properties of the fat during crystallisation. Using a low torque amplitude (0.005 Pa, which was within the linear viscoelastic region of all samples studied) and a frequency of 1 Hz, the viscoelastic properties of melted fat during cooling were studied. All samples, prior to crystallisation, showed weak viscoelastic liquid behaviour (G″, loss modulus >G′, storage modulus). After crystallisation, a more “solid like” behaviour was observed (G′ similar to or greater than G″). The blend having the highest concentration of POs was found to have the earliest onset of crystallisation (27% w/w POs; 12 mins, 22% w/w POs; 13.5 mins, 17% w/w POs, 15 mins, respectively). However, there were no significant differences in the time to the point when G′ became greater than G′ among the three blends.     

Gelation properties of salt-extracted pea protein isolate catalyzed by microbial transglutaminase cross-linking

Gelation is a fundamental functional characteristic of plant proteins. In this paper, a salt-extracted pea protein isolate (PPI) was mixed with microbial transglutaminase (MTG) to produce gels and the gelation properties were studied. When the MTG level increased, the magnitude of both the G′ and G″ moduli also increased, which means the gel strength increased. A second order polynomial equation was used to describe the relationships between the G′, G″ modulus and TG level. It was found that with increased heating and cooling rate at the same MTG level, G′ and G″ tended to decrease, resulting in a weaker gel. This was attributed to the rearrangement time of pea protein molecules; slower heating and cooling rates enabled protein molecules to have more time to rearrange and therefore form a stronger gel. At the same MTG level, higher pea protein concentration resulted in higher G′ and G″ values and a power law relationship was found between G′ and pea protein concentration or G″ and pea protein concentration. Frequency sweep data of PPI show that the MTG treatment resulted in higher G′ values and lower tan delta values, indicative of a stronger more elastic gel. The minimum gelation concentration was found to be 3% (w/v) with 10 U MTG treatment, lower than 5.5% required when no MTG was present. When compared to PPI and soy protein isolate (SPI) with and without 10 U MTG treatment, the gel strength of PPI with MTG was stronger than that of SPI with MTG treatment, whereas the opposite was true without the MTG treatment. SDS-PAGE showed that at the same pea protein concentration, higher MTG level induced more cross-linking as fainter bands were seen on the gel and there was a shift in the relative intensities of the bands in the molecular weight range of 35–100 kDa.     

The effect of lactose, NaCl and an aero/anaerobic environment on the tyrosine decarboxylase activity of Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis

The aim of this work was to study, under model conditions, combined effects of the concentration of lactose (0-1% w/v), NaCl (0-2% w/v) and aero/anaerobiosis on the growth and tyramine production in 3 strains of Lactococcus lactis subsp. lactis and 2 strains of L. lactis subsp. cremoris. The levels of the factors tested were chosen with respect to the conditions which can occur during the real process of natural cheese production, including the culture temperature (10 ± 1 °C). In all strains tested, tyrosine decarboxylation was most influenced by NaCl concentration; the highest production of tyramine was obtained within the culture with the highest (2% w/v) salt concentration applied. Two of the strains L. lactis subsp. lactis produced tyramine only in broth with the highest NaCl concentration tested. In the remaining 3 strains of L. lactis, tyramine was detected under all conditions applied. The tested concentration of lactose and aero/anaerobiosis had a less significant effect on tyramine decarboxylation. However, it was also found that at the same concentrations of NaCl and lactose, a higher amount of tyramine was detected under anaerobic conditions. In all strains tested, tyramine decarboxylation started during the active growth phase of the cells.     

Cell wall invertase immobilisation within gelatin gel

Yeast cell wall invertase (CWI) was immobilised within 10% gelatin hydrogel. The result of entrapment was the complete immobilisation of all the added CWI. The activity of immobilised biocatalyst was 93 ± 3 U/g, with activity yield of 30%. The optimum pH was in range of 4.5–5.0 for free and immobilised biocatalyst. The optimum temperature was 60 °C for both free and gelatin immobilised CWI. Immobilised CWI was more stable than free CWI above optimum activity temperatures. The K_m of free and immobilised CWI was 35.10 ± 2.99 mM and 71.45 ± 3.23 mM, respectively. The V_max values were estimated as 8.23 ± 0.24 mM/min and 0.121 ± 0.002 mM/min, respectively. Immobilised CWI was tested in a batch reactor using 50% sucrose (w/v). After 70 consecutive cycles gelatin immobilised CWI retained 75% of its original activity.     

Viscoelastic properties of aqueous and milk systems with carboxymethyl cellulose

Carboxymethyl cellulose (CMC) is widely used as a stabilizer and thickener in the food industry. Previously published work has been carried out in predominantly monophasic systems, i.e. aqueous solutions, but there are few studies of complex systems like dairy desserts where CMC may interact with carbohydrates and milk proteins. Oscillatory rheological methods were used to study the influence of CMC concentration (0.75%, 1.00%, 1.25% and 1.50% w/w) and type of dispersing media (aqueous solution, skimmed milk and whole milk) on the viscoelastic properties of aqueous and milk systems. Both the type of dispersing media and the CMC concentration clearly affected the viscoelastic behaviour of samples, which ranged from fluid-like to weak gel. At the lowest CMC concentration (0.75% w/w), no significant differences in G′, G″ and η* values at 6.28 rad/s were observed between the three systems studied. At the highest CMC concentration (1.5% w/w) G′ and η* values at 6.28 rad/s were significantly higher for whole-milk samples than for skimmed-milk samples, which in turn were higher than for aqueous solutions.     

Radical scavenging capacities and inhibition of human prostate (LNCaP) cell proliferation by Fortunella margarita

Lyophilised nagami kumquat (Fortunella margarita) powder was extracted with five different solvents. Dried extracts of EtOAc and MeOH-water (4:1, v/v) had the highest and lowest total phenolics, respectively, by Folin-Ciocalteu method. LC-MS analysis confirmed the presence of different levels of rutin, narirutin, poncirin, apigenin 8-C-rutinoside and 3′,5′,di-C-β-glucopyranosyl phloretin in all the extracts except n-hexane. EtOAc and MeOH extracts exhibited the highest and the lowest 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, respectively. The order of antioxidant capacity was found to be MeOH-water (4:1, v/v) > EtOAc > MeOH > n-hexane > acetone by phosphomolybdenum complex and oxygen radical absorbance capacity (ORAC) values. Among five extracts, n-hexane extract exhibited the highest inhibition of human prostate cancer (LNCaP) cells (86.4%) after 96 h at 100 μg/mL, followed by EtOAc (82.8%), MeOH (76.7%) and MeOH-water (4:1, v/v) (68.2%). Fragmentation of DNA suggests the ability of extracts to induce apoptosis in LNCaP cells. The cleavage of caspase-3 was the highest in n-hexane and EtOAc extracts, whereas the ratio of Bax/Bcl2 was the highest in MeOH and MeOH-water (4:1, v/v) extracts. The results of the present study were also supported by fluorescent images of LNCaP cells treated with kumquat extracts. The maximum cell proliferation inhibition activity of n-hexane extract may be due to the presence of one or cumulative effect of β-carotene, β-cubebene and hexadecanoic acid. Remaining four extracts exhibited differential antioxidant activity and cytotoxicity which may be due to the presence of various levels of rutin, narirutin, poncirin, apigenin-8-C-rutinoside and 3′,4′-di-C-β-glucopyranosyl phloretin in each extract.     

Enzymatic hydrolysis of protein isolate from hull-less pumpkin oil cake: Application of response surface methodology

Enzymatic hydrolysis of protein isolate from hull-less pumpkin (Cucurbita pepo L.) oil cake was studied by response surface methodology, using a central-composite experimental design. The hydrolysis was carried out with an acid protease, at temperature of 30 °C and pH 3.00. Second-order polynomial model was proposed with regard to of effect of time, enzyme and NaCl concentration. The mathematical model showed good fit with the experimental data, since the R² of 0.946 indicated that 94.6% of the variability within the range of values studied could be explained by the model. A hydrolysis time of 32.5 h, enzyme concentration of 0.137% (v/v) and NaCl concentration of 0.84% (w/v) were found to be the optimal conditions to achieve the highest value of degree of hydrolysis (DH).     

Salinity impact on fruit yield,essential oil composition and antioxidant activities of Coriandrum sativum fruit extracts

This study is designed to examine the fruit essential oil composition, the total phenolic amounts and the antioxidant activities in methanolic extracts of Coriandrum sativum under saline conditions. Increasing NaCl levels to 75 mM reduced significantly the fruit yield by 36%. The essential oil yield was 0.30%, based on the dry weight; it increased by 77% and 84% at 50 and 75 mM NaCl, respectively, in comparison to the control. The major constituents were linalool and camphor, whose amounts increased with increasing NaCl concentrations. Antioxidant activities of the methanol extracts were determined by three different test systems, namely DPPH, β-carotene/linoleic acid and reducing power assays. In these three test systems, the highest activity was exhibited in control plants and was reduced significantly with increasing NaCl levels. In control plants, the total phenolic amount was 1.04 mg GAE/g DW which decreased by 43% and 66% at 50 and 75 mM NaCl, respectively.     

Formation of gal-sorbitol during lactose hydrolysis with β-galactosidase

The objective of the work was to determine the effect of selected parameters: content of dry matter in reaction mixture, temperature, pH and concentration of NaCl on the enzymic synthesis of gal-sorbitol with β-galactosidase from Kluyveromyces lactis. The highest content of gal-sorbitol (16.8% w/w in dry matter) was obtained using 35% (w/v) solution of lactose and sorbitol (1:1). Temperature had a minimal effect on the amount of the sorbitol derivative synthesised. An increase in pH from 6.5 to 9.0 caused approximately a 9% increase in the amount of gal-sorbitol. The presence of 0.25–0.75 M NaCl caused approximately an 11% increase in the amount of the product synthesised. An increase in pH and an addition of NaCl caused an increase in the process duration.     

Antioxidative activity of chitosans with varying molecular weights

Antioxidant activity of chitosans of different molecular weights (30, 90 and 120 kDa chitosan) in salmon (Salmo salar) was investigated. The progress of oxidation was monitored by employing the 2-thiobarbituric acid-reactive substances (TBARS) and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assays. In general, all chitosans exhibited antioxidative activities in salmon. The addition of chitosans to salmon reduced lipid oxidation for seven days of storage. The TBARS values of salmon containing chitosan were significantly lower than those of the control (p < 0.01). At 0.2% (w/v) and 0.5% (w/v) concentrations, the TBARS with chitosan addition was decreased by 75% and 45%, respectively, over 15 days. At 1% concentration, the TBARS value with native chitosan addition was decreased by 32% after 15 days of storage. 90 kDa chitosan showed an increased DPPH free radical-scavenging activity with increasing concentration in the range of 0.2–1% (w/v). The free radical-scavenging activity of the 0.2 mM DPPH solution was saturated by 30 kDa chitosan at a concentration of ?0.7% (w/v), resulting in a strong antioxidant activity of approximately 85%. This was comparable to the DPPH free radical-scavenging activity of BHT.     

Dynamic oscillatory shear properties of O/W model system meat emulsions: Linear viscoelastic analysis for effect of temperature and oil concentration on protein network formation

Effects of oil concentration (57.50%, 58.75%, 60.00% and 61.25%) and temperature (5, 10 and 15 °C) on O/W model system meat emulsions were analyzed using oscillatory dynamic shear tests, allowing all emulsion systems to be characterized as linear viscoelastic solids exhibiting a pseudoplastic flow. The emulsion systems were characterized as weak gel-like macromolecular dispersions with G′ much greater than G″, exhibiting a plateau region. A modified Cox-Merz rule was applicable using shift factors. Frequency dependence of complex modulus (G^∗) was studied to measure strength of cross-linking protein network of the emulsion systems by calculating a practically constant order of the relaxation function (α = 0.10) and a concentration dependent stiffness parameter (A_α) using Friedrich and Heymann theory. It was concluded that the viscoelastic characteristics and strength of the emulsion systems increased with increasing oil level, but decreased with temperature. Different mathematical models were successfully constructed to predict the rheological parameters.     

Physical properties of a composite film containing sunflower seed meal protein and its application in packaging smoked duck meat

Sunflower seed meal protein (SP) films were prepared using various plasticizers, cross-linking agents, Cloisite Na⁺ or red algae, and their physical properties, such as tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) were determined. The TS, E, and WVP of the SP film containing sucrose and fructose (2:1) as a plasticizer and cinnamaldehyde as a cross-linking agent were 3.05 MPa, 34.42%, and 2.25 × 10⁻⁹ g m/m² s Pa, respectively. The incorporation of Cloisite Na⁺ improved the physical properties of the SP film. The TS of the SP/Cloisite Na⁺ composite film containing 3% Cloisite Na⁺ increased by 2.19 MPa, and the WVP of the composite film decreased by 0.52 × 10⁻⁹ g m/m² s Pa compared to the SP film. The incorporation of red algae also improved the TS of the SP film. The TS of the SP composite film containing 1.2% red algae increased by 3.82 MPa compared to the SP film. In addition, an SP/red algae composite film containing grapefruit seed extract (GSE) was prepared and used in food packaging. After 12 days of storage, the population of Listeria monocytogenes inoculated on smoked duck meats packed with the SP/red algae composite film containing 1.2% GSE decreased by 1.31 log CFU/g compared to the control packaging. Therefore, these results suggest that SP composite films can be prepared by the addition of red algae to the SP film–forming solution and that the SP/red algae composite film containing GSE can be used as an antimicrobial food packaging material.     

Rheological and functional properties of gelatin from the skin of Bigeye snapper (Priacanthus hamrur) fish: Influence of gelatin on the gel-forming ability of fish mince

The rheological and functional properties of gelatin from the skin of bigeye snapper (Priacanthus hamrur) fish were assessed. The protein content of dried gelatin was 94.6% and moisture content was 4.2%. The amino acid profile of gelatin revealed high proportion of glycine and imino acids. The bloom strength of solidified gelatin was 108 g. The average molecular weight of fish skin gelatin was 282 kDa as determined by gel filtration technique. The emulsion capacity (EC) of gelatin at a concentration of 0.05% (w/v) was 1.91 ml oil/mg protein and with increase in concentration, the EC values decreased. The gelling and melting temperatures of gelatin were 10 and 16.8 °C, respectively as obtained by small deformation measurements. The flow behavior of gelatin solution as a function of concentration and temperature revealed non-Newtonian behavior with pseudoplastic phenomenon. The Casson and Herschel–Bulkley models were suitable to study the flow behavior. The yield stress was maximum at 10 °C with the concentration of 30 mg/ml. Thermal gelation behavior of threadfin bream (Nemipterus japonicus) mince in presence of different concentration of gelatin was assessed. Gelatin at a concentration of 0.5% yielded higher storage modulus (G′) value than control. Frequency sweep of heat set gel with gelatin revealed strong network formation.     

Rheology and microstructure of myofibrillar protein-plant lipid composite gels: Effect of emulsion droplet size and membrane type

Composite gels were prepared from 2% myofibrillar protein (MP) with 10% imbedded pre-emulsified plant oils (olive and peanut) of various particle sizes at 0.6 M NaCl, pH 6.2. Dynamic rheological testing upon temperature sweeping (20-70 °C at 2 °C/min) showed substantial increases in G′ (elastic modulus) of MP sols/gels with the addition of emulsions, and the G′ increases were inversely related to the emulsion droplet size. Furthermore, gels containing emulsified olive oil had a greater (P < 0.05) hardness than those containing emulsified peanut oil. Regardless of oil types, MP-coated oil droplets exhibited stronger reinforcement of MP gels than Tween 80-stablized oil droplets; the latter composite gels had considerable syneresis. Light microscopy with paraffin sectioning revealed a stable gel structure when filled with protein-coated oil droplets, compared to gels with Tween 80-treated emulsions that showed coalesced oil droplets. These results suggest that rheological characteristics, hardness, texture, and water-holding capacity of MP gels were influenced by type of oils, the nature of the interfacial membrane, and the size of emulsion droplets.     

Microemulsions as nanoreactors to produce whey protein nanoparticles with enhanced heat stability by thermal pretreatment

Native whey proteins (NWPs) may form gels or aggregates after thermal processing. The goal of this work was to improve heat stability of NWPs by incorporating protein solutions in nanoscalar micelles of water/oil microemulsions to form whey protein nanoparticles (WPNs) by thermal pretreatment at 90 °C for 20 min. The produced WPNs smaller than 100 nm corresponded to a transparent dispersion. The WPNs produced at NWP solution pH of 6.8 had a better heat stability than those produced at pH 3.5. The salt concentration (0–400 mM NaCl) in NWP solutions did not significantly change the size of corresponding WPNs. Compared to NWPs, the 5% (w/v) dispersion of WPNs at pH 6.8, 100 mM NaCl did not form a gel after heating at 80 °C for 20 min. The improved heat stability and reduced turbidity of WPNs may enable novel applications of whey proteins in beverages.     

Stabilization of oil-in-water emulsions by enzyme catalyzed oxidative gelation of sugar beet pectin

Enzyme catalyzed oxidative cross-linking of feruloyl groups can promote gelation of sugar beet pectin (SBP). It is uncertain how the enzyme kinetics of this cross-linking reaction are affected in emulsion systems and whether the gelation affects emulsion stability. In this study, SBP (2.5% w/v) was mixed into an oil-in-water emulsion system (4.4% w/w oil, 0.22% w/w whey protein, pH 4.5). Two separate, identically composed, emulsion systems were prepared by different methods of preparation. The emulsions prepared separately and subsequently mixed with SBP (referred as Mix A) produced significantly larger average particle sizes than the emulsions in which the SBP was homogenized into the emulsion system during emulsion preparation (referred as Mix B). Mix B type emulsions were stable. Enzyme catalyzed oxidative gelation of SBP helped stabilize the emulsions in Mix A. The kinetics of the enzyme catalyzed oxidative gelation of SBP was evaluated by small angle oscillatory measurements for horseradish peroxidase (HRP) (EC 1.11.1.7) and laccase (EC 1.10.3.2) catalysis, respectively. HRP catalyzed gelation rates, determined from the slopes of the increase of elastic modulus (G′) with time, were higher (P < 0.05) than the corresponding laccase catalyzed rates, but the final G′ values were higher for laccase catalyzed gels, regardless of the presence of emulsions or type of emulsion preparation (Mix A or Mix B). For both enzymes, rates of gelation in Mix A were higher (P < 0.05) than in Mix B, and higher stress was needed to break the gels in Mix A than in Mix B at similar enzyme dosage levels. These differences may be related to a lower availability of the feruloyl groups for cross-linking when the SBP was homogenized into the emulsion system during preparation.     

Oxidative properties of lactoferrins of different iron-saturation in an emulsion consisting of metmyoglobin and cod liver oil

Lactoferrins (LFs) at iron-saturation 8 (native) and 100%, respectively, were present in an oil-in-water (O/W) emulsion composed of 5% (w/v) cod liver oil (CLO) and metmyoglobin (metMb) in 50 mM phosphate buffer at pH 6.0. Initially both LFs acted as antioxidants and reduced initial peroxide formation, but after 48 h holo LF revealed the most peroxides but the least trienes. Native LF (0.8 mg/ml) gave the highest (p < 0.05) amounts of lipid derived volatiles after 48 h incubation at 4 °C. Both LFs gave similar increases in adducts to metMb with time. The most extensive aggregation induced by radicals or peroxides was found for native LF. The results pointed at reactions at the O/W interphase as highly influential for lipid and protein oxidation kinetics. Added ascorbic acid (1 mM), however, behaved as an antioxidant in the pro-oxidative oil-in-water emulsion system and prevented lipid degradation and protein adductation as well as protein aggregation.     

Yeast leavened banana-bread: Formulation,processing, colour and texture analysis

Banana powder (BP) was added to hard-red spring wheat (HRSW) flour intended for yeast-leavened bread formulation. Five different formulations containing 10%, 15%, 20%, 25%, and 30% BP were prepared with varying amounts of base flour, while vital gluten was maintained at 25% in all blends. Based on the added BP amounts only, the prepared bread could deliver 42.87–128.6 mg potassium/30 g of bread (one regular slice) and 0.33–1.00 g of fibre. Although the dough water absorption was increased, due to BP addition, the dough mixing tolerance (MTI) decreased. The bread loaf volume was significantly higher than the control except for the 30% blend, where the loaf volume was similar to the control. Bread staling increased with BP levels due to the high sugar content but, this effect was limited to the first two days of storage. Blends exhibited darker colour due to the high sugar and protein, while the 25% and 30% blends had the lowest percent of freezable water. The amounts of acetic acid extractable proteins from the dry blends and the dough decreased with increase in BP. The linear rheological properties of the control, 10%, and 30% blends exhibited similar viscoelastic solid behaviour, where both G′ and G′′ had plateaus (G′ > G′′) and they were parallel to each other over three decades of the frequency. Blends showed higher moduli values than the control.