High hydrostatic pressure modification of whey protein concentrate for improved functional properties

Whey protein concentrate (WPC) has many applications in the food industry. Previous research demonstrated that treatment of whey proteins with high hydrostatic pressure (HHP) can enhance solubility and foaming properties of whey proteins. The objective of this study was to use HHP to improve functional properties of fresh WPC, compared with functional properties of reconstituted commercial whey protein concentrate 35 (WPC 35) powder. Fluid whey was ultrafiltered to concentrate proteins and reconstituted to equivalent total solids (8.23%) as reconstituted commercial WPC 35 powder. Solutions of WPC were treated with 300 and 400 MPa (0- and 15-min holding time) and 600 MPa (0-min holding time) pressure. After HHP, the solubility of the WPC was determined at both pH 4.6 and 7.0 using UDY and BioRad protein assay methods. Overrun and foam stability were determined after protein dispersions were whipped for 15 min. The protein solubility was greater at pH 7.0 than at pH 4.6, but there were no significant differences at different HHP treatment conditions. The maintenance of protein solubility after HHP indicates that HHP-treated WPC might be appropriate for applications to food systems. Untreated WPC exhibited the smallest overrun percentage, whereas the largest percentage for overrun and foam stability was obtained for WPC treated at 300 MPa for 15 min. Additionally, HHP-WPC treated at 300 MPa for 15 min acquired larger overrun than commercial WPC 35. The HHP treatment of 300 MPa for 0 min did not improve foam stability of WPC. However, WPC treated at 300 or 400 MPa for 15 min and 600 MPa for 0 min exhibited significantly greater foam stability than commercial WPC 35. The HHP treatment was beneficial to enhance overrun and foam stability of WPC, showing promise for ice cream and whipping cream applications.     

Effect of phosvitin on lipid and protein oxidation in ground beef treated with high hydrostatic pressure

In this study, we aimed to examine the effect of phosvitin on lipid and protein oxidation of raw and cooked ground beef treated with high hydrostatic pressure (HHP). Ground beef patty with 0, 500, or 1000 mg phosvitin/kg meat was treated with HHP at 0.1, 300, or 600 MPa. Half of the patties were used in a raw meat analysis, and the other half were used in a cooked meat analysis. Phosvitin and HHP treatment at 300 MPa synergistically reduced microbial growth, and HHP treatment at 600 MPa reduced microbial counts to undetectable levels (< 1 log CFU/g) throughout the length of the study in all samples. Phosvitin delayed lipid and protein oxidation in HHP-treated cooked and raw ground beef, respectively. However, phosvitin had no effect on the color changes of raw ground beef attributable to HHP. The results indicated that phosvitin could enhance the stability of lipids and proteins but not color changes of raw ground beef caused by HHP.     

Effect of lactoferrin and its derivatives against gram-positive bacteria in vitro and, combined with high pressure, in chicken breast fillets

The bactericidal activity of lactoferrin (LF), amidated lactoferrin (AMILF), pepsin digested lactoferrin (PDLF), and its activated (ALF) commercial form, against six strains of three gram-positive bacterial species was investigated. Listeria monocytogenes was most sensitive in vitro, Staphylococcus aureus showed a moderate resistance, and Enterococus faecalis was highly resistant to antimicrobials. When chicken breast fillets were inoculated with L. monocytogenes CECT5725 and treated with antimicrobials, reductions were below 0.5 log CFU/ml in all cases. In combination with high pressure (HHP) treatment at 400 MPa for 10 min, antimicrobials showed a slight additional bactericidal effect, always below 1 log CFU/g. Incorporation of antimicrobials 18 h before or 1 h after HHP treatment generally yielded better results than incorporation 1 h before HHP treatment, although reductions remained below 1.5 log CFU/g in all cases. LF and its derivatives showed a limited potential for pathogen control in meat.     

Partial characterization of protease from a thermophilic fungus, Thermoascus aurantiacus, and its hydrolytic activity on bovine casein

Proteases are one of the most important groups of industrial enzymes, with considerable application in the food industry. The aim of this work was to study a novel protease produced by the thermophilic fungus, Thermoascus aurantiacus, through solid-state fermentation (SSF). The enzyme acted optimally at pH 5.5 and 60 °C; it was stable up to 60 °C for 1 h and in the pH range 3.0–9.5. To elucidate the enzyme’s proteolytic activity, its hydrolytic profile on bovine casein, an important protein in the food industry, was studied by enzymatic hydrolysis on skim milk, analyzed by gel electrophoresis (UREA-PAGE), which clearly showed that the protease does not have the same specificity as bovine chymosin.     

Effects of high hydrostatic pressure on physicochemical and functional properties of walnut (Juglans regia L.) protein isolate

BACKGROUND: Walnut (Juglans regia L.) is a good source of protein that has potential application in new product formation and fortification. The main objectives of this study were to investigate the effects of high hydrostatic pressure (HHP) treatment (300–600 MPa 20 min) on physicochemical and functional properties of walnut protein isolate (WPI) using various analytical techniques at room temperature. RESULTS: The results showed significant modification of solubility, free sulfhydryl content and surface hydrophobicity with increased levels of HHP treatment, indicating partial denaturation and aggregation of proteins. Differential scanning calorimetry and fluorescence spectrum analyses demonstrated that HHP treatment resulted in gradual unfolding of protein structure. Emulsifying activity index was significantly (P < 0.05) increased after HHP treatment at 400 MPa, but significantly decreased (P < 0.05) relative to the untreated WPI with further increase in pressure. HHP treatment at 300–600 MPa significantly decreased emulsion stability index. Additionally, HHP‐treated walnut proteins showed better foaming properties and in vitro digestibility. CONCLUSION: These results suggest that HHP treatment could be applied to modify the properties of walnut proteins by appropriate of pressure levels, which will help in using walnut protein as a potential food ingredient. © 2012 Society of Chemical Industry     

Pressure and temperature combination for inactivation of soymilk trypsin inhibitors

High hydrostatic pressure (HHP) processing, an emerging technology for food preservation, in combination with thermal treatment (250/50, 550/19, 550/65, and 550/80 MPa/°C) was applied to soymilk made from previously soaked soybeans (in distilled water or 0.5% sodium bicarbonate solution). First order kinetics constants ranging from 0.081 to 0.217 min⁻¹, for residual trypsin, were estimated in soymilk from soaked soybeans at selected pressure–temperature combinations. Residual trypsin, at 550 MPa and 80 °C, was high at higher HHP holding times. The highest percentage of residual trypsin (76%) was estimated after a 15 min holding time. The use of sodium bicarbonate for soaking of soybeans synergistically decreased the trypsin inhibitor activity in soymilk in comparison with residual trypsin using distilled water alone.     

Effects of high hydrostatic pressure treatment on allergenicity and structural properties of soybean protein isolate for infant formula

The objective of this study is to investigate the influences of HHP treatment on the allergenic properties of SPI for infant formula. The processing parameters, including HHP pressure and duration time, could significantly influence the allergenicity reducing efficiency. At 300 MPa and 15 min, the allergenicity decreased 48.6%, compared to the native SPI. In the ranges of 200-300 MPa and 5-15 min, the free SH content and hydrophobicity of SPI significantly increased. Meanwhile, at the levels above 300 MPa and 15 min, the two interactions progressively decreased. Whatever HHP pressure and time, the maximum emission wavelength indicated blueshifts. At 300 MPa and 15 min, there was an 11.5-fold increase in fluorescence intensity and the maximum emission wavelength shifted from 516 to 466 nm. After HHP treatment, the helix1 and turns content, significantly increased and the strand1 and unordered content considerably decreased; whereas the amount of the helix2 and strand2 did not indicate any obvious change. The average length of helices significantly increased, while the helices (per 100 residues) did not strikingly change after HHP modification. However, both the strand (per 100 residues) and the average length of strands clearly decreased. Some documents indicate that the epitopes of SPI allergens could be closely related to the secondary structure of α-helix and β-sheet. These interactions and secondary structure results can provide direct evidence, or explanation, for HHP-induced modification of soy proteins, which could alter the allergenicity of SPI and enhance the security of SPI for cow milk allergic babies.     

Effect of high hydrostatic pressure on the structure,physicochemical and functional properties of protein isolates from cumin (Cuminum cyminum) seeds

The effect of high hydrostatic pressure (HHP) treatment on the structure, physicochemical and functional properties of cumin protein isolate (CPI) was investigated. More aggregates, pores, irregular conformations and bigger particle size were observed for HHP-treated CPI. HHP resulted in an increase in α-helix, a decrease in β-strand and fluorescence intensity of CPI. Surface hydrophobicity (H_o) of CPI significantly increased after HHP treatment, from 343.35 for native CPI to 906.22 at 600 MPa (P < 0.05). HHP treatment at 200 MPa reduced zeta-potential and solubility of CPI, while had little effect at 400 and 600 MPa. Emulsifying activity and stability of CPI decreased after HHP treatment, of which droplet size of emulsions significantly increased (P < 0.05). HHP-treated CPI could form heat-induced gelation at lower temperature (68.5 °C) and improved storage modulus (G′) comparing to native one (80.6 °C), suggesting that CPI might be potential protein resources as gelation substitute in food system.     

Effects of high hydrostatic pressure and varying concentrations of sodium nitrite from traditional and vegetable-based sources on the growth of Listeria monocytogenes on ready-to-eat (RTE) sliced ham

The objective of this study was to determine the effect the source of added nitrite and high hydrostatic pressure (HHP) had on the growth of Listeria monocytogenes on ready-to-eat (RTE) sliced ham. Use of 600 MPa HHP for 3 min resulted in an immediate 3.9–4.3 log CFU/g reduction in L. monocytogenes numbers, while use of 400 MPa HHP (3 min) provided less than 1 log CFU/g reduction. With the 600 MPa HHP treatment, sliced ham with a conventional concentration of sodium nitrite (200 ppm) was not different in L. monocytogenes growth from use with 50 or 100 ppm of sodium nitrite in pre-converted celery powder. Instrumental color values as well as residual nitrite and residual nitrate concentrations for cured (sodium nitrite and nitrite from celery powder) and uncured ham formulations are discussed.     

Effect of tannic acid on properties of soybean (Glycine max) seed ferritin: A model for interaction between naturally-occurring components in foodstuffs

There are many components with different properties co-existing in food, so interactions among these components are likely to occur, thereby affecting food quality. However, relatively little information is available on such interactions. In this study, we focus on the interaction between tannic acid (TA) and soybean seed ferritin (SSF), since they co-exist in many foodstuffs, and the consequence of this interaction. As expected, TA interacts with SSF, resulting in changes in the tertiary/quaternary structure of the protein, while having no effect on its primary and secondary structure. On one hand, such interaction leads to protein association, which markedly inhibited ferritin degradation by pepsin at pH 4.0 and trypsin at pH 7.5. On the other hand, iron release was faster with TA than with ascorbic acid, and such release has a negative effect on iron supplementation. These results help to understand the interactions of food components.     

High hydrostatic pressure modification of whey protein concentrate for improved body and texture of lowfat ice cream

Previous research demonstrated that application of high hydrostatic pressure (HHP), particularly at 300 MPa for 15 min, can enhance foaming properties of whey protein concentrate (WPC). The purpose of this research was to determine the practical impact of HHP-treated WPC on the body and texture of lowfat ice cream. Washington State University (WSU)-WPC was produced by ultrafiltration of fresh separated whey received from the WSU creamery. Commercial whey protein concentrate 35 (WPC 35) powder was reconstituted to equivalent total solids as WSU-WPC (8.23%). Three batches of lowfat ice cream mix were produced to contain WSU-WPC without HHP, WSU-WPC with HHP (300 MPa for 15 min), and WPC 35 without HHP. All lowfat ice cream mixes contained 10% WSU-WPC or WPC 35. Overrun and foam stability of ice cream mixes were determined after whipping for 15 min. Ice creams were produced using standard ice cream ingredients and processing. The hardness of ice creams was determined with a TA-XT2 texture analyzer. Sensory evaluation by balanced reference duo-trio test was carried out using 52 vol.nteers. The ice cream mix containing HHP-treated WSU-WPC exhibited the greatest overrun and foam stability, confirming the effect of HHP on foaming properties of whey proteins in a complex system. Ice cream containing HHP-treated WSU-WPC exhibited significantly greater hardness than ice cream produced with untreated WSU-WPC or WPC 35. Panelists were able to distinguish between ice cream containing HHP-treated WSU-WPC and ice cream containing untreated WPC 35. Improvements of overrun and foam stability were observed when HHP-treated whey protein was used at a concentration as low as 10% (wt/wt) in ice cream mix. The impact of HHP on the functional properties of whey proteins was more pronounced than the impact on sensory properties.     

High hydrostatic pressure modification of whey protein concentrate for use in low-fat whipping cream improves foaming properties

Whey is the inevitable by-product of cheese production. Whey can be incorporated into a variety of foods, but little has been done to investigate its suitability in whipping cream. The objective of this work was to evaluate the foaming properties of selected low-fat whipping cream formulations containing whey protein concentrate (WPC) that did or did not undergo high hydrostatic pressure (HHP) treatment. Fresh whey was concentrated by ultrafiltration, pasteurized, and standardized to 8.23% total solids and treated with HHP at 300 MPa for 15 min. Viscosity, overrun, and foam stability were determined to assess foaming properties. Sensory evaluation was conducted with 57 panelists using a duo-trio difference test. The optimal whipping time for the selected formulations was 3 min. Whipping cream containing untreated WPC and HHP-treated WPC resulted in greater overrun and foam stability than the control whipping cream without WPC. Panelists distinguished a difference between whipping cream containing untreated WPC and whipping cream containing HHP-treated WPC. High hydrostatic pressure-treated WPC can improve the foaming properties of low-fat whipping cream, which may justify expansion of the use of whey in whipping cream and application of HHP technology in the dairy industry.     

Effect of high hydrostatic pressure on physicochemical, thermal and morphological properties of mung bean (Vigna radiata L.) starch

Mung bean starch-water suspension was subjected to high pressure treatment at 120, 240, 360, 480 and 600 MPa for 30 min, and changes in the structure, morphology and some physicochemical properties were investigated. Light transmittance, swelling power and solubility decreased after the high hydrostatic pressure treatment. A significant increase in the peak viscosity, trough viscosity, final viscosity, pasting temperature and setback, and decrease in breakdown viscosity with increase in pressure treatment was observed. The differential scanning calorimeter (DSC) analysis showed a decrease in gelatinization temperatures and gelatinization enthalpy upon high pressure treatments. The X-ray analysis showed that high hydrostatic pressure (HHP) treatment converted starch that displayed the C-type X-ray pattern to the B-type-like pattern. The HHP treatments altered the shape of starch granules and changed their surface appearance according to SEM analysis. HHP treatment (600 MPa, 30 min) caused a completely gelatinize of mung bean starch.     

Antioxidant effect of Majorana syriaca extract in bulk corn oil and o/w emulsion after applying high hydrostatic pressure

Bulk oils and oil-in-water emulsions were subjected to high hydrostatic pressure (HHP) (200, 650 MPa) treatment so as to estimate the effect of applied pressures on lipid oxidation. HHP-treated and non-treated samples were left to autoxidise under accelerated conditions (2 weeks, 70 °C) and their oxidative status was periodically estimated by measurement of conjugated dienes and peroxide value. Total changes of thiobarbituric acid-reactive substances were recorded as additional oxidative markers for emulsions. Results showed an increase in oxidation as pressure was increased especially at 650 MPa. Lipid oxidation rates that were more pronounced for HHP-treated samples can be correlated to measured dissolved oxygen that was also higher. HHP did not seem to have an effect on emulsion droplet size. The addition of Majorana syriaca (200 ppm) ethyl acetate extract led to protection against lipid oxidation under HHP and atmospheric conditions, 20.9–38.7% and 28.9–43.2%, respectively. It was observed that the antioxidant effect of M. syriaca extract under HHP was weaker.     

High hydrostatic pressure effects on immunoreactivity and nutritional quality of soybean products

The aim of this research was to evaluate the protein pattern, immunoreactivity and amino acid composition of soybean seeds and commercial tofu after treating by high hydrostatic pressure (HHP) (300 MPa, 15 min, 40 °C), as well as of sprouts obtained from unpressurised and HHP-treated seeds. HHP did not affect the electrophoretic profile of soybean seeds or tofu protein extracts, but lower intensity of some protein bands were observed in HHP-treated products. A significant (P ? 0.05) reduced antigenicity was observed in the sprouts from HHP-treated seeds compared to the sprouts from untreated seeds, while higher antigenicity of the pressurised seeds compared with the untreated ones was found. HHP decreased the total essential amino acid content as well as two nutritional indexes, the Chemical Score (CS) and the Essential Amino Acid Index (EAAI), but only by 18%. The findings suggest that HHP applied to soybean seeds before germination could constitute a valuable technological approach for the industrial production of nutritive hypoallergenic soybean sprouts.     

Tempeh flour from chickpea (Cicer arietinum L.) nutritional and physicochemical properties

The effects of solid state fermentation (SSF) on physicochemical and nutritional properties of chickpea flour were studied. Fermented (tempeh) flour showed higher particle size index, gelatinization temperature, dispersability and resistant starch content, and lower gelatinization enthalpy and water solubility than unfermented flour. SSF increased the content of the essential amino acids (EAA) Ile, total sulphur (Met + Cys), total aromatic (Phe + Tyr), and Thr in 37, 41, 107, and 39 g kg⁻¹ protein, respectively; Trp content decreased 8 g kg⁻¹ protein. Total sulphur (EAA score = 0.87) was limiting in unfermented flour and Trp (0.93) in tempeh flour. SSP improved the in vitro and true protein digestibility (72.2–83.2% and 83.7–88.8%, respectively), protein efficiency ratio (PER, 1.59–2.31), cPER (1.54–2.21), and corrected protein digestibility (0.73–0.89). Chickpea tempeh flour may be considered for the fortification of widely consumed legume-based food products.     

The effect of high hydrostatic pressure,sodium nitrite and salt concentration on the growth of Listeria monocytogenes on RTE ham and turkey

Growth of Listeria monocytogenes was evaluated for up to 182 days after inoculation on ready-to-eat (RTE) sliced ham and turkey breast formulated with sodium nitrite (0 or 200 ppm), sodium chloride (1.8% or 2.4%), and treated (no treatment or 600 MPa) with high hydrostatic pressure (HHP). HHP at 600 MPa for 3 min resulted in a 3.85–4.35 log CFU/g reduction in L. monocytogenes. With formulations at similar proximate analyses, one of the evaluation days (day 21) without HHP showed significantly greater growth of L. monocytogenes in ham than in turkey breast, but there were no significant differences on other evaluation days or with HHP. There were no differences in growth of L. monocytogenes due to sodium chloride level. Sodium nitrite provided a small, but significant inhibition of L. monocytogenes without HHP, but addition of sodium nitrite did not significantly affect growth of L. monocytogenes with use of HHP.     

Antioxidant and antihypertensive properties of liquid and solid state fermented lentils

The effect of liquid (LSF) and solid state fermentation (SSF) of lentils for production of water-soluble fractions with antioxidant and antihypertensive properties was studied. LSF was performed either spontaneously (NF) or by Lactobacillus plantarum (LP) while SSF was performed by Bacillus subtilis (BS). Native lactic flora in NF adapted better than L. plantarum to fermentative broth and BS counts increased 4.0 log CFU/g up to 48 h of SSF. LSF water-soluble fractions had higher (P ? 0.05) free amino groups, GABA content, antioxidant and angiotensin I-converting enzyme inhibitory (ACEI) activities than SSF. In addition, GABA and ACEI activity of LSF increased in a time-dependent manner. Proteolysis by BS was limited, with slight changes in free amino groups, while GABA, total phenolic compounds and antioxidant capacity increased throughout fermentation. Higher antihypertensive potential was observed in NF (96 h) characterised by the highest GABA content (10.42 mg/g extract), ACE-inhibitory potency (expressed as IC₅₀) of 0.18 mg protein/ml and antioxidant capacity of 0.26 mmol Trolox equivalents/g extract. Therefore, water-soluble fermented lentil extracts obtained by LSF are particularly promising as functional ingredients in preventing hypertension.     

Short communication: Low-fat ice cream flavor not modified by high hydrostatic pressure treatment of whey protein concentrate

The purpose of this study was to examine flavor binding of high hydrostatic pressure (HHP)-treated whey protein concentrate (WPC) in a real food system. Fresh Washington State University (WSU, Pullman) WPC, produced by ultrafiltration of separated Cheddar cheese whey, was treated at 300 MPa for 15 min. Commercial WPC 35 powder was reconstituted to equivalent total solids as WSU WPC (8.23%). Six batches of low-fat ice cream were produced: A) HHP-treated WSU WPC without diacetyl; B) and E) WSU WPC with 2 mg/L of diacetyl added before HHP; C) WSU WPC with 2 mg/L of diacetyl added after HHP; D) untreated WSU WPC with 2 mg/L of diacetyl; and F) untreated commercial WPC 35 with 2 mg/L of diacetyl. The solution of WSU WPC or commercial WPC 35 contributed 10% to the mix formulation. Ice creams were produced by using standard ice cream ingredients and processes. Low-fat ice creams containing HHP-treated WSU WPC and untreated WSU WPC were analyzed using headspace-solid phase microextraction-gas chromatography. Sensory evaluation by balanced reference duo-trio test was carried out using 50 untrained panelists in 2 sessions on 2 different days. The headspace-solid phase microextraction-gas chromatography analysis revealed that ice cream containing HHP-treated WSU WPC had almost 3 times the concentration of diacetyl compared with ice cream containing untreated WSU WPC at d 1 of storage. However, diacetyl was not detected in ice creams after 14 d of storage. Eighty percent of panelists were able to distinguish between low-fat ice creams containing untreated WSU WPC with and without diacetyl, confirming panelists’ ability to detect diacetyl. However, panelists were not able to distinguish between low-fat ice creams containing untreated and HHP-treated WSU WPC with diacetyl. These results show that WPC diacetyl-binding properties were not enhanced by 300-MPa HHP treatment for 15 min, indicating that HHP may not be suitable for such applications.     

Fate of Staphylococcus aureus in cheese treated by ultrahigh pressure homogenization and high hydrostatic pressure

We evaluated the influence of ultrahigh pressure homogenization (UHPH) treatment applied to milk containing Staphylococcus aureus CECT 976 before cheese making, and the benefit of applying a further high hydrostatic pressure (HHP) treatment to cheese. The evolution of Staph. aureus counts during 30 d of storage at 8°C and the formation of staphylococcal enterotoxins were also assessed. Milk containing approximately 7.3 log₁₀ cfu/mL of Staph. aureus was pressurized using a 2-valve UHPH machine, applying 330 and 30 MPa at the primary and the secondary homogenizing valves, respectively. Milk inlet temperatures (T_in) of 6 and 20°C were assayed. Milk was used to elaborate soft-curd cheeses (UHPH cheese), some of which were additionally submitted to 10-min HHP treatments of 400 MPa at 20°C (UHPH+HHP cheese). Counts of Staph. aureus were measured on d 1 (24 h after manufacture or immediately after HHP treatment) and after 2, 15, and 30 d of ripening at 8°C. Counts of control cheeses not pressure-treated were approximately 8.5 log₁₀ cfu/g showing no significant decreases during storage. In cheeses made from UHPH treated milk at T_in of 6°C, counts of Staph. aureus were 5.0 ± 0.3 log₁₀ cfu/g at d 1; they decreased significantly to 2.8 ± 0.2 log₁₀ cfu/g on d 15, and were below the detection limit (1 log₁₀ cfu/g) after 30 d of storage. The use of an additional HHP treatment had a synergistic effect, increasing reductions up to 7.0 ± 0.3 log₁₀ cfu/g from d 1. However, for both UHPH and UHPH+HHP cheeses in the 6°C T_in samples, viable Staph. aureus cells were still recovered. For samples of the 20°C T_in group, complete inactivation of Staph. aureus was reached after 15 d of storage for both UHPH and UHPH+HHP cheese. Staphylococcal enterotoxins were found in controls but not in UHPH or UHPH+HHP treated samples. This study shows a new approach for significantly improving cheese safety by means of using UHPH or its combination with HHP.