Application of ultrasonic wave celerity measurement for evaluation of physicochemical properties of olive oil at high pressure and various temperatures

High-pressure processing is a powerful technology for food preservation. The knowledge of foods properties in the high-pressure range is important to develop and optimize such processes by means of mathematical modeling and simulation. Ultrasonic methods are rapid, non-invasive and can be used to characterize foods like edible oils (e.g., composition, purity, and quality assessment). In this paper, they were applied for the investigation of physicochemical properties of olive oil at high pressure at different temperatures. The sound wave velocity was measured by the pulse-transmission method and the corresponding oil density was additionally determined from the monitoring of sample volume change. Measurements were conducted in the pressure range up to 600 MPa, for temperatures from 20 to 50 °C. Intermolecular free length, isothermal and adiabatic compressibility versus pressure were calculated using measured sound speed and density isotherms. Discontinuities in the measured isotherms of sound speed and density versus pressure indicate the presence of liquid-to-solid phase transitions. The kinetics of the liquid-to-solid phase transition was also investigated. The transformation times of olive oil augment with increasing temperature. This study can be broadened to other liquid foodstuffs to investigate the influence of temperature on their physicochemical properties at high pressure.     

Enhancement of Functional Properties of Rice Bran Proteins by High Pressure Treatment and Their Correlation with Surface Hydrophobicity

Changes in functional properties of rice bran proteins as influenced by high-pressure (HP) treatment (100–500 MPa, 10 min) were studied. Properties evaluated were protein solubility, water absorption capacity, oil absorption capacity, foaming capacity, foam stability, emulsifying activity, emulsion stability, least gelation concentration, and surface hydrophobicity. HP treatment at 100 and 200 MPa significantly improved the solubility and oil absorption capacity, while water absorption and foaming capacities increased further reaching the maximum at 500 MPa. Compared with the untreated control sample, the emulsifying activity and foam stability of treated samples were significantly higher and least gelation concentration was lower, but none of them showed any specific trend with pressure level. Emulsion stability and surface hydrophobicity increased with the pressure level until 400 MPa and decreased slightly at 500 MPa. Pearson correlation coefficients clearly showed that surface hydrophobicity was positively correlated with water absorption capacity, foaming capacity, emulsifying activity index, and emulsion stability index, but negatively correlated with least gelation concentration. The pressure treated rice bran protein possessed good functional properties for use as a food ingredient in the formulations.     

Effects of High-Pressure Treatments on the Redox State of Porcine Myoglobin and Color Stability of Pork During Cold Storage

This study investigated the effects of high-pressure treatment on the redox states of myoglobin (Mb) species and the associated color stability of porcine during cold storage. Mb was denatured with increasing pressure and temperature. Ferric Mb exhibited more denaturation at the given pressure and temperature conditions as compared to its ferrous analog, part of ferric Mb was reduced back into ferrous form by high-pressure treatment, and the maximum reduction was shown at the pressure level of 150 MPa at 50 °C. Based on the model study, metMb reduction was favorable when the pressure was below 170 MPa, while Mb denaturation was dominant at higher pressures. Pressure treatment of pork resulted in irreversible Mb denaturation, which prevented the restoration of meat color during cold storage, despite the fact that pressure treatment also improved the metMb-reducing activity of pork. Thus, the results of this study demonstrated that pressure-treated pork color was affected by a balance of the redox systems and by the degree of Mb denaturation. In addition, pressurization at around 150–200 MPa was determined to be ideal in terms of improving the color stability of pressurized pork during storage.     

超临界CO2流体萃取锦橙精油研究

以锦橙皮为实验材料,通过混合正交试验,优化了超临界CO2流体萃取锦橙精油的条件,探讨了原料粒度、萃取温度、萃取压力、萃取时间、分离器压力及温度等因素对精油得率的影响。结果表明:采用二级分离方法,得到萜烯烃类精油较多的最优工艺组合是:30目,32℃,16MPa,150min,分离器I温度40℃,分离器I压力8MPa,分离器II温度40℃,精油得率为4.56‰;获得低萜精油的最优工艺组合是:30目,45℃,12MPa,60min,分离器I温度45℃,分离器I压力10MPa,分离器II温度40℃,精油得率为3.78‰。     

Deacidification of Coconut Oil by Membrane Filtration

Ultrafiltration (UF) of coconut oil was carried out using a Millipore membrane cell at different pressures (0.1–0.4 MPa) and with different molecular weight cutoff membranes, that is,YM-1 (1 kDa), YM-3 (3 kDa), YM-10 (10 kDa), YM-30 (30 kDa), and PLTK-30 (30 kDa). Reduction of free fatty acids (FFAs) was 93.6%, 92.7%, 83.5%, 82.6%, and 81.6% with ethanol, methanol, acetone, n-propanol, and isopropyl alcohol, respectively, in three-stage filtration. The effects of temperature and applied pressure on the permeate flux and oil rejection were also studied with membranes using multistage filtration. As pressure increased from 0.1 to 0.4 MPa, the permeate flux and oil rejection increased linearly. A significant reduction of FFA was observed, which is in proportional with the amount of solvent in the feed used. The oil loss was less at lower temperature (25 °C) and pressure (0.2 MPa). Using PLTK 30 membrane with three-stage filtration, reduction of FFA was achieved up to 93% and 94% with methanol and ethanol solvents, respectively.     

Effect of High-Pressure Processing on Physical, Biochemical, and Microbiological Characteristics of Black Tiger Shrimp (Penaeus monodon)

The effect of high-pressure processing on quality and shelf life of black tiger shrimp was studied. Shrimp was high-pressure processed at selected pressure levels of 100, 270, and 435 MPa for 5 min at room temperature (25?±?2 °C). Changes in physical, biochemical, and microbiological characteristics after processing and during subsequent chilled storage were examined for 35 days. After processing significant (P?<?0.05) increase in moisture content and parallel reduction in protein content was observed. No significant changes were observed in TVB-N and TMA-N levels of shrimp after processing; however, these significantly increased with storage. Whiteness index increased with pressure intensity imparting brighter and mildly cooked appearance. Pressure-induced hardening effect was observed, which showed decreasing trend during storage. The treated samples maintained lower viable counts throughout the storage, thus having better microbial quality than untreated sample. Shelf life was extended to 15 days in shrimp treated at 435 MPa compared with 5 days in untreated sample. Pressure treatment of 435 MPa was found to be most effective in preserving the quality and extending the shelf life of black tiger shrimp.     

Effect of pH on Enzyme Inactivation Kinetics in High-Pressure Processed Pineapple (Ananas comosus L.) Puree Using Response Surface Methodology

Effect of pH and high-pressure process treatments viz. pressure, temperature, and dwell time on inactivation of polyphenoloxidase (PPO), peroxidase (POD), bromelain (BRM), and pectinmethylesterase (PME) in pineapple puree was studied. Experiments were conducted according to rotatable central composite design (RCCD) within the range (?α to?+?α) of 100–600 MPa, 20–70 °C, and 0–30 min at three different pH levels (3.0, 3.5, and 4.0) followed by analysis through response surface methodology (RSM). Enzyme inactivation was significantly (p?k in min^?1) revealed that PPO was the most resistive (k ranged between 0.0020 and 0.0379 min^?1) when compared with other three enzymes within the experimental domain. Increased k at lower pH with constant pressure and temperature depicted that pH had negative effect on the inactivation process. The optimized conditions targeting maximum inactivation of PPO, POD and PME with simultaneous retention of BRM in pineapple puree, were 600 MPa/60 °C/9 min, 600 MPa/60 °C/10 min and 600 MPa/60 °C/10 min for the samples of pH 3.0, 3.5, and 4.0, respectively.     

Some interrelated thermophysical properties of liquid water and ice. I. A user-friendly modeling review for food high-pressure processing

A bibliographic search yielded a set of empirical equations that constitute an easy method for the calculation of some thermophysical properties of both liquid water and ice I, properties that are involved in the modeling of thermal processes in the high-pressure domain, as required in the design of new high-pressure food processes. These properties, closely interrelated in their physical derivation and experimental measurement, are specific volume, specific isobaric heat capacity, thermal expansion coefficient, and isothermal compressibility coefficient. Where no single equation was found, an alternative method for calculation is proposed. Keeping in mind the intended applications and considering the availability of both experimental data and empirical equations, the limits for the set of equations where set in -40 to 120 degrees C and 0 to 500 MPa for liquid water and -30 to 0 degrees C and 0 to 210 MPa for ice I. The equations and methods selected for each property are described and their results analyzed. Their good agreement with many existing experimental data is discussed. In addition, the routines implemented for the calculation of these properties after the described equations are made available in the public domain.     

Assessing the Impact of High-Pressure Processing on Selected Physical and Biochemical Attributes of White Cabbage (Brassica oleracea L. var. capitata alba)

The aim of this study was to investigate the effect of combined pressure/temperature treatments (200, 400 and 600 MPa, at 20 and 40 °C) on key physical and chemical characteristics of white cabbage (Brassica oleracea L. var. capitata alba). Thermal treatment (blanching) was also investigated and compared with high-pressure processing (HPP). HPP at 400 MPa and 20–40 °C caused significantly larger colour changes compared to any other pressure or thermal treatment. All pressure treatments induced a softening effect, whereas blanching did not significantly alter texture. Both blanching and pressure treatments resulted in a reduction in the levels of ascorbic acid, effect that was less pronounced for blanching and HPP at 600 MPa and 20–40 °C. HPP at 600 MPa resulted in significantly higher total phenol content, total antioxidant capacity and total isothiocyanate content compared to blanching. In summary, the colour and texture of white cabbage were better preserved by blanching. However, HPP at 600 MPa resulted in significantly higher levels of phytochemical compounds. The results of this study suggest that HPP may represent an attractive technology to process vegetable-based food products that better maintains important aspects related to the content of health-promoting compounds. This may be of particular relevance to the food industry sector involved in the development of convenient novel food products with excellent functional properties.     

超临界CO2流体及夹带剂萃取锦橙精油研究

研究了夹带剂添加到超临界CO2流体萃取锦橙精油的工艺条件。获得萜烯烃类精油的最优工艺组合是:夹带剂为乙醇,添加量为CO2摩尔百分流量的5%,40℃,16MPa,精油得率为59.03‰;获得低萜精油的最优工艺组合是:夹带剂为乙酸乙酯,添加量为CO2摩尔百分流量的7%,45℃,16MPa,精油得率为8.79‰。运用傅立叶变换红外光谱仪对超临界CO2流体萃取锦橙精油和加入夹带剂萃取锦橙精油的红外图谱进行了比较,证明夹带剂在萃取过程中与锦橙精油中的不饱和键发生了反应,提高了超临界CO2流体对锦橙精油的提取率。     

The Inactivation Kinetics of Soluble and Membrane-Bound Polyphenol Oxidase in Pear during Thermal and High-Pressure Processing

Polyphenol oxidase (PPO) from pear was characterized with catechol as substrate. The Michaelis constant of soluble and membrane-bound PPO were 15.6 and 23.8 mM, respectively, and their optimum pH for activity were 6.0 and 6.5, respectively. The inactivation kinetics of soluble and membrane-bound PPO during thermal (45–75 °C) and high-pressure thermal processing (600 MPa, 40–80 °C) were studied. The inactivation kinetics of pear PPO were described by a first-order model at all processing conditions. Compared to soluble PPO, membrane-bound PPO was more sensitive to thermal and high-pressure inactivation. Both soluble and membrane-bound PPO displayed higher sensitivity towards thermal inactivation at pH 3.5 (pH of pear puree made from pears dipped in citric acid prior to blending) compared to pH 4.4 (pH of non-acidified pear puree). High pressure and temperature had synergistic inactivation effects on pear PPO at pH 4.4 while slight antagonistic effects were observed at pH 3.5.     

Optimisation of the supercritical extraction of toxic elements in fish oil

This study aims to optimise the operating conditions for the supercritical fluid extraction (SFE) of toxic elements from fish oil. The SFE operating parameters of pressure, temperature, CO₂ flow rate and extraction time were optimised using a central composite design (CCD) of response surface methodology (RSM). High coefficients of determination (R²) (0.897–0.988) for the predicted response surface models confirmed a satisfactory adjustment of the polynomial regression models with the operation conditions. The results showed that the linear and quadratic terms of pressure and temperature were the most significant (p < 0.05) variables affecting the overall responses. The optimum conditions for the simultaneous elimination of toxic elements comprised a pressure of 61 MPa, a temperature of 39.8ºC, a CO₂ flow rate of 3.7 ml min^?1 and an extraction time of 4 h. These optimised SFE conditions were able to produce fish oil with the contents of lead, cadmium, arsenic and mercury reduced by up to 98.3%, 96.1%, 94.9% and 93.7%, respectively. The fish oil extracted under the optimised SFE operating conditions was of good quality in terms of its fatty acid constituents.     

Thermal and High-Pressure Stability of Pectin-Converting Enzymes in Broccoli and Carrot Purée: Towards the Creation of Specific Endogenous Enzyme Populations Through Processing

The thermal and pressure stability of broccoli and carrot pectin-converting enzymes, in particular pectinmethylesterase (PME), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af), were investigated in vegetable purée matrices. In situ enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25–80 °C at 0.1 MPa and 10 min at 0.1–800 MPa at 20 °C) was evaluated by measuring the residual enzyme activity in crude extracts of treated carrot, broccoli floret, and broccoli stem purée samples. PME was completely inactivated in all vegetable purée matrices after a 5-min treatment at 80 °C. After a treatment at 800 MPa (20 °C, 10 min) only 77–90 % of pressure stable PME was inactivated, depending on the matrix. β-Gal and α-Af enzymes were inactivated in the vegetable purée matrices by thermal treatments respectively at 67.5–72.5 and 80 °C. These enzymes showed some pressure resistance: treatments respectively at 600–700 and 600–750 MPa were necessary for one log-reduction of β-Gal and α-Af activity in the different purées at 20 °C. Under the assumption of a first-order inactivation model, inactivation rate constants and their temperature or pressure dependency were determined for the different enzymes. Based on differences in process stability of the enzymes in the individual purée matrices, the feasibility for the creation of specific endogenous enzyme populations by selective processing was evaluated.     

超临界CO2 萃取佛手挥发油的工艺研究及GC-MS 分析

本实验运用超临界CO2 萃取技术提取佛手挥发油,采用正交试验研究萃取温度、萃取压力、分离温度、分离压力等因素对佛手挥发油萃取率及成分的影响,以提取率为主要标准,确定最佳工艺条件。结果表明：萃取温度60℃,萃取压力40MPa,分离温度35℃,分离压力10MPa 为最佳提取工艺。挥发油产品透明、橙黄、有浓郁的香味。通过GC-MS 分析,鉴定出54 种主要成分。     

Thermal and High-Pressure Stability of Pectinmethylesterase, Polygalacturonase, β-Galactosidase and α-Arabinofuranosidase in a Tomato Matrix: Towards the Creation of Specific Endogenous Enzyme Populations Through Processing

The thermal and pressure stability of tomato pectinmethylesterase (PME), polygalacturonase (PG), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af) were investigated in situ. Enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25–95 °C at 0.1 MPa and 10 min at 0.1–800 MPa at 20 °C) was monitored by measuring the residual activity in crude enzyme extracts of treated tomato purée samples. PME was completely inactivated after a 5-min treatment at 75 °C. Only 30 % of the pressure stable PME was inactivated after a treatment at 800 MPa (20 °C, 10 min). A 5-min treatment at 95 °C and a treatment at 550 MPa (20 °C, 10 min) caused complete PG inactivation. β-Gal and α-Af activities were already reduced significantly by thermal treatments at 42.5–52.5 °C and 45–60 °C, respectively. These enzymes were, however, rather pressure resistant: treatments at respectively 700 and 600 MPa were necessary to reduce the activity below 10 % of the initial value. Assuming that first-order, fractional conversion or biphasic inactivation models could be applied to the respective enzyme inactivation data, inactivation rate constants and their temperature or pressure dependence for the different enzymes were determined. Based on differences in process stability of the enzymes, possibilities for the creation of specific “enzyme populations” in tomato purée by selective enzyme inactivation were identified. For industrially relevant process conditions, the enzyme inactivation data obtained for tomato purée were shown to be transferable to intact tomato tissue.     

Combination of Homogenization, Citrus Extract and Vanillic Acid for the Inhibition of Some Spoiling and Pathogenic Bacteria Representative of Dairy Microflora

This research proposes the optimization of a preserving treatment (homogenization—high-pressure homogenization (HPH)—and some safe antimicrobial compounds) able to inhibit the spoiling and pathogenic microflora of milk. In the first phase, 16 strains, including lactobacilli and bifidobacteria, pseudomonads and enterobacteria, were studied in order to assess their resistance to homogenization (pressure ranging from 50 to 150 MPa for single-step treatments; multi-step treatments were performed at 150 MPa through two or three passes across the homogenizing valve). Lactobacilli and bifidobacteria were the most resistant microorganisms (as a threefold treatment at 150 MPa was required to achieve a cell reduction of 1–2 log cfu/ml), followed by pathogens and then by pseudomonas and enterobacteria. Then, a mixture design was further used to define combinations of homogenization (0–150 MPa pass^?1), vanillic acid (0–0.24 %) and citrus extract (0–300 ppm), to control the growth of a mixture of pseudomonas, enterobacteria and lactic acid bacteria; results were used to build two successive models: a primary model for the estimation of the physiological parameters of the microorganisms, whose fitting parameters were used to build a secondary model (polynomial equation) to predict the effectiveness of the combinations of HPH, citrus extract and vanillic acid. Statistical analysis highlighted that a prolongation of shelf life by 4 days (evaluated by pseudomonas cell counts) could be achieved combining homogenization at 75 MPa with either 0.12 % of vanillic acid or 150 ppm of citrus extract.     

Mass Transfer Kinetic and Quality Changes During High-Pressure Impregnation (HPI) of Jumbo Squid (<Emphasis Type="Italic">Dosidicus gigas</Emphasis>) Slices

Jumbo squid is an important marine resource commercialized in Chile as well as American countries such as Perú, México, and USA. In order to find the best conditions for prevention of squid meat degradation, this study presented the simultaneous application of high hydrostatic pressure and osmotic dehydration (high-pressure impregnation (HPI)) on jumbo squid (Dosidicus gigas) slices. Diffusion coefficients for both components water and solids are improved by the high-pressure processing. The pressures used were 100, 250, and 400 MPa for a 15 g/100 mL salt concentration for time intervals of 30 s. The mathematical expressions used for mass transfer simulations of both water and salt were those corresponding to Newton, Henderson and Pabis, Page, and Weibull models, where the Weibull model presented the best fitted to the experimental data for both components. As to quality parameters studied for texture profile analysis, the treatment at 250 MPa yielded on the samples a minimum hardness, whereas springiness, cohesiveness, and chewiness at 100-, 250-, and 400-MPa treatments presented statistical differences regarding unpressurized samples. The color parameters L^* (lightness) increased; however, b^* (yellowish) and a^* (reddish) parameters decreased when increasing pressure level. This way, samples presented a brighter aspect and a mildly cooked appearance. The results presented in this study could support the potential of high hydrostatic pressure application as a technique novel for other compound impregnation under high pressure.     

Determination of thermophysical properties of foods under high hydrostatic pressure in combined experimental and theoretical approach

In the present contribution high pressure phase change of food in a 3.4 ml high pressure chamber is investigated by means of numerical simulation and experimental techniques. The researches of freezing and thawing in samples of potato, pork and cod at atmospheric pressure and two high pressure levels up to 200 MPa are carried out. In order to enable numerical simulations at high pressures the comparison with experimental results and determination of thermophysical properties of food were necessary. The numerical model is based on the enthalpy method. Additionally, a dimensional analysis of phase transition is carried out. The results indicate a strong influence of high pressure on the kinetics of phase transition. Thermophysical properties of food at high pressure are determined and discussed.Industrial relevanceKnowledge about thermophysical properties and kinetics of freezing and thawing of food is of major importance for proper planning of industrial food processing and developing new technological processes. The proposed dimensional analysis enable the scale-up and transfer of explored in laboratories processes into the industrial scale.     

Reduction in cholesterol and fractionation of butter oil using supercritical CO2 with adsorption on alumina

Cholesterol reduction together with the fractionation of triglycerides in butter oil was obtained using a combined supercritical CO₂ extraction/alumina adsorption process in a high-pressure apparatus that allows the independent control of temperature and pressure. Cholesterol levels in butter oil fractions extracted at 40 °C and 27.6 MPa were reduced from 2.5 to 0.1 mg g⁻¹ of oil. Butter oil was also fractionated into low-, intermediate- or high-molecular-weight triglycerides. This single-stage combined process is a clear indication of the important technological possibilities with a more efficient multistage fractionation followed by the subsequent blending and formation of desired milk fat products. A comparison of solubility data of pure cholesterol in CO₂ with those for cholesterol contained in butter oil revealed the co-solvency effects of triglycerides on the solvation of cholesterol.     

High-Pressure Processing of Manuka Honey: Improvement of Antioxidant Activity,Preservation of Colour and Flow Behaviour

Manuka honey in New Zealand is known for its superior antimicrobial and antioxidant properties. However, these valuable properties are known to be compromised when raw honey goes through conventional thermal processing, thus reducing its final quality. As such, this present work is undertaken to assess the effect of high-pressure processing on quality of honey, namely, the antioxidant activity, colour and viscosity. The honey was subjected to different pressures (200–600 MPa) at ambient temperatures (25 to 33 °C) and combined with moderate temperatures (53 to 74 °C) for holding times (10 to 30 min). Thermal processing (49 to 70 °C) was also carried out for comparison purpose. In the absence of heat, the antioxidant activity of high-pressure processing (HPP)-treated samples (600 MPa, 10 min) was found to increase by about 30 % with no colour changes detected. The shear-thinning behaviour of the honey was also retained after HPP at ambient temperature, whereas for combined HPP–thermal treatment, no added benefit in antioxidant activity was observed particularly at higher temperature. Colour was significantly degraded when processed for ≥15 min at 70 °C and the flow behaviour was brought about from shear thinning to Newtonian. Thus, it can be concluded that the quality of honey can be enhanced by using high-pressure processing at ambient temperature.