Inactivation of peroxidase and lipoxygenase in carrots, green beans, and green peas by combination of high hydrostatic pressure and mild heat treatment

The efficiency of high hydrostatic pressure (HHP) with the combination of mild heat treatment on peroxidase (POD) and lipoxygenase (LOX) inactivation in carrots, green beans, and green peas was investigated. In the first part of the study, the samples were pressurized under 250–450 MPa at 20–50 °C for 15–60 min. In the second part, two steps treatments were performed as water blanching at 40–70 °C for 15 and 30 min after pressurization at 250 MPa and 20 °C for 15–60 min. Carrot POD was decreased to 16% residual activity within the first 30 min at a treatment condition of 350 MPa and 20 °C and then it decreased to 9% at 60 min. When the carrots were water blanched at 50 °C for 30 min after HHP treatment of 250 MPa at 20 °C for 15 min, 13% residual POD activity was obtained. For green beans, the most effective results were obtained by two steps treatment and approximately 25% residual POD activity was obtained by water blanching at 50 °C for 15 min after pressurization at 250 MPa and 20 °C for 60 min. An effective inactivation of POD in green peas was not obtained. For carrots, LOX activity could not be measured due to very low LOX activity or the presence of strong antioxidants such as carotenoids. After pressurization at 250 MPa and 20 °C for 15 or 30 min, water blanching at 60 °C for 30 min provided 2–3% residual LOX activity in green beans. The treatment of 250 MPa for 30 min and then water blanching at 50 °C for 30 min provided 70% LOX inactivation in green peas.     

Effect of high hydrostatic pressure and temperature on carrot peroxidase inactivation

The combined effects of pressure and temperature on the activity of carrot peroxidase (POD) were investigated in the pressure range 0.1–600 MPa and the temperature range 25–45 °C. At lower pressures (<396 MPa), carrot POD stability increased compared to unpressurized samples. Inactivation of 91% was obtained at 600 MPa and 45 °C. High hydrostatic pressure (HHP) combined with temperature treatment enhanced the inactivation of carrot POD. Regeneration of POD activity with the combined HHP and temperature treatments followed first order kinetics at 25, 35 and 40 °C. Regeneration was not observed at 506 MPa and 45 °C. HHP had no significant effect on the loss of vitamin C or on protein content. HHP combined with mild heat treatment was found to be better than the thermal treatment at high temperatures for inactivation of POD in carrot processing.     

Synergistic impact of sonication and high hydrostatic pressure on microbial and enzymatic inactivation of apple juice

The combination of innovative, non-thermal technologies for the production of safe and quality fruit juices is a recent trend in food processing. The purpose of this study was to evaluate the effects of combined treatment of ultrasound (US) and high hydrostatic pressure (HHP) on enzymes (polyphenolase, peroxidase and pectinmethylesterase), microorganisms (total plate counts, yeasts and molds) and phenolic compounds (total phenols, flavonoids and flavonols) of apple juice. Moreover, its effects on ascorbic acid, antioxidant capacity and DPPH free radical scavenging activity, color values, pH, soluble solids and titratable acidity were investigated. Fresh apple juice was treated with US (25 kHz and 70% amplitude) at 20 °C for 60 min with subsequent HHP treatment at 250, 350 and 450 MPa for 10 min at room temperature. The results revealed that the combined US-HHP450 treatment caused highest inactivation of enzymes with complete inactivation of total plate counts, yeasts and molds. It also significantly improved the phenolic compounds, ascorbic acid, antioxidant capacity, DPPH free radical scavenging activity and color values. The present results suggest that the combination of US and HHP can act as a potential hurdle to produce safe and high quality apple juice with reduced enzymes and microbial activity and improved nutrition.     

干制状态气体对胡萝卜干燥过程特性及制品品质的影响

分别以空气及氮气、二氧化碳气体置换部分空气等3种状态的气体作为干燥介质，采用QTM干制实验设备对胡萝卜粒进行对比干燥试验，探讨干制状态气体对胡萝卜粒的干燥过程特性及制品品质的影响。结果表明，干制状态气体与胡萝卜粒的干燥过程特性及制品的品质关系密切。降低干燥室内气氛了体的氧气含量，可维持较佳的糖酸比及显著提高Vc保存率，制品的质量较好；在气体的氧气含量相同状态下，充人氮气置换部分空气的制品质量最好，且具有较高的干燥速度和复水比。     

Effect of high hydrostatic pressure pretreatment on drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera (Aloe barbadensis Miller) gel

The effect of High Hydrostatic Pressure (HHP) and other pretreatments on the drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera gel was investigated during convective drying at 70 °C. The pretreatments analyzed were high hydrostatic pressure, blanching, enzymatic and microwaves. Simulation of drying curves was studied through the application of several mathematical models such as Newton, Henderson and Pabis, Page, Modified Page, Wang and Singh, and Weibull. Among them, the Weibull model provided the best fit for the experimental data. All pretreatments increased the water diffusion coefficient compared to the control sample. Microwaves followed by HHP presented the fastest drying rates. All pretreatments modified the microstructure and hence the texture of the product. HHP and microwaves increased firmness while blanching and enzymatic treatments produced a softer final product. Blanching, microwaves and HHP enhanced A. vera antioxidant activity. However, the HHP pretreated samples showed the highest antioxidant activity compared to the rest. Based on these results, HHP together with convective drying offers the chance of producing dried aloe with high antioxidant attributes.     

A comparative study of changes in the microbiota of apple juice treated by high hydrostatic pressure (HHP) or high pressure homogenisation (HPH)

The objective of this study was to assess the effect of High Pressure Homogenisation (HPH) compared with High Hydrostatic Pressure (HHP) on the microbiological quality of raw apple juice during storage at ideal (4 °C) and abuse (12 °C) temperatures. In the case of HPH, only low numbers of micro-organisms were detected after treatment at 300 MPa (typically between 2 and 3 log.ml⁻¹). These were identified as Streptomyces spp., and numbers did not increase during storage of the juice for 35 days, irrespective of storage temperature. In the case of HHP, the total aerobic counts were also reduced significantly (p < 0.05) after treatment for 1 min at 500 and 600 MPa and the numbers did not increase significantly during storage at 4 °C. However, during storage at 12 °C the counts did increase significantly (p < 0.05) and by day 14 counts at 500 MPa were not significantly different from the control juice. This confirms that good temperature control is important if the full benefits of HHP treatment are to be realised.Frateuria aurantia dominated the microbiota of the HHP apple juice stored at 12 °C along with low levels of Bacillus and Streptomyces spp.The HPH and HHP juices both turned brown during storage indicating that neither treatment was sufficient to inactivate polyphenol oxidase. The enzyme is known to be pressure resistant and this discolouration was controlled by a heat treatment (70 °C for 1 min) used in commercial practice and given prior to HP treatment.     

高静压技术在谷物和豆类加工中的应用

高静压技术是基于帕斯卡流体力学理论基础上发展的一种新型的非热加工技术,近年来在材料、冶金、果蔬和肉制品加工等领域的应用日益广泛。高静压技术在谷物和豆类加工中的作用主要体现在微生物灭活、大分子物质改性、产品质量改善、产品功能提升等几个方面。综述了高静压技术对谷物和豆类的蛋白质、淀粉、酶及其他有机组分的影响及其应用研究进展,并展望了高静压技术在谷物和豆类等粮食加工领域中的应用前景。     

Influence of sonication and high hydrostatic pressure on the quality of carrot juice

The combined effects of ultrasound (US) and high hydrostatic pressure (HHP) on enzymes, micro‐organisms, colouring pigments, total polyphenols, ascorbic acid and physicochemical properties of carrot juice were investigated. Carrot juice was treated with sonication (20 kHz, 70% amplitude) and HHP (250, 350, 450 MPa) at room temperature for 10 min. For comparison, fresh carrots were water blanched (WB) at 100 °C for 4 min and carrot juice was then extracted. As results, highest improvements in colouring pigments were observed in WB and US‐HHP450 treatments, which also completely inactivated micro‐organisms. The highest reduction in enzymes was observed in WB treatment followed by US‐HHP450. Total polyphenol contents increased significantly in US, HHP and US‐HHP treatments with the highest increase in US‐HHP450, but it decreased significantly in WB treatment. Ascorbic acid contents significantly decreased in WB and HHP450, while increased in US and US‐HHP treatments. Results indicate that US‐HHP450 treatment improves the quality of carrot juice and serves as a good alternative for blanching treatment.     

Effects of high hydrostatic pressure (HHP) on bioaccessibility,as well as antioxidant activity,mineral and starch contents in Granny Smith apple

The aim of this work was to study the effect of high hydrostatic pressure on the bioaccessibility of specific nutrients (antioxidant, minerals and starch) in apple and to establish processing conditions that maximise the health benefits. The apple was pressurised at 500 MPa during 2, 4, 8 and 10 min. The antioxidant activity, mineral and starch content and bioaccessibility of apple samples were significantly affected by the processing and digestion conditions. Therefore, these results indicated that in vitro digestion has a noticeable effect on the antioxidant concentration, IC₅₀, with much lower values (a smaller IC₅₀ value corresponds to a higher antioxidant activity) of apple samples compared with those untreated and non-digestion. Apple has the highest calcium content (30.33 ± 1.94 mg/100 g), iron (14.46 ± 3.49 mg/100 g) and zinc (6.22 ± 0.91 mg/100 g). High hydrostatic pressure increased the mineral contents availability by 2.11–303.00% for calcium, 4.63–10.93% for iron and 8.68–28.93% for zinc. The dialysability and solubility of calcium, iron and zinc with respect to the values for the untreated sample were reduced by this high pressure technique. Consumption of apple under high hydrostatic pressure may supply substantial antioxidants, mineral and starch, which may provide health promoting and disease preventing effects.     

高压对从苹果渣中提取酚类物质的影响

考察高压对乙醇溶液提取苹果渣中酚类物质的影响。结果表明：乙醇浓度70％（V：V）比较适宜。随着处理压力的增大，酚类物质的得率逐渐升高（400MPa除外），且在500MPa以前得率提高的幅度较大，压力达到600MPa以上后得率增幅不大。随着提取时间的延长，酚类得率先升后降，提取时间以10min为宜。酚类物质的得率先随温度升高而增大，到50℃达到最高，随后又下降。高压对乙醇溶液提取苹果渣中酚类物质有显著的促进作用。     

Effect of high pressure/high temperature processing on cell wall pectic substances in relation to firmness of carrot tissue

Thermal processing for food preservation results in undesired softening of fruits and vegetables. To explore the potential of high pressure sterilization in food processing, the effects of combined high pressure/high temperature (HP/HT) treatments on carrot pectic polysaccharides and the related textural properties were investigated and compared with that of samples thermally processed at atmospheric pressure. Disks of fresh carrot (Daucus carota var. Yukon) tissue were subjected to three different treatments (80 °C–0.1 MPa, 100 °C–0.1 MPa and 80 °C–600 MPa) for varying time intervals. Subsequently, the residual texture and microstructural changes of the carrots were evaluated. Alcohol-insoluble residues were prepared from the samples and sequentially fractionated with water, cyclohexane-trans-1,2-diamine tetra-acetic acid (CDTA) and Na₂CO₃ solutions. Thermal treatments at 0.1 MPa caused extensive tissue softening. This was marked by increased cell separation, an increase in water soluble pectin (WSP) paralleled by a decrease in chelator (CSP) and sodium carbonate (NSP) soluble pectin. HP/HT treated carrots showed minimal softening and negligible changes in intercellular adhesion. This was accompanied by a significant reduction in the degree of methyl esterification of pectin, low WSP in contrast to the high CSP and NSP fractions, minor changes in the different pectin fractions during treatment, and a substantial amount of pectin in the fractionation residue. There was a clear difference between HP/HT and thermally processed carrot pectin; HP/HT showing pronounced texture preservation.     

Effects of microwave and infrared drying on the quality of carrot and garlic

The effects of microwave and infrared drying on the quality of carrot and garlic were studied and compared with the effects of conventional hot air (tray drier for carrot and fluid bed drier for garlic) drying. The quality of carrot and garlic were evaluated by instrumental and sensory analysis. Rehydration, moisture content, water activity, particle density, bulk density, porosity and colour values were obtained for microwave, infrared and hot-air dried vegetables. In addition, total moisture content versus time was represented by drying rate curves of carrot and garlic samples. Finally, free moisture content versus drying rate were compared for the three different drying methods.     

Shrinkage, vitamin C degradation and aroma losses during infra-red drying of apple slices

The goal of this study was to determine the effect of drying temperature on the shrinkage, ascorbic acid (vitamin C) degradation and aroma retention of apples. Apple samples were found to shrink continuously until a water content value of 2 kg/kg d.b. The degradation of ascorbic acid followed a pseudo-first-order reaction and the degradation rate constant increased when temperature increased from 40 to 70 °C. The loss of aroma volatiles increased with temperature and drying time.     

超高压处理对胡萝卜果肉饮料中果粒品质的影响

含有果粒的果肉饮料,其品质受果肉影响很大。本文利用超高压技术,处理三种不同果肉型(苹果、荸荠、梨)的胡萝卜汁,分析不同压力(300、400、500 MPa)对多酚氧化酶和过氧化物酶的活性、总酚含量、体外总抗氧化值以及对果肉褐变的影响。并研究了400 MPa压力对于含不同颗粒大小(6、8、10 mm)胡萝卜汁上述指标的影响。结果表明,不同压力处理对苹果和荸荠多酚氧化酶的酶活变化不显著,而梨的酶活与压力呈正相关;苹果和梨过氧化物酶的酶活受压力抑制;果肉总酚含量经超高压处理均有不同程度的下降;体外总抗氧化值随着压力上升普遍呈下降趋势,其中梨果肉抗逆环境的能力较好;超高压处理对于果肉褐变有显著效果。400 MPa下不同颗粒大小果肉对PPO酶活影响与水果种类有关。      

Preservation of Manzanilla Aloreña cracked green table olives by high hydrostatic pressure treatments singly or in combination with natural antimicrobials

High hydrostatic pressure (HHP) treatments (singly or in combination with natural antimicrobials) were tested for stabilization of Manzanilla Aloreña seasoned olives stored at 25 °C. HHP (5 min) was highly effective on yeast populations at 300 MPa or higher. No viable yeasts were detected in samples treated at 400 MPa for up to three months. Low levels of endospore-forming bacteria were always detected after HHP treatments. Addition of nisin to the brines reduced bacterial counts by 1.4 log cycles but it had no effect on yeasts when tested singly or in combination with HHP treatment (400 MPa, 5 min). Thyme oil had almost no effect on yeast concentrations, but rosemary oil reduced yeast viable counts progressively during storage. Essential oils in combination with HHP (400 MPa, 5 min) significantly (p < 0.05) reduced the concentrations of aerobic mesophilic bacteria. Low-salt brined olives purged with N₂ or supplemented with ascorbic acid and then pressurized for 5 min at 450 or 550 MPa were preserved for up to 5 months without spoilage, suggesting that the NaCl content in brines of packed Manzanilla Aloreña table olives could be reduced considerably by application of HHP as a stabilization treatment.     

Effects of high hydrostatic pressure on the RS content of amaranth,quinoa and wheat starch

RS exerts a range of beneficial effects on human health. Therefore, ways to increase the RS content in processed food products are looked for. The effects of high hydrostatic pressure treatments on the RS content of wheat, quinoa and amaranth starch were analysed in this study. A 2³ factorial screening design of experiments was used. Experimental factors were pressure (100–600 MPa), temperature (40–60°C) and time (10–30 min). RS in wheat starch increased with increasing pressure by a factor of up to 10 to a value of 4%. In detail, RS content increased significantly at pressures higher than 100 MPa in wheat starch, whereas in quinoa starch significant changes occurred at pressures above 350 MPa (up to 3.3% RS compared to 0.2% in native quinoa starch). Contrary, in amaranth starch the RS content of all pressure treated samples (about 0.5%) was lower than that of the native starch (1.3%). Wheat starch granules swelled to a maximum of 3.67 times their original size and quinoa starch up to 3.36 times. The extent of swelling (2.90) was lowest in amaranth starch.     

The application of high hydrostatic pressure for the stabilization of functional foods: Pomegranate juice

The paper aims at investigating the potential application of non-thermal innovative technologies, such as high hydrostatic pressure, for the sanitization of functional liquid foodstuffs. A 100% pomegranate juice was selected for the experiments, due to its high bioactive compounds content. The operating pressure, temperature and holding times at the pressure set point were changed over a wide range, with the aim of optimizing the processing condition in order to assure the microbiological stability of the processed juice as well as preserve the natural content of the functional compounds. The experiments clearly demonstrate that the high pressure treatment at room temperature improves the quality of pomegranate juice, increasing the intensity of red color of the fresh juice and preserving the content of natural anthocyanins. The residual activity of some enzymes at the end of high pressure processing, independently on the processing conditions, such as the polyphenoloxidase (PPO), causes the degradation of the nutraceutical compounds as observed in particular processing conditions, thus suggesting that the optimal combination of the processing parameters should take into account the degradation of the anthocyanins as well as the enzymatic activity.     

The effect of high hydrostatic pressure on the microbiological quality and safety of carrot juice during refrigerated storage

The microbial quality of untreated and pressure-treated carrot juice was compared during storage at 4, 8 and 12 °C. High pressure treatment at 500 MPa and 600 MPa (1 min/20 °C) reduced the total counts by approximately 4 log CFU ml⁻¹ and there was very little growth of the survivors during storage at 4 °C for up to 22 days. Total counts increased during storage of pressure-treated juice at 8 °C and 12 °C but took significantly longer to reach maximum levels compared to the untreated juice. The microflora in the untreated juice consisted predominantly of Gram-negative bacteria, identified as mostly Pantoea spp., Erwinia spp. and Pseudomonas spp. Initially the pressure-treated juice contained low numbers of spore-forming bacteria (Bacillus spp. and Paenibacillus spp.) and Gram-positive cocci; the spore-formers continued to dominate during storage.     

Gelatinization of waxy starches under high pressure as influenced by pH and osmolarity: Gelatinization kinetics, final structure and pasting properties

We investigated the influence of pH and osmolarity on the high-pressure-induced gelatinization of waxy corn and waxy rice starches in salt solutions, and the properties of the resulting gels. Gelatinization kinetics, the gel swelling power of starches, their structure and their rheological properties were studied for starch suspensions treated at 500 MPa. Gelatinization took place mostly in the first 15 min of the pressure treatment and both the gelatinization speed and the maximal level of gelatinized starch decreased with increasing osmolarity. pH had a minor influence on gelatinization kinetics differing from one starch to another. The resulting gels appeared as a mix of a gel and starch granules with a higher proportion of native granules with increasing osmolarity. Gel strength and swelling were positively correlated to their proportion of gelatinized starch. Thus, gels with different structures and gelatinization levels can be obtained under pressure depending on pH and osmolarity.     

The effect of high pressure treatment and cryotexturization on odorant mixture binding by corn,sorghum and amaranth starch

The binding extent of odorant mixtures from aqueous suspensions by native, high pressure-treated starches and starch cryotexturizates was studied using capillary gas chromatography. The materials were corn, sorghum and amaranth starches. The native and high pressure-treated (650 MPa/9 min) starches were mixed with odorants and incubated (24 h) at room temperature. To obtain the cryotexturizate-odorant product, starch gels were frozen with odorants (−24 °C), stored (48 h) and thawed. Terpene hydrocarbons were strongly bound from the mixture by all the starches analyzed. The nonpolar molecules of terpene hydrocarbons modified the nature of hydrophobic binding sites in starch which in turn affected binding affinity of alcohols, ketones and phenols to the preparations. The competition effect between odorants for the binding sites was found. The varied ability of starch preparations to bind odorants was also related to the granule morphology and alteration in their structure upon treatment used.