High hydrostatic pressure (HHP) inactivation of foodborne pathogens in low‐acid juices

Consumption of unpasteurised fruit/vegetable juices has increased in recent years due to their freshness, low calorie contribution and good nutritional quality. However, unpasteurised fresh juices with low acidity (pH > 4.6) and high water activity (a_w > 0.85) can support the growth of pathogens. Hence, pasteurisation is a necessary process in the production of low‐acid juices. Consumer demand has required minimally processed high‐quality foods that are free from additives, that are fresh tasting and microbiologically safe, and with an extended shelf life. High hydrostatic pressure (HHP) treatment is considered to be an alternative to thermal pasteurisation for fruit and vegetable juices. HHP treatment could preserve nutritional value and the sensory properties of fruits and vegetables due to its limited effect on the covalent bonds of low‐molecular‐mass compounds such as colour, flavour compounds and vitamins. However, inactivation of important foodborne pathogens in low‐acid foods by HHP is most urgent and critical. More research should be performed in order to satisfy consumer demands for fresh‐tasting products while retaining safety.     

High hydrostatic pressure treatment for manufacturing of garlic powder with improved microbial safety and antioxidant activity

The traditional method of manufacturing garlic powder (GP) that includes simple grinding of air-dried garlic slices has problems of microbial safety and a pungent flavour for this product. Microbiologically safe GP with a less pungent flavour and better antioxidant activities was manufactured using high hydrostatic pressure (HHP), wet grinding and freeze-drying process. The numbers of total aerobic bacteria and yeasts and molds in untreated (without HHP) GP were 3.64 and 2.47 log CFU/g respectively. Garlic powder treated with 600 MPa HHP for 5 min exhibited a total aerobes count of 1.62 CFU/g and a yeasts and molds count of 1.43 log CFU/g. The diallyl disulfide content, which is responsible for the pungent odour of garlic, was also significantly reduced by HHP due to a decrease in the alliinase activity. Hence, a novel process using HHP can help to produce GP with improved microbial safety, flavour and nutrition.     

芹菜、番茄、胡萝卜复合蔬菜汁的研制

研究了芹菜汁、番茄汁、胡萝卜汁的提取方法。通过正交试验确定生产复合蔬菜汁的最佳配方,并较好地解决了蔬菜汁的沉淀及特有风味的保留等问题。     

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.     

Removal of pesticide residue in cherry tomato by hydrostatic pressure

The reduction of Chlorpyrifos (CP) in cherry tomatoes by High hydrostatic pressure (HHP) treatment was demonstrated and compared with other washing methods. CP is commonly used as a broad-spectrum insecticide in pest control, and high residual levels have been detected in vegetables. Samples were treated at several pressures (0.1–400 MPa) and at two temperatures (5 or 25 °C) for 30 min. The optimum HHP conditions for reducing CP were around 75 MPa at 5 °C, and the removal rate was about 75%. This removal rate is slightly higher than other treatments such as soaking in ethanol solution and ultrasonic, accompanied by no visual changes (color, size and shape) in appearance. Also, no toxic intermediates were identified in the extracts of the high-pressure treated cherry tomatoes under these experimental conditions. The present results indicate that HHP can be a useful choice for removing residual pesticides.     

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。      

苹果、胡萝卜、番茄复合果蔬汁的研制

对苹果、番茄、胡萝卜复合果蔬汁生产工艺及其成品稳定性进行了研究。采用单因素试验和正交试验研究出的最佳配方为：苹果汁22%、番茄汁9%、胡萝卜汁17%、蔗糖10%、柠檬酸0.15%;复合稳定剂的最佳组合参数为：海藻酸钠1.2g/L、羧甲基纤维素钠（CMC-Na）0.4g/L、黄原胶0.4g/L。该工艺生产的饮料色泽明亮,口感清爽,富含有机酸、氨基酸、维生素和矿物质,具有苹果、番茄、胡萝卜营养价值与保健功能。     

Antioxidant properties of tomato juice as affected by heating

The changes in the overall antioxidant properties of tomato juice samples and model solutions as a consequence of heat treatments were studied. The antioxidant properties were evaluated both through the measurement of the chain breaking and the oxygen scavenging activities. While a decrease in the antioxidant potential was found for short heat treatments, a recovery of these properties was measured by prolonging heating times. Results suggested that the initial reduction in the overall antioxidant activity can be attributed not only to the thermal degradation of naturally occurring antioxidants but also to the formation of early Maillard reaction products (MRP) with pro‐oxidant properties. The gain in antioxidant activity coincided with the formation of brown MRP. © 1999 Society of Chemical Industry     

超高压加工对鲜榨胡萝卜汁品质的影响

重点研究了热敏性胡萝卜汁经200～600MPa超高压处理10min后其感官品质、理化性质及营养品质的变化情况。实验结果表明:经高压处理后胡萝卜汁色泽、可溶性固形物、总糖、α-和β-胡萝卜素含量与对照样相比差异不明显(P>0.05);总抗氧化能力在400MPa压力处理后降低较显著,600MPa处理有较显著的提高(P<0.05);此外,超高压处理后胡萝卜汁的pH降低,总酸含量增加,且样品的沉降稳定性提高,且变化都比较显著(P<0.05)。综合实验各方面的处理效果,600MPa处理后的胡萝卜汁品质最佳。因此,超高压能较好保持胡萝卜汁原有的品质和营养价值,可达到保持营养、提高品质和延长货架期的目的。     

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.     

Effect of mechanical and thermal treatments on the microstructure and rheological properties of carrot,broccoli and tomato dispersions

BACKGROUND: The food industry has shown an increased interest in the manufacture of healthier and more natural food products. By tailored processing fruit and vegetables can be used as structurants thus reducing artificial gums and stabilisers. The effect of different thermal and mechanical treatments, including high‐pressure homogenisation, on the microstructural and rheological properties of carrot, broccoli and tomato dispersions was studied. As part of the rheological characterisation small oscillatory deformation as well as shear flow measurements were performed. RESULTS: Carrot and broccoli showed a different behaviour from tomato under the conditions studied. Changing the order of thermal and mechanical treatment led to microstructures with different flow properties. The resulting microstructures differed in the manner of cell wall separation: either breaking across the cell walls or through the middle lamella. High‐pressure homogenisation decreased the viscosity of carrot and broccoli dispersions, while it increased the viscosity of tomato. Cryo‐scanning electron microscopy showed that the cell walls of carrot and broccoli remained as compact structures after homogenisation whereas tomato cell walls were considerably swollen. CONCLUSIONS: Based on the type of vegetable, the different processes applied led to microstructures with different rheological properties. This study shows that particle size distribution, morphology and phase volume are important parameters to explain the complex relationship between rheology and microstructure for these types of systems. Copyright © 2010 Society of Chemical Industry     

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.     

高静压对水产品加工及其致敏性影响的研究进展

水产品过敏已成为当今世界性的重大卫生和食品安全问题之一。高静压作为一种新的非热加工技术, 在水产品中具有潜在的应用前景。本文介绍了高静压加工的基本原理、高静压加工在水产品中的应用、水产品过敏的流行性, 重点阐述了水产品过敏原蛋白类型及特性、高静压对过敏原蛋白结构及其致敏性影响的研究概况, 提出了今后高静压水产品加工和过敏原蛋白研究的方向和建议。     

超高压与高温短时杀菌对甘蔗汁品质的影响比较

研究了超高压(HHP,500 MPa/4 min)和高温短时(HTST,95℃/15 s)对甘蔗浊汁和清汁p H、可滴定酸(TA)、可溶性固形物(TSS)、总酚、色泽、褐变度、澄清度、浊度和微生物指标的影响,并分析了4℃,贮藏15 d内甘蔗汁品质的变化。结果表明:HTST和HHP处理对甘蔗汁均具有较好的杀菌效果,HHP和HTST甘蔗清汁p H显著降低,HTST甘蔗清汁可滴定酸(TA)含量升高,HHP和HTST对甘蔗清汁和浊汁的可溶性固形物(TSS)和总酚含量无影响,与HTST相比HHP对甘蔗汁颜色的影响较小,HHP处理后甘蔗清汁澄清度升高,甘蔗浊汁浊度下降,HHP甘蔗汁感官性能优于HTST甘蔗汁。经在4℃贮藏15 d,甘蔗浊汁的菌落总数显著升高,但浊汁和清汁的霉菌和酵母菌数基本保持稳定,贮藏期间甘蔗清汁和HTST甘蔗浊汁p H降低,总酚含量均有明显升高,甘蔗清汁的澄清度和甘蔗浊汁的浊度有所降低,HHP甘蔗清汁的b*值和褐变度增加,HTST甘蔗汁颜色稳定。结论:超高压杀菌有利于保持甘蔗汁品质,是适合甘蔗汁的加工技术。      

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.     

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.     

Differences in properties of myofibrillar proteins from bovine semitendinosus muscle after hydrostatic pressure or heat treatment

Hydrostatic pressure (HP) and heat treatments of myofibrillar proteins have both been shown to induce protein denaturation, but different gel formation properties result from these treatments. To characterise differences in the properties of proteins resulting from HP or heat treatment, Ca‐ and Mg‐ATPase activities (ATP, adenosine triphosphate) and protein solubility in 0.1 and 0.6 mol L^?1 KCl buffers (pH 7) were evaluated in this study. The inactivation rate of Ca‐ATPase of myofibrillar proteins (Mf) induced by HP was slower than that of Mg‐ATPase at each of the tested pressures. However, the inactivation rate of Ca‐ATPase induced by heating was faster than that of Mg‐ATPase at each of the tested temperatures. The level of soluble proteins in Mf suspension induced by HP in 0.1 mol L^?1 KCl buffer increased with increasing pressure up to 400 MPa and then decreased slightly at 500 MPa. However, the level of soluble proteins in Mf suspension induced by heat treatment in 0.1 mol L^?1 KCl buffer increased with increasing temperature up to 55°C. According to the results of sodium dodecyl sulfate polyacrylamide gel electrophoresis, the levels of soluble myosin heavy chain and actin in Mf suspension induced by HP in 0.6 mol L^?1 KCl buffer decreased simultaneously at pressures higher than 300 MPa. The level of soluble MHC in 0.6 mol L^?1 KCl buffer decreased gradually with increasing temperature, but there were no changes in the level of soluble actin in 0.6 mol L^?1 KCl buffer with increasing temperature up to 50°C. These results showed that the mechanism of HP‐induced protein denaturation was different from the mechanism underlying heat‐induced protein denaturation. Copyright © 2006 Society of Chemical Industry     

High pressure carbon dioxide treatment for fresh-cut carrot slices

The effects of high pressure carbon dioxide (HPCD) treatment on natural microorganisms, indigenous enzyme activity, damage to cell membranes and hardness in fresh-cut carrot slices were investigated. 1.86 log₁₀ cycle reduction for aerobic bacteria (AB) and 1.25 for yeasts and molds (Y&M) were achieved at 5 MPa and 20 °C for 20 min. The residual activity (RA) of peroxidase (POD), polyphenol oxidase (PPO), and pectinmethylesterase (PME) exhibited initially increase and secondly decrease with treatment time and their minimum activity was 75.8%, 90.9% and 52.8% at 5 MPa and 20 C for 15 min, respectively. Membrane damage was evaluated by relative electrolyte leakage (REL) and malondialdehyde (MDA) content. HPCD caused a significant increase of REL in carrot slices and the REL of carrot slices treated at 5 MPa and 20 °C for 15 min was 5.7 times as much as that of the untreated, however, HPCD showed no effect on MDA content. The hardness was well retained after HPCD treatment and the largest loss was 7.9% at 5 MPa and 20 °C for 15 min.

Industrial relevance

Fresh-cut carrot slices are one of the most widely used products in prepared salads, and it required strict treatment conditions to protect its quality, especially to prevent microbial spoilage and enzymatic discoloration. HPCD is one promising novel non-thermal technique without compromising the flavor, taste and nutrition aspect of food. This study analyzed the effectiveness of HPCD as a method of preserving fresh-cut carrot slices, including inactivating natural microorganisms and enzymes which are crucial to quality control. Available data provided in this study will benefit the fresh-cut fruits and vegetables industry.