深海粗鱼油的精炼工艺研究

对深海杂鱼粗鱼油精炼工艺进行优化,考察了磷酸体积分数、超量碱和活性白土添加量对鱼油酸值、回收率和感官品质的影响,并对精炼鱼油的理化指标及脂肪酸组成进行分析。结果表明:适宜的精炼条件为采用占鱼油质量1%、体积分数80%的磷酸脱胶,脱胶油中加入占鱼油质量1.5%的超量碱和理论碱量的Na OH(4 mol/L)脱酸,脱色选用添加占鱼油质量20%的活性白土;精炼鱼油的理化指标均达到我国水产行业精制鱼油的一级标准(SC/T 3502—2000),酸值(KOH)由(5.52±0.12)mg/g下降到(0.29±0.11)mg/g;精炼工艺对鱼油脂肪酸组成的影响较小,其中二十碳五烯酸和二十二碳六烯酸的总量约占总脂肪酸含量的38%,且分别占多不饱和脂肪酸含量的35.99%和51.59%,品质较优。     

Enzymatic hydrolysis of fish gelatin under high pressure treatment

The effect of high pressure treatment on the hydrolysis of fish skin gelatin and the antioxidant properties of the hydrolysates was evaluated. Hydrolysis was performed by Alcalase, collagenase, trypsin and pepsin both at atmospheric pressure and under high pressure (100 MPa/15 and 30 min, 200 MPa/15 and 30 min, 300 MPa/15 min). The degree of hydrolysis (DH) was determined according to the base consumption via pH‐stat as well as the percentage of soluble nitrogen in trichloroacetic acid (TCA). About 16% of nitrogen in the gelatin was still soluble in 10% TCA, indicative of a significant amount of low molecular weight components. The high pressure treatment increased the DH with all the enzymes used between 5% and 10%. However, in comparison with the hydrolysates obtained at atmospheric pressure after 3 h of digestion under controlled conditions (using a pH‐stat), the radical scavenging capacity of the pressured hydrolysates was only significantly enhanced when Alcalase or collagenase were used. High pressure may be a useful tool for the quick obtaining of gelatin hydrolysates with antioxidant capacity.     

Effect of high pressure thermal sterilization on the formation of food processing contaminants

The use of high pressure thermal sterilization (HPTS) as an emerging technology for the sterilization of foods could be a big turning point in the food industry. HPTS can result in a better overall food quality, lower thermal load applied to the product and less unwanted food processing contaminants (FPCs) as e.g. furan and monochloropropanediol/-esters.Hence, within the EU FP7 founded Prometheus-project HPTS treatments were performed for selected food systems. Therefore, two spore strains were tested, the Geobacillus stearothermophilus and the Bacillus amyloliquefaciens, in the temperature range from 90 to 121 °C at 600 MPa. The treatments were carried out in different fish system and ACES-buffer. The treatment at 90 and 105 °C showed that the G. stearothermophilus is more pressure sensitive than the B. amyloliquefaciens. The formation of FPCs was monitored during the sterilization process and compared to the amounts found in retorted samples of the same food systems. Depending on the food system the amounts of furan could be reduced between 71 and 97% for the tested temperature pressure combination even at sterilization conditions of F₀-value 7 min.Industrial relevanceThe high pressure thermal sterilization (HPTS) process is an emerging technology to produce high quality low acid food products, which are shelf-stable at ambient temperature. In addition the consumer today demands foods which are minimally processed and are healthy and safe. However, an industrial scale process has not yet been implemented.The work in this paper shows different temperature combinations (90 to 121 °C) at 600 MPa and their influence on the endospore inactivation and also on the formation of unwanted food process contaminants (FPCs), such as furan and monochloropropanediol/-esters, in comparison to retorting. The use of HPTS could lead to shorter process times and a means by which a better quality of the foods could be achieved.     

Ionization equilibria at high pressure

The equilibria of reactions forming or dissipating ions or those which change the charge of existing ions, such as the dissociation of acids or dissolving of salts, depend on pressure as equilibrium constants The term equilibrium constant is misleading, as it is a function of both temperature and pressure. and activity coefficients are both functions of pressure. In particular, acid–base reactions which are responsible for the pH value of the medium and for reactions of proteins play an important role in high-pressure microbiology and food science. To understand more about such reactions it is important to understand the pressure behaviour of such reactions. In this study the background and the most important methods from previous studies to determine this pressure behaviour are introduced and discussed, specifically for reactions affecting the pH value. A comprehensive theory has not yet been proposed, but some models described in the literature show adequate agreement with existing measurements and can be used to interpret experimental results. The reason for the changes of equilibrium constants with pressure and the basis for the calculation is the volume change accompanying a reaction. This volume change is caused mainly by the electrostatic interaction between an ion and surrounding water.     

Response surface methodology to investigate the effect of high pressure processing on Salmonella inactivation on dry-cured ham

The lethal effect of high pressure on microorganisms is influenced by a number of factors in relation to the technological variables, microorganisms and food matrix, which have to be considered when designing high pressure processes. The present work aimed to develop and validate a model of the inactivation of Salmonella enterica on dry-cured ham by high pressure processing (HPP), as a function of the technological parameters: intensity, length and fluid temperature. Dry-cured ham inoculated with S. enterica was treated at different HPP conditions (at 347 to 852 MPa; for 2.3 to 15.75 min; at 7.6 to 24.4 °C) following a central composite design. Bacterial inactivation was assessed in terms of logarithmic reductions of Salmonella counts on selective media. According to the best fitting and most significant polynomial equation, pressure and time were the most important factors determining the inactivation extent. Temperature showed significant influence through its interaction with both pressure and holding time. The model was validated with results obtained from further experiments within the range of the experimental domain. The accuracy factor and bias factor were within the proposed acceptable values indicating the suitability of the model for predictive purposes, for instance to predict the process criteria to meet the lethality safety standards. The results of this work may help food processors to select optimum processing conditions of HPP to ensure the microbiological safety of pressure-treated foods.     

高压处理对鱼制品影响的研究进展

消费者对新鲜和安全食品的追求促使食品工业不断开发新技术.与加热处理相比,高压处理因其对食品性质的改变最小而被视为一个新的替代技术,但是此技术应用于鱼制品时不但导致其质构和外观的重大改变,而且随着压力大小,处理时间、营养成分、温度及其它条件的不同其影响也有所不同;同时造成脂肪氧化、蛋白质变性、微生物和酶的失活,以及质构、色泽、持水能力的变化.文章介绍并讨论当前关于高压处理对鱼制品性质变化的影响及减少高压处理负面作用研究的最新进展.     

A comparative study on properties of fish meat hydrolysates produced by an enzymatic process at high pressure

Food Science and Biotechnology - Fish meat hydrolysates (FMHs) were produced from nine fishes at a high pressure of 300 MPa using Flavourzyme 500MG and a protease mixture including...     

Quality improvement of non-sulphited mango slices by drying at high temperatures

An optimum drying routine for producing non-sulphited mango slices has been developed. The interaction of essential drying parameters (air temperature, air velocity, dew point, slice thickness and drying time) on water activity (a_W) and browning was determined. Microbiological stability of the dried product was achieved at a moisture content of 17% wet base (w.b.) corresponding to a_W = 0.6. Browning was monitored by the red colour shade of the product (CIE-Lab chromaticity coordinate a*). Drying air temperature and drying time were shown to be the primary factors influencing product colour and a_W. In contrast to common practice, drying for about 6 h at elevated air temperature (80 °C), instead of 50 or 60 °C for a longer time, was optimal, since significant colour changes of the mango slices were not observed even without the use of any chemical or thermal pre-treatment. Moreover, at increased temperature, drying time was considerably shortened from about 9 h to 6 h, resulting in significant extension of the drying capacity.

Industrial Relevance

The suggested process concept for dried mango slices based on high-temperature drying is of utmost significance for the international marketing of dried fruit products. Chemical pre-treatments such as sulphitation often used to minimise quality deficiencies could be avoided. Sulphitation has been recently under critical consideration with respect to allergen labelling of foodstuffs implemented by EU-Member States in November 2004 (Directive 2003/89/EC) [Directive 2003/89/EC. Official Journal of the European Union, 25.11.2003, pp. L308/15–18 (http://europa.eu.int/eur-lex/pri/en/oj/dat/2003/l_308/l_30820031125en00150018.pdf)]. Export quality was improved and the drying process simplified, improving the utilisation of drying capacities. Particularly referring to an application of the technology in small- and medium-sized enterprises with limited investment possibilities, the suggested novel drying procedure in mango processing aimed at the optimisation of well-established simple drying methods instead of choosing technically more sophisticated technologies.     

Effect of high pressure on the calpain-calpastatin system in fish muscle

ABSTRACT:  Calpains (calcium-activated neutral proteases) of sea bass ( Dicentrarchus labrax L.) muscle may participate in the degradation of muscle tissue during postmortem storage. These enzymes are regulated by calpastatin, their endogenous specific inhibitor. The objective of this study was to evaluate the changes encountered by the calpain system during the postmortem storage of fish muscle after high-pressure treatment. From 100 MPa, high-pressure treatment of purified calpains results in a loss of their activity as well as in the dissociation of the heterodimeric form. In muscle, the high-pressure processing decreases the initial activity of calpain. This loss in activity may be due to an inactivation by a change of structure. Initial calpastatin activity is not modified by the high-pressure treatment, but it decreases during the storage from the beginning for a treatment at 300 MPa after which calpastatin is stable during 2 d. Therefore, this study also suggests that high-pressure treatment could be a useful way to improve fish flesh quality.     

Chemical characterization and properties of five deep-sea fish species

Some important flesh properties were determined for the deep-sea species Portuguese dogfish (Centroscymnus coelolepis), leafscale gulper shark (Centrophorus squamosus), black dogfish (Centroscyllium fabricii), roughhead grenadier (Macrourus berglax), and mora/deepsea cod (Mora moro).Chemical composition, water holding capacity, cook loss and shelf-life, as indicated by bacterial counts, were determined. For some of the species investigated, variations could be observed between fish caught in spring and fish caught in summer. The fish used in this study were caught at Hatton Bank in the North Atlantic, where fishing takes place mainly from April to September.     

深海鱼油精炼真空系统的应用实践

通过深海鱼油精炼生产线的实践,对鱼油精炼工艺流程进行简介。根据工艺特点,对真空系统进行了选型及应用实践。生产实践表明该真空系统满足工艺要求,产品指标优于国标一级精炼鱼油要求,具有较好的推广意义。     

Preservation of fatty duck liver by high pressure treatment

Fatty liver samples from duck were treated with high pressures and packaged in multilayer films. Microbiological analysis, permeability of the films to oxygen and fat loss, caused by melting, were assessed after pressure or thermal treatment. Microbiological analysis showed a noteworthy reduction in the total aerobic mesophilic flora and eradication of the coliform flora, whichever film or treatment was used. Nevertheless, a significant bacterial flora was observed during storage at 4 °C from 42 days with a polyethylene/polyamide/polyethylene film and a sample which had been treated with pressure. But, treatment at 550 MPa for 55 °C and 20 min, in combination with two low oxygen permeability films (ethylene and vinyl alcohol copolymer) gave a product with long storage life (90 days) at 4 °C and a significant reduction in the melting of lipids.     

Accumulation of contaminants in fish from wastewater treatment wetlands

Increasing demands on water resources in arid environments make reclamation and reuse of municipal wastewater an important component of the water budget. Treatment wetlands can be an integral part of the water-reuse cycle providing both water-quality enhancement and habitat functions. When used for habitat, the bioaccumulation potential of contaminants in the wastewater is a critical consideration. Water and fish samples collected from the Tres Rios Demonstration Constructed Wetlands near Phoenix, Arizona, which uses secondary-treated wastewater to maintain an aquatic ecosystem in a desert environment, were analyzed for hydrophobic organic compounds (HOC) and trace elements. Semipermeable membrane devices (SPMD) were deployed to investigate uptake of HOC. The wetlands effectively removed HOC, and concentrations of herbicides, pesticides, and organic wastewater contaminants decreased 40-99% between inlet and outlet. Analysis of Tilapia mossambica and Gambusia affinis indicated accumulation of HOC, including p,p'-DDE and trans-nonachlor. The SPMD accumulated the HOC detected in the fish tissue as well as additional compounds. Trace-element concentrations in whole-fish tissue were highly variable, but were similar between the two species. Concentrations of HOC and trace elements varied in different fish tissue compartments, and concentrations in Tilapia liver tissue were greater than those in the whole organism or filet tissue. Bioconcentration factors for the trace elements ranged from 5 to 58,000 and for the HOC ranged from 530 to 150,000.     

Effect of high hydrostatic pressure pretreatment on flavour and physicochemical properties of freeze-dried carambola slices

Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g⁻¹, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g⁻¹. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing.     

High pressure technology as a tool to obtain high quality carpaccio and carpaccio-like products from fish

This work evaluates the physicochemical and sensorial qualities of salmon, tuna and desalted “bacalao”, thinly sliced as carpaccios, and subjected to 15-min of continuous pressure and pulsed pressure in three 5-min steps (200–300 MPa at 7 °C). Pressurization of salmon and tuna gave rise to an increase in the shear strength of carpaccios, a reduction of the water and lipid binding properties and an increase in the total colour difference. Though these changes were also detected by the sensory panel, the resulting pressurized products obtained high scores for acceptability. Desalted “bacalao” carpaccio was more stable under high pressure and sensory analysis revealed that in most treatments the raw attributes had been retained. The results obtained by applying pressure in one or three consecutive cycles were, in general, the same. High-pressure treatment was shown to be an adequate tool for obtaining high-quality desalted “bacalao” carpaccio, whereas salmon and tuna suffered a loss of raw attributes. However the resulting products acquired new sensory features which were highly accepted by the sensory panel.Industrial relevanceNowadays, there is a growing interest in consuming raw or minimally processed foods and among fishery products, carpaccio are becoming increasingly popular. The present work deals with the effect of high pressure on the physico-chemical and sensory attributes of carpaccios made from salmon, tuna, and desalted “bacalao”. High pressure may be an adequate tool to obtain high quality carpaccio or carpaccio-like products, as the products acquired new sensory features which were highly accepted by the sensory panel. From the industry viewpoint the application of high pressure to fish carpaccios may be appealing in a two way: firstly, the resulting carpaccio are presumably free of parasites and present a better microbiological quality, thereby increasing the shelf-life. Secondly, products may acquire new sensory attributes that can be very appreciated by consumers.     

Numerical simulation of lyophilization of carrot slices at atmospheric pressure in a fluidized bed

Two-dimensional numerical simulations were carried out to describe the lyophilization process at atmospheric pressure and its optimization. The finite differences method succeeded in describing correctly the complex motion of the sublimation interface in foodstuff. Comparison of unidirectional and bidirectional mass and energy transport showed considerable differences in the drying kinetics. These differences decreased as the geometric ratio (GR) decreased and the physical situation approached to that of an infinite plate. The temperature and vapor pressure distributions were analyzed as functions of ice saturation. Two-dimensional numerical simulations showed a good fit with the experimental data.     

The use of carbon dioxide at high pressure to control nine stored-product pests

The development of alternative treatments for pest control in food commodities is an increasing demand from the food industry, which should meet consumer demands for the reduced use or elimination of pesticides. The use of carbon dioxide (CO₂) at high pressure is one of the most rapid options for arthropod pest control among current commercial treatments, offering complete control within hours. The present study aimed to establish the efficacy of the technique against different stages of several insect and mite pests that affect stored-food products. Standard food diets containing eggs, larvae, pupae and adults of Oryzaephilus surinamensis, Cryptolestes ferrugineus, Lasioderma serricorne, Sitophilus oryzae, Rhyzopertha dominica, Acanthoscelides obtectus, Ephestia kuehniella, Liposcelis bostrychophila and Tyrophagus putrescentiae were treated with CO₂ for different times at two high pressures, 15 and 20 bar. A high level of control was achieved for most species and development stages when they were treated with CO₂ at 20 bar for 60 min. However, the efficacy at 15 bar was much lower. The eggs of L. bostrychophila and L. serricorne showed the highest tolerance of all species/stages and survived the most extreme conditions tested. The beetle O. surinamensis, the moth E. kuehniella, and the mite T. putrescentiae were easier to kill than the other species tested. Our results confirmed that the use of high-pressure CO₂ offers an effective and fast way to control most stored-product pests that affect food commodities.