Microbiological aspects and technological need: technological needs for nitrates and nitrites.

Nitrate and nitrite are used in meat and fish curing, and in the manufacture of certain cheeses. Nitrate itself has little antimicrobial effect and in most applications could be replaced by lower concentrations of nitrite. Further, improved hygiene diminishes the need for nitrite. The antimicrobial activity and technological needs for nitrate and nitrite are reviewed. It is concluded that the technological needs for nitrite in meat products stored at < 10 degrees C could be met by added nitrite concentrations of 50 mg/kg. The overall effect of nitrate in salted fish appears to be marginal. In such products, Vibrio parahaemolyticus does not grow at salt concentrations of 10% and food poisoning by this organism is not related to the absence of nitrate or nitrite; growth of Clostridium botulinum Type E (the predominant cause of botulism from fish products) is arrested by salt concentrations of 3-4%. Listeria monocytogenes in seafood cannot be controlled by nitrite. The use of nitrate in cheese production could be avoided, or at least reduced to a low level by avoiding silage with a high count of gas-producing Clostridia and hygienic milk collection.     

低盐腌制对腌肉制品品质的影响

了解低盐腌制对腌肉品质的影响,以金华火腿和咸肉为参照,采用L16(45)正交实验,探讨了食盐、蔗糖和乳酸盐的添加量、腌制时间、脱水率对腌肉水分活度、蛋白质降解、颜色及质构的影响,结果表明,腌肉最优工艺条件为:食盐添加2.8%,白糖添加2%,乳酸盐添加5%,7℃腌制12d,15℃脱水39%。蔗糖和乳酸盐代替部分食盐进行低盐腌制可有效降低腌肉食盐含量和硬度,而不影响腌肉蛋白降解及贮存性。     

The application of technology to the processing of dry-salted fish in peninsular Malaysia: comparison of sun-dried and oven-dried fish

Investigation of processing of dry-salted fish is described. The use of a satisfactory ratio of salt to fish, optimization of salting time and the use of mechanical driers to reduce drying time, insect infestation and microbial spoilage were investigated. Results indicated that oven-dried fish salted at 10% and 20% levels were most acceptable. The corresponding sun-dried samples had an undesirable odour, flavour and texture due to their higher moisture contents. At the 30% and 40% salt levels for both processes, the differences were less pronounced, but the samples that were sun-dried were more acceptable mainly as a result of a better appearance.     

Effect of Salt, Sugar and Storage Time on Microbiological, Chemical and Sensory Properties of Chinese Style Dried Pork

A Chinese dried pork product was manufactured with combinations of 15, 22.5, and 30% sugar and 0.5, 1.5, and 2.5% salt and evaluated for microbiological, chemical and sensory properties at 0, 7, 14, and 21 days of storage. Aerobic and anaerobic plate counts and TBA values increased during storage with the high sugar and salt combination resulting in the least microbial growth. No major rancidity problems developed. A 30% sugar and 2.5% salted product resulted in the highest panel flavor scores when evaluated by a group of panelists from the Orient.     

In situ activity of chymotrypsin in sugar‐salted herring during cold storage

In situ activity of intestinal chymotrypsin in sugar‐salted whole herring during cold storage was evaluated by analysing changes in the low‐molecular‐weight nitrogen fraction when a specific inhibitor was added. Addition of chymostatin (0.01 mM ) to sugar‐salted herring gave 100% inhibition of chymotrypsin activity compared to sugar‐salted herring without chymostatin. Inhibition of chymotrypsin did not affect the profile of low‐molecular‐weight peptides analysed by capillary zone electrophoresis, but resulted in 22% lower content after 26 weeks of storage. Inhibition of chymotrypsin resulted in 17% lower content of free amino acids. The relative amount of single free amino acids was unaffected by the presence of inhibitor, except for valine, leucine, isoleucine, methionine, phenylalanine and tyrosine, which were formed in lower relative amount. Removal of intestines (gutted herring) and thereby all intestinal proteolytic activity did not change the free amino acid profile, except for the concentration of histidine which decreased more when intestines were present. © 2000 Society of Chemical Industry     

The storage of herring (Clupea harengus) in ice,refrigerated sea water and at ambient temperature. Chemical and sensory assessment

Herring caught during the winter and summer were stored in ice, refrigerated sea water (RSW) and at ambient temperature. Chemical tests and a sensory assessment of the fish were made on samples stored for up to 13 days. Results indicate that herring can be chilled simply and rapidly using an RSW plant and that spoilage changes in the fish stored in ice and RSW are similar during the first 4 or 5 days of storage. The chemical tests investigated serve more as indicators of spoilage rather than quantitative guides.     

响应面法优化发酵鸭的工艺

研究用复合发酵剂生产发酵鸭的工艺条件.通过正交试验确定鸭胚腌制的最佳条件为食盐浓度5%,蔗糖3%,复合香辛料4%,腌制时间16h.通过单因素试验与响应面分析确定最佳的发酵条件:植物乳杆菌、戊糖乳杆菌、变异微球菌与汉逊德巴利氏酵母菌之间的菌种比例1:2:1:2,接种量3.15%,发酵温度31.5℃,发酵时间22.7h.     

KEEPING QUALITY OF DIFFERENT PACKAGED SALTED ATLANTIC BONITO "LAKERDA"

Quality and shelf life of salted Atlantic bonito (lakerda) packaged in brine, under vacuum and in oil conditions and stored at 4  ±  1C were studied. The sensory scores of lakerda stored in all package types at 4C were 14 weeks, respectively. The microbiological count of the vacuum-packaged lakerda was extended than that lower of other group sample. Overall results of this study showed that 9 weeks of storage of lakerda in brine was the beginning of spoilage, whereas storage of samples in oil and vacuum package delayed onset of spoilage about 2–3 weeks in terms of chemical analysis. Lakerda stored in cold storage as sensory, chemical and microbiological results for brine- and oil-packaged lakerda showed us that week 11 was the beginning of spoilage, and for vacuum-packaged lakerda, week 13 was the beginning of spoilage.

PRACTICAL APPLICATIONS

Raw fish and processed fish product is highly perishable and has a short shelf life. Packing processing is finding increasing use in the food industry because of its relative advantages versus other food processing methods in eliciting minimal changes in the flavor, microbiological and nutritional qualities of the final product. This paper illustrates the changes induced in salted fish by packaging at different types. By using oil- and vacuum-packaged treatment, shelf life of traditional-packaged (in brine) lakerda could be extended at 4C from 9 weeks to 11–13 weeks.     

Changes in concentrations of dioxins and dioxin-like PCBs during processing of fish

Fish among meat and dairy products mainly contribute to the human exposition with dioxins and dioxin-like PCBs. Contaminant levels of fish are mainly determined in the edible part of the raw material. In Germany fish are not consumed raw but industrially processed to manifold products and cooked, fried or deep-fried in household. To study the influence of processing on the contaminant levels, changes of dioxins and partly of dioxin-like PCBs were followed during canning of herring fillets, hot smoking of mackerel fillets and Greenland halibut cutlets and during sugar salting of beheaded whole herring. The hot smoking process and sugar salting of herring led to an increase of the dioxin content in the edible part of the final product. The increase was related to the loss of water during processing whereas the fat and thus the lipophilic dioxins remained in the muscle meat. For sugar salting also changes of dioxin-like PCB levels were followed and the same effect was observed. Otherwise the production of canned herring fillets in tomato sauce led to a “dilution” of the dioxin content due to the addition of the sauce.     

Microbiological quality of maatjes herring stored in air and under modified atmosphere at 4 and 10 degrees C

Microbiological and sensory changes of maatjes herring stored in air (experiment I) and under modified atmosphere (MAP) (experiments II and III) were evaluated during storage at 4 and 10 degrees C. Microbial (total and psychrotrophic viable bacteria, lactic acid bacteria and Enterobacteriaceae) counts and chemical analyses (chloride content, fat content, dry matter, ash and pH) were performed. A Quality Index Method (QIM) scheme developed for maatjes herring was used for sensory evaluation. The main reasons for sensory rejections at both storage temperatures were a strong rancid taste for herring stored in air (Experiment I) and a sour, bitter, rotten taste and an aftertaste like old flower water for MAP herring (Experiments II and III). A soft texture of freshly produced samples (Experiment II) was noticed. The sensory shelf-life of maatjes herring stored in air (Experiment I) was three days at both 4 and 10 degrees C. The MAP herring in Experiments II and III had a shelf-life of 5 and 6 days, respectively, at both storage temperatures. Rancidity due to oxidation of fat was the main spoilage indicator for air-stored maatjes herring. Autolytic enzymes may affect textural deterioration. The characteristic off-odour and off-taste in the MAP herring (Experiments II and III) were may well be attributable to microbial metabolism. On the day of sensory rejection, total viable counts for herring in all three experiments (Experiments I-III) stored at 4 degrees C did not reach 10(6)cfu/g, which is considered the limit of acceptability for maatjes herring given by the Dutch fishery authorities. It appears that total viable counts have minor significance in the sensory assessment of maatjes herring.     

Leuconostoc gelidum and Leuconostoc gasicomitatum strains dominated the lactic acid bacterium population associated with strong slime formation in an acetic-acid herring preserve

Spoilage characterised by strong slime and gas formation affected some manufacture lots of an acetic-acid Baltic herring (Culpea haerengus membras) preserve after few weeks of storage at 0-6 degrees C. The product consisted of herring filets in acetic acid marinade containing sugar, salt, allspice and carrot slices. Microbiological analyses of the spoiled product showed high lactic acid bacterium (LAB) levels ranging from 4.5x10(8) to 2.4x10(9) CFU/g. Yeasts were not detected in any of the herring samples. Since LAB contaminants are seldom associated with fresh fish, LAB populations associated with marinade ingredients (carrots, allspice) were also analyzed. The highest LAB levels exceeding 10(7) CFU/g were detected in equilibrium modified atmosphere packaged baby carrots whereas the levels detected in the allspice samples did not exceed 4.3x10(5). A total of 176 randomly selected LAB isolates originating from herring, carrot and allspice samples were further identified to species level using a 16 and 23S rRNA gene RFLP (ribotyping) database. Leuconostoc gelidum and Leuconostoc gasicomitatum strains dominated both in the spoiled herring and carrot samples. These species are heterofermentative-producing CO(2) from glucose and they also produce dextran from sucrose. Inoculation of some commercial-herring products with spoilage-associated L. gelidum and L. gasicomitatum strains verified that these strains have the capability of producing slime and gas in herring preserves although slime formation was not as strong as in the original samples. Since L. gelidum and L. gasicomitatum strains were commonly detected in carrots, carrot slices used for the fish marinade were considered to be the probable source of these specific spoilage organisms.     

电解式臭氧水对盐渍青菜中微生物及风味的影响

利用电解式臭氧水对盐渍青菜进行脱盐处理,探讨臭氧水对盐渍青菜中病原/腐败微生物、理化指标和风味成分的影响。 通过平板计数,检测到质量浓度为6 mg/L的臭氧水流水处理盐渍青菜10 min后,对阴沟肠杆菌（Enterobacter cloacae）、大肠杆菌（Escherichia coli）、单核增生李斯特氏菌（Listeria monocytogenes）和金黄色葡萄球菌（Staphylococcus aureus）的杀灭率均可达到100%。 臭氧处理对盐渍青菜中维生素C含量有明显的降解作用,但对青菜中还原糖和总糖含量无显著影响（P＞0.05）。 气相色谱-质谱法检 测未处理、臭氧水和自来水各处理10 min后盐渍青菜中可挥发性风味成分分别为67、59和39种,并且臭氧处理后盐渍青菜中醛类和 烯类化合物增多。 研究结果表明,臭氧水脱盐工艺能有效杀灭盐渍青菜中的病原/腐败微生物,对盐渍青菜的风味有一定影响,但不 同于自来水处理。     

EFFECT OF PROCESS VARIABLES ON THE QUALITY OF SWORDFISH FILLETS FLAVORED WITH SMOKE CONDENSATE

An alternative technique to traditional smoking of swordfish was evaluated. Fillets were dry salted and/or brine salted in 30% NaCl, and smoked by dipping in smoke condensate solution at different concentrations. Chemical (water‐phase salt, pH, total volatile basic nitrogen, lipid oxidation), microbiological (total mesophilic count and fecal coliforms count) and sensory analyses were carried out in order to establish which technique gave the best results in terms of sensory quality. The different salting techniques gave different water‐phase salt contents, which influenced the microbial growth and the production of volatile bases. The smoke condensate concentration was ineffective toward microbial growth, but it was a differentiating factor for sensory panel. The dry‐salted product smoked with 5% smoke condensate was preferred because it maintained the natural taste of fish, coupled with a pleasant flavor of smoke.     

风鸭的腌制发酵工艺研究

本试验研究了用复合发酵剂生产风鸭的工艺条件。通过正交试验确定了鸭胚腌制的最佳条件为食盐浓度8%,蔗糖3%,复合香辛料(花椒八角1:1混合)1.5%,腌制时间12 h。通过单因素试验与正交试验确定了最佳的发酵条件:植物乳杆菌、戊糖乳杆菌、变异微球菌与汉逊德巴利氏酵母菌之间的菌种比例1:2:1:2,接种量1.5%,发酵温度22℃,发酵时间73 h,所得风鸭pH值为5.18,氨基酸态氮含量为0.75%。     

DETERMINATION OF DIFFERENT VOLATILE BASE COMPONENTS AS QUALITY CONTROL INDICES IN FISH BY OFFICIAL METHODS AND FLOW INJECTION ANALYSIS

Flesh concentration of Trimethylamine Oxide‐Nitrogen (TMAO‐N), Trimethylamine‐Nitrogen (TMA‐N) and Total Volatile Base Nitrogen (TVB‐N) are the most studied parameters used as indices of spoilage in fish and fishery products. In the present work, the official methods to determine TVB‐N, TMA‐N and TMAO‐N were compared with the Flow Injection Analysis (FIA) technique using three different fish species over their storage in melting ice for a period of 16 days. There was a good correlation between determinations made using official and FIA methods with no apparent significant differences. FIA thus appears to be a suitable method for TMAO‐N, TMA‐N and TVB‐N in fish extract and the use of this system is much faster and simpler than the official methods for determination of these parameters. On the other hand, the individual concentrations of TMAO‐N, TMA‐N and TVB‐N were not found to represent reliable indices of spoilage in fish, which had been frozen and thawed and then presented in chilled format.     

风鸭的腌制发酵工艺研究

本试验研究了用复合发酵剂生产风鸭的工艺条件。通过正交试验确定了鸭胚腌制的最佳条件为食盐浓度8％,蔗糖3％,复合香辛料（花椒八角1：1混合）1．5％,腌制时间12h。通过单因素试验与正交试验确定了最佳的发酵条件：植物乳杆菌、戊糖乳杆菌、变异微球菌与汉逊德巴利氏酵母菌之间的菌种比例1：2：1：2,接种量1．5％,发酵温度22℃,发酵时间73h,所得风鸭pH值为5．18,氨基酸态氮含量为0．75％。     

Textural and biochemical changes during ripening of old-fashioned salted herrings

BACKGROUND: Understanding of the biochemical reactions taking place during ripening of salted herring is still rather limited. Therefore, salted herrings were traditionally produced and the impact of the brine composition was evaluated in relation to the development of the characteristic texture of salted herrings. The aim of this study was to measure the texture changes during ripening using two different methods and to correlate the texture changes with brine composition and with biochemical modifications at the molecular level. RESULTS: During ripening (up to 151 days), hardness was higher in salted herrings compared to raw herrings, irrespective of the brine composition. However, the increase in hardness of herring prepared with extra brine occurred later. After prolonged storage (371 days), hardness was found for both batches to decrease to the level of raw herring. The increase in hardness during the ripening period could be explained by free‐radical‐induced cross‐linking of myosin and the formation of aggregates. In addition, degradation of these aggregates correlated with the decrease in hardness observed at 371 days. CONCLUSIONS: Texture changes during ripening of salted herrings can be explained by oxidative reactions inducing myosin cross‐linking followed by subsequent degradation of these myosin aggregates. The brine composition might play a role in the development of herring texture but this need to be investigated in more details. Copyright © 2010 Society of Chemical Industry     

基于Illumina MiSeq技术分析腌干鱼加工过程中微生物群落多样性

为研究传统和乳酸菌法加工腌干鱼过程微生物的变化规律,为优化腌干鱼工艺提供理论依据,采用MiSeq测序技术,研究腌干鱼在不同加工阶段的细菌多样性,结果表明:腌干鱼加工过程微生物种类丰富,主要分为三大类:拟杆菌门(Bacteroidetes)、厚壁菌门(Firmicutes)和变性菌门(Proteobacteria);蓝圆鲹初始菌相中优势细菌为肠杆菌科(Enterbacteriaceae)、肠球菌科(Enterococcactae)、假单胞菌科(Pseudomonadaceae)和希瓦氏菌科(Shewanellaceae);海鲈初始菌相中优势菌主要是气单胞菌科(Aeromonadaceae)、芽孢杆菌科(Bacillaceae)、葡萄球菌科(Staphylococcaceae)、丛毛单胞菌科(Comamonadaceae)、肠杆菌科(Enterbacteriaceae)、肠球菌科(Enterococcaceae)、摩式摩根菌科(Moraganellaceae)、链球菌科(Streptococcaceae)等。传统腌制加工过程中菌相比较单一,优势菌主要是弧菌科(Vibrionaceae)、葡萄球菌科(Staphylococcaceae)、假单胞菌科(Pseudomonadaceae)和动性球菌科(Planococcaceae);而接种乳酸菌发酵后,加工过程中细菌多样性呈现增加趋势,并且乳酸菌成为优势菌,促进了微杆菌科(Exiguobacteracea),葡萄球菌(Staphylococcaceae)等优势菌的繁殖;此外还检测到气单胞菌(Aeromonadaceae)和乳杆菌(Lactobacillaceae)等传统蓝圆鲹腌制加工过程中没有出现的菌。海鲈在腌制加工过程中细菌多样性明显高于蓝圆鲹,乳酸菌法腌制加工过程中细菌多样性明显增加。