Determination of biogenic amines in selected Malaysian food

The biogenic amines tryptamine (TRP), putrescine (PUT), histamine (HIS), tyramine (TYR) and spermidine (SPD) were determined in 62 selected food items commonly consumed in Malaysia. This include the local appetisers “budu” and “cincalok”, canned fish, salt-cured fish, meat products, fruit juice, canned vegetables/fruits and soy bean products. After the aqueous extraction, the samples were derivatised with dansyl chloride before analysing using reversed phase HPLC with UV detection. Mean levels of TRP, PUT, HIS, TYR and SPD in eight budu samples were 82.7, 38.1, 187.7, 174.7 and 5.1 mg kg⁻¹, respectively. The main biogenic amines found in cincalok were PUT, HIS and TYR where the mean values were 330.7, 126.1 and 448.8 mg kg⁻¹, respectively. With the exception of “pekasam” and “belacan”, significantly lower levels of biogenic amines were found in canned fish and salt-cured fish samples. Non detectable or low levels of biogenic amines were found in meat, fruit juice and canned vegetables/fruit samples.     

Evaluation of a freshness indicator for quality of fish products during storage

A freshness indicator consisting of a polymer matrix solution containing the pH-sensitive dye bromocresol green was investigated for monitoring visible color changes of fish spoilage volatile compounds based on the quantity of volatile amines. Mackerel fillets were inoculated with Pseudomonas fragi and stored in incubators at 5, 12, 18, and 25°C. Chromaticity values of the freshness indicator accurately tracked an increase in the trimethylamine content in the packaging headspace. Gradual color changes of the freshness indicator response correlated with the quality of fish, including growth of P. fragi and pH values during storage. Results will be useful to establish a basis for development of a freshness indicator and to determine the suitability of freshness indicator formulations for intelligent food packaging applications.     

Volatile compounds in low-acid fermented sausage “espetec” and sliced cooked pork shoulder subjected to high pressure processing. A comparison of dynamic headspace and solid-phase microextraction

Two extraction techniques, dynamic headspace extraction (DHE) and solid-phase microextraction (SPME), were compared to assess the effect of high-pressure treatment (400 MPa, 10 min, 12 °C) on the volatile compounds of low-acid fermented sausage “espetec” and sliced cooked pork shoulder stored at 4 °C. DHE was more efficient at extracting low-boiling compounds such as ethanal, 2,3-butanedione and alcohols, while SPME extracted more efficiently a higher number of chemical families, especially fatty acids. The effect of pressurisation on the volatile fraction of “espetec” was better categorized by DHE, whereas SPME was more appropriate for cooked pork shoulder. The volatile fraction of “espetec” changed slightly after pressurisation, mainly showing a decrease in the levels of lipid-derived compounds, like linear alkanes, aldehydes, or 1-alcohols in pressurised samples. The volatile profile of cooked pork shoulder underwent substantial changes during refrigerated storage, mainly due to microbial metabolism, most of these changes being limited by HPP.     

Neural-network-integrated electronic nose system for identification of spoiled beef

A commercially available Cyranose-320™ conducting polymer-based electronic nose system was used to analyse the headspace from fresh beef strip loins (M. Longissimus lumborum) stored at 4° and 10 °C. The raw signals obtained from the electronic nose system were pre-processed by various signal-processing techniques to extract area-based features. Principal component analysis was subsequently performed on the processed signals to further reduce the dimensionalities. Classification models using radial basis function neural networks were developed using the extracted features. The performance of the developed models was validated using leave-1-out cross-validation method. The developed models classified meat samples stored at two storage temperatures into two groups, i.e., “unspoiled” (microbial counts<6.0 log₁₀ cfu/g) and “spoiled” (microbial counts ?6.0 log₁₀ cfu/g). Maximum total classification accuracies of 100% were obtained for both the samples stored at 10 and 4 °C. Classification models based on “Area scaled” feature showed higher accuracies than that obtained using “Area unscaled feature.”     

Histamine contents of fermented fish products in Taiwan and isolation of histamine-forming bacteria

Twenty-seven imported fermented fish products from Southeast Asian countries and sold in the supermarkets in Taiwan, including fish sauce, fish paste and shrimp paste, were tested to determine the occurrence of histamine and histamine-forming bacteria. The levels of pH, salt content, total volatile basic nitrogen, trimethylamine, and aerobic plate count in all samples ranged from 4.8% to 6.5%, 16.2% to 45.3%, 51 to 275 mg/100 g, 5.4 to 53.9 mg/100 g and 1.0 to 4.2 log CFU/g, respectively. The average content for each of eight different biogenic amines in all samples was less than 90 ppm, except for histamine which has an average content of 394 ppm in fish sauce, 263 ppm in fish paste, and 382 ppm in shrimp paste. Most of the tested fermented fish products (92.6%) had histamine levels greater than the FDA guideline of 50 ppm, while seven of them (25.9%) contained >500 ppm of histamine. Although Bacillus coagulans and Bacillus megaterium were identified as the two histamine-producing bacteria capable of producing 13.7 and 8.1 ppm of histamine, respectively, in trypticase soy broth broth supplemented with 1.0% l-histidine, they were not determined to be the main contributors to histamine accumulation in these fermented fish products.     

Edible Antimicrobial Coating Incorporating a Polymeric Iron Chelator and Its Application in the Preservation of Surimi Product

To explore a novel efficient method in food preservation, edible zein coating which incorporates a polymeric chelator was developed and its preservative effect on commercially manufactured fish balls was investigated. The quality indicators of the fish ball during the storage, including sensory quality, total bacterial count, total basic volatile nitrogen (TVB-N) content, thiobarbituric acid reactive substances (TBARS), and pH value were determined. It has been demonstrated that a zein film containing a polymeric chelator significantly (P?<?0.05) improves the sensory properties, retards the growth of spoilage bacteria, and decreases TVB-N and TBARS values. The increase of the microbial load of fish balls coated with antimicrobial zein during a 16-day refrigeration storage period was less than 1 log cfu/g, while the microbial load increased to about 5 log cfu/g for the control group lacking the coating treatment. Although statistically significant differences in the pH values were not observed between coated and uncoated fish balls (P?>?0.05), fish balls coated with antimicrobial zein maintained a relatively stable state during storage. Zein coating which incorporates a polymeric chelator extends fish ball shelf life to 19 days at 4 °C, being more efficient than zein coating lacking a polymeric chelator (13 days). Clearly, polymeric chelator-incorporated zein film could find application in the preservation of surimi products by preventing the growth of bacteria and oxidation of fat during storage.     

The Influence of Debaryomyces hansenii, Candida deformans and Candida zeylanoides on the aroma formation of dry-cured “lacón”

The volatile profile of dry-cured “lacón” that has been inoculated with three different yeasts were determined and compared with a non-inoculated dry-cured “lacón”. Yeasts (Debaryomyces hansenii, Candida deformans and Candida zeylanoides) that were used as starter cultures in the present study were selected among yeasts that were isolated from native dry-cured “lacón” at different stages of ripening process. These starters were spread on dry-cured “lacón” surface in order to test their capacity to contribute on the generation of volatile compounds. A total of forty two volatile compounds were detected by dynamic headspace sampling followed by gas chromatography–mass spectrometry analysis. Significant differences (P < 0.001) on the volatile profiles of different batches were found in comparison with non-inoculated samples, showing the highest total area values for the inoculated ones. Esters were the most abundant chemical family in all batches studied except for C. zeylanoides batch, which showed greater amount of hydrocarbons than esters. The second more abundant family was hydrocarbons for control and C. deformans batches (147.6 and 445.24 × 10⁶ area units, respectively), alcohols for D. hansenii (363.77 × 10⁶ area units) and esters for C. zeylanoides (248.33 × 10⁶ area units). However, the aldehyde compound group in control batch samples was found to be significantly higher than in the inoculated ones (P < 0.001). Among inoculated batches, D. hansenii batch showed the lowest hexanal content (14.42 × 10⁶ area units) in comparison with non-inoculated batch (105.99 × 10⁶ area units). Among all batches studied, D. hansenii batch presented the highest area values for esters, alcohols, linear hydrocarbons, ketones, acids and furans; control batch for aldehydes and C. zeylanoides batch for branched hydrocarbons. Therefore, the study showed that every yeast strain produced a specific volatile profile which was also different from that of the control dry-cured “lacón”.     

市售东海鱼鲞生物胺及相关质量指标分析

为研究零售期东海鱼鲞的生物胺潜在风险及生物胺与品质指标的相关性,以浙江地区的4种鱼鲞（鳗鱼、大黄鱼、鲳鱼和马鲛鱼）为研究对象,对理化指标（水分含量、NaCl、pH、TVB-N和POV）、微生物指标（菌落总数）和8种生物胺进行测定分析。结果表明,4类鱼鲞的理化、微生物和生物胺指标各不相同。水分含量为25.6%～59.7%,NaCl含量为3.4%～24.1%,pH为6.08～6.97,TVB-N为7.7～56.4 mg/100 g,菌落总数为3.43～5.67 lg CFU/g,POV为0.04～1.76 g/100 g,其中50%样品超过水产干制品POV限值。鱼鲞样品的主要生物胺为亚精胺、组胺、尸胺和腐胺。15%的样品组胺含量>100 mg/kg,超过FDA和/或欧盟的限量标准,其中黄鱼鯗B4的组胺含量达到了1405.88 mg/kg。全部样品的酪胺含量均<100 mg/kg,符合FDA限量标准。生物胺总量在96.05～2164.64 mg/kg之间,其中15%的样品>1000 mg/kg,超过FDA限量标准。相关分析表明,部分生物胺指标与菌落总数和NaCl含量呈中度或高度相关（P<0.05）,相关系数r分别为0.727～0.975和?0.828～?0.970。综上,东海鱼鯗,包括以非高组胺鱼为原料的产品,可能存在生物胺超标风险及其他质量问题。本研究为鱼鲞类水产干制品的品质评价和安全控制提供了基础数据和参考依据。     

Effects of combined treatment of electrolysed water and chitosan on the quality attributes and myofibril degradation in farmed obscure puffer fish (Takifugu obscurus) during refrigerated storage

The obscure puffer fish (Takifugu obscurus) is underutilized as a food fish. To improve the quality of puffer fish flesh, the fish samples were preserved after treating them with electrolysed water (EW), a combination of EW and chitosan (EW/chitosan), or a combination of EW and carboxymethyl chitosan (EW/CMC). The effects of these treatments were compared by analysing changes in the total viable count of aerobic bacteria, firmness, total volatile basic nitrogen, trimethylamine, pH, the thiobarbituric acid and sensory attributes of the refrigerated puffer fish. Changes in the myofibril length of puffer fish flesh was also studied, which is related to flesh softening. The findings suggest that during storage, EW/chitosan treatment is more effective than both EW and EW/CMC treatments in inhibiting microbial growth and myofibril degradation, and in maintaining the quality of obscure puffer fish flesh. This could extend the shelf life by 50% of the original shelf-life of about 4 days of the fish samples.     

冰温发酵鳜鱼对鱼肉滋味及其生物胺含量的影响

以新鲜鳜鱼为原料,分别在冰温带(-2.5～0℃)和10℃条件下进行低盐自然发酵,研究冰温发酵鳜鱼相对于10℃发酵鱼肉滋味及鱼肉中生物胺含量的变化.分别测定2组发酵鱼肉呈味核苷酸、游离氨基酸、生物胺、pH、微生物、总挥发性盐基氮(total volatile basic nitrogen,TVB-N)等指标,结果表明,冰...     

A non-destructive ammonium detection method as indicator for freshness for packed fish: Application on cod

This paper introduces a non-destructive method for monitoring headspace ammonium as an indicator for changes in the freshness status of packed fish. Electrodes in an aqueous phase in the package monitor changes in the concentration of ammonia produced in/on the packed fish and released in the headspace. The outputs of an ammonium ion-selective electrode (NH₄⁺-ISE) were compared with the volatile amines content of the fish fillets. The method was tested in triplicate with fresh cod fillets stored between −0.5 and 1.9 °C. Changes in the ammonia content of the fish could be monitored in the aqueous phase with the NH₄⁺-ISE. The changes in the NH₄⁺-ISE signal correlated with the content of volatile amines (TVB-N) in the cod fillets. This non-destructive method might be the basis for the development of an intelligent packaging for monitoring freshness of packed fish.     

Analysis of the volatile profile and identification of odour-active compounds in Bayonne ham

The aim of this work was to reliably identify odour-active compounds in dry-cured ham using powerful analysis methods for the volatile fraction. For this purpose, dynamic headspace gas chromatography combined with eight-way olfactometry using a panel of eight sniffers was used. One- and two-dimensional gas chromatography coupled with mass spectrometry and (or) olfactometry were also used. More than 600 compounds from the volatile fraction of dry-cured ham were identified and their biochemical origins are discussed. They covered a wide diversity of structures and chemical functions. Only 29 of them proved odour-active. Comparison of the results of GC–O analysis with those obtained by orthonasal sniffing of the dry-cured ham helped to gain a better understanding of how these substances contributed to the overall aroma of the product. Thus, “Fruity–Floral”, “Green–Vegetable” or “Plastic–Chemical” odours intensively perceived by GC–O have been poorly perceived by orthonasal sniffing. By contrast, “Animal–Meat products” or “Butter–Lactic–Cheesy” odours have been much better perceived by orthonasal sniffing. These results indicate that to understand the interactions between odour-active compounds, experimental doping with carefully selected odour-active compounds will be necessary.     

Volatile fraction of DOP “Castelo Branco” cheese: Influence of breed

“Castelo Branco” cheese is a Portuguese DOP cheese made from raw ewe’s milk coagulated with Cynara cardunculus, ripened for at least 40 days. “Merino da Beira Baixa” pure race is frequently used to produce milk for this cheese, however, exotic races such as Assaf and crusade of these two races are also used. The aim of this work has been to compare the volatile profile and sensory characteristics of DOP “Castelo Branco” cheeses manufactured during winter season with milk of breeds from Merino, Assaf and crusade of these two races and identify volatile compounds that can distinguish these cheeses.     

Volatile profiling of Ficus carica varieties by HS-SPME and GC–IT-MS

Aroma is one of the essential parameters for the evaluation of fruit quality, with volatile components being determinant for this characteristic. During this work, the volatile profile of fresh fruits (pulp and peel) and leaves of Portuguese Ficus carica L. white (“Pingo de Mel” and “Branca Tradicional”) and dark (“Borrasota Tradicional”, “Verbera Preta” and “Preta Tradicional”) varieties were characterised by HS-SPME/GC–IT-MS.     

Olfactometric characterization of aroma active compounds in fermented fish paste in comparison with fish sauce,fermented soy paste and sauce products

Aroma active compounds in commercial fermented fish meat paste product (fish miso), fermented soy paste (soy miso), fish sauce and soy sauces were characterized by using a dynamic headspace method for volatile isolation and GC olfactometry for odor perception. A total of 123 volatile compounds consisting mainly of aldehydes, alcohols, esters, ketones, furans, sulfur and nitrogen-containing compounds, aromatics and acids were consistently identified. A major 16 odor-active compounds were distinguished to contribute as key aroma compounds for the miso and sauce products. Olfactometric and sensory findings clearly differentiated miso products with caramelic, fruity aroma notes, whereas fish sauce products were characterized by ammoniacal, fishy, nutty and cheesy odor note. Soy sauce products, however, were dominated by nutty and cheese aroma. Use of koji for fish miso production was found effective to enhance sweet aroma to the product with a reduction of nutty, meaty and rancid nuance. Principal component analysis employed for statistical interpretations clearly elucidated the relationship among different types of fermented products.     

发酵生产鱼酱油过程中生化特性研究

对鱿鱼加工过程中副产物进行回收利用,不仅提高鱿鱼的经济价值,还可以减少副产物引起的环境污染。本研究采用三种工艺条件利用鱿鱼加工副产物发酵生产鱼酱油,测定了发酵过程中总氮、总酸、氮转化率、pH值、氨基态氮、挥发性盐基氮(T-VBN)和蛋白酶活的变化情况,并对产品进行了感官评价。结果表明,发酵过程中总氮、氮转化率、氨基态氮和T-VBN不断增加,而pH值、总酸和蛋白酶活在发酵的不同阶段呈现不同的变化趋势,并且获得的鱼酱油风味鲜美,没有任何不良风味。     

Barcode High Resolution Melting (Bar-HRM) analysis for detection and quantification of PDO “Fava Santorinis” (Lathyrus clymenum) adulterants

Legumes considered as one of the most important crops worldwide. Due to high price as a PDO product, commercial products of “Fava Santorinis” are often subjected to adulterations from other legume products coming from other Lathyrus or Vicia and Pisum species. Using plant DNA barcoding regions (trnL and rpoC) coupled with High Resolution Melting (Bar-HRM) we have developed a method allowing us to detect and authenticate PDO “Fava Santorinis”. Bar-HRM proved to be a very sensitive tool able to genotype Lathyrus and its closed relative species and to detect admixtures, being sensitive enough to as low as 1:100 of non-“Fava Santorinis” in “Fava Santorinis” commercial products. In conclusion, Bar-HRM analysis can be a faster, with higher resolution and cost effectiveness alternative method to authenticate PDO “Fava Santorinis” and to quantitatively detect adulterations in “Fava Santorinis” with other relative commercial “Fava” food products.