Effects of rosemary and sage tea extracts on the sensory,chemical and microbiological changes of vacuum‐packed and refrigerated sardine (Sardina pilchardus) fillets

The effect of the natural antioxidants and antimicrobials from ethanol extracts of rosemary and sage tea on sensory, chemical [Total volatile basic nitrogen (TVB‐N), thiobarbituric acid reactive substances (TBARs), peroxide value (PV), free fatty acid (FFA)] and microbiological (total viable count‐TVC and total coliform count) changes of vacuum‐packaged sardine (Sardina pilchardus) fillets stored at 3 ± 1 °C was investigated for 20 days. The fish fillets were divided into three groups: untreated group (control, C) and treated groups that were immersed in a 1 L of distilled water containing 10 g rosemary (R group) or sage tea (S group) extracts for 4 min. The shelf life of sardine fillets was found to be 13 days for control (C), 20 days for R and S groups according to sensory assessment results, whose corresponded microbiological assessment showed a shorter shelf life (5 days for C group, 9 for R and S groups). At the end of storage period, TBARs values were 0.98 mg malonaldehyde kg^?1 for C group, 0.66 malonaldehyde kg^?1 for R group and 1.44 mg malonaldehyde kg^?1 for S group. Microbiological results showed that natural compounds from rosemary and sage tea resulted in a lower bacterial growth in fish fillets during the storage period.     

The effect of ultrasonic treatments on turbidity,microbial load,and polyphenol oxidase (PPO) activity of plum nectar

This study examined the effects of ultrasound on several quality parameters of plum nectars, such as turbidity, microbial load, PPO activity, phenolic content, and physicochemical quality. The ultrasonic treatment was applied to the plum nectars at different treatment temperatures (40, 50, 60, and 70?°C) and durations (2.5, 5, 7.5, and 10 min). Ultrasound processing caused a significant increase in the turbidity level and stability of the plum nectars, which were correlated with increases in treatment temperature and duration. Similar effects were also observed in reduction of microbial load. Ultrasonic treatments at 7.5 min at 60?°C and 5 min at 70?°C reduced the total yeast and mold counts (<?1 log cfu/mL). The total mesophilic-aerobic microorganism (TMAB) count was also reduced by up to 2 log. The maximum inactivation of polyphenol oxidase (PPO) was ~46?% at 70?°C. No dramatic trends were observed for the pH, brix, and the total phenolic compound content of the plum nectar, while the flavonoid content dramatically increased. The ultrasonic treatment caused a slight positive color change by increasing the L* value of the plum nectars. In conclusion, the ultrasonic treatment was important process for increasing the turbidity quality and for inactivation of yeasts and molds, but it was not effective at inactivating the PPO enzyme.     

Quality Properties,Fatty Acids,and Biogenic Amines Profile of Fresh Tilapia Stored in Ice

This work determines quality properties and fatty acids content of Nile tilapia (Oreochromis niloticus) stored in ice for 21 d. The quality properties consist of thiobarbituic acid (TBA), total volatile basic nitrogen (TVB‐N), trimethylamine (TMA), and microbiological analysis (total viable count (TVC), total coliform, Salmonella and Staphylococcus aureus) and determination of biogenic amines content (histamine, cadaverine, putrescine, spermine, spermidine, 2‐phenylethylamine, agmatine, tyramine, and ammonia). Moreover, the fat, moisture, and ash composition as well as fatty acids profile have also been analyzed. The TBA, TVB‐N, and biogenic amines analysis showed rather low levels of spoilage even after 21 d of storage. The microbiological analysis, however, showed that tilapia was unsuitable for consumption after just 10 d. The fat, ash, moisture, and fatty acids profile analysis showed that tilapia is not a good source of n?3 fatty acids. The research indicated that the microbiological analysis was the best method to establish spoilage of tilapia stored in ice, of all analytical methods performed in this study.     

Volatile Compounds and Sensory Properties in Various Melons,Which were Chosen from Different Species and Different Locations,Grown in Turkey

Gas chromatography coupled to mass spectrometry using a static head space technique was applied to analyze the volatile aromatic compounds of various melons collected from different locations in Turkey. Some physicochemical and sensory analyses were also made. A total of 33 volatile compounds were identified. Differences in the physicochemical and sensory properties of various Turkish melon samples were observed. The multivariate analyses by the volatile compounds separated the three varieties into groups successfully. The most abundant volatile compounds as mean value in all melon varieties were ethyl acetate (22.10%), acetaldehyde (13.65%), and ethanol (23.25%). The results showed that Cantaloupe melons were more preferred by panelists, which had relatively high levels of esters being responsible for strong fruit flavor, like melon, as well as high total soluble solid content and low titratable acidity compared with Inodorus and Simama.     

The Influences of Natural Zeolite (cliptinolite) on Ammonia and Biogenic Amine Formation by Foodborne Pathogen

The influence of natural zeolite on biogenic amines (BAs) and ammonia (AMN) production by eight common gram negative and positive foodborne pathogens (FBP) were investigated in histidine decarboxylase broth (HDB). Presence of 1% zeolite in the HDB resulted in significantly higher AMN production. Histamine (HIS) production by gram positive bacteria was as low as 0.5 mg/L, whereas Escherichia coli produced 18.96 mg/L of HIS. The use of zeolite also significantly suppressed HIS accumulation by E. coli, Pseudomonas aeruginosa, S. paratyphi A (P < 0.05), although zeolite addition stimulated HIS production by K. pneumonia and Aeromonas hydrophila. The range of tyramine (TYR) production by gram positive bacteria was 1.19 and 4.06 mg/L for Enteroccus faecalis and Listeria monocytogenes respectively. The results of study showed that the effect of zeolite on BAs and AMN production was dependent on bacterial strains, as well as zeolite concentrations used. Practical Application: Natural zeolites are the main absorptive, low-cost material used in agriculture and industry. Although the effect of zeolite on ammonia formation in some industrial systems is well known, there is limited information regarding the impact of zeolite on biogenic amine (BA) production by foodborne pathogens. The data presented in this article will help us to understand the impact of natural zeolite on BA and ammonia production by eight common foodborne pathogens.     

Biogenic Amine Formation and Microbiological Quality of Anchovy (Engraulis encrasicolus) Treated with Lavender and Lemon Balm Ethanol Extracts

Biogenic amine formation and bacterial growth of vacuum‐packed European anchovy treated with 1% lemon balm (LB) or lavender (LD) ethanol extracts was investigated. The treated samples were stored at 2 ± 1 °C for 11 d and analyzed for biogenic amines, total viable count, fecal coliform count, and lactic acid bacterial count. The analyses were done on 0, 4, 7, 9, and 11 d of storage. Both LB and LD extracts proved effective in reducing most biogenic amines, with histamine reduced by 3‐fold compared to control. The calculated biogenic amine index showed that LB extract was the most effective in inhibiting the biogenic amine formation. The reduction in total viable count was low and the bacterial contamination reached more than 7 log cfu/g at the end of the storage period for all the samples. Moreover, the reduction in fecal coliform and lactic acid bacterial count by LB and LD extracts was below 1 log cfu/g. Treatment of European anchovy with LB and LD extracts proved to be a very effective preservation technique to reduce the biogenic amine formation and lower the risk of histamine fish poisoning but is not effective in reduction of bacterial load. Consequently, LB and LD extracts could be used to reduce the biogenic amine formation which provides additional safety prior to spoilage for histamine sensitive fish species.     

Antimicrobial Activity of Lactoperoxidase System Incorporated into Cross-Linked Alginate Films

ABSTRACT:  In this study, the antimicrobial effect of lactoperoxidase (LPS) incorporated alginate films was investigated on Escherichia coli (NRRL B-3008), Listeria innocua (NRRL B-33314), and Pseudomonas fluorescens (NRRL B-253) in presence of different concentrations of H₂O₂ (0.2, 0.4, and 0.8 mM) and KSCN (1, 2, and 4 mM). The incorporation of 70 nmol ABTS/min/cm² LPS into alginate films gave 0.66 to 0.85 nmol ABTS/min/cm² enzyme activity at 0.2 to 0.8 mM H₂O₂ concentration range. The antimicrobial activity of LPS system on target bacteria changed according to the concentrations of KSCN and H₂O₂. The growth of all tested bacteria was prevented for a 6-h period by applying LPS system in presence of 0.4 or 0.8 mM H₂O₂ and 4 mM KSCN. At 0.8 mM H₂O₂ and 4 mM KSCN, the LPS system also inhibited growth of L. innocua and P. fluorescens for a 24-h incubation period, whereas E. coli growth could not be inhibited for 24 h under these conditions. At 0.2 mM H₂O₂ and 1 to 4 mM KSCN, a considerable inhibitory effect was obtained only on P. fluorescens . The decreasing order of the resistance of studied bacteria to LPS system is as follows: E. coli , L. innocua , and P. fluorescens . The developed antimicrobial system has a good potential for use in meat, poultry, and seafood since alginate coatings are already used in these products. Further studies are needed to test the LPS incorporated edible films in real food systems.     

A robust optimization method for label noisy datasets based on adaptive threshold: Adaptive-k

The use of all samples in the optimization process does not produce robust results in datasets with label noise. Because the gradients calculated according to the losses of the noisy samples cause the optimization process to go in the wrong direction. In this paper, we recommend using samples with loss less than a threshold determined during the optimization, instead of using all samples in the mini-batch. Our proposed method, Adaptive-k, aims to exclude label noise samples from the optimization process and make the process robust. On noisy datasets, we found that using a threshold-based approach, such as Adaptive-k, produces better results than using all samples or a fixed number of low-loss samples in the mini-batch. On the basis of our theoretical analysis and experimental results, we show that the Adaptive-k method is closest to the performance of the Oracle, in which noisy samples are entirely removed from the dataset. Adaptive-k is a simple but effective method. It does not require prior knowledge of the noise ratio of the dataset, does not require additional model training, and does not increase training time significantly. In the experiments, we also show that Adaptive-k is compatible with different optimizers such as SGD, SGDM, and Adam. The code for Adaptive-k is available at GitHub.