Effect of Linalool and Piperine on Chicken Meat Quality During Refrigerated Conditions

This study was conducted to evaluate the effect of bioactive compounds (BACs): linalool (LIN) and piperine (PIP) on chicken meat characteristics. The meat was treated with 500, 1000 ppm of BACs, vacuum packaged and stored at 4 °C for 8 days. Physicochemical characteristics, lipid oxidation (thiobarbituric acid reactive substances, TBARS), microbiological status, and sensorial (electronic-nose based) properties were investigated. Both BACs significantly increased the redness (a*) and chroma (C*) values in meat compared to increased lightness (L*) and higher TBARS in control. Although both BACs showed overlapping aroma profile, the E-nose was able to distinguish between the different meat groups. LIN with various dilution ratios, particularly 1:10 (v:v), showed in vitro growth inhibition against Escherichia coli, Staphylococcus aureus, Salmonella Typhimurium, and Bacillus cereus, concomitantly Listeria monocytogenes required 1:80 (v:v) to be inhibited, and no inhibition was detected for Pseudomonas lundensis. In contrast, PIP at different dilutions did not exhibit inhibitory activity. Regarding aerobic mesophilic counts (AMC), less than 7 log CFU g−1 were recorded except for control showing higher log. Both BACs have potential to improve quality characteristics and increase the shelf life of meat and meat products

Different Sequence of High-Hydrostatic Pressure and Mild-Heat Treatment on the Colour and Sensory Characteristics of Strawberry Puree

The effect of high pressure processing (300 and 600 MPa) combined with mild heat treatment (55 and 75 8C) on the colour parameters, anthocyanin content, and sensory characteristics of strawberry puree were examined after the treatments and 2 weeks of cold storage at 2 and 15 8C. As on an industrial scale the simultaneous implementation of these treatments remains a challenge, the HHP and heat treatments were carried out consecutively in different sequences. The colour parameters and the anthocyanin content did not change significantly due to the treatments, but decreased during cold storage, at 15 8C storage the changes were more intensive than at 2 8C. Regarding the sensory test results, the different sequence of the 600 MPa-75 8C combined treatments is not detectable even after 2 weeks of storage at 15 8C, but in case of 300 MPa-55 8C, the enzyme inactivation is probably not sufficient enough as differences between the samples were detected

Chemical composition and antimicrobial activity of Nigella sativa crude and essential oil

Nigella sativa L. (black cumin) is well known for its benefits in the field of traditional medicine. The aim of this study was to determine the chemical composition and investigate the antimicrobial activity of cold pressed oil (CO) and essential oil (EO) of Nigella sativa L. on food-borne pathogenic and spoilage bacteria. The microdilution method was used to determine the minimal inhibitory concentration (MIC) of Nigella sativa crude oil (CO) and essential oil (EO) against 4 Gram-positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, and Listeria monocytogenes) and 3 Gram-negative (Salmonella Hartford, Pseudomonas aeruginosa, and Escherichia coli) foodborne pathogenic and spoilage bacteria occurring in food products. Total fatty acid composition of CO was analysed by GLC, while the EO was analysed by GC-MS to detect its active compounds. The results showed that the major fatty acid of CO was palmitic acid (C16:0), as saturated fatty acid, however, linoleic acid (C18:2) was the main unsaturated fatty acid. The major compounds of the EO were p-cymene and thymoquinone. The inhibition on all tested bacteria of EO was 10 times higher than of CO, and the lowest concentration value was observed in case of Bacillus subtilis (0.003%). Hence, results reinforce the ambition to apply Nigella sativa oils in food as natural preservative

Activity of natural antimicrobials against Zygosaccharomyces lentus

Zygosaccharomyces lentus is a significant, recently discovered new osmophilic spoilage yeast, capable of growth at low temperatures. It is remarkably resistant to commonly used preservatives above the legally permitted levels. Therefore, antimicrobial effect of chitosan, cinnamic acid, carvacrol and cymene as new preservatives was tested against Z. lentus in phosphate buffered saline at pH 7.3. Z. lentus was resistant to the antimicrobial action of chitosan (0.5 and 1.0%) and cinnamic acid (0.5–2.0 mM) but was sensitive to the biocidal action of 1.5 and 2.0 mM cymene and 1.5 and 2.0 mM carvacrol in pH-neutral buffer. Further work would need to be done to check the sensitivity of this organism to these compounds at other pH values and temperatures

Studies on the growth of Listeria monocytogenes and Lactobacillus casei in mixed cultures

The effect of lactic acid production of Lactobacillus casei on the growth characteristics of Listeria monocytogenes was examined in milk. The effect of temperature (7, 13, 20 °C) and the co-ratios with Lb. casei at different cell count ratios (10:1, 100:1, 10 000:1) on the growth of L. monocytogenes were studied. At a 10 000:1 ratio induction of an early stationary phase of L. monocytogenes occurred. An exponentially decreasing correlation was observed between the logarithmic maximum population of L. monocytogenes and the initial log counts of lactobacilli. The Baranyi model was fitted to the obtained growth curves. The Baranyi equation provided good fit for the lag and exponential phase of L. monocytogenes. According to our observations, pH decrease does not seem to be the main factor of early stationary phase induction of L. monocytogenes in milk

Chitosan inactivates spoilage yeasts but enhances survival of Escherichia coli 0157:H7 in apple juice

AIMS:  To develop new measures for controlling both spoilage and pathogenic micro-organisms in unpasteurized apple juice using chitosan. METHODS AND RESULTS:  Micro-organisms were isolated and identified from apple juice treated or untreated with chitosan using enrichment, selective media, microscopy, substrate assimilation patterns and ribosomal DNA profiling. Chitosan (0·05–0·1%) delayed spoilage by yeasts at 25°C for up to 12 days but the effect was species specific: Kloeckera apiculata and Metschnikowia pulcherrima were inactivated but Saccharomyces cerevisiae and Pichia spp. multiplied slowly. In challenge experiments at 25°C, total yeast counts were 3–5 log CFU ml−1 lower in chitosan-treated juices than in the controls for 4 days but the survival of Escherichia coli O157:H7 was extended from 1 to 2 days; at 4°C, chitosan reduced the yeast counts by 2–3 log CFU ml−1 for up to 10 days but survival of the pathogen was prolonged from 3 to 5 days. The survival of Salmonella enterica serovar Typhimurium was unaffected by chitosan at either temperature. CONCLUSIONS:  The addition of chitosan to apple juice delayed spoilage by yeasts but enhanced the survival of E. coli O157:H7. SIGNIFICANCE AND IMPACT OF THE STUDY:  The results suggest that the use of chitosan in the treatment of fruit juices may potentially lead to an increased risk of food poisoning from E. coli O157:H7

Efficacy of disinfectants against static biofilms on stainless steel surface

Inactivation and removing efficiency of disinfectants (Descosal and Domestos) was tested against Pseudomonas aeruginosa and Candida albicans and their biofilms (2 and 72 h, 3, 7 and 14 days old, respectively). The survival of microbes was studied by pour plating and impedimetry, and the attachment by epifluorescent microscopy.In the surface test, both disinfectants were effective against both test organisms with no significant difference in their efficiency. The decreasing detection times during impedimetric measurements showed higher resistance of the older Ps. aeruginosa biofilms. Both disinfectants tested were fungicidal against C. albicans and bactericidal against Ps. aeruginosa but for biofilm removal Domestos was more efficient

Preliminary studies on developing a new method for quality control of tomato purée

In the industrial practice Howard mould count (Howard, 1911) is used for the estimation of mould contamination of foods. It was developed originally for the investigation of mould contamination of tomato purée. It is also used nowadays for quality control purposes for other food products as well. Recently this constitutes the basis of the acceptance of the finished products in international trade. This technique demands experts with a lot of practice and morphological proficiency. The investigation makes use of eyes and so the tiredness of the investigator can cause uncertainties.The possibility of other methods for the determination of mould contamination of tomato purée was investigated to replace the Howard method. The NIR technique — as a rapid, non-destructive, reagentless and accurate method — was anticipated as a suitable method for the mentioned purpose. Canned tomato purée had been allowed to become mouldy then the sample was blended with non-mouldy samples in different ratio, so a series of tomato purées containing known amounts of mouldy purée was prepared. Howard mould counts and ergosterol content — another mould contamination relating value — was used as reference for NIR calibration.At quantitative investigation better results were obtained using ergosterol values. The best correlation coefficient (R=0.93) and the smallest standard error of calibration (SEC=0.008 mg g−1 ergosterol) was achieved with triangular smoothing and second derivation of the spectra. At qualitative investigation Polar Qualification System (PQS) was used. Clusters between samples with low and high ergosterol levels could be separated