Potravinarstvo Slovak Journal of Food Sciences
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The qualitative parameters of potato tubers in dependence on variety and duration of storage
Get PDFThe qualitative parameters of the potatoes tubers may be significantly changed depending on the variety, group of ripening, way, regime, and duration of storage. So, these researches aimed to define the influence of the variety characteristics and duration storage on qualitative parameters of tuber potatoes. Five potato varieties of two ripening groups were used for testing: medium-early (Satina, Red Lady, Mozart) and medium-ripe (Aroza, Sifra). The chemical properties such as dry matters (DM), starch, sugars (total and reducing), crude protein (CP), ascorbic acid (AA), and nitrates content were determined before and after 2, 4, and 6 months of storage. DM lost during the storage of potato tubers, especially during the period from 4 to 6 months. The group of ripening did not influence this index. Potato tubers of all varieties had high starch content and the duration of storage had a light effect on the level of its losses. In the medium-early group, maximum changes of starch were 1% but in the medium-ripe – 1.9%. A strong effect on the quantities of total sugars (TS) had varietal characteristics of the potato but a group of ripening had light influence. The highest content of sugars was Satin (0.65%) and the smallest Sifra (0.22%) and Mozart (0.23%). After 6 months of storage content of TS depending on the variety increased from 2 till 5 times, while the reducing sugars (RS) increased at least five times and at the end of storage were 0.4% to 0.65%. The amount of AA and its losses during storage depended on the variety. The relative losses during the total storage period were 21.9% in the medium-early group and 28.1% in the medium-ripe. Influence ripening group on level changing AA was not detected. Nitrates' content did not exceed the maximum permissible level (250 mg.kg-1). Their quantities after 6 months were 47 – 61 mg.kg-1
Wheat bran stabilization and its effect on cookies quality
Get PDFWheat bran are widely used as a source of dietary fiber with enhanced health benefits. However, its hight application level in bakery products caused lower quality of these products (eg. reduced volume and increased hardness of product). Different mechanical, physical or chemical methods are used for modification of wheat bran physicochemical properties. Wheat bran obtained from two wheat variety was used to evaluate the effect of bran stabilization process on qualitative properties of baked goods. Stabilization was performed using hot air and microwave heating. Threated and unthreated wheat bran were blended with wheat flour at 5, 10 and 15% substitution level. Influence of bran addition on rheological properties was evaluated using Mixolab 2. Stabilized wheat bran increased water absorption up to 11.7% (hot air stabilization) and 11.9% (microwave stabilization), respectively. Hot air stabilization of wheat bran improved heat resistance of dough proteins during mixing and the stability of hot gel during heating. Stabilization process of wheat bran using both methods also increased the volume and spread ratio values of enriched cookies. Cookies incorporated with hot air treated bran were significantly softer than cookies contained raw bran. Sensory evaluation showed that addition of stabilized bran improved the shape and taste of cookies. Additionally, it was concluded that the most acceptable cookies were obtained at 5% addition level of bran stabilized using microwave heating
Bioactive compounds evaluation in different types of Czech and Slovak honeys
Get PDFHoney contains important bioactive compounds (enzymes, phenolic compounds, vitamins, and minerals) with several positive health effects for humans. In the study six types of honey (acacia, rape, floral, multi flower, forest, and honeydew honeys), of Czech and Slovak origin, were evaluated for bioactive compounds by means of color, polyphenols and antioxidant capacity analyses. The brightest color of honeys, the lowest values measured spectometrically, had acacia and rape honeys, followed by floral, and darker multi flower and forest honeys, and honeydew honeys. Polyphenols (PP) amount, determined by spectrophotometric method with Folin-Ciocalteu reagent, was highest for the darkest honeydew honeys, followed by multi flower and forest honey, brighter floral honeys, and rape and acacia honey. Honeys polyphenols were in the range from 54.0 to 254.2 mg GAE.100g-1. The total antioxidant capacity (TAC) was analyzed by spectrometric methods with ABTS and DPPH reagents. Antioxidant capacity values are in agreement with the PP contents order. They were highest also for honeydew honeys (59.2 - 89.6 and 73.1 - 118.7 mg TE.100g-1), followed by multi flower (66.0 and 56.7 mg TE.100g-1) and forest honey (56.0 and 49.1 mg TE.100g-1), then floral honeys (33.0 - 49.2 and 27.8 - 38.7 mg TE.100g-1) and the lowest values for rape (19.0 and 28.1 mg TE.100g-1) and acacia (15.5 and 11.3 mg TE.100g-1)honey. A positive correlation between color, PP amount and TAC was evaluated for analyzed honeys. Darker honey samples showed higher values of phenolic compounds and antioxidant potential, therefore they belong to the honey types with higher amount of bioactive compounds such as antioxidants
Risk associated with foreign bodies in food in the Czech Republic
Get PDFThe food safety is the main concern of the politicians and inhabitants in whole Europe. According the currently valid legislation the food should be save. The food should be safe from all aspects: chemical, microbiological, physical and radiological. Physical hazard/foreign body in food is perceived by public as something to be very simply solved by food business operators. However, foreign body is the biggest single source of customer complaints received by food business operators, retailers and enforcement authorities. In even the best-managed processes, the accidental presence of unwanted items could occasionally occur. Foreign body in food is believed to be a matter of concern to all food business operators. However, the level of inclusion of physical hazards by Czech food business operators in the hazard analysis is still low. Consumers experience with foreign bodies in food or even health problems caused by foreign bodies is continuing high level. Consumer complaints regarding foreign bodies reported from food products should be an important question for the food industry that should implement corrective actions to prevent such unwanted events
Application of electronic nose for determination of Slovak cheese authentication based on aroma profile
Get PDFElectronic nose with sensors is used in many industries and for various applications such as quality control, process monitoring, shelf life evaluation, origin or authenticity assessment. The aim of this work was to investigate the electronic nose with FID detectors applicability for characterization of steamed cheese and for the assessment of steamed cheese quality decay during storage. Samples of smoked and unsmoked steamed cheese varieties from 5 Slovak enterprises concerning different regions of Slovakia were analysed. Data from aroma profiles were processed by statistical technique PCA. Compounds like acetaldehyde, 1-propanal, propanoic acid, ethyl hexanoate, furfural, butan-2-one, isovaleric acid, 1-hexanol or α-pinene were determined as significant flavours in fresh steamed cheese samples. In the current study, no significant differences in aroma profiles between fresh and stored cheese samples were confirmed. Thus, differences in main odour substances composition of steamed cheese varieties, obtained from various producers in several geographic regions of Slovakia, were minor
Thermo-degradative changes of rapeseed and sunflower oils during deep-frying French fries
Get PDFThe purpose of this study was to investigate changes in TPCs, acid value and peroxide value as well as fatty acids composition in edible oils during french fries production. Lower TPCs content was found in rapeseed oil (3.3%) and the threshold (24%) was achieved on the fourth day. The total time for the deterioration of deep-frying rapeseed oil was 23½ hours. On the contrary, in fresh sunflower oil at the first day was TPCs content 5.5% and the limit of 24% was reached on the third day. The total time for the deterioration of deep-frying sunflower oil was 17½ hours. The results indicated significant differences (<0.05) in TPCs content between rapeseed and sunflower oils during deep-frying process. At the beginning of deep-frying French fries in rapeseed oil, the acid number was 0.374 mg KOH.g-1 and 1.271 mg KOH.g-1 at the fourth day of deep-frying. The measured peroxide value was 4.3 mEq O2.kg-1 at the beginning and at the end of deep-frying 10.5 mEq O2.kg-1. The initial peroxide and acid values were higher in sunflower oil compared with rapeseed oil, respectively. It should be note, then the acid values and peroxide values, respectively, in the two fresh oils used in this study were below the limit of refined oil according to Slovak legislation (peroxide value - not more than 10 mEq O2.kg-1, acid value - not more than 0.6 mg KOH.g-1). However, detected values varied during deep-frying process. Monounsaturated fatty acids were predominantly observed in fresh rapeseed oil (61.22%) wherever in sunflower oil they were much lower (29.77%). A slight increase of MUFA was found in both oils. The initial content of saturated fatty acids in rapeseed oil was 6.94%, in fresh sunflower oil was observed slightly higher content of SFA (10.37%). The major groups of fatty acids in fresh sunflower oil were polyunsaturated fatty acids (PUFA) which have in principle a significant effect on oil deterioration. A slight decrease of PUFA was observed in both oils throughout the frying period. The content of PUFA was reduced by about 9.42% in rapeseed oil and by 10.8% in sunflower oil. The initial content was 28.14% and 58.91%, respectively
Effect of sous-vide heat treatment on the phthalic acid esters content in meat
Get PDFThe aim of the study was to monitor the migration of the phthalic acid esters dibutyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) from packaging to meat wrapped in plastic when heat treated by sous-vide method. A heat treatment temperature of 80 °C was used for 4 and 8 hours with reheating at 80 °C for 1 hour. The average DBP and DEHP concentrations in meat ranged from 2.24 to 4.66 mg.kg-1 and 2.29 to 10.35 mg.kg-1 of the original sample, respectively. The average DBP and DEHP concentrations found in plastic packaging ranged from 3.06 to 6.37 µg.g-1 and 5.70 to 7.83 µg.g-1 of plastic, respectively. The average concentrations of DBP in water bath range from 16.25 to 23.38 µg.l-1, while the average concentrations of DEHP in water bath were determined between 0.24 and 1.82 µg.l-1. The above results were compared with the results measured at sous-vide treatment temperature of 70 °C for 4 hours, 8 hours, and with 1 hour of reheating. The average concentrations of DBP and DEHP in all meat samples exceeded the specific migration limits of both phthalates (0.3 mg.kg-1 for DBP and 1.5 mg.kg-1 for DEHP)
Increasing of selenium content and qualitative parameters in tomato (Lycopersicon esculentum Mill.) after its foliar application
Get PDFThe effect of genotype and selenium foliar biofortification in the form of an aqueous solution of sodium selenate on the content of total carotenoids, vitamin C, total polyphenols and selenium content in the tomato fruits was studied. Field experiment was held in the Botanical garden of the Slovak University of Agriculture in 2016. Seven determinant varieties of tomato in the two variants were observed. The results of experiments show that treatment of plants with the dose of Se concentration (150 g Se.ha-1) at the flowering stage significantly increased the total Se content in the in tomato fruits. Foliar application of selenium had a positive effect on the increase of total polyphenol. The influence of Se biofortification on the content of vitamin C and carotenoids was not detected. Selenium foliar fertilization in dosage 150 g.ha-1 is suitable way of tomato fruits enriching in polyphenols, without negative effect on other antioxidants content
Alternaria SPP. in food commodities of Slovak origin: occurrence and mycotoxin production abilities
Get PDFVarious food commodities of Slovak origin were analysed for the occurrence of Alternaria species-groups. Totally we analysed 14 samples of grapes, 3 samples of barley, 2 samples of wheat, 17 samples of fruit, vegetable and fruit-vegetable juices, 6 samples of red kuri squash with macroscopically visible infection. Mycological analyses were performed by using plate dilution method, method of direct placing of berries or grains on the plates with dichloran, rose bengal and chloramphenicol agar or by direct inoculation by mycological needle to the identification medium (potato-carrot agar). In all grape, barley, wheat and squash samples the presence of representatives of this genus was detected (100% isolation frequency). In juices, 41% of the samples were positive for their occurrence. The highest relative density of Alternaria isolates was found in grape samples (87%). All detected strains were segregated into four morphological species-groups: A. alternata, A. arborescens, A. infectoria and A. tenuissima. The most dominant species-group in grapes was A. arborescens, in barley and wheat A. tenuissima, followed by A. alternata, in juices only A. alternata and A. arborescens species-groups were detected and isolates of squashes were not classified to the species-groups. Randomly selected 67 isolates were analysed for the ability to produce mycotoxins alternariol (AOH), alternariol monomethylether (AME) and altenuene (ALT) by means of thin-layer chromatography. Of all tested isolates, AOH production was most frequently reported (70% of tested isolates). AME was produced by 60% and ALT by 49% of tested isolates. The largest share of the productive strains originated from the squashes, where all tested isolates produced ALT and AOH, followed by isolates of juices. From the viewpoint of individual species-groups, A. arborescens isolates and Alternaria spp. appeared to be the most productive in all mycotoxins tested
Influence of temperature, humidity, and diluent type on survival of Salmonella spp. on the surface of raw tomatoes
Get PDFTomatoes are an important commodity, placing fourth among most popular vegetables in the U.S. However, fresh tomatoes lack a final pathogen elimination step and have been implicated in Salmonella-related outbreaks. The purpose of the study was to evaluate survival of Salmonella post-drying in three diluents on the surface of green mature tomatoes at 12 °C or 25 °C. Additionally, low and high air relative humidity influence was evaluated at 25 °C on pathogen survival. A five Salmonella rifampin-resistant strain cocktail was double-washed in buffered peptone water (BPW) and resuspended in 0.1% peptone, BPW, or fresh tomato serum. Inoculum (0.1 mL) was allowed to dry on the surface of tomatoes. For study I, tomatoes were placed in 12 °C and 25 °C incubators with no humidity control and sampled on days 0, 1, 3, and 5. For study II, tomatoes were sampled on days 0, 1 (biosafety hood storage) and on day 5 after storage in two 25 oC incubators (low and high relative humidity). Salmonella was recovered from tomatoes (20 mL BPW) and plated (TSA-rif80, 37 °C, 48 hours). Post-drying Salmonella counts (ca. 4.5 - 5.0 log10 CFU.mL-1) remained at 4.03 and 4.40 log10 CFU.mL-1 in serum after 5 days of storage at 12 °C and 25 °C, respectively. Conversely, corresponding counts in BPW and peptone were lower at ca. 1.4 to 1.8 and 2.2 to 2.8 log units at 12 °C and 25 °C, respectively. At low humidity, post-drying Salmonella counts showed highest decline for peptone (final 1.98 log10 CFU.mL-1) compared to BPW (3.79 log10 CFU.mL-1) and tomato serum (4.75 log10 CFU.mL-1) on day 5. Counts declined rapidly to 0.03, 0.56, and 0.44 log10 CFU.mL-1 for peptone, BPW, and tomato serum, respectively, at high humidity on day 5. To summarize, it was shown that increased solutes have protective effect on Salmonella in desiccated conditions, while high humidity storage causes accelerated death of stationary culture within five days storage period