Ksenija Marković

Rapid honey characterization and botanical classification by an electronic tongue

In this paper a commercial electronic tongue (αAstree, Alpha M.O.S.) was applied for botanical classification and physicochemical characterization of honey samples. The electronic tongue was comprised of seven potentiometric sensors coupled with an Ag/AgCl reference electrode. Botanical classification was performed by PCA, CCA and ANN modeling on 12 samples of acacia, chestnut and honeydew honey. The physicochemical characterization of honey was obtained by ANN modeling and the parameters included were electrical conductivity, acidity, water content, invert sugar and total sugar. The initial reference values for the physicochemical parameters observed were determined by traditional methods. Botanical classification of honey samples obtained by ANN was 100% accurate while the highest correlation between observed and predicted values was obtained for electrical conductivity (0.999), followed by acidity (0.997), water content (0.994), invert sugar content (0.988) and total sugar content (0.979). All developed ANN models for rapid honey characterization and botanical classification performed excellently showing the potential of the electronic tongue as a tool in rapid honey analysis and characterization. The advantage of using such a technique is a simple sample preparation procedure, there are no chemicals involved and there are no additional costs except the initial measurements required for ANN model development.

Correlation of trans-Lycopene Measurements by the HPLC Method with the Optothermal and Photoacoustic Signals and the Color Readings of Fresh Tomato Homogenates

The trans-lycopene content of fresh tomato homogenates was assessed by means of the laser photoacoustic spectroscopy, the laser optothermal window, micro-Raman spectroscopy, and colorimetry; none of these methods require the extraction from the product matrix prior to the analysis. The wet chemistry method (high-performance liquid chromatography) was used as the absolute quantitative method. Analytical figures of merit for all methods were compared statistically; best linear correlation was achieved for the chromaticity index a* and chroma C*.

Development and Application of Quality Index Method Scheme in a Shelf-Life Study of Wild and Fish Farm Affected Bogue (Boops boops, L.)

UNLABELLED Quality index method scheme was developed for raw bogue (Boops boops) and evaluated it in a shelf-life study, using samples from wild fish aggregations at fish farms (BF) and from area not influenced by the fish farms (BW). Different environment influenced the shelf life of bogues; thus the maximum ice storage, evaluated from cooked samples, was found to be 17 d for BF and 12 d for BW. The calculated quality indexes (QIs) evolved linearly with storage time on ice (QI(BF) = 0.968x + 0.583, R(2) = 0.947, Std. Err. Est. = 1.41; QI(BW) = 1.212x + 0.474, R(2) = 0.972, Std. Err. Est. = 0.95). The multivariable analysis was used to identify the most effective variables during spoilage evolution. The sum of all demerit points showed higher correlation (R > 0.99) then any single parameters itself, indicating that the individual parameters could not replace the usage of 20 demerit points QIM scoring scheme in sensory assessment. The impact of farming cages was observed in fat (BF > 19%; BW < 2%) and water content (BF = 55%; BW = 77%) of bogues, but also in pH, dielectric properties, thiobarbituric acid index, and volatile amine changes. High correlations of these parameters with storage time and sensory assessment were observed. PRACTICAL APPLICATIONS The catch landings of bogue make this species very important in the Mediterranean fishery production. The effect of finfish farms makes individual fish samples of this species different in size and chemical content, thus changing the rate and in which their postmortem changes occur. The practical use of the article is a new developed and species adopted descriptive scheme for bogue, ready to use for scientific and industrial freshness assessment providing the information on fish quality and its remaining shelf life in ice, taking into account the environmental conditions such as catching ground.

Comparison of spectrophotometric and HPLC methods for determination of carotenoids in foods

This report is aimed at intra-laboratory and inter-laboratory comparison of the results obtained during spectrophotometric and HPLC analyses of lycopene, β-carotene and total carotenoids in tomato products and yellow maize flours/grits. Extensive statistical analyses are performed in order to identify the main sources of uncertainties which may occur when using: (i) different techniques/methods/approaches in the same/different laboratories, in various food samples, and (ii) to indicate the facts/conditions under which the biases between results may remain unidentified after applying statistical testing. Our data points to the inertness of t-test to detect significance of differences, particularly at low R values: in general, the higher correlation coefficient, the higher is sensitivity of statistical testing, especially of the paired t-test. Therefore, simple deviation of relationship line slope from unity could be used as additional evaluation parameter. This adds to reliable and objective quality assurance of foods in regard to carotenoids.

Ultratraces of carotenes in tomato purées: HPLC-TLS study

The present study was designed to provide information about (i) the profile of carotene pigments and (ii) trace quantities of lycopene and β-carotene left in tomato purees. The ultrasensitive method comprising HPLC and thermal lens spectrometric (TLS) detection enabled us to detect as low as 0.3 and 1.1 ng ml−1 lycopene and β-carotene in puree extracts, respectively. Total concentration of β-carotene and lycopene (varying from 3 to 170 ng g−1) in the examined tomato purees may serve as an indicator of the carotene-specific antioxidative capacity of these products. Although conventional spectrophotometry can be used to rapidly assess the quality of products derived from tomatoes, a highly sensitive and selective method such as HPLC-TLS is needed for reliable analyses of samples such as, for example, those subjected to inappropriate storage and/or handling.

Phenolic Content, Antioxidant Capacity and Quality of Chokeberry (Aronia melanocarpa) Products

In this study, the influence of lactic acid fermentation on the quality of tomato powder was evaluated. The effect of adding fermented tomato powder to ready-to-cook minced pork meat to improve its nutritional value and sensory characteristics was also analysed. The cell growth of Lactobacillus sakei (7.53 log CFU/g) was more intense in the medium containing tomato powder, compared to the growth of Pediococcus pentosaceus (6.35 log CFU/g) during 24 h of fermentation; however, higher acidity (pH=4.1) was observed in the tomato powder samples fermented with Pediococcus pentosaceus. The spontaneous fermentation of tomato powder reduced cell growth by 38% and pH values slightly increased to 4.17, compared to the fermentation with pure LAB. The lactofermentation of tomato powder increased the average β-carotene and lycopene mass fractions by 43.9 and 50.2%, respectively, compared with the nonfermented samples. Lycopene and β-carotene contents in the ready-to-cook minced pork meat were proportional to the added tomato powder (10 and 30%). After cooking, β-carotene and lycopene contents decreased, on average, by 24.2 and 41.2%, respectively. The highest loss (up to 49.2%) of carotenoids was found in samples with 30% nonfermented tomato powder. Tomato powder fermented with 10% Lactobacillus sakei KTU05-6 can be recommended as both a colouring agent and a source of lycopene in the preparation of ready-to-cook minced pork meat.Chokeberries (Aronia melanocarpa) are rarely used in diet in Croatia but they have high content of polyphenolic compounds and one of the highest in vitro antioxidant activities among fruits. The aim of this study is to compare the quality, phenolic content and antioxidant capacity of different chokeberry products (juices, powders, fruit tea, capsules and dried berries). It can be expected that processing influences antioxidant activity and phenolic content of final products reaching consumers. Characterisation of phenolic compounds was carried out by using spectroscopic methods (Folin-Ciocalteu and pH differential methods). Antioxidant activity of chokeberry products was determined using 2,2-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. The results show that the investigated products contain high amount of phenols (3002 to 6639 mg per L and 1494 to 5292 mg per 100 g of dry matter) and lower amount of total anthocyanins (150 to 1228 mg per L and 141 to 2468 mg per 100 g of dry matter). The examined juices and other chokeberry products possess high antioxidant capacity (12.09 to 40.19 mmol per L or 58.49 to 191.31 mmol per 100 g of dry matter, respectively) and reducing power (38.71 to 79.86 mmol per L or 13.50 to 68.60 mmol per 100 g of dry matter, respectively). On the basis of phenolic content and antioxidant activity, capsules and powders stand out among other products. The study indicates that there are significant differences (p<0.05) in the quality, phenolic content and antioxidant capacity among examined products.

Quantification of lycopene in the processed tomato-based products by means of the light-emitting diode (LED) and compact photoacoustic (PA) detector

The combined use of a high power light emitting diode (LED) and the compact photoacoustic (PA) detector offers the possibility for a rapid (no extraction needed), accurate (precision 1.5%) and inexpensive quantification of lycopene in different products derived from the thermally processed tomatoes. The concentration of lycopene in selected products ranges from a few mg to several tens mg per 100 g fresh weight. The HPLC was used as the well established reference method.