Pulsed electric field for shalgam juice: effects on fermentation, shelf-life, and sensory quality.

BACKGROUND: Pulsed electric field (PEF) has become a reality in the food industry as a non-thermal application. PEF is used due to its benefits such as increasing the extraction of anthocyanin or other bioactive substances, shortening the fermentation time, and reducing the microbiological load by electroporation. This study aimed to determine the effect of PEF pretreatment on the fermentation, chemical, microbiological, and sensory properties of shalgam juice. For this purpose, PEF with 1 kV cm-1 of field strength was used as a pretreatment for shalgam juice and changes in control and PEF-treated samples were monitored during fermentation and 70 days of cold storage (4 °C). RESULTS: The pH and lactic acid content during fermentation were similar for both samples. The effect of PEF on pH (3.15-3.39), titratable acidity (4.35-5.49 g L-1 ), total phenolic content (279-766 mg mL-1 GAE) and antioxidant activity (694-2091 µmol Trolox mL-1 ) during storage was insignificant. PEF-treated samples had lower total aerobic mesophilic bacteria (~9%) and lactic acid bacteria (~3%) counts than the control samples at the end of 70 days. Sensory analyses performed at 30th and 60th days of storage with 74 panelists revealed that the color, taste, sourness, saltiness, bitterness, and general acceptability were not inversely affected by PEF. CONCLUSION: Our results could be a basis to produce shalgam juice commercially by PEF treatment. Although more studies with new experimental designs should be carried out, preliminary results indicated that the use of PEF might have a potential for fermented products such as shalgam juices. © 2023 Society of Chemical Industry.

Investigating the effects of geographical origin, roasting degree, particle size and brewing method on the physicochemical and spectral properties of Arabica coffee by PCA analysis.

Effects of geographical origin of Coffee Arabica beans (Brazil, Colombia and Peru), roasting degree, particle size and different brewing methods (French press, chemex and cold brew) on physicochemical and spectral properties of coffee samples were investigated in this study. Analyses of pH, total phenolic content (TPC) and total antioxidant activity (TA), UV and fluorescence spectroscopy measurements were performed. Principal component analysis (PCA) was used to obtain the most effective parameters on chemical changes. Results indicated that the increase of roasting degree caused decrements in the intensities of UV-spectra because of the degradation of trigonelline and chlorogenic acid molecules while counterpart trend was observed in the fluorescence spectra due to formation of fluorescence Maillard reaction products (MRP) during roasting. French press and cold brew methods caused similar TPC (1873.33-3818.33 and 2648.88-3824.44 µg/mL gallic acid equivalent, respectively) and TA (0.18-0.32 and 0.16-0.27 µmol/mL Trolox equivalent, respectively) values whereas chemex method showed different physicochemical properties (TPC: 1008.88-3543.88 µg/mL gallic acid equivalent and TA: 0.08-0.26 µmol/mL Trolox equivalent). Roasting degree and brewing method-compared to other parameters-were the most discriminating factors on the basis of UV spectra and fluorescence spectra of coffee brew samples, respectively. All roasting degrees could be distinguished with the rate of 71.42% on PC1 and 23.45% on PC2 of total variance according to UV-spectra while chemex and French press-cold brew methods could be differentiated with the rate of 97.24% on PC1 and 1.79% on PC2 of total variance based on fluorescence spectra on PCA score graphs.

Synchronous fluorescence spectroscopy combined with chemometrics for determination of total phenolic content and antioxidant activity in different tea types.

BACKGROUND: The aim of this study is to monitor the antioxidant activity (AA) and total phenolic content (TPC) variations of different kinds of teas depending on the infusion temperature and time by using synchronous fluorescence spectroscopy (SFS) combined chemometrics as a rapid method. In this study, black tea, oolong tea, green tea, and green tea powder (matcha) samples were brewed at 80 °C and 96 °C for 2.5 to 30 min. Synchronous fluorescence spectra were recorded at different wavelength interval (Δλ) values for optimal models. AA and TPC of tea samples were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and Folin-Ciocalteu methods as reference methods, respectively. Partial least square (PLS) method was used for correlation between reference methods and SFS method. RESULTS: Results showed that SFS combined with chemometrics could be an alternative rapid way to monitor TPC and AA of teas with 0.932 and 0.918 of validation R2 values in fermented teas (black tea-oolong) while with 0.961 and 0.860 of validation R2 values in non-fermented teas (green tea and green tea powder), respectively. Limit of detection (LOD) and root mean square error of prediction (RMSEP) values were ≤ 6.61 µg mL-1 and ≤ 17.42, respectively. CONCLUSION: Based on the lowest R2 value (0.860) on TPC analysis, the proposed method is more appropriate for AA analysis of green tea and green tea powder. Furthermore, infusion time was more effective for obtaining different amounts of TPC and AA in fermented tea types while only infusion temperature was effective on green tea and green tea powder samples. Therefore, obtained calibration-validation models gave better results for fermented tea types.

Identification of cow, buffalo, goat and ewe milk species in fermented dairy products using synchronous fluorescence spectroscopy.

In the dairy industry, substitution of high priced milk species with low priced ones is a common practice, and determination of milk species is critical. In this study, synchronous fluorescence spectroscopy (SFS) method was developed for identification of milk species in fermented dairy products (yoghurt and cheese). Three partial least square-discriminant analysis models were developed in order to identify pure-mixed samples, milk species and binary mixture type, and partial least square (PLS) model was utilized to quantify the mixing ratio in binary mixtures. PLS models used for yoghurt and cheese samples showed that detection limits of adulteration were below 3.3%. Apart from the buffalo-cow yoghurt and goat-cow cheese, precision of the measurements was found to be below 6.2. It can be said that SFS technique is applicable on yoghurt and cheese samples as it's a less destructive and a less costly method compared to DNA and protein based conventional methods.

Detection of Pistacia vera adulteration by using laser induced breakdown spectroscopy.

BACKGROUND: Pistachio has high economic value because of its high consumption rate and consumer demand. Therefore, it has become an important target for adulteration. Green pea and spinach are the most frequently used foods for pistachio adulteration as a result of their kernel color. The present study aimed to detect pistachio adulteration with green pea and spinach samples using laser induced breakdown spectroscopy (LIBS) combined with chemometric methods. RESULTS: In the first step of the study, principal component analysis was employed for qualitative analysis of pure pistachio, green pea, spinach and adulterated pistachio samples, and discrimination was achieved successfully. A score plot clearly discriminating pure pistachio, green pea and spinach samples, as well as their blind samples, was drawn using principle component (PC)1 and PC2 which explained 86.86% and 12.16% of the variance, respectively. The results showed that the calibration curve for green pea adulterated pistachio provides successful determination of adulteration level and had an R2 of 0.995 and a limit of detection (LOD) of 2.04%, whereas the calibration curve for spinach adulterated pistachio had an R2 of 0.993 and a LOD of 1.64%. CONCLUSION: The results of the present study demonstrate that LIBS with the chemometric methods showed a good performance based on the high value of prediction accuracy for pistachio adulteration. This technique has high potential as a rapid method for pistachio identification and detection of adulteration. © 2018 Society of Chemical Industry.

Coffee arabica adulteration: Detection of wheat, corn and chickpea.

Coffee is globally one of the most widely consumed beverages. Due to the high economic importance for the countries that produce, export and import it, its purity and detection of external impurities have been constant concern. In some cases, visual inspection is unreliable in roasted ground coffee because of resemblance in color and the texture of the cheapest fillers. The objective of this work was to evaluate the feasibility of employing Laser Induced Breakdown Spectroscopy (LIBS) for determination of coffee adulteration with chickpea, corn and wheat. For this purpose, LIBS spectra was evaluated with chemometrics methods for classification and quantification of the adulteration ratio. Coefficient of determination and limit of detection values for chickpea, corn and wheat adulteration with Coffee arabica were found as 0.996, 0.995, 0.995 and 0.56%, 0.52% and 0.45%, respectively. With LIBS, prevention of unfair competition, protection of consumers and determination of coffee quality can be achieved.

Identification of offal adulteration in beef by laser induced breakdown spectroscopy (LIBS).

Minced meat is the major ingredient in sausages, beef burgers, and similar products; and thus it is the main product subjected to adulteration with meat offal. Determination of this kind of meat adulteration is crucial due to religious, economic and ethical concerns. The aim of the present study is to discriminate the beef meat and offal samples by using laser induced breakdown spectroscopy (LIBS). To this end, LIBS and multivariate data analysis were used to discriminate pure beef and offal samples qualitatively and to determine the offal mixture adulteration quantitatively. In this analysis, meat samples were frozen and LIBS analysis were performed. The results indicate that by using principal component analysis (PCA), discrimination of pure offal and offal mixture adulterated beef samples can be achieved successfully. Besides, adulteration ratio can be determined using partial least square analysis method (PLS) with 0.947 coefficient of determination (R2) and 3.8% of limit of detection (LOD) values for offal mixture adulterated beef samples.

Detection and quantification of a toxic salt substitute (LiCl) by using laser induced breakdown spectroscopy (LIBS).

The use of Li salts in foods has been prohibited due to their negative effects on central nervous system; however, they might still be used especially in meat products as Na substitutes. Lithium can be toxic and even lethal at higher concentrations and it is not approved in foods. The present study focuses on Li analysis in meatballs by using laser induced breakdown spectroscopy (LIBS). Meatball samples were analyzed using LIBS and flame atomic absorption spectroscopy. Calibration curves were obtained by utilizing Li emission lines at 610nm and 670nm for univariate calibration. The results showed that Li calibration curve at 670nm provided successful determination of Li with 0.965 of R2 and 4.64ppm of limit of detection (LOD) value. While Li Calibration curve obtained using emission line at 610nm generated R2 of 0.991 and LOD of 22.6ppm, calibration curve obtained at 670nm below 1300ppm generated R2 of 0.965 and LOD of 4.64ppm.

A rapid tool for determination of titanium dioxide content in white chickpea samples.

Titanium dioxide (TiO2) is a widely used additive in foods. However, in the scientific community there is an ongoing debate on health concerns about TiO2. The main goal of this study is to determine TiO2 content by using laser induced breakdown spectroscopy (LIBS). To this end, different amounts of TiO2 was added to white chickpeas and analyzed by using LIBS. Calibration curve was obtained by following Ti emissions at 390.11nm for univariate calibration, and partial least square (PLS) calibration curve was obtained by evaluating the whole spectra. The results showed that Ti calibration curve at 390.11nm provides successful determination of Ti level with 0.985 of R2 and 33.9ppm of limit of detection (LOD) value, while PLS has 0.989 of R2 and 60.9ppm of LOD. Furthermore, commercial white chickpea samples were used to validate the method, and validation R2 for simple calibration and PLS were calculated as 0.989 and 0.951, respectively.

Laser-Induced Breakdown Spectroscopy Based Protein Assay for Cereal Samples.

Protein content is an important quality parameter in terms of price, nutritional value, and labeling of various cereal samples. However, conventional analysis methods, namely, Kjeldahl and Dumas, have major drawbacks such as long analysis time, titration mistakes, and carrier gas dependence with high purity. For this reason, there is an urgent need for rapid, reliable, and environmentally friendly technologies for protein analysis. The present study aims to develop a new method for protein analysis in wheat flour and whole meal by using laser-induced breakdown spectroscopy (LIBS), which is a multielemental, fast, and simple spectroscopic method. Unlike the Kjeldahl and Dumas methods, it has potential to analyze a high number of samples in considerably short time. In the study, nitrogen peaks in LIBS spectra of wheat flour and whole meal samples with different protein contents were correlated with results of the standard Dumas method with the aid of chemometric methods. A calibration graph showed good linearity with the protein content between 7.9 and 20.9% and a 0.992 coefficient of determination (R2). The limit of detection was calculated as 0.26%. The results indicated that LIBS is a promising and reliable method with its high sensitivity for routine protein analysis in wheat flour and whole meal samples.

Determination of whey adulteration in milk powder by using laser induced breakdown spectroscopy.

A rapid and in situ method has been developed to detect and quantify adulterated milk powder through adding whey powder by using laser induced breakdown spectroscopy (LIBS). The methodology is based on elemental composition differences between milk and whey products. Milk powder, sweet and acid whey powders were produced as standard samples, and milk powder was adulterated with whey powders. Based on LIBS spectra of standard samples and commercial products, species was identified using principle component analysis (PCA) method, and discrimination rate of milk and whey powders was found as 80.5%. Calibration curves were obtained with partial least squares regression (PLS). Correlation coefficient (R(2)) and limit of detection (LOD) values were 0.981 and 1.55% for adulteration with sweet whey powder, and 0.985 and 0.55% for adulteration with acid whey powder, respectively. The results were found to be consistent with the data from inductively coupled plasma - mass spectrometer (ICP-MS) method.

Identification of meat species by using laser-induced breakdown spectroscopy.

The aim of the present study is to identify meat species by using laser-induced breakdown spectroscopy (LIBS). Elemental composition differences between meat species were used for meat identification. For this purpose, certain amounts of pork, beef and chicken were collected from different sources and prepared as pellet form for LIBS measurements. The obtained LIBS spectra were evaluated with some chemometric methods, and meat species were qualitatively discriminated with principal component analysis (PCA) method with 83.37% ratio. Pork-beef and chicken-beef meat mixtures were also analyzed with partial least square (PLS) method quantitatively. Determination coefficient (R(2)) and limit of detection (LOD) values were found as 0.994 and 4.4% for pork adulterated beef, and 0.999 and 2.0% for chicken adulterated beef, respectively. In the light of the findings, it was seen that LIBS can be a valuable tool for quality control measurements of meat as a routine method.

Analysis of bakery products by laser-induced breakdown spectroscopy.

In this study, we focused on the detection of Na in bakery products by using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method. LIBS experiments were performed to examine the Na at 589 nm to quantify NaCl. A series of standard bread sample pellets containing various concentrations of NaCl (0.025-3.5%) were used to construct the calibration curves and to determine the detection limits of the measurements. Calibration graphs were drawn to indicate functions of NaCl and Na concentrations, which showed good linearity in the range of 0.025-3.5% NaCl and 0.01-1.4% Na concentrations with correlation coefficients (R(2)) values greater than 0.98 and 0.96. The obtained detection limits for NaCl and Na were 175 and 69 ppm, respectively. Performed experimental studies showed that LIBS is a convenient method for commercial bakery products to quantify NaCl concentrations as a rapid and in situ technique.