Extraction optimization for the antioxidants from Nigella sativa seeds using response surface methodology

Although many studies have explored the bioactive compound content of Nigella sativa (black seed – BS) essential oil, data on the phenolic compound content in the extracts of Nigella sativa seeds gives inconclusive results [1–3]. In this study, response surface methodology (RSM) with a central composite plan (CCP) was used for the experimental design and identification of the optimal conditions for maximizing the phenolic content and the antioxidant activity of BS extract. The independent variables were as followed: temperature (22.9–67.1ºC), time (31.7–208.2 min), and methanol concentration in water (5.9–94.1% v/v). Different response variables (total polyphenols – TPC, total flavonoids – TFC and the antioxidant activity – DPPH and TEAC) required different optimal conditions to maximize them. The multi-response optimization was performed to determine the extraction conditions, which would simultaneously ensure the highest phenolic content and the antioxidant activity. The optimal conditions derived from the multi-response desirability function were as followed: 120 min, 56 °C and 50% methanol, giving the TPC = 7.05 mg/g, TFC = 3.05 mg/g, DPPH = 9.04 µmol/g and TEAC = 33.24 µmol/g (with desirability function coefficient = 0.83). Solvent concentration was established as a crucial parameter for the extraction of antioxidants from BS. A quercetin derivative and two derivatives of kaempferol were determined by HPLC (high performance liquid chromatography) analysis of the BS extract at the optimal conditions. The accuracy of the models for all response variables was confirmed by a high correlation coefficient (r = 0.99) between the experimental values and those predicted under optimal conditions.

Controlled fermentation of curly kale juice with the use of autochthonous starter cultures

The aim of this paper was to evaluate the influence of different indigenous lactic acid bacteria isolates - as a single culture or bacterial consortium - on the functional and physicochemical properties of fermented curly kale juice. All tested variants exhibited good growth parameters, manifested by efficient pH lowering, increases in acidity, and fructose and glucose metabolism, as well as a significant inhibition of pathogens. A slight increase in total phenolic content was observed, while antioxidant activity remained unchanged. L. sakei and MIX A were associated with an increase in riboflavin and pyridoxine content, while L. plantarum only contributed to an increase in vitamin B₆ content. Bioconversion of individual phenolic compounds, carotenoids, and glucosinolates strongly depended on the strain-specific metabolism. In the process, the levels of ferulic acid and other hydroxycinnamic acids were maintained, while the content of 9-cis lutein increased. Considering presented results and our previous research regarding probiotic features of LAB strains, among tested starter cultures - L. plantarum seemed to possess the best characteristics as a potential starter culture for controlled fermentation of curly kale juice.

Selected dried fruits as a source of nutrients

Dried fruits are an excellent alternative to unhealthy snacks. Twelve commercially available dried fruits were selected: dates, raisins, prunes, Goji berry, chokeberry, rose hip, sea buckthorn, berberis, physalis, haritaki, noni and juniper. The nutritional value in terms of moisture, ash, protein, fat, carbohydrate, dietary fiber, energy value, mineral composition, antioxidant activity and tannins was compared. It is a novelty in the literature in relation to the particular analytes (e.g., minerals, tannins) and/or fruits (e.g., berberis, noni, haritaki). Especially rich in protein were Goji berry (13.3%), sea buckthorn (9.3%), noni (8.9%) and physalis (8.0%); in fat − sea buckthorn (11.2%); in dietary fiber (4.4–53.0%) − most of analyzed products. High antioxidant capacity was noticed for haritaki, berberis, rose hip, Goji berry, and physalis. An important source of minerals was 100 g of: noni (345 mg of Ca; 251 mg of Mg), rose hip (844 mg of Ca; 207 mg of Mg), juniper (564 mg of Ca), sea buckthorn (58 mg of Fe), berberis (24 mg of Fe) and haritaki (14 mg of Fe). The nutritionally attractive dried fruits have the potential for wider application in food formulations.

A predictive approach to the antioxidant capacity assessment of green and black tea infusions

Contemporary consumers drink significant amounts of tea because of its health–benefits mainly associated to the presence of polyphenols with high antioxidant activity. Therefore, the information how to obtain tea infusion of the highest quality, i.e. with high antioxidant capacity is needed. In this study, the various models for the prediction of total polyphenols and antioxidant activity of green and black tea infusions were developed and compared. Three mathematical equations: Spiro’s, Peleg’s and logarithmic, and two data mining techniques: multivariate adaptive regression splines (MARS) and artificial neural networks (ANNs) were used to build the predictive models. The results obtained show that Spiro’s model could be used for the prediction of green tea quality expressed as total phenolic content or the antioxidant activity (determination coefficients above 0.99), whereas Peleg’s model is more suitable for black tea quality prediction (determination coefficients above 0.99). Data mining techniques (MARS and ANNs) enable to create models fast and of simple application with very good acceptability (determination coefficients above 0.99).

Front-Face Fluorescence Spectroscopy and Chemometrics for Quality Control of Cold-Pressed Rapeseed Oil During Storage

The aim of this study was to test the usability of fluorescence spectroscopy to evaluate the stability of cold-pressed rapeseed oil during storage. Freshly-pressed rapeseed oil was stored in colorless and green glass bottles exposed to light, and in darkness for a period of 6 months. The quality deterioration of oils was evaluated on the basis of several chemical parameters (peroxide value, acid value, K₂₃₂ and K₂₇₀, polar compounds, tocopherols, carotenoids, pheophytins, oxygen concentration) and fluorescence. Parallel factor analysis (PARAFAC) of oil excitation-emission matrices revealed the presence of four fluorophores that showed different evolution throughout the storage period. The fluorescence study provided direct information about tocopherol and pheophytin degradation and revealed formation of a new fluorescent product. Principal component analysis (PCA) performed on analytical and fluorescence data showed that oxidation was more advanced in samples exposed to light due to the photo-induced processes; only a very minor effect of the bottle color was observed. Multiple linear regression (MLR) and partial least squares regression (PLSR) on the PARAFAC scores revealed a quantitative relationship between fluorescence and some of the chemical parameters.

Characterization of Fulvic Acid Beverages by Mineral Profile and Antioxidant Capacity

The main purpose of the study was to investigate the quality of fulvic acid-based food products. The concentrations of Ca, K, Mg, Na, Cu, Fe, Mn, and Zn, and antioxidant capacities of fulvic acid concentrates and ready-to drink beverages available on the global market were determined. The concentrations of minerals were determined using microwave plasma-atomic emission spectrometry. Antioxidant capacity was expressed as total polyphenol (TP) and flavonoid (TF) contents, the trolox equivalent antioxidant capacity (TEAC) and ferric reducing ability of plasma (FRAP) values. The daily portion of eight out of 14 products realized 45–135% of recommended daily allowance (RDA) for Fe. One of ready-to-drink beverages was also a good source of Mg (about 40% of RDA), and another one of Mn (about 70% of RDA). The concentrations of TP and TF in ready-to-drink beverages varied from 6.5 to 187 µg/mL, whereas in concentrates, from 5886 to 19,844 µg/mL. Dietary supplements or food products with fulvic acids may be a good source of antioxidant polyphenolic compounds and some minerals.

Chemometric analysis of minerals in gluten-free products

BACKGROUND

Numerous studies indicate mineral deficiencies in people on a gluten-free (GF) diet. These deficiencies may indicate that GF products are a less valuable source of minerals than gluten-containing products. In the study, the nutritional quality of 50 GF products is discussed taking into account the nutritional requirements for minerals expressed as percentage of recommended daily allowance (%RDA) or percentage of adequate intake (%AI) for a model celiac patient. Elements analyzed were calcium, potassium, magnesium, sodium, copper, iron, manganese, and zinc. Analysis of %RDA or %AI was performed using principal component analysis (PCA) and hierarchical cluster analysis (HCA).

RESULTS

Using PCA, the differentiation between products based on rice, corn, potato, GF wheat starch and based on buckwheat, chickpea, millet, oats, amaranth, teff, quinoa, chestnut, and acorn was possible. In the HCA, four clusters were created. The main criterion determining the adherence of the sample to the cluster was the content of all minerals included to HCA (K, Mg, Cu, Fe, Mn); however, only the Mn content differentiated four formed groups.

CONCLUSION

GF products made of buckwheat, chickpea, millet, oats, amaranth, teff, quinoa, chestnut, and acorn are better source of minerals than based on other GF raw materials, what was confirmed by PCA and HCA. © 2017 Society of Chemical Industry.

The Influence of Packaging on Cosmetic Emulsion during Storage Assessed by FT-NIR Spectroscopy and Color Measurements

FT-NIR spectroscopy and color measurements were applied to evaluate the influence of packaging on cosmetic cream stored at room and refrigerated conditions. Commercial cosmetic cream was stored for 2 and 4 mo in five containers intended for cosmetics: aluminum jar with polypropylene thermos (Al/PP), acrylic jar with polypropylene thermos (Ac/PP), glass (G) jar, polypropylene (PP) jar, and styrene acrylonitrile (SAN) jars. Principal component analysis (PCA) of the FT-NIR spectra showed the effect of time on tested samples stored in all applied packagings; separate groups were formed by fresh samples and samples stored for 2 and 4 mo. The changes in samples stored in the cold for 2 mo were similar for all applied packagings as compared with fresh samples, although samples stored in SAN jars formed a separate group. After 4 mo, a separate group was formed by samples stored in G jars. For samples stored at room temperature, the influence of packaging material on cosmetic emulsion was clearly visible; four separate groups (Al/PP with PP, Ac/PP, G, and SAN) were created by samples stored for 4 mo. Using partial least squares (PLS1) regression, it was found that the FT-NIR spectra of tested samples correlated with their lightness L*, a* parameter, and total color difference ΔE ^* _ab . FT-NIR spectroscopy is a rapid technique which could be useful to make the best choice of packaging for cosmetics protecting the original quality of products during long-term storage.

The effect of antioxidants on quantitative changes of lysine and methionine in linoleic acid emulsions at different pH conditions

BACKGROUND

Plants are an important source of phenolic compounds. The antioxidant capacities of green tea, thyme and rosemary extracts that contain these compounds have been reported earlier. However, there is a lack of accessible information about their activity against lipid oxidation in emulsions and inhibit the interaction of lipid oxidation products with amino acids. Therefore, the influence of green tea, thyme and rosemary extracts and BHT (butylated hydroxytoluene) on quantitative changes in lysine and methionine in linoleic acid emulsions at a pH of isoelectric point and a pH lower than the isoelectric point of amino acids was investigated.

METHODS

Total phenolic contents in plant extracts were determined spectrophotometrically by using Folin-Ciocalteu's reagent, and individual phenols by using HPLC. The level of oxidation of emulsion was determined using the measurement of peroxides and TBARS (thiobarbituric acid reactive substances). Methionine and lysine in the system were reacted with sodium nitroprusside and trinitrobenzenesulphonic acid respectively, and the absorbance of the complexes was measured.

RESULTS

Extract of green tea had the highest total polyphenol content. The system containing antioxidants and amino acid protected linoleic acid more efficiently than by the addition of antioxidants only. Lysine and methionine losses in samples without the addition of antioxidants were lower in their isoelectric points than below these points. Antioxidants decrease the loss of amino acids. The protective properties of antioxidants towards methionine were higher in a pH of isoelectric point whereas towards lysine in pH below this point.

CONCLUSIONS

Green tea, thyme and rosemary extracts exhibit antioxidant activity in linoleic acid emulsions. Moreover, they can be utilized to inhibit quantitative changes in amino acids in lipid emulsions. However, the antioxidant efficiency of these extracts seems to depend on pH conditions. Further investigations should be carried out to clarify this issue.

Green tea extract as an anti-browning agent for cloudy apple juice

BACKGROUND

Enzymatic browning of fruits and vegetables and their products is an important factor worsening their quality. The influence of five green tea extracts at the concentrations of 1 g L^-1 , 2 g L^-1 and 3 g L^-1 on polyphenol oxidase (PPO) activity in fresh cloudy apple juice was investigated. Moreover, PPO inhibition by tea extract and colour stability of juice during short-time refrigerated storage was studied. The changes of juice colour during storage was expressed as the total colour differences (ΔE*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A₄₂₀ ).

RESULTS

All extracts inhibited PPO activity in fresh apple juice in concentration-dependent manner. PPO activity in pure apple juice decreased by 7% after 48 h, whereas PPO activity in samples with 1 g L^-1 , 2 g L^-1 and 3 g L^-1 tea extract decreased by 53%, 74%, and 96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48 h, extract at 1 g L^-1 , 2 g L^-1 and 3 g L^-1 inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice.

CONCLUSION

Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices. © 2016 Society of Chemical Industry.

Commercial plant extracts may act as antioxidants or pro-oxidants in cosmetic emulsions based on argan oil

Cosmetic emulsions containing plant extracts should be tested in a range of temperatures from 5°C to 40°C to be sure that they will be stable during general use by consumers and that plant extracts used as antioxidants do not accelerate oxidative degradation of their oil base. The oxidative stability of argan oil-in-water emulsions containing 1% and 5% commercial acerola, willow, and rose extracts [or 0.01% butylhydroxytoluene (BHT)], stored at 5°C and 20°C for 6 months and at 40°C for 4 weeks, was monitored by the determination of peroxide content. The antioxidant or pro-oxidant activities of extracts or BHT in emulsions were expressed as the protection factor (PF) and inhibition of peroxide formation (Ip). At the end of storage, 5% willow, 0.01% BHT, 1% willow, and 5% acerola were the most protective for emulsions stored at 5°C. At 20°C, the most effective was 0.01% BHT, 5% rose, and 5% acerola. At 40°C, inhibition of peroxide formation calculated for 1% rose, 5% acerola, and 0.01 % BHT was similar. Altogether, the results show that some plant extracts, depending on storage conditions, may act as pro-oxidants, whereas the others can be applied as natural antioxidants instead of synthetic BHT.

Effect of Extraction Method on the Phenolic and Cyanogenic Glucoside Profile of Flaxseed Extracts and their Antioxidant Capacity

The application of flaxseed extracts as food ingredients is a subject of interest to food technologists and nutritionists. Therefore, the influence of the extraction method on the content and composition of beneficial compounds as well as anti-nutrients is important. In the study, the effects of two solvent extraction methods, aqueous and 60 % ethanolic, on phenolic and cyanogenic glucoside profiles of flaxseed extract were determined and compared. The impact of extracted phenolic compounds on the antioxidant capacity of the extracts was also investigated. Defatted meals from brown and golden flax varieties were used as extraction material. The ethanolic extraction was more selective for phenolics (100.8-131.7 mg g-1) than the aqueous one (11.5-15.7 mg g-1). However, the contribution of particular phenolic compounds to total phenolics was much more dependent on flax variety than extraction method. A strong relationship was observed between both radical scavenging and ferric reducing activity and the content of phenolics (particularly secoisolariciresinol diglucoside). The correlation between extract chelating ability and phenolics was moderate suggesting that other flaxseed compounds are involved in this activity. The extraction method strongly affected cyanogenic glucoside content of flaxseed extracts; the aqueous extraction caused 96 % reduction in cyanogenic glucoside content (0.56-0.62 mmol g-1) when compared to the content in defatted meal (9.1-11.6 mmol g-1). On the contrary, ethanolic extraction resulted in the high cyanogenic glucoside content in the extracts (71-89 mmol g-1). The results reveals that ethanolic extraction gives extracts rich in antioxidant lignans; aqueous extracts have lower antioxidant activity than ethanolic but cyanogenic glucosides are significantly reduced.

Selenium in Gluten-free Products

The nutritional value of gluten-free products is the subject of interest for food technologists and nutritionists, as the only effective treatment for celiac disease is a lifelong gluten-free diet. As selenium deficiencies in celiac disease are observed, the aim of the study was to determine the selenium content in 27 grain gluten-free products available on the European Union (EU) market. Moreover, selenium content in products based on popular gluten-free cereals like corn, rice, and buckwheat and in relatively new or less popular products based on oat, amaranth, teff, and quinoa was compared. Selenium content in the tested products ranged from 0.9 to 24.5 μg/100 g. The average content of selenium in products based on popular gluten-free cereals was 2.8 μg/100 g and in products based on oat, amaranth, teff, and quinoa was 10.8 μg/100 g. It indicates that products based on less popular grains, especially on oat, should be more frequently chosen as a source of selenium by people on gluten-free diet than traditionally consumed gluten-free grains.