Total Monomeric Anthocyanin Content Research Articles

Evaluation of antioxidant properties and phenolic and aromatic profiles of cornelian cherry pestil samples prepared with sucrose and stevia addition

This study aimed to produce three types of pestil samples (stevia added, sucrose added, and without a sweetener) using the Cornelian cherry (Cornus mas L.) fruit and determine changes in the antioxidant properties and aromatic profile during the three months of storage at 20 ± 2°C. For this purpose, the lyophilized pestil samples were analyzed in terms of DPPH radical scavenging activity, total phenolic content, total anthocyanin content, aromatic components, phenolic, and anthocyanin profiles. The aromatic, phenolic, and anthocyanin profiles were determined by GC–MS and HPLC, respectively. The samples' total phenolic content varied between 305.54 μg GAE/mg and 489.66 μg GAE/mg. The total monomeric anthocyanin content decreased in all samples during the storage period. The lowest total monomeric anthocyanin content was 41.21 mg Cy-3-Gal/100 g in the third month of storage in the control group, while the highest content (228.49 mg Cy-3-Gal/100 g) belonged to the sucrose-added pestil group. Pestil samples had DPPH radical scavenging activity values between 8.35 μg/ml and 148.49 μg/ml as IC50. In general, the increase in storage time decreased antioxidant activity in all pestil types. It is remarkable that all pestil samples showed antioxidant activity in the first month of storage at a level of standard antioxidants (Trolox, α-Tocopherol, BHA, and BHT). The predominant phenolic compound in Cornelian cherry pestil samples was chlorogenic acid, while the predominant anthocyanin was cyanidin-3-O-galactoside. The aromatic profile data showed that alcohols were the dominant group regarding the number of volatiles. However, the major aromatic component in the pestil samples was an aldehyde, 5-(hydroxymethyl)furfural. The results demonstrated that Cornelian cherry pestil exhibited high antioxidant activity and was a rich source of phenolic compounds and anthocyanins. In light of the data obtained from this study, it is concluded that Cornelian cherry pestil with or without a sweetener may be a good option as a functional food that can replace traditional confectionery. Novelty impact statement This research is the first to investigate the changes in the phenolic and aroma profiles of Cornelian cherry pestil samples prepared with the addition of sucrose and stevia over three months. The predominant phenolic compound was chlorogenic acid, while the major aromatic compound was 5-(hydroxymethyl)furfural in all pestil groups. Additionally, the storage period significantly affected phenolic content, total anthocyanin content, and DPPH radical scavenging activity of pestil samples.

Impact of molar absorbance on anthocyanin content of the foods

Anthocyanins are present in bright colored fruit and vegetables with growing evidence for their health benefits. Several methods exist in the literature to measure the total monomeric anthocyanin content in foods. Although the simplest method uses UV–Vis spectrophotometry, it requires the use of anthocyanin molar absorption coefficients (Ɛ). While commonly reported for some compounds, these values vary substantially between studies. This study collated and compared existing Ɛ values for a range of anthocyanin-3-glucosides, measured new Ɛ values for these compounds and underwent an inter-laboratory validation of spectrometry methods. The Ɛ values used for the determination of anthocyanin content in Australian blueberries, were shown to greatly affect the estimated total anthocyanin. Significant differences in the Ɛ values were observed when measured at 520 nm, or their absorbance maximum and substantial difference in the estimated total anthocyanins were observed when expressed as equivalent of cya-3-glu or mal-3-glu.

Anthocyanin Extraction from Jaboticaba Skin (Myrciaria cauliflora Berg.) Using Conventional and Non-Conventional Methods.

This study evaluated the effect of different extraction technologies and conditions in order to obtain jaboticaba skin extracts. Firstly, the skins were extracted by conventional extraction, according to a rotatable central composite design, varying ethanol concentration, solid:liquid ratio, and temperature. Next, ultrasound-assisted extraction was performed using different power densities and times. Finally, high-pressure extractions were performed with varying pressures and times. For agitated bed extraction, the highest anthocyanin content was observed for ethanol concentrations varying between 60% and 80%. Thus, the independent variables which more influenced anthocyanin content were ethanol concentration and solid:liquid ratio. Folin–Ciocalteu reducing capacity was linearly affected by the increase in temperature. Ethanol concentration was the variable that most influenced ABTS+. On the other hand, the increase in ethanol concentration decreased the antioxidant capacity by ABTS+. Considering the ultrasound extraction, increasing its power did not affect total monomeric anthocyanins content, while the increase in process time had better yields. The highest antioxidant capacity and total monomeric anthocyanins were found for the highest extraction time. Similarly, with ultrasound, the increase in high hydrostatic-assisted extraction time positively influenced anthocyanin content and antioxidant capacity. As a result, the ultrasound-assisted method was found to be the best extraction technology for anthocyanins recovery.

ქართული ყურძნის ჯიშებისგან წარმოებული კახური და ევროპული სტილის ღვინოების ბიოაქტიური კომპონენტების და ანტიოქსიდანტური აქტივობის შესწავლა

In this work, the following biochemical parameters: tannins content (%), antioxidant activity mg /L-AAC-1, monomeric anthocyanins content and total polyphenols content mg/L GAE-1 in white wines 16 samples (Rkatsiteli, Msvane Kakhuri, Kisi, Khikhvi) obtained by European and Kakhetian method were studied to identify differences among variety and winemaking methods. The mentioned parameters range for tannin content from 0.067 to 0.155%, for total monomeric anthocyanin content :2.093-14.472 mg/L, for total polyphenol content 174.634-743.740 mg/L GAE-1, antioxidant activity 317.323 mg/L (AAE-1) in Kakhetian wines. While corresponding results 0.037-0.055%, 1.202-2.004 mg/L; 20.764-53.772 mg/L GAE-1; 130.702-367.935 mg/L AAC-1 are shown in European style wine. Based on the biochemical parameters of the wine, both European and Kakhetian style Kisi and Khikhvi are distinguished. A high positive correlation was observed between total polyphenol content and antioxidant activity (r2 = 0.934). However, the highest was determined in tannins-antioxidant activity and tannins-total polyphenol content (r2 = 0.957). A relatively weak correlation was found between total monomeric anthocyanin content and the antioxidant activity (r2 = 0.767) and total monomeric anthocyanin -total polyphenols (r2 = 0.767).

Ultrasound-assisted natural deep eutectic solvent extraction of anthocyanin from black carrots: Optimization, cytotoxicity, in-vitro bioavailability and stability

In the present study, natural deep eutectic solvent-based ultrasound-assisted extraction was introduced for the extraction of cyanidin-3-O-glycoside from black carrots. Response surface methodology (RSM) with central composite design with 27 experimental runs were used for the optimization studies. The analysis of variance indicated that the solid/solvent ratio and ultrasound power had a significant effect on the responses. The measured parameters corresponded to the predicted results. Cytotoxicity analyzes were performed after the verification of the data obtained as a result of the optimization. Based on the results of cytotoxicity analysis, the inhibitory effect of the extracts was proven on Caco-2 and HUH7 cell lines. Microencapsulation was achieved with the complex coacervation with three different wall materials to provide ease of use and to extend the shelf life. The pH, temperature and storage stability analysis results of the samples showed that +4 °C was the best storage temperature and the total monomeric anthocyanin content of the samples decreased with increasing storage time. Based on the findings, an eco-friendly, high efficient and green metholodology alternative was offered to extract anthocyanin from food matrices.

Heat treatment and microwave applications on homemade sour cherry juice: The effect on anthocyanin content and some physicochemical properties

This study aimed to investigate the effects of different treatments applied on the anthocyanin content and some physicochemical properties of homemade sour cherry juice. Titration acidity, pH, color, total monomeric anthocyanin content, polymeric color, color density, polymeric color ratio, total phenolic content and antioxidant activity properties and formation of hydroxymethylfurfural (HMF) were investigated by heat treatment (70–75 °C), boiling (90–95 °C) and microwave application at 2450 MHz, 400 W power. When the results were evaluated, all treatments and treatment time did not make a statistical difference on color values, total monomeric anthocyanin content, color intensity, polymeric color ratio and antioxidant activity of the samples (p˃0.05). The microwave application caused a significant change in the amount of phenolic substance (p˂0.05) and had the highest phenolic substance content. In addition, it was observed that HMF formation was at the lowest level in sour cherry juices obtained by microwave application. As a result, while the bioactive components are significantly preserved in microwave-produced homemade sour cherry juice, HMF formation occurs at a lower level compared to conventional methods, resulting in higher quality products in terms of food safety.

Otimização do processamento da farinha e da extração de antocianinas do mirtilo

Abstract The objective of this work was to determine the ideal conditions for the processing of flour and extraction of anthocyanins from blueberries (Vaccinium corymbosum). A central composite design (CCD) with response surfaces was used. For the processing of blueberry flour, different dehydration temperatures (53ºC-67ºC) and times (43.18-48.82 hours) were used. The extraction of anthocyanins was performed with ethanol solutions (15-85% v/v) at different pH values (1.0-4.0). ). The total monomeric anthocyanin content was 1,538.39±25.63 mg 100 g-1 (0.89 desirability value) for fresh blueberries in the optimal extraction condition (53.5% ethanol, 2.5 pH) and 3,101.04±11.57 mg 100 g-1 (0.96 desirability value) for blueberry flour in the optimum processing condition (53ºC, 46 hours). The optimized extraction and dehydration of blueberries provide high levels of anthocyanins in the samples.

Maceration time over antioxidant activity, volatile compounds and temporal dominant sensation of fermented jabuticaba

Jabuticaba is a fruit sensory appreciated and has significant nutritional and functional value. However, it is quite perishable, and its use is interesting for the preparation of other products such as fermented jabuticaba, from a nutritional, biological and technological point of view. This study evaluated the interference of maceration time over antioxidant capacity, volatile compounds profile and temporal dominant sensation of fermented jabuticaba. Four different treatments of fermented jabuticaba in different fermentation times were prepared (96, 120, 144 and 168 h). After preparation, total monomeric anthocyanin content, total antioxidant activity by 2,2-azino-bis 3-ethylbenzthiazoline-6-sulfonic acid and iron reduction method, volatile compounds profile by gas chromatography and sensory analysis of temporal dominance of sensations were performed of fermented jabuticaba. The highest concentration of total anthocyanins (25.81 mg/100 g) and antioxidant activity (78.34 μmol Trolox/g e 84.69 μM FeSO4/g) of jabuticaba is in its skin. Regarding the antioxidant activity by FRAP method, the fermented beverages presented higher value than the whole fruit. However, after 96 h of maceration, the values decreased, followed by an increase after 144 h. In all maceration times the predominant sensation was acidic taste, initially and then astringency, the most persistent sensation in all treatments. However, there was a downward trend in this sensation with the increase in maceration time, as well as isoamyl alcohol content.

BLUEBERRY, SEA BUCKTHORN FRUITS AND APPLE BEVERAGE: BIOCHEMICAL AND SENSORIAL CHARACTERIZATION

This work aimed at optimizing the extraction of total phenolic (TP) and total monomeric anthocyanin (TMA) content for the development of a potentially functional wild blueberry smoothie (BP) with apple puree (AP), apple juice (AJ) and sea buckthorn puree (SBJ) in various proportions using conventional extraction (CE) and advanced extraction techniques [ultrasound-assisted (UAE)]. There were also analyzed the rheological behavior and the color attributes (lightness and redness respectively) of smoothie samples. S7 smoothie sample [30 AP/30 AJ/20 SBJ/20 BP (UAE)] provided a beverage with significant higher amount (21.40%) of anthocyanins (TMA) compared to sample S10 [30 AP/30 AJ/20 SBJ/20 BP (CE)] in which the extraction of anthocyanins was by the classical method. Further, different color attributes, particularly brightness (L *), redness (a *) and yellow (b *) decreased considerably for the samples with 15 and 20% addition of blueberry puree. Therefore, ultrasound-assisted extraction had a significant effect on the amount of anthocyanins extracted, compared to the classical extraction method.

Determination of some physicochemical properties and anthocyanin extraction conditions of Rosa damascena Mill.

In this study, some physicochemical and bioactive properties of Rosa damascena Mill. and the effect of different extraction methods and conditions on total monomeric anthocyanin (TMA) extraction were investigated. The average petal weights, petal areas, L*, a*, and b* values, dry matter, pH, titration acidity, L-ascorbic acid, TMA, and total phenolic content of the samples were 2.49 g, 6.04 cm2, 54.01, 37.30, 22.72, 18.65%, 5.45, 0.11 mg/100 g, 1,366.52 mg/kg DW, 515.79 mg C3G Eq./100 g DM and 4,353.52 mg GAE/100 g DM, respectively. Catechin, ellagic acid, rutin, gallic acid, and two different anthocyanins were detected. The mass transfer coefficient values in conventional (20, 40, and 60°C) and ultrasound-assisted extraction (50%, 75%, and 100% amplitude) were 0.068, 0.324, and 0.922 ml/cm2 and 2.178, 3.822, and 7.812 ml/cm2 min, respectively. Results showed that anthocyanins can be extracted faster and with higher yields by ultrasound-assisted extraction. Novelty impact statement Rosa damascena Mill. petals have attractive red color and are rich sources of anthocyanins. Anthocyanins are water-soluble natural pigment and have the positive effects on human health. The anthocyanin extraction, which takes 210 min at 60°C with conventional extraction, can be shortened up to 18 min at 100% ultrasound amplitude by ultrasound-assisted extraction.

Possibilities of using extracts obtained from Rosa pimpinellifolia L. flesh and seeds in ice cream production

In this study, extracts were prepared from the flesh and seeds of Rosa pimpinellifolia L. using different solvents and different extraction methods. Flesh pulp, seed powder, and the obtained extracts were added to the ice cream at 5%. Changes in some physical and chemical properties of the ice cream at the beginning and in the 2nd, 4th, and 6th months of storage were determined. It was found that the process had a very significant effect on dry matter content, pH value, titratable acidity, volume increase, complete melting time, L*, a*, b*, C, H°, and ΔE values, total phenolic content, and total monomeric anthocyanin content (p < .01). It was revealed that storage time had a very significant effect on dry matter content, pH value, titratable acidity, complete melting time, b* and C values, total phenolic content, and ABTS•+ (p < .01). There was no change in the total content of monomeric anthocyanins during the storage period of ice cream samples. Novelty impact statement Nowadays, the use of natural colorants has become widespread and artificial colorants are considered to cause harm to human health. Color and color stability in foods are important factors that determine consumer preference. The ways of obtaining anthocyanins, which give the red color, from many plants and their stability are currently being investigated. However, the growing conditions of these plants and the storage stability of the obtained natural colorant are commercially important. Anthocyanin-based extracts were obtained from the flesh and seeds of R. pimpinellifolia, acquired from a shrub that is naturally grown in Turkey and can meet its water needs with rainwater, and the possibilities of using anthocyanin-based extracts as natural colorants were investigated for the first time. It was concluded that the fruit and extracts of R. pimpinellifolia were a good commercial source of anthocyanins and could be used as a natural colorant due to their color stability during storage.

Effect of blanching, acid type, and temperature on the extraction of anthocyanin from Tibouchina semidecandra flower

Extraction is the most common way to obtain anthocyanins from their natural matrices. During the extraction, the anthocyanin may degrade due to the heat and acidic solvent. The objectives of this research were to determine the best acidic aqueous solution and temperature to extract anthocyanin from Tibouchina semidecandra flower and to decide if the blanching process has a significant effect on the extracted anthocyanin. The T. semidecandra petals were separated into two groups: steam blanched for 6 mins and without blanching. Both were dried for 24 hrs at 45°C and powdered. The extract was prepared by macerating the powdered petal into pH 3 aqueous solutions made of three different acids (citric, malic, and hydrochloric acid, respectively) in a water bath shaker at various temperatures (30, 45, 60, and 75°C) for an hour. The extracts were then filtered, centrifuged, and analysed for their colour intensity, browning index, monomeric anthocyanin, polymeric anthocyanin, and total phenolic content. The best method to obtain the highest colour intensity, monomeric anthocyanin, total phenolic content, and lowest browning index was using steam-blanched dried petal, citric or malic acid as solvent and extraction temperature at 60°C. The total monomeric anthocyanin and phenolic content of the extract was 3.63±0.35 mg/g dried petal and 74.47±11.47 mg/g dried petal, respectively.

Sensory evaluation and antimicrobial activity of snack bar from black soybean and black rice containing anthocyanins

Snack bars made from black soybean and black rice could be used as a food product to complement the energy and nutrients needs. Both have anthocyanins content in black soybean and black rice as well as the potential as an antimicrobial agent. The purpose of this study was to obtain an optimal formula, evaluate the sensory acceptance, analyze the total monomeric anthocyanin content of the snack bars, and compare the growth of probiotic and pathogenic bacteria in anthocyanins crude extracts from the snack bars. The production of snack bars was done by using three variations of main ingredients, including 30% of black soybean + 70% of black rice (formula 1), 50% of black soybean + 50% of black rice (formula 2), and 70% of black soybean + 30% of black rice (formula 3). The results performed that consumers acceptance for formulas 2 and 3 was not significantly different (P &gt; 0.05), but significantly higher (P &lt; 0.05) than formula 1. Total monomeric anthocyanin content analyzed by the pH differential method in these three snack bars formulas had no significant difference (P &gt; 0.05). The growth analysis of probiotic and pathogenic bacteria showed that the percentage of growth inhibition of Escherichia coli and Salmonella enterica serovar Typhi bacteria was significantly higher (P = 0.00) compared to Lactobacillus acidophilus. Also, formulas 1 and 2 could significantly inhibit E. coli and S. enterica ser. Typhi bacteria (P = 0.00) compared to formula 3. It could be concluded that formula 2 showed the best snack bar based on sensory evaluation and pathogenic bacteria inhibition assay.

Influence of different types of AGROTEX™ mulching material on the yield of lettuce (Lactuca sativa) introduced in Moscow region

Non-woven agrotextile coverings accelerate the growth and development of vegetable crops, as well as their nutritional value. The spectral composition of the absorbed, reflected and transmitted radiation depends on the colour of the nonwoven covering material. This study was conducted during 2018 at the Federal Scientific Vegetable Center, Moscow region to evaluate the effectiveness of various mulching materials. The nonwoven AgrotexTM mulching materials used were: white (W30), foil-clad (F), white-red (WR30), red-yellow (RY40) and yellow (Y20). The research was carried out on the Gourmet variety of lettuce (Lactuca sativa L.). The germination rate, productivity and accumulation of biologically active substances of lettuce depending on the type of covering material were determined. The total carotenoid, flavonoid and hydroxycinnamic acids content were higher with nonwoven materials, reaching an optimum with the RY40 material. On the contrary, the total monomeric anthocyanin content was lower when using AgrotexTM materials compared to the control. Agrotextile changes the spectrum of light incident on leaves, enhancing the regulatory effect, this explains the multidirectional change of antioxidant levels.

Effect of Different Processing Conditions on Bioactive Compounds of Selected Grape Varieties

Bioactive compounds in grapes vary in terms of cultivar and processing conditions. Raw juice and treated grape juices from locally grown Israel blue and locally available, imported, Red Globe and Michele Palieri varieties in Sri Lanka were used for the analysis. Grape juices were subjected to different processing conditions such as pasteurization and pectinase enzyme treatment. Total Monomeric Anthocyanin content (TAC), Total Phenolic Content (TPC), and antioxidant activity were analyzed. Compared to the imported grape varieties, the locally grown, pectinase enzyme-treated Israel blue grape juice with 2% pectinase enzyme concentration, 40 0C incubation temperature, and 2 hours incubation time, under dark condition had the significantly highest values (p &lt; 0.05) for TAC at 177.03±4.15 mg/L of malvidin-3-O-glucoside (M3G), TPC at 527.07 ± 3.55 mg/L of Gallic acid equivalents and antioxidant activity in terms of DPPH radical scavenging assay with IC50 value at 7.05±0.35 mg/mL Gallic acid equivalents and ABTS radical scavenging assay with IC50 value at 0.31±0.01 mg/mL of Trolox equivalents. TAC, TPC, and antioxidant activity of three grape varieties showed the highest values in pectinase enzyme-treated grape juice which was followed by raw juice and the pasteurized juice respectively. This research has taken an approach to enhance the bioactivity of grape juices via pectinase enzyme treatment and evaluate the suitability of locally grown Israel blue grape variety in Sri Lanka to form as a functional beverage to meet nutritional and health requirements.

Valorization of Peel Wastes of Purple Turnip (Brassica rapa L.): Extraction of Polyphenolics Through Ultrasonic-Assisted Extraction and Investigation of Changes in Total Phenolic Content, Total Monomeric Anthocyanin Content and Total Antioxidant Capacity During in vitro Gastro-Intestinal Digestion

Fruits and vegetables include high levels of bioactive compounds with health-promoting effects. Especially, peels, which are one of the generaly inedible fractions of fruit or vegetable, have higher amount of polyphenolic compounds than their pulps or seeds, since they accumulate in their peels. Purple turnip (Brassica rapa L.) is one of the important members of Brassicaceae family due to its nutritional composition. In this context, the aim of the study was to reveal the potency of peels from purple turnip as a natural antioxidant ingredient To reach this aim, the spectrophotometric assays including the Folin-Ciocalteu method for total phenolic content (TPC), the pH differential method for total monomeric anthocyanin content (TMAC) and CUPRAC and DPPH methods for total antioxidant capacity (TAC) before and after in vitro gastro-intestinal digestion were carried out. According to results of the study, TPC and TMAC of the polyphenolic axtract obtained by ultrasound-assisted extraction were 169.29±6.89 mg GAE/g dw and 159.53±10.82 mg CGE/L, respectively. The TAC of the extracts was 44.19±0.10 mg TE/g dw in CUPRAC assay and 38.52±0.06 mg TE/g dw in DPPH assay. The bioaccessibilities of total phenolics and anthocyanins from extracts after in vitro digestion process were approximately 17% and 6% and the antioxidant capacity of the bioaccessible extract fraction was approximately 28% (CUPRAC) and 0% (DPPH).

Changes in Elderberry (Sambucus nigra L.) Juice Concentrate Polyphenols during Storage

Elderberry (Sambucus nigra L.) juice concentrate is highly rich in polyphenols, particularly anthocyanins and flavonols, which have been associated with a wide range of health-promoting properties. Phenolic compounds, in particular anthocyanins, are unstable and may change during storage, which might influence the product color quality and its potential health effects. The aim of this study was to evaluate the changes in the polyphenols profile of elderberry juice concentrate produced at an industrial scale during seven months of storage at 5 °C and at room temperature. The total phenolic content, the total monomeric anthocyanins, the percent polymeric color, and the ABTS•+ scavenging activity were monitored over time. In addition, the profile and content of the main individual phenolic compounds were also assessed by HPLC-DAD. The results show that cyanidin-3-O-sambubioside, cyanidin-3-O-glucoside, cyanidin-3-O-sambubioside-5-O-glucoside, cyanidin-3,5-O-diglucoside, chlorogenic acid, rutin, and quercetin-3-O-glucoside were the main phenolic compounds identified. Storage at room temperature resulted in a strong reduction in total monomeric anthocyanin content accompanied by an increase in percent polymeric color values. Cyanidin-3-O-sambubioside and cyanidin-3-O-glucoside degraded faster than cyanidin-3,5-O-diglucoside and cyanidin-3-O-sambubioside-5-O-glucoside. Concentration of chlorogenic acid also decreased over storage, whereas rutin and quercetin-3-O-glucoside were quite stable. Storage at 5 °C caused a lower impact on the contents of anthocyanins and chlorogenic acid and the percent polymeric color was not affected. The total phenolic content and the in vitro antioxidant activity remained quite similar over the time, for both temperatures, suggesting that elderberry concentrates still preserve their health benefits of antioxidant capacity after seven months of storage.

Prebiotic activity of Indonesian black soybean (Glycine max (L.) Merr) anthocyanin

Anthocyanins are well known have potential as a prebiotic source as they could increase the growth of probiotic bacteria and inhibit the growth of pathogenic bacteria. This study was conducted to obtain the prebiotic activity from Indonesian black soybean anthocyanin. Black soybean anthocyanin was extracted with 80% methanol + 1 M HCl solution under room temperature using a water bath shaker. In vitro prebiotic activity assay of anthocyanin extract was done using the spread plate technique to measure the growth of probiotic and pathogenic bacteria. Lactobacillus acidophilus was used as the probiotic bacteria, while Escherichia coli and Salmonella typhi were used as the pathogenic bacteria. The whole soybean flour and extract residue were used to compare with the prebiotic activity of the extract. The total monomeric anthocyanin content of the extract was 0.33 mg/g. The highest prebiotic activity was obtained from anthocyanin extract, followed by the whole black soybean flour and anthocyanin extract residue, respectively. The prebiotic activity of the extract was higher compare with prebiotic activity standard (&gt;0.25). It could be concluded that Indonesian black soybean anthocyanin can be used as the source of prebiotic food.

Optimization of a natural low-calorie antioxidant tea prepared from purple corn (Zea mays L.) cobs and stevia (Stevia rebaudiana Bert.)

Purple corn (Zea mays L.) is a crop native to Peru and also widely cultivated in some countries around the world. It contains anthocyanins and other phenolic compounds that help reduce the incidence of a variety of chronic diseases. Here, a natural low-calorie antioxidant purple corn cob and stevia-based tea was optimized after being developed from five ingredients: purple corn cob (PCc), quince (Q), stevia (S), cinnamon (C) and cloves (Cv). A corn fiber filtration bag was selected to package single doses of the tea mixtures, based on the porosity, solid leakage during preparation and infusion absorption spectrum of four different types of bag. The tea was then optimized using an I-optimal mixture design to maximize the antioxidant capacity (AC) and total monomeric anthocyanin (TMA) content of the infusions. The optimum formulation given by the regression model consisted of decimal fractions of 0.8672 for PCc, 0.0464 for Q and 0.0864 for S, with a desirability of 91.2%, AC of 9.51 ± 1.21 μmol TE/mL and TMAs of 98.49 ± 6.00 mg C3GE/L, which were validated. The C and Cv contents were set at 0.0333 and 0.0025 of the total mixture, respectively.

Rapid Assessment of Anthocyanins Content of Onion Waste through Visible-Near-Short-Wave and Mid-Infrared Spectroscopy Combined with Machine Learning Techniques

A sustainable process for valorization of onion waste would need to entail preliminary sorting out of exhausted or suboptimal material as part of decision-making. In the present study, an approach for monitoring red onion skin (OS) phenolic composition was investigated through Visible Near-Short-Wave infrared (VNIR-SWIR) (350–2500 nm) and Fourier-Transform-Mid-Infrared (FT-MIR) (4000–600 cm−1) spectral analyses and Machine-Learning (ML) methods. Our stepwise approach consisted of: (i) chemical analyses to obtain reference values for Total Phenolic Content (TPC) and Total Monomeric Anthocyanin Content (TAC); (ii) spectroscopic analysis and creation of OS spectral libraries; (iii) generation of calibration and validation datasets; (iv) spectral exploratory analysis and regression modeling via several ML algorithms; and (v) model performance evaluation. Among all, the k-nearest neighbors model from 1st derivative VNIR-SWIR spectra at 350–2500 nm resulted promising for the prediction of TAC (R2 = 0.82, RMSE = 0.52 and RPIQ = 3.56). The 2nd derivative FT-MIR spectral fingerprint among 600–900 and 1500–1600 cm−1 proved more informative about the inherent phenolic composition of OS. Overall, the diagnostic value and predictive accuracy of our spectral data support the perspective of employing non-destructive spectroscopic tools in real-time quality control of onion waste.