Response surface optimisation for the extraction of phenolic compounds and antioxidant capacities of underutilised Mangifera pajang Kosterm. peels

The optimum extraction conditions for highest recovery of total phenolics content (TPC) and antioxidant capacities (AC) were analysed for Mangifera pajang peels (MPP), using response surface methodology. The effects of ethanol concentration (X₁: 20–80%), extraction temperature (X₂: 30–65 °C) and liquid-to-solid ratio (X₃: 20–50 mL/g) on the recovery of total phenolics (Y₁) and antioxidant capacity (Y₂) were investigated. A second order polynomial model produced a satisfactory fitting of the experimental data with regard to total phenolic content (R² = 0.9966, p < 0.0001) and antioxidant capacity (R² = 0.9953, p < 0.0001). The optimum extraction conditions for TPC were 68%, 55 °C and 32.7 mL/g, and for AC were 68%, 56 °C and 31.8 mL/g, respectively. Predicted values for extraction of TPC and AC agreed well with the experimental values. Liquid chromatography–mass spectrometry of the optimally obtained extracts from MPP revealed the major phytochemicals as mangiferin, gallic acid, catechin and epicatechin.     

Lycopene-rich fractions derived from pink guava by-product and their potential activity towards hydrogen peroxide-induced cellular and DNA damage

Effects of solvent and supercritical carbon dioxide (SC-CO₂) extraction on antioxidant and cytotoxic activities of lycopene-rich fractions of decanted pink guava by-product (decanter) were determined with lycopene-equivalent antioxidant capacity, β-carotene bleaching and MTT (3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide) assays. Extraction with SC-CO₂ gave a higher yield than solvent extraction (3.15 vs. 0.68 mg/100 g dried decanter, corresponding to 42.99 and 33.63 mg of lycopene). No cytotoxicity was found in Chang liver cells supplemented with either extracts (6.25–200 μg/ml). Solvent extract at 25 μg/ml (2.32 μM lycopene) and SC-CO₂ extract at 200 μg/ml (5.09 μM lycopene) had protective effect against hydrogen peroxide-induced cytotoxicity. However, only high concentrations of solvent extract (200 μg/ml; lycopene = 18.65 μM) or lycopene standard (10 μM) protected cells against DNA damage. Supercritical fluid extraction demonstrated a higher yield in lycopene-rich fraction from decanter. These fractions have the potential to be developed as a functional ingredient to prevent oxidative stress and other related diseases.     

Optimisation of the solvent extraction of bioactive compounds from Parkia speciosa pod using response surface methodology

Central composite design was employed to optimise the buffer-to-solids ratio (X₁: 20–50 ml/g), incubation temperature (X₂: 35–55 °C) and time (X₃: 100–200 min), obtaining extracts from Parkia speciosa pod with high total phenolic and flavonoid contents and high antioxidant activities. Analysis of variance showed that the contribution of a quadratic model was significant for the responses. An optimisation study using response surface methodology was performed and 3D response surfaces were plotted from the mathematical models. The optimal conditions based on combination responses were: X₁ = 20 ml/g, X₂ = 35–36 °C and X₃ = 100–102 min. These optimum conditions yielded total phenolic contents of 664–668 mg gallic acid equivalents/100 g, total flavonoid contents of 47.4–49.6 mg pyrocatechol equivalents/100 g, %DPPH_sc of 81.2–82.1%, %ABTS_sc of 78.2–79.8% and FRAP values of 3.2–3.3 mM. Close agreement between experimental and predicted values was found. This methodology could be applied in the extraction of bioactive compounds in the natural product industry.     

Effect of maturity stage on the content of fatty acids and antioxidant activity of ‘Hass’ avocado

Avocado (Persea americana) is an important tropical fruit and a good source of lipophilic phytochemicals such as monounsaturated fatty acids, carotenoids, vitamin E and sterols that have been inversely related to cardiovascular diseases. However, their antioxidant capacities have received far less attention compared with hydrophilic phytochemicals in this fruit. In this context, this study evaluated the effect of the stage of ripeness of ‘Hass’ avocado on the content of lipophilic and hydrophilic phytochemicals and their correlation with the antioxidant capacity. In every ripeness stage the fatty acids, total phenolic and flavonoid content as well as the antioxidant capacity were evaluated. Physiological and physico-chemical analysis were also performed including respiration rate, ethylene production, firmness, color (L*, °Hue, and Chroma), dry matter and oil content. In general, total phenols increased during ripening, while flavonoids slightly decreased. The main fatty acid identified was oleic acid (about 67-70% of total content). In general, a significant increase in monounsaturated and saturated fatty acids was observed during avocado ripening while polyunsaturated fatty acid content decreased (p < 0.05). Lipophilic extracts showed higher values of antioxidant capacity than hydrophilic, however, both extracts had similar trends for DPPH, TEAC and ORAC assays. DPPH and TEAC assays had a positive correlation with some unsaturated fatty acids. Avocado at different ripeness stages showed a better antioxidant capacity in the lipophilic fraction, which correlated with the fatty acid content evaluated.     

Processing optimization and characterization of gelatin from lizardfish (Saurida spp.) scales

Response surface methodology (RSM) with a 4-factor, 5-level central composite design (CCD) was conducted to ascertain the optimum gelatin extraction conditions from lizardfish scales. The effects of concentration of NaOH (%, X₁), treatment time (h, X₂), extraction temperature (°C, X₃) and extraction time (h, X₄) were determined. The responses included extraction yield (%), gel strength (g) at 9-10 °C and viscosity (cP) at 25 °C. The results showed the optimum conditions for the highest values of the three responses when a concentration of NaOH at 0.51%, a treatment time at 3.10 h, an extraction temperature at 78.5 °C and an extraction time at 3.02 h. The predicted responses were 10.7% extraction yield, 240 g gel strength and 5.61 cP viscosity. The experimental values were 10.6 ± 0.82% extraction yield, 252 ± 1.21 g gel strength and 7.50 ± 0.28 cP viscosity. The physicochemical properties of the lizardfish scales gelatin were characterized and the results indicated high protein and low ash content. Texture profile analysis (TPA) with compression was carried out at 30% deformation. The lizardfish scales gelatin was found to contain 20.4% imino acids (proline and hydroxyproline). Furthermore, slightly loose strands of the gel microstructure were observed using scanning electron microscopy (SEM).     

Effects of supercritical fluid extraction parameters on lycopene yield and antioxidant activity

The effects of various parameters of supercritical carbon dioxide (SC-CO₂) fluid extractions of tomato skins on the extraction yields and antioxidant activities of lycopene-rich extracts were investigated. A Box–Behnken design was applied to study the effects of three independent variables (temperature ranging from 40 to 100 °C, pressure ranging from 20 to 40 MPa, and flow rate ranging from 1.0 to 2.0 mL/min) on lycopene yield. The model showed good agreement with the experimental results, by the coefficient of determination (r² = 0.9834). Temperature, pressure, and the quadratic term for the temperature of SC-CO₂ extraction were large significantly positive factors affecting lycopene yield (P < 0.05). The maximum total lycopene content of 31.25 μg/g of raw tomato was extracted at the highest temperature of 100 °C, 40 MPa and 1.5 mL/min. TEAC assay was applied to assess the antioxidant activity of lycopene-rich extracts from SC-CO₂ fluid extraction. The effects of SC-CO₂ fluid extraction parameters on the antioxidant activities of the extracts differed with the yield. For each unit of lycopene extract, the antioxidant activity level was constant below 70 °C, but then gradually decreased above 70 °C due to isomerization occurring as a result of the higher temperature. The ratio of all-trans-lycopene to the cis-isomers changed from 1.70 to 1.32 when the operating temperature was adjusted from 40 to 100 °C, indicating an increased bioavailability due to the generation of the cis-isomers. No significant effects of pressure or flow rate of SC-CO₂ fluid extraction on the antioxidant activity were observed.     

Effect of minimal processing on bioactive compounds and color attributes of fresh-cut tomatoes

The feasibility of minimal processing and modified atmosphere packaging (5%O₂+5%CO₂) to preserve color attributes and bioactive compounds of fresh-cut tomato from different cultivars (Rambo, Durinta, Bodar, Pitenza, Cencara and Bola) was evaluated through storage under refrigeration. The phenolic compounds and vitamin C content of the six cultivars varied between 187.4 and 335.9 mg/kg fw and from 69.6 and to 212.3 mg/kg fw, respectively. The highest content of lycopene was found in Bodar tomatoes (80.5 mg/kg fw) while the concentration in the other cultivars ranged between 20.0 and 43.1 mg/kg fw. Antioxidant capacity, measured on the basis of the DPPH stable radical, was higher than 9.8% of DPPH inhibition. Neither the content of health-related compounds (lycopene, vitamin C and phenolic compounds) nor the antioxidant capacity changed significantly between whole and just-processed fresh-cut tomatoes. Furthermore the initial colors of fresh-cut tomatoes as well as vitamin C were maintained for 3 weeks under cold storage. The antioxidant capacity was well correlated with vitamin C and phenolic content, whereas lycopene was directly related to color measurements (a^*, L^* and H^*). Minimal processing maintains the main antioxidant compounds and color parameters of slices tomatoes for 21 days at 4 °C, thus preserving their initial nutritional value.     

Optimisation of serine protease extraction from mango peel (Mangifera Indica Cv. Chokanan)

This study investigated the possible relationship between the enzyme extraction variables, namely amount of buffer (25–75 ml, X₁), temperature (−20, 25 °C, X₂) and mixing time (1–3 min, X₃) on total protein (Y₁), total activity (Y₂), specific activity (Y₃), storage stability (Y₄), temperature stability (Y₅) and pH stability (Y₆) of serine protease from mango peel. It was found that there was significant (p < 0.05) fit of the response surface models for all the response variables investigated. There was indication of high coefficient of determination (R²) values (between 0.954 and 1.000) in the regression models describing variations of the response variables. It was found that there was no significant (p > 0.05) difference between the experimental and predicted values. This ensured that the response surface models used to indicate property changes of serine protease as a function of enzyme extraction conditions were sufficient.     

A comparative evaluation of methodologies for water content determination in green coffee

The main objective of this study was to compare methods for mass loss evaluation in green coffee to water content determination by Karl Fischer titration (KFT). The following methodologies were tested: (i) ISO 6673 (oven drying at 105 °C for 16 h); (ii) the reference method employed by the Brazilian Agriculture Ministry (oven drying at 105 °C for 24 h)—BRAMw, employing whole beans and BRAMg, employing ground beans; and (iii) infrared drying (IRD). Reference oven drying methodologies ISO 6673 and BRAMw presented results statistically equivalent (p>0.05) to those from KFT in the moisture content range that is of interest for green coffee commercialization (8-13 g/100 g), whereas IRD results were lower than those for KFT. ISO 6673 and BRAMw also presented the highest values of correlation coefficients to KFT. Differences in moisture content determination became more significant for lower moisture content values (4-7 g/100 g), probably due to loss of organic volatile substances during drying and occurrence of moisture loss during sample grinding.     

Impact of limited drying on Momordica cochinchinensis Spreng. aril carotenoids content and antioxidant activity

Food product based on gac fruit (Momordica cochinchinensis Spreng.) arils have a high potential due to the high carotenoids content of this fruit. Drying is a key preparation step for carotenoids extraction from gac fruit in a economically viable process. The impact of different drying technics, temperature, final product moisture content on the carotenoid content, hydrophilic and lipophilic antioxidant activity (evaluated with three methods) and color of the gac arils is discussed based on laboratory scale experimental tests. The results highlight an optimal temperature between 50 °C and 60 °C to conserve the color, the carotenoid content and the antioxidant activity. Also, these properties are better preserved by limiting the drying to dry based moisture content between 15% and 18% while the advantages of drying for further processing and for refrigerated conservation for a few months are achieved.     

Onion high-pressure processing: Flavonol content and antioxidant activity

Onion flavonol content and antioxidant activity have been related to human health promoting effects. Quercetin and quercetin glucosides (quercetin-4′-glucoside and quercetin-3,4′-diglucoside) have been reported the main onion flavonols in recent literature. Impact of combined treatments of high-pressure processing (HPP) and temperature on onion nutritional attributes has been scarcely studied.Our study aimed to investigate the impact of HPP technology combined with temperature on onion (Allium cepa L. var. cepa, ‘Grano de Oro’) total phenol content, flavonol content, and antioxidant capacity. The experimental design comprised a response surface methodology according to a central composite face-centred design. The variable ranges were 100-400 MPa (pressure) and 5-50 °C (temperature), time was set up constant to 5 min.Response surfaces of onion total quercetin, quercetin-4′-glucoside, and quercetin-3,4′-diglucoside content showed a similar pattern. The application of low temperature (5 °C) combined with pressures of 100 and 400 MPa triggered to a better extraction of these flavonols among the treatments analysed. Response surface of the EC₅₀ antioxidant parameter as a function of pressure and temperature showed a clear trend towards an increase in onion antioxidant activity when applying pressures from 100 to 400 MPa. Four hundred megapascals/5 °C-processed onion showed an approximately 33% higher quercetin-4′-glucoside content compared with the untreated onion, and maintained the antioxidant activity of the untreated onion.     

Effect of air-drying temperature on physico-chemical properties,antioxidant capacity,colour and total phenolic content of red pepper (Capsicum annuum, L. var. Hungarian)

Red pepper has been recognised as an excellent source of antioxidants, being rich in ascorbic acid and other phytochemicals. Drying conditions, particularly temperature, leads to pepper modifications that can cause quality degradation. In this work, the effects of process temperatures between 50 and 90 °C on physico-chemical properties, rehydration, colour, texture, vitamin C, antioxidant capacity and total phenolics during the drying of red pepper were studied. The rehydration ratio decreased with temperature and the maximum water holding capacity was achieved at 50 °C. Both vitamin C content and the total phenolic content decreased as air-drying temperature decreased. The radical scavenging activity showed higher antioxidant activity at high temperatures (i.e. 80 and 90 °C) rather than at low temperatures (i.e. 50, 60 and 70 °C). Chromatic parameters (L*, a*, b*, C* and H°), non-enzymatic browning compounds and extractable colour were affected by drying temperature, which contributed to the discolouring of pepper during this process.     

TG–DTA approach for designing reference methods for moisture content determination in food powders

There is no systematic procedure described in the literature to establish a robust and accurate reference method for determining the moisture content in any solid food product. In this paper, we are proposing a new approach based on simultaneous thermogravimetry and differential thermal analysis (TG–DTA), with data for several amorphous food powders that result from spray-drying, freeze-drying or extrusion. In the first step, by heating a representative sample of about 20 mg at 2 °C/min we would detect the temperature and the mass loss at the inflection point that characterises, if there is an inflection, the end of the drying and the onset of chemical reactions. In cases of not too much sensitive products, the mass loss at the inflection may be considered as a good estimation of the moisture content. At 2 °C/min heating rate, the inflection temperature T_i is an indicator that allows estimating the optimal isothermal drying temperature T_d about 15–30 °C below T_i, depending on the product sensitivity to heat treatments and the kinetics of water molecule diffusion through the amorphous matrix. Then, a series of three isothermal drying are performed at about T_d−12 °C, T_d and T_d+8 °C, and a simple multilinear model allows calculating the best oven temperature to achieve the optimal moisture content determination in 2 h. This procedure is described and results are shown for several dehydrated food products: milk, coffee, cereal and pet food. This fast procedure may be applied either for establishing optimal oven conditions for most amorphous new products or for revising conditions that have been established in the past but are not robust enough for several ones.     

The effect of delactosed whey permeate on phytochemical content of canned tomatoes

The effect of delactosed whey permeate (DWP) treatment on antioxidant and phyto-chemical components of canned Irish plum tomatoes were investigated. Tomatoes were sterilised for 5 min (F₀) at 120 °C and stored for 6 months. The DWP treatment retained significantly (p < 0.05) higher levels of ascorbic acid and lycopene of tomatoes. The antioxidant activity of DWP treated tomatoes was higher (7%) than the control at the end of storage. The firmness in DWP-treated fruits was around 40% higher than that in control. All the parameters decreased significantly (p < 0.05) during storage except lycopene and total phenols. Lycopene content showed no significant change and total phenols increased during storage. The changes in ascorbic acid, antioxidant activity and texture were fitted well to Weibull kinetic models with high coefficients of determination (R²) and low RMSE (root mean sum of squared error). The results clearly indicate that DWP enhanced the retention of antioxidant compounds in tomatoes during storage.     

Quantification of polyphenols and ergothioneine in cultivated mushrooms and correlation to total antioxidant capacity

Agaricus bisporus, Lentinula edodes, Pleurotus ostreatus, Pleurotus eryngii and Grifola frondosa were analyzed for antioxidant capacity, as measured by oxygen radical absorbance capacity (lipophilic and hydrophilic) (ORAC_total), hydroxyl radical averting capacity (HORAC), peroxynitrite radical averting capacity (NORAC), superoxide radical averting capacity (SORAC) assays, Folin-Ciocalteu reagent and ergothioneine (ERG) content. ORAC_totalvalues ranged from 39 to 138 μmol of Trolox equivalents (TE)/g dry weight (dw). HORAC values ranged from 3.0 to 13.6 μmol of caffeic acid equivalents/g dw. NORAC values ranged from 2.0 to 9.0 μmol TE/g dw. SORAC values ranged from 0.37 to 2.6 kunit superoxide dismutate equivalents/g dw. Polyphenols ranged from 4.2 to 10.6 mg gallic acid equivalents/g dw. A. bisporus mushrooms, especially portabellas, had higher antioxidant capacity relative to the specialty mushrooms tested. ERG ranged from 0.21–2.6 mg/g dw with L. edodes, P. ostreatus, G. frondosa containing a statistically significant greater amount compared to A. bisporus. A good correlation was found between ORAC_total and polyphenols (R² = 0.86).     

Effect of drying methods on the phenolic constituents of meadowsweet (Filipendula ulmaria) and willow (Salix alba)

The objective of this study was to investigate the effect of drying conditions on the phenolic constituents and colour of extracts of organically grown white willow and meadowsweet for incorporation into a functional beverage with potential anti-inflammatory properties. The herbs were freeze-dried, air-dried, oven or tray-dried at 30 or 70 °C. The drying kinetics of the herbs was first determined. Both drying temperature and method had a significant effect (p ≤ 0.05) on the drying rate, the samples tray-dried had a faster drying rate than those oven-dried. Results show that for meadowsweet and willow, freeze-drying and oven or tray drying at 30 °C had no significant effect on the phenolic constituents (e.g. total phenols, salicylates, quercetin) or the colour of the extracts in comparison to traditional air-drying. Although increasing the drying temperature to 70 °C resulted in an increase in the drying rate of both herbs it also led to the loss of some phenolic compounds. Also, the extracts from both herbs dried at 70 °C were significantly (p ≤ 0.05) redder than the other drying methods. Therefore, tray drying these herbs at low temperatures may reduce drying time without having a significant effect on the phenolic content and colour of the extracts.     

Isolation,characterization and antioxidant capacity assessment of the bioactive compounds derived from Hypoxis rooperi corm extract (African potato)

The rhizome of the plant Hypoxis rooperi (“African potato”) is known for its traditional and ethnomedical uses in the treatment of benign prostatic hyperplasia and other diseases. We have characterized an extract derived from H. rooperi, isolated its major bioactive compound, hypoxoside, and obtained its aglycone, rooperol, by enzymatic digestion. Absorption, fluorescence emission and bidimensional NMR complete spectral data of these compounds were obtained. The antioxidant capacity of both compounds was fully analyzed through the thiobarbituric acid reactive substances (TBARS) and Trolox equivalent antioxidant capacity (TEAC) assays, and it was compared to catechins and olive biophenolics. Both compounds showed a strong antioxidant capacity, although rooperol exhibited a higher antioxidant activity against lipid peroxidation which correlated to its strong affinity for phospholipid membranes as derived from its extremely high lipid/water partition coefficient (K_p = 3.4 × 10⁴). The study of the lipophilic (EtOH) and hydrophilic (water) TEAC values revealed that more hydrophobic compounds, had greater lipophilic TEAC values than hydrophilic ones, probably indicating that lipophilic TEAC assay may be more reliable for these compounds. The H. rooperi extract also showed higher antioxidant efficacy compared to other strong antioxidant herbal extracts, such as olive leaf or green tea. Moreover, neither evidence of acute oral toxicity nor adverse effects were observed when the H. rooperi commercial extract containing 45% hypoxoside was used at a dosage of 2000 mg/kg. The results obtained in this work may contribute to understanding the biological activity described for these dicatechols and the African potato extract for food and cosmetic applications.     

Effect of drying method on the antioxidant capacity of six Lamiaceae herbs

The present study investigated the changes in total phenols (TP), rosmarinic acid content and antioxidant capacity of six Lamiaceae herbs (rosemary, oregano, marjoram, sage, basil and thyme) after three drying treatments (air-, freeze- and vacuum oven-drying) stored for 60 days at −20 °C and compared to fresh samples. Ferric reducing antioxidant property (FRAP) and oxygen radical absorbance capacity (ORAC) were used as markers for antioxidant capacity. Air-dried samples had significantly (p < 0.05) higher TP, rosmarinic acid content and antioxidant capacity than had freeze-dried and vacuum oven-dried samples throughout the storage period. Fresh samples had the lowest values for the parameters tested. Vacuum oven-drying resulted in higher TP and FRAP values in rosemary and thyme during 60 days of storage than did freeze-drying. In ORAC assay, the difference was significantly higher only in thyme. Storage did not show any effect on the dried samples for the parameters tested.     

Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products

Dehydration promoted important modifications affecting both the physico-chemical properties of dietary fibre (DF) and the antioxidant capacity of orange by-products (peel and pulp remaining after juice extraction). The significance of such changes was largely dependent on the air-drying temperature used (from 30 °C to 90 °C). The major modifications on the DF components were observed when either extended drying periods, i.e. at lower temperatures, or elevated drying temperatures were applied. Dehydration around 50–60 °C apparently promoted the minor disruption of cell wall polymers, in particular of pectic substances. Pulp samples exhibited higher values of swelling (SW) and fat adsorption capacity (FAC) than those derived from orange peel. Although, significant decreases in water retention capacity (WRC), FAC and solubility values were detected for both by-products as the air-drying temperature increased. The antioxidant capacity associated to dehydrated citrus by-products was significantly higher for orange peel than for pulp samples. In general, the by-products studied proved to be quite resistant to the different heat treatments applied within the range of 40–70 °C. In overall, the study shows that, in order to preserve either the DF quality and/or the antioxidant capacity, air-drying temperature should be controlled since both types of compounds, DF components and antioxidants, might be degraded or modified either when extended drying periods and/or high drying temperatures are applied.     

The use of photochemiluminescence for the measurement of the integral antioxidant capacity of baobab products

The number of methods to measure antioxidants in botanicals, foods, nutraceuticals and other dietary supplements are increased considerably in the last 10 years. However most techniques require long experimental times and high costs to determine antioxidant capacity of hydrophilic or lipophilic compound in a food mixture. By means of a photochemiluminescence method, we assessed the Integral Antioxidant Capacity (IAC) which represents the sum of the antioxidant capacity of hydrophilic and lipophilic antioxidants. In this study the IAC of extracts from Adansonia digitatata (i.e. red fiber, fruit pulp and leaves), was assessed in comparison to those deriving from other natural sources of antioxidants (i.e. orange, kiwi, apple and strawberry). When compared, IAC values for the examined product resulted as follows: Adansonia digitata red fibre ? Adansonia digitata fruit pulp ? Adansonia digitata fresh leaves ? Adansonia digitata seeds ? Adansonia digitata radix cuticle ? orange fresh pulp ? strawberry fresh fruit pulp > Adansonia digitata radix > bilberry fresh pulp ? kiwi fruit pulp. Results clearly indicate the interesting antioxidants properties of Adansonia digitata red fibre, in particular the IAC value of baobab red fibre was 66 time higher than that of orange pulp, with value of 1617.3 μmol/g and 24.3 μmol/g, respectively.