Effects of temperature,solid content and pH on the stability of black carrot anthocyanins

Anthocyanin stability of black carrots was studied at various solid contents (11, 30, 45 and 64° Brix) and pHs (4.3 and 6.0) during both heating, at 70–90 °C, and storage at 4–37 °C. Monomeric anthocyanin degradation fitted a first-order reaction model. Degradation of monomeric anthocyanins increased with increasing solid content during heating, while it decreased during storage. For example, at pH 4.3, half-life periods for anthocyanins at 30, 45 and 64° Brix were, respectively, 8.4, 6.9 and 5.2 h during heating at 80 °C and 18.7, 30.8 and 35.9 weeks during storage at 20 °C. At 30–64° Brix, increasing pH from 4.3 to 6.0 enhanced the degradation of anthocyanins during heating. The effect of pH on thermal stability of anthocyanins was also studied at six different pHs (2.5–7.0) in citrate-phosphate buffer solutions and significant decrease in anthocyanin stability was observed at pHs above 5.0. Higher activation energies (E_a) were obtained during heating than during storage with increasing solid contents. At 30–64° Brix, E_a values ranged from 68.8 to 95.1 kJ mol⁻¹ during heating and from 62.1 to 86.2 kJ mol⁻¹ during storage. Q₁₀ values at 20–37 °C were as high as 3.1 at 45° Brix and 3.6 at 64° Brix.     

The effect of pre-treatment on the anthocyanin and flavonol content of black currant juice (Ribes nigrum L.) in concentration by reverse osmosis

Reverse osmosis process for the concentration of black currant juice was carried using AFC-99 tubular membrane at 30 °C and 45 bar. The contents of selected flavonols and anthocyanins were analyzed after centrifugation; enzyme treatment by Panzym Super E and by Rohapect berry followed by centrifugation; and ultrafiltration black currant juices and juice concentrates. The total soluble solid (TSS) content of the juices increased from the initial 17.6–17.9 °Brix to 24–24.8 °Brix in the case of the centrifuged juice in the concentration process. Similarly, it increased from 14.5–15.5 °Brix to 23.1–23.4 °Brix for the Panzym Super E treated juice, and from 16.1–16.9 °Brix to 22.5–23.1 °Brix for the Rohapect berry treated black currant juices. The ultrafiltered juice had the lowest initial TSS content between 14.1 and 14.9 °Brix and it increased to 22.1–23.1 °Brix. The average permeate fluxes during the concentration process were 7.3 L m⁻² h⁻¹ for the centrifuged juice, 11.9 L m⁻² h⁻¹ for the Panzym Super E treated juice, 9.2 and 13.1 L m⁻² h⁻¹ for the Rohapect berry treated and ultrafiltered juice, respectively. Analysis indicated that the enzymatic treatment resulted in the increase of anthocyanin and flavonol content of the juices. The centrifugation process decreased the amount of anthocyanins and flavonols to some extent. The juice clarified by ultrafiltration had significantly lower concentrations of anthocyanins and flavonols, while the juices treated by Panzym Super E had the highest levels of these flavonoids. This study recommends enzymatic pre-treatment by Panzym Super E, since it improves the permeate flux in reverse osmosis during the concentration process, and results in a juice concentrates highest in anthocyanins and flavonols.     

Anthocyanin stability studies in Tibouchina semidecandra L.

The effects of pH, storage period, temperature, light and dark conditions on the stability of anthocyanins extracted from Tibouchina semidecandra flowers of different developmental stages was evaluated. Fully formed but unopened flower bud had the highest amount of total anthocyanin extracted from fresh petals. The anthocyanin contents for all flower developmental stages were stable at pH 0.5–3.0 but the colour of the extracts faded at higher pH values. Degradation percentages of total anthocyanins in the extracts kept at 25 °C were 7–20% lower than that maintained at 31 °C. Extracts stored in darkness at 25 °C maintained their purple colour for 26 days while light exposure reduced it to an average of 10 days. The study shows that suitable storage condition for coloured anthocyanin pigments in extracted form is in acidic conditions in the dark. This implies the potential usage of coloured anthocyanins as natural food colourants and shelf life indicator for acidic foods.     

Storage quality of pineapple juice non-thermally pasteurized and clarified by microfiltration

Microfiltration (MF) is classified as a non-thermal process for the fruit juice industry. It could provide a better preservation of the phytochemical property and flavor of the juice. This work aimed to study the stability of phytochemical properties including vitamin C, total phenolic content, antioxidant capacity (2-Diphenly-1-picrylhydrazyl: DPPH, free radical scavenging capacity and Oxygen Radical Absorbance Capacity: ORAC assays), microbial and chemical–physical (color, browning index, pH and total soluble solid) properties of MF-clarified pineapple juice during storage at various temperatures (i.e. 4, 27, and 37 °C). The juices were clarified by microfiltration using hollow fiber module. The results showed that most of the phytochemical properties and soluble components were retained in the juice after microfiltration. No microbial growth was detected after 6 months of storage. The storage time and temperature did not affect total soluble solids and pH (P > 0.05). The color (L^*) of clarified juice stored at 4 °C was lighter than the juices stored at higher temperature levels (P < 0.05). The phytochemical properties and total phenol content of the juice significantly decreased as storage time and temperature increased (P < 0.05). Vitamin C content was the attribute that affected storage time and temperature most as indicated by reaction rate constant and activated energy. Storage of non-thermally pasteurized and clarified pineapple juice at 4 °C was the most suitable since it allowed the best quality preservation.     

Effects of light,temperature and water activity on the kinetics of lipoxidation in almond-based products

Lipoxidation in almond-derived products was investigated using the chemiluminescence (CL) and thiobarbituric acid-reactive substances (TBARS) methods to detect the first and later reaction products, respectively. The effects of light during storage at 5 °C, 22 °C and 40 °C were studied, as well as the effects of combined heat/water activity treatments in the 60–120 °C and 0.38–0.72 range. During storage, light was found to enhance the CL and TBARS values, and specific responses were observed in almond paste and the final Calisson product. During the heating of almond paste, as the initial water activity (a_w) increased, the CL rate constants increased during heating to 60 °C and 80 °C, but interestingly, these values decreased during further heating to 120 °C, whereas the maximum TBARS rate constants occurred at a_w 0.57 at all the heating temperatures tested. The activation energies, based on the CL and TBARS values, decreased specifically when the a_w increased from 0.38 to 0.72, giving overall values ranging from110 kJ mol⁻¹ to 60 kJ mol⁻¹. Likewise, in the same water activity range, the temperature-dependent rate constant enhancing factor (Q₁₀) decreased from 3.3 to 1.6.     

Heat resistance of Neosartorya fischeri in various juices

Heat resistance of Neosartorya fischeri was studied in three different juices (apple, pineapple and papaya). The optimum heat activation temperature and time for the ascospores of the N. fischeri (growth for 30 days at 30 °C) was 85 °C for 10 min. Of the three juices tested, apple juice exhibited maximum 1/k values at 80, 85 and 90 °C (208.3, 30.1 and 2.0 min, respectively). The 1/k values for papaya juice (129.9, 19.0 and 1.9 min) and pineapple juice (73.5, 13.2 and 1.5 min) decreased with acidity and °Brix/acidity (ratio) level. The Z^* values for apple, papaya and pineapple juices were 5, 5.5 and 5.9 °C, respectively. The sterilization F values (4-log reduction) for apple, pineapple and papaya juices were 56.3, 38.0 and 7.2 s, respectively. Considering the thermal treatments commercially applied to pineapple (96 °C/30 s) and apple juices (95 °C/30 s), it is concluded that such treatments will not guarantee that less than 1 ascospore in each set of 10³ packs survive. Only the treatment applied to papaya juice (100 °C/30 s) will be sufficient because the F value is less than 30 s.     

Degradation kinetics of anthocyanins in acerola pulp: Comparison between ohmic and conventional heat treatment

Degradation kinetics of monomeric anthocyanins in acerola pulp during thermal treatment by ohmic and conventional heating was evaluated at different temperatures (75–90 °C). Anthocyanin degradation fitted a first-order reaction model and the rate constants ranged from 5.9 to 19.7 × 10⁻³ min⁻¹. There were no significant differences between the rate constants of the ohmic and the conventional heating processes at all evaluated temperatures. D-Values ranged from 116.7 to 374.5 for ohmic heating and from 134.9 to 390.4 for conventional heating. Values of the free energy of inactivation were within the range of 100.19 and 101.35 kJ mol⁻¹. The enthalpy of activation presented values between 71.79 and 71.94 kJ mol⁻¹ and the entropy of activation ranged from −80.15 to −82.63 J mol⁻¹ K⁻¹. Both heating technologies showed activation energy of 74.8 kJ mol⁻¹ and close values for all thermodynamic parameters, indicating similar mechanisms of degradation.     

Characterisation of Italian commercial apricot juices by high-performance liquid chromatography analysis and multivariate analysis

The modern fruit juice industry needs their products to be characterized by high-quality attributes to meet consumers’ expectation. In this view, the composition of 26 Italian commercial apricot juices obtained from organic, integrated and conventional agriculture was analysed for carbohydrates, organic acids, amino acids, phenolic compounds and furanic compounds by high-performance liquid chromatography (HPLC). The content of 5-hydroxymethylfurfural in apricot juices (range 0.1–18 mg/l) was within the regulatory limit of 20 mg/l. The lack of furanic compounds in apricot fresh fruits confirmed their importance as quality markers of heating condition during processing and storage of fruit juices. Univariate analysis disclosed some significant differences among the composition of the apricot juices in terms of glucose, fructose, malic acid, glycine, chlorogenic acid, rutin, and a^∗-parameter (redness). Principal component analysis on chemical composition of apricot juices resulted in two principal components (PCs) that accounted for 66% of the total variance. Organic apricot juices showed some separation from the other juices, whereas a lack of distinction between integrated and conventional juices appeared.     

Matrix dependent impact of sugar and ascorbic acid addition on color and anthocyanin stability of black carrot,elderberry and strawberry single strength and from concentrate juices upon thermal treatment

Heat stability of strawberry, elderberry and black carrot juices prepared from concentrate and fresh plant material was investigated at pH 3.5 by heating at 95 °C for 2 and 4 h, respectively. The impact of added saccharides (glucose, fructose, sucrose) and ascorbic acid on 5-hydroxymethylfurfural (HMF) formation, browning together with the stability of anthocyanins and their color properties were assessed using high performance liquid chromatography coupled to diode array detection (HPLC-DAD) and ultraviolet–visible (UV–Vis) spectrophotometry. Thermal degradation products of anthocyanins and saccharides were identified using liquid chromatography coupled to multistage mass spectrometry (LC–MSⁿ). Pigment stability and color changes depended on anthocyanin structure and juice matrix. Whereas a slight but insignificant stabilizing effect of added sugars and ascorbic acid was observed in juice prepared from black carrot concentrate, obvious color differences were detected in strawberry and elderberry juices when ascorbic acid was added. Manually squeezed juices from fresh plant material showed higher color stability compared to juices prepared from concentrate which might be due to the retention of polymeric matrix compounds in the former. The data presented may contribute to the development of advanced technological processes for the production of coloring foodstuff and food with improved color stability.     

Extraction and characterisation of pectin methylesterase from black carrot (Daucus carota L.)

This study was carried out to determine some of the biochemical properties of pectin methylesterase (PME) from black carrot. The enzyme showed very high activity in a broad pH range of 6.5–8.5, with the optimum pH occurring at 7.5. The optimum temperature for maximal PME activity was found to be 55 °C. NaCl enhanced PME activity, particularly at 0.2 M. K_m and V_max values for black carrot PME using apple pectin as substrate were found to be 2.14 mg/ml (r² = 0.988) and 3.75 units/ml, respectively. The enzyme was stable between the temperatures of 30–50 °C/5 min whereas it lost nearly all of its activity at 70 °C/5 min. E_a and Z values were found to be 196.8 kJmol⁻¹ (r² = 0.996) and 2.16 °C (r² = 0.995), respectively.     

High hydrostatic pressure protection of a pectinase cocktail against thermal inactivation

Pectinase cocktails, containing pectinases, hemicellulases, and cellulases are used in the production of commercial apple juice to reduce juice viscosity, increase yield, and to clarify the final product. The kinetics of inactivation of a commercial pectinase formulation was studied at 0.1–400 MPa and 55.0–85.0 °C. High hydrostatic pressure slowed the rate of inactivation of the pectinase cocktail treated at inactivating temperature conditions by up to 19-fold at 77.0 °C, 350 MPa compared to inactivation at atmospheric pressure at the same temperature. Apparent activation energies of enzyme inactivation at 200–400 MPa were lower (107.3–154.4 kJ mol⁻¹) than at 0.1 MPa (195.6 kJ mol⁻¹).     

Effect of dielectric microwave heating on the color and antiradical capacity of betanin

The decomposition of betanin under dielectric heating (microwave irradiation, power: 25–200 W (3–24 kJ g⁻¹)) follows first-order kinetics with a rate constant similar to that obtained during conventional conduction heating (half-life < 2 min at 100 °C). Color coordinate analysis indicates that betanin is bleached upon thermal treatment, whereas beetroot juice and spray-dried beetroot powder tend to form colored decomposition products. The antiradical capacity of betanin decreases upon heating, but is still much higher than that of standard antioxidants such as ascorbic acid and trolox. Betalamic acid, a high capacity antiradical, was detected by mass spectrometry and second-derivative absorption spectroscopy in betanin samples submitted to thermal treatment.     

Rheological properties of ultraviolet-irradiated and thermally pasteurized Yankee pineapple juice

The rheological behaviour of Yankee pineapple juice was examined for the effect of ultraviolet (UV) irradiation (53.42 mJ/cm²) and compared with untreated juice and a thermally pasteurized (80 °C for 10 min) juice. A rheological test was performed on all types of juice in the temperature range 5 °C to 25 °C using a concentric cylinder rheometer at a shear rate range of 10–290 s⁻¹. The comparative analysis found that the best flow curves were described by the Bingham model with an initial shear stress. The entangled pulps in the juices prevented free flow at zero shear rate. There was no significant variation between the plastic viscosities of the untreated and UV-irradiated juice at all temperatures. The activation energy (E_a) of the untreated, UV-irradiated and thermally pasteurized juice was 6.80, 8.19 and 8.50 kJ/mol respectively.     

Anthocyanin and glucosinolate occurrences in the roots of Chinese red radish (Raphanus sativus L.), and their stability to heat and pH

Roots of three unique Chinese radish cultivars were evaluated as potential sources for anthocyanin-type colourants or value-added products. These cultivars showed high variation in anthocyanins (63.77–160.74 mg/100 g FW). Seventeen pigments were tentatively identified by mass spectroscopy as pelargonidin-3-sophoroside-5-glucoside derivatives with multiple acylation of hydroxycinnamic acids. A bright colour (CIELab) of radish anthocyanins has been shown at a wide pH range, comparably stable at pH < 4.2. Those anthocyanins also showed a remarkable thermal stability, following a zero-order kinetics at pH 2.5 with half-lives of 14.5 or 8.7 h at 90 or 100 °C, respectively. Additionally, those cultivars varied in glucosinolate contents (59.69–163.91 mg/100 g FW), whereas their degradation was sensitive to pH and followed a first-order kinetics at pH 5.8 with half-lives of 11.44 or 7.05 h at 90 or100 °C, respectively. However, the stable pH ranges for anthocyanins and glucosinolates were different: pH < 4.2 and pH > 3.6, respectively. In a radish juice model (pH 5.8/2.5), thermal degradation of anthocyanins or glucosinolates was associated closely with media pH values. In conclusion, cultivar selection, and thermal and pH conditions during processing or storage should be taken into account for quality, stability, and health benefits of radish derived natural colourants or nutraceutical products.     

Kinetics of the formation of radicals in meat during high pressure processing

The kinetics of the formation of radicals in meat by high pressure processing (HPP) has been described for the first time. A threshold for the radicals to form at 400 MPa at 25 °C and at 500 MPa at 5 °C has been found. Above this threshold, an increased formation of radicals was observed with increasing pressure (400–800 MPa), temperature (5–40 °C) and time (0–60 min). The volume of activation (ΔV^#) was found to have the value −17 ml mol⁻¹. The energy of activation (E_a) was calculated to be 25–29 kJ mol⁻¹ within the pressure range (500–800 MPa) indicating high independence on the temperature at high pressures whereas the reaction was strongly dependent at atmospheric pressure (E_a = 181 kJ mol⁻¹). According to the effect of the processing conditions on the reaction rate, three groups of increasing order of radical formation were established: (1) 55 °C at 0.1 MPa, (2) 500 and 600 MPa at 25 °C and 65 °C at 0.1 MPa, and (3) 700 MPa at 25 °C and 75 °C at 0.1 MPa. The implication of the formation of radicals as initiators of lipid oxidation under HPP is discussed.     

Thermal inactivation of lactoperoxidase in goat,sheep and bovine milk – A comparative kinetic and thermodynamic study

Using isothermal heating, inactivation of lactoperoxidase (LPO) in goat, sheep and cow milk was studied in the temperature range of 70–77 °C. Kinetic and thermodynamics studies were carried out at different time–temperature combination in order to evaluate the suitability of LPO as marker for the heat-treatment of milk and dairy products from different species. The thermal inactivation of LPO followed the first-order kinetics. D- and k-values decreased and increased, respectively with increasing temperature, indicating a more rapid LPO inactivation at higher temperatures. The influence of temperature on the inactivation rate constant was quantified using the Arrhenius and thermal death time models. The corresponding z-values were 3.38 ± 0.013, 4.11 ± 0.24 and 3.58 ± 0.004 °C in goat, sheep and cow milk, respectively. Activation energy values varied between milk species with 678.96 ± 21.43 kJ mol⁻¹ in goat milk, 560.87 ± 28.18 kJ mol⁻¹ in sheep milk and 641.56 ± 13.12 kJ mol⁻¹ in cow milk, respectively.     

Quality of nectarine and peach nectars as affected by lye-peeling and storage

This study was focused on nectarine and peach nectars, with the aim to evaluate different quality indices at the time of production and to devise a predictive model for quality variation during storage at 23 and 37 °C. Nectars were produced from the Elegant Lady and Redhaven peach varieties and from the Stark Red Gold nectarine variety, from both peeled and unpeeled fruits. The effects of processing on antioxidant contents, antioxidant activity and colour were evaluated. At the time of production, β-carotene ranged from 0.52 to 0.79 mg/kg, hydroxycinnamic acids (chlorogenic and neochlorogenic) from 34 to 73 mg/kg, catechin from 0 to 24 mg/kg, quercetin 3-O-glycosides from 3.9 to 12.7 mg/kg, and cyanidin 3-O-glucoside from 0 to 9.4 mg/kg. Within the same variety, carotenoid and phenolic contents were lower in the nectars obtained from peeled fruits than in those obtained from unpeeled fruits. However, as ascorbic acid was adjusted to a level of 300 mg/kg during blending, which is far higher than the observed levels of phenolics and carotenoids, it mainly accounted for nectar radical-scavenging activity towards the 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical, which on average was 1.8 mmoles Trolox equivalents/kg. The colour of nectars was improved by processing lye-peeled fruits at room temperature, whatever the variety used; i.e., this process decreased the redness index, a^∗, and increased the lightness index, L^∗, and yellowness index, b^∗, with respect to the traditional process.     

Kinetic and thermodynamic study of thermal inactivation of the antimicrobial peptide P34 in milk

The knowledge on thermal inactivation of biopreservatives in a food matrix is essential to allow their proper utilisation in food industry, enabling the reduction of heating times and optimisation of heating temperatures. In this work, thermal inactivation of the antimicrobial peptide P34 in skimmed and fat milk was kinetically investigated within the temperature range of 90–120 °C. The inactivation kinetic follows a first-order reaction with k-values between 0.071 and 0.007 min⁻¹ in skimmed milk, and 0.1346 and 0.0119 min⁻¹ in fat milk. At high temperatures, peptide P34 was less resistant in fat milk, with a significant decrease in residual activity as compared with skimmed milk. At temperatures below 110 °C, the fat globules seem to have protective effect to the peptide P34. Results suggest that peptide P34 is heat stable in milk with activation energy of 90 kJ mol⁻¹ in skimmed milk and 136 kJ mol⁻¹ in fat milk.     

Effect of spray drying and storage on the stability of bayberry polyphenols

Bayberry juice was spray dried with maltodextrin (DE 10) as a carrier and then stored under different temperature and water activities (aw). The retention of the total phenolic content (TPC) and total anthocaynins (ACN) during the drying process were about 96% and 94%, respectively, suggesting spray drying was a satisfactory technique for drying heat sensitive polyphenols. Under an aw of 0.11–0.44, the TPC and ACN in bayberry powders decreased by about 6–8% and 7–27%, respectively, after 6 months storage at 4 °C; at 25 °C for the same storage period the decreases were between 6–9% and 9–37%, respectively, while at 40 °C the decreases were in the range 7–37% and 9–94%. The anthocyanin component was more readily degraded relative to other phenolic compounds. The results suggest that bayberry powder should be stored at less than 25 °C and aw of 0.33, on account of greater polyphenol stability under such conditions.     

Postharvest stilbenes and flavonoids enrichment of table grape cv Redglobe (Vitis vinifera L.) as affected by interactive UV-C exposure and storage conditions

Flavonoids and stilbenes are secondary metabolites produced in plants that can play an important health-promoting role. The biosynthesis of these compounds generally increases as a response to biotic or abiotic stress; therefore, in order to achieve as high phenolic accumulation as possible, the interactive effects of storage conditions (temperature and time) and UV-C radiation on polyphenols content in postharvest Redglobe table grape variety were investigated. During a storage time longer than 48 h, both cold storage (4 °C) and UV-C exposure of almost 3 min (2.4 kJ m⁻²) positively enhanced the content of cis- and trans-piceid (34 and 90 μg g⁻¹ of skin, respectively) together with quercetin-3-O-galactoside and quercetin-3-O-glucoside (15 and 140 μg g⁻¹ of skin, respectively) up to three fold respect to control grape samples. Conversely, catechin was not significantly affected by irradiation and storage treatments. With regard anthocyanins, the highest concentrations of cyanidin-3-O-glucoside and peonidin-3-Oglucoside were observed in Redglobe, stored at both room temperature and 4 °C, after 5 min (4.1 kJ m⁻²) of UV-C treatment and 24 h of storage. Gathered findings showed that combined postharvest treatments can lead to possible “functional” grapes, within normal conditions of market commercialization, responding to the rising consumers demand to have foods that support and promote health.