Quality changes of pasteurised mango juice during storage. Part I: Selecting shelf-life markers by integration of a targeted and untargeted multivariate approach

For the first time, a multivariate approach combining targeted and untargeted data was used to obtain insight into quality changes in pasteurised mango juice (cv. ‘Totapuri’) as a function of storage (42 °C for 8 weeks). Mango juice samples were formulated with addition of different potential precursors for different quality-related chemical reactions: ascorbic acid, citric acid and sugars. Control (diluted mango puree with water), ascorbic acid-enriched (AA₂₅₀ and AA₅₀₀), citric acid-enriched (CA, CA + AA₂₅₀ and CA + AA₅₀₀) and sugar-enriched (S) samples were characterised for a range of targeted quality parameters as well as for a volatile fingerprint (untargeted). Selection of shelf-life markers or quality parameters significantly changing during shelf-life was performed over all formulations as well as per mango juice formulation. Our study showed that a common trend over all formulations was observed for colour values (VID > │0.90│), while specific shelf-life markers were selected for each formulation. In acidified mango juice samples (CA, CA + AA₂₅₀, CA + AA₅₀₀), more terpene oxides were selected compared to other formulations. In ascorbic acid-enriched samples (AA₂₅₀, AA₅₀₀, CA + AA₂₅₀, CA + AA₅₀₀), furfural and ascorbic acid were significantly changing during shelf-life. It seems that the reaction pathways for compounds being formed or degraded upon shelf-life are clearly affected by the acidity level.     

Furfurals removal from roasted coffee powder by vacuum treatment

The possibility of removing 5-hydroxymethylfurfural (HMF) and furfural from roasted coffee by application of vacuum treatments was studied. In particular, different combinations of pressure and time were used. Results showed that the vacuum treatment was ineffective in removing HMF and furfural from anhydrous (commercial) coffee powder, while it proved effective if applied to previously hydrated samples. Besides, the hydration step alone was responsible for furfurals removal, although prolonged times were needed. By applying a hydration step up to a_w 0.7, followed by a vacuum treatment at 2.7 kPa and 60 °C for 10 min, 20% and 100% HMF and furfural removals were achieved, respectively. These differences in the percentages of HMF and furfural removal can be attributed to differences in the chemical and physical properties of the two molecules. However, the vacuum treatments caused a significant decrease in the coffee headspace total volatiles that in turn was responsible for a lower odour intensity of the samples. Therefore further studies are needed to reveal process conditions able to minimise the loss of sensory properties, making this technology a reliable strategy to mitigate the furfural contents in coffee.     

Study of chemical changes in pasteurised orange juice during shelf-life: A fingerprinting-kinetics evaluation of the volatile fraction

The current work used fingerprinting-kinetics for the first time to monitor shelf-life changes in a low-pH, pasteurised, shelf-stable product, more particular in orange juice. Orange juice samples were stored as a function of time at four different storage temperatures (20, 28, 35 and 42 °C). To obtain insight into chemical changes in the volatile food fraction, samples were fingerprinted with headspace GC–MS. The objectives of this work were twofold: (i) to identify major chemical changes of pasteurised orange juice during shelf-life and (ii) to study the kinetics of selected shelf-life compounds in the context of accelerated shelf-life testing (ASLT). At 20 °C, changes in terpenes and a decrease in aldehydes were observed. Oxides and sulphur compounds increased and esters decreased at increased storage temperatures (at 28 °C and above). Concerning ASLT, four volatile compounds had clear temperature and time dependent kinetics within the investigated temperature range.     

Evolution of potential and free furfural compounds in milk-based infant formula during storage

HPLC-DAD was used to monitor the evolution of potential and free furfural compounds (5-hydroxymethyl-2-furaldehyde, HMF; 2-furaldehyde, F; 2-furyl methyl ketone, FMC; and 5-methyl-2-furaldehyde, MF) over the shelf life of two types of infant powder formula: one supplemented with long-chain polyunsaturated fatty acids (LC-PUFA) in the form of microencapsulated fish oil (MFO), the other not supplemented with LC-PUFA. Following production, the formulae were stored at 25 and 37 °C. The initial furfural content in the supplemented formula was as follows: potential HMF (485.88 μg/100 g), potential F (167.13 μg/100 g), and free HMF (58.23 μg/100 g), while free F was not detected. In the unsupplemented formula, the following values were recorded: potential HMF (515.85 μg/100 g), potential F (170.29 μg/100 g), free HMF (84.92 μg/100 g), and free F (1.19 μg/100 g). In general, increased furfural content was observed during storage, an increase more pronounced in formula stored at 37 °C. Hardly any differences in furfural evolution during storage were observed between supplemented and unsupplemented infant formulae. The results suggest that the uses of MFO material for supplement formula not affected furfural formation. Neither FMC nor MF was formed in the formulae studied.     

Effects of high hydrostatic pressure and high-temperature short-time on mango nectars: Changes in microorganisms,acid invertase, 5-hydroxymethylfurfural,sugars, viscosity,and cloud

High hydrostatic pressure (HHP, 600 MPa/1 min) and high-temperature short-time (HTST, 110 °C/8.6 s) treatments of mango nectars were comparatively evaluated by examining their effects on natural microorganisms, acid invertase, 5-hydroxymethylfurfural (HMF), sugars, pH, titratable acid (TA), viscosity, and cloud, immediately after treatments and during 16-week storage at 4 and 25 °C. At both stages of the experiment, the counts of yeast and mold in treated mango nectars were less than 1.00 log₁₀CFU/mL, while total aerobic bacteria were less than 1.70 log₁₀CFU/mL. Both HHP and HTST treatments caused a significant decrease in fructose, glucose and total sugar, as well as a significant increase in HMF and cloud of mango nectars, while changes in sucrose, pH, and TA were insignificant. During the 16-week storage, however, fructose, glucose, TA and HMF increased, while sucrose, total sugar, pH and cloud decreased significantly. The kinetic data of changes in sucrose, fructose and glucose fitted well into a combined model. The activity of acid invertase was reduced by 91.4% in HTST-treated mango nectars and, increased by 8.57% after HHP treatment. In both cases, these levels remained stable during storage. There was no significant change in the viscosity of mango nectars after HHP treatment, while a significant increase after HTST treatment. Both HHP- and HTST-treated mango nectars showed a gradual decrease in the viscosity during storage.Industrial relevanceMango (Mangifera indica L.) is one of the important tropical fruits, and its processed products are of high commercial and economic importance. This work presents a comparison on HHP- and HTST-treated mango nectars after processing and during storage, on natural microorganisms, acid invertase, 5-hydroxymethylfurfural, sugars, pH, titratable acid, viscosity, and cloud. The available data would provide technical support for the evaluation and application of HHP or HTST in the mango nectar industry, and also for the establishment of criteria for commercial production of high quality mango nectars with safety requirements.     

Change of microbial and quality attributes of mango juice treated by high pressure homogenization combined with moderate inlet temperatures during storage

The effects of high pressure homogenization (HPH) on microbial inactivation and quality attributes (physio-chemical properties, bioactive components and antioxidant capacity) of mango juice, as well as their changes during storage at 4 °C and room temperature were investigated. Pressure levels ranged from 40 to 190 MPa, the inlet temperature from 20 °C to 60 °C and the number of passes from 1 to 5. Complete inactivation of molds and yeasts was achieved by 1 and 3 passes at 190 MPa and 60 °C, while total plate count was below 2.0 log₁₀ CFU/mL. No multiplication of microorganisms was observed in mango juice over 60 days of storage at 4 °C. HPH treatment could retain or even increase the carotenoids and total phenols by 11.8% and 21.4%, respectively, while significant reductions were found for heat treatment (HT) samples. During the storage of 60 days, HPH treatment also provided better preservation of color, bioactive components and antioxidant capacity of mango juice than HT.Industrial relevanceHigh pressure homogenization (HPH) is a novel non-thermal technique, particularly suitable for continuous production of liquid foods limiting thermal damage and promoting “freshness”. Results showed that high pressure homogenization had the advantage of notably reducing the microbial load to levels equivalent to thermal pasteurization. Moreover, HPH treatment was superior to heat treatment with regard to post-treatment levels of bioactive.     

Investigation and kinetic evaluation of furan formation in tomato paste and pulp during heating

Due to its high ascorbic acid content and acidic environment, tomato is susceptible for furan formation during heat treatment. In this study, kinetics of furan formation was analyzed in order to have an understanding of the reactions taking place in tomato pulp during heating. Also several tomato paste samples were investigated in terms of their furan and hydroxymethylfurfural (HMF) concentrations, and the possible furan precursors. Paste samples were found to contain 3.3–13 ng/g furan and 0.9–39.4 μg/g HMF (dry weight basis). Freshly prepared tomato pulps were heated at 70, 80, and 90 °C for different times, and analyzed for ascorbic acid, dehydroascorbic acid, and furan concentrations. The formation rates of furan in the very first 5 min of heating at 70, 80, and 90 °C were 0.0071, 0.0130, and 0.0168 nmol/g·min, respectively. Rate constants related to reactions taking place during furan formation were estimated by multi-response kinetic modeling. The results revealed that ascorbic acid oxidation is the critical step in furan formation reaction mechanism during heating of tomato pulp, and prevention of oxidation during processing might help to limit furan formation.     

Degradation of various fruit juice anthocyanins by hydrogen peroxide

Degradation kinetics of anthocyanins was studied in sour cherry nectar, pomegranate and strawberry juices at high hydrogen peroxide (H₂O₂) concentrations (9.31–27.92 mmol l⁻¹) at 10–30 °C and in only sour cherry nectar at low H₂O₂ concentrations (0.23–2.33 mmol l⁻¹) at 20 °C. Degradation of anthocyanins followed the first-order reaction kinetics. Sour cherry anthocyanins were the most resistant to H₂O₂, followed by pomegranate and strawberry anthocyanins. Degradation of anthocyanins was also studied in sour cherry nectar and pomegranate juice in the presence of ascorbic acid at 60 and 80 mg l⁻¹ concentrations at 20 °C. At 80 mg level, ascorbic acid significantly accelerated the degradation of anthocyanins in sour cherry nectar at 4.65, 6.98 and 9.31 mmol l⁻¹ H₂O₂ concentrations. In contrast, ascorbic acid at both 60 and 80 mg levels protected the anthocyanins from degradation by H₂O₂ in pomegranate juice.     

Modelling of 5-hydroxymethylfurfural photo-degradation by UV irradiation. Influence of temperature and pH

The main aims of this study were (a) to prove that the UV irradiation of juices prevents the formation of 5-hydroxymethylfurfural (HMF), (b) to know the influence of temperature and pH on the UV photo-degradation of the HMF when it is unfortunately present in the juice (for example, after a previous thermal treatment or after a long storage period) and (c) to model this photo-degradation, proposing a reaction mechanism related to the power absorbed by the solution that depends on the HMF concentration.For these purposes a mid-pressure mercury lamp with emission wavelengths between 250 and 740 nm was used.Firstly, nectarine juice was irradiated to be sure that HMF was not synthesised. Then, aqueous solutions of 100 mg·L^− 1 HMF at pH 3, 4 and 5 were irradiated at 12, 25, 35 and 45 °C for 120 min. Aliquots were analysed to measure their HMF contents and absorption spectra.The photo-degradation data fitted well to both zero-order and pseudo-first-order kinetic models and the constant values were similar. The increases in both temperature and pH enhanced the photo-degradation, the optimal conditions inside the ranges studied being 45 °C and pH = 5, when a reduction of 60% of the initial content of HMF was reached.The spectral radiant power absorbed by the whole solution and the incident spectral radiant power reaching any depth of the reactor were evaluated taking into account the linear spherical emission model and using the Simpson integration method. Its dependence on the HMF concentration was also studied. A three stage degradation mechanism was proposed, matching both the zero-order and pseudo-first-order kinetic models previously obtained.     

Identification of odour-active compounds of pasteurised orange juice using multidimensional gas chromatography techniques

Odour-active compounds present in pasteurised orange juice were identified by gas chromatography–olfactometry (GC–O) employing heart-cut multidimensional GC techniques with olfactometry (O) and mass spectrometry (H/C MDGC–O/MS) and comprehensive two-dimensional gas chromatography–accurate mass time-of-flight MS (GC × GC–accTOFMS). Headspace solid phase microextraction sampling proved to be qualitatively adequate for the analysis of pasteurised orange juice. The GC–O approach distinguished 13 potent odour regions (detection frequency ≥ 3) in the orange juice extract, in which 7 regions were then subjected to detailed identification of the compounds that contribute to the odour, by using higher resolution H/C MDGC–O/MS. This analysis permitted the odour-active peaks to be better resolved on the ²D column, with removal from background matrix, for the seven regions. GC × GC–FID and GC × GC–accTOFMS reveal the overall complexity of the volatile compounds in the product and assisted in assignment of the isolated peaks of the odour-active compounds, confirming the identification in a number of cases. Four aldehydes (hexanal, heptanal, octanal, citral), 2 esters (ethyl butanoate, methyl hexanoate), and 4 monoterpenes (α-pinene, D-limonene, linalool, α-terpineol) were confirmed in accordance with olfactometry assessment in the processed juice. This multi-assessment instrument approach of GC–O, GC × GC, and H/C MDGC provided an effective insight into the processed orange juice aroma.     

Formulation with ascorbic acid and sucrose modulates catechin bioavailability from green tea

In order to investigate the impact of common food ingredients on catechin absorption, green tea (GT) extract (50 mg) was formulated plain, with sucrose (GT + S), with ascorbic acid (GT + AA) and with sucrose and ascorbic acid (GT + S + AA). Bioavailability and bioaccessibility were assessed in Sprague Dawley rats and an in vitro digestion/Caco-2 cell model respectively. Absorption of epigallocatechin (EGC) and epigallocatechin gallate (EGCG) was significantly (P < 0.05) enhanced in GT + S + AA formulations (AUC_0–6 h = 3237.0 and 181.8 pmol h/L plasma respectively) relative to GT control (AUC_0–6 h = 1304.1 and 61.0 pmol h/L plasma respectively). In vitro digestive recovery was higher for EGC and epicatechin (EC) (～51–53%) relative to EGCG and epicatechin gallate (ECG) (<20%) and was modestly enhanced in GT + S and GT + S + AA formulations. Accumulation of EGC, EGCG and ECG by Caco-2 cells was significantly (P < 0.05) higher from GT + S + AA compared to other formulations while retention of catechins was enhanced in presence of ascorbic acid. These data suggest that formulation with sucrose and ascorbic acid may improve catechin bioavailability by enhancing bioaccessibility and intestinal uptake from tea.     

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.     

Mitigation of acrylamide and hydroxymethyl furfural in instant coffee by yeast fermentation

Acrylamide being known as carcinogenic and hydroxymethyl furfural (HMF) being known as cytotoxic compounds are heat induced process contaminants found in instant coffee. Today's instant coffee production method involves roasting of coffee beans, grinding, flavor and aroma separation, extraction, concentration, and drying steps. During roasting, acrylamide and HMF are formed in varying amounts depending upon the degree of heat treatment as a result of the Maillard reaction. This study was conducted in order to reduce the concentrations of acrylamide and HMF in instant coffee. Instant coffee (20%, w/v) was mixed with sucrose (0–10, w/v) and baker's yeast (Saccharomyces cerevisiae, 1–2%, w/v) in a tightly closed glass vessel. The mixture was fermented at 30 °C for 48 h. The kinetics of acrylamide and HMF degradation was investigated. HMF and acrylamide contents were reduced exponentially at varying rates, depending upon fermentation medium and time. After 24 h, HMF concentration was decreased by 61.2%, 75.7%, 93.6% and 99.2% in the fermentation media containing none, 1%, 5%, and 10% of sucrose, respectively. After 48 h, acrylamide concentration was decreased by about 70%. These results revealed that yeast fermentation is promising for the mitigation of HMF and acrylamide in instant coffee.     

Performance evaluation of a novel food packaging material based on clay/polyvinyl alcohol nanocomposite

The effectiveness of a novel, laminated clay/polyvinyl alcohol nanocomposite food-packaging film was examined by barrier analysis and food shelf-life monitoring. The effect of storage conditions on the film's oxygen permeability was studied and compared to commercial LLDPE/PET film as control. Additionally, pouches of 14 cm × 10.5 cm prepared from both films were filled with tomato paste as the food model, and stored at different temperatures (20–50 °C) and humidities (20–85% RH) for 10 days. Incorporating a coating layer containing 30 wt% (d.b.) of clay into polymer was found to improve its barrier properties, with drastic reduction of oxygen transmission rates (OTR) up to 99%, especially at 20% RH. While surrounding humidity affected the OTR of composite film significantly more than that of control film, the OTR of composite film was lower and less susceptible to temperature changes. The changes of food physical-chemical properties with time showed that the pouches of composite film significantly decreased ascorbic acid and lycopene oxidation of tomato paste by up to 88 and 37%, respectively. Furthermore, no discolouration occurred to the samples packaged by the nanocomposite film as compared to the control.Industrial relevanceA novel clay/polyvinyl alcohol nanocomposite film was developed with excellent barrier properties against oxygen. Evaluation of the performance of this food-packaging film indicated that incorporation of montmorillonite enhanced food preservation as suggested by decreased ascorbic acid and lycopene oxidation, and no discolouration of tomato paste. This new approach could be adopted by the food industry to assist commercial producers and retailers for preserving and extending the shelf-life of a variety of food products.     

Effects of high hydrostatic pressure and high temperature short time on antioxidant activity,antioxidant compounds and color of mango nectars

High hydrostatic pressure (HHP, 600 MPa/1 min) and high temperature short time (HTST, 110 °C/8.6 s) treatments of mango nectars were comparatively evaluated by examining their effects on antioxidant activity, antioxidant compounds, color, and browning degree (BD) immediately after treatments and during storage of 16 weeks at 4 and 25 °C. Steam blanching was used prior to HHP and HTST to inactive endogenous enzymes. Results showed that antioxidant capacity (FRAP assay), L-ascorbic acid, sodium erythorbate, total phenols, total carotenoids, the redness (a*), the yellowness (b*), and BD changed insignificant after HHP or HTST treatment. The lightness (L*) exhibited a significant decrease in HTST-treated mango nectars, while no significant changes in HHP-treated samples. After 16 weeks storage at 4 and 25 °C, there were significant changes in antioxidant activity, antioxidant compounds, color, and BD of mango nectars, whereas differences between HHP- and HTST-treated samples were not significant except for the decrease in L-ascorbic acid and sodium erythorbate, which was more pronounced in HHP-treated samples. Kinetic data of changes in L-ascorbic acid, sodium erythorbate, total phenols, and total carotenoids during storage fitted well into a combined model for both HHP- and HTST-treated samples.Industrial relevanceMango (Mangifera indica L.) is one of the important tropical fruits, and its processed products are of high commercial and economic importance. This research paper presents a comparison on HHP- and HTST-treated mango nectars, and also provides information about storage stability of antioxidant activity, antioxidant compounds, and color of mango nectars. The available data would provide technical support for the evaluation and application of HHP or HTST in the mango nectar industry, and also for the establishment of criteria for commercial production of high quality mango nectars with safety requirements.     

Optical instrument for the rapid detection of microorganisms in dairy products

MicroFoss, an optical instrument capable of detecting metabolic changes due to microbial activity, was tested for the detection of various groups of microorganisms in dairy products. Optical changes in the growth medium are monitored in a semi-fluid zone that separates the liquid medium containing the sample. Raw and pasteurised milks were evaluated for total viable counts (TVC), coliform and Enterobacteriaceae. Yoghurt was evaluated for coliform, Enterobacteriaceae and yeast.The MicroFoss TVC method for both pasteurised and raw milk utilised pre-filled vials containing 8 mL of Nutrient Broth with Bromcresol purple with 2 mL of milk sample. In a comparison of the instrument TVC methodology to the standard plate count methodology, correlation coefficients R=−0.93 and R=−0.92 were obtained for raw and pasteurised milk, respectively. An advantage of using the MicroFoss method was that results are obtained in 2–11 h rather than 24–48 h, with samples with bacterial counts above the acceptable levels detecting in most cases within an 8 h shift.The MicroFoss methodology for the estimation of numbers of coliform and Enterobacteriaceae utilises pre-filled vials containing 5 mL of broth. In a comparison between the MicroFoss coliform methodology and the corresponding plate count methodology utilising Violet Red Bile Agar (VRBA), a correlation coefficient of R=−0.95 was obtained. An identical correlation coefficient of R=−0.95 was obtained for the comparison of the MicroFoss Enterobacteriaceae methodology and the corresponding plate count methodology utilising VRBA+1% glucose. In 60 pasteurised milk samples tested, only 2 samples were positive by the MicroFoss method, one of which had 1 cfu mL⁻¹ by the plate method while the other had <1 cfu mL⁻¹. Coliform or Enterobacteriaceae were isolated from the detecting vials demonstrating the higher sensitivity of MicroFoss.The MicroFoss method for the detection of the presence of yeast in yoghurt required a 1:10 dilution of the product followed by a pH adjustment. Presence of yeast in yoghurt and soft cheeses was always detected without any false positive results. Results were available in less than 40 h.     

Effect of ozone on microbial,chemical and sensory attributes of shucked mussels

The effect of ozonation in aqueous solution (O₃ concentration=1 mg/l, time of ozonation: 60 and 90 min) on the shelf-life of shucked, vacuum-packaged mussels, stored under refrigeration was studied by monitoring the microbiological, chemical and sensory changes occurring in mussel samples, for a period of 12 days. Non-ozonated vacuum-packaged mussels served as the control sample. Ozonation affected populations of bacteria namely, aerobic plate count (APC) (0.7–2.1 log cycle reduction), Pseudomonas spp. (0.5–1.1 log cycle reduction) and H₂S-producing bacteria (1.1–2.5 log cycle reduction), Brochothrix thermosphacta (0.3–1.4 log cycle reduction), lactic acid bacteria (0.3–0.8 log cycle reduction) and Enterobacteriaceae (0.5–1.5 log cycle reduction). The effect of ozonation was more pronounced at the longer time of ozonation. Of the chemical indicators of spoilage monitored, trimethylamine values of all mussel samples remained relatively low throughout the entire storage period, attaining values of 7.5, 6.0 and 6.4 mg N/100 g for the control and ozonated for 60 and 90 min samples, respectively, on day 12 of storage. Total volatile basic nitrogen (TVB-N) values similarly remained relatively low (⩽20 mg N/100 g) until day 6 of storage, and increased to 31.9, 24.2 and 26.9 mg N/100 g mussel meat for the control and ozonated for 60 and 90 min samples, respectively, on day 12 of storage. Initial TBA values were surprisingly high (30–35 mg MA/kg) and decreased to 23.0, 21.7 and 13.3 mg MA/kg mussel meat on day 12 of storage for the control and the ozonated for 60 and 90 min samples, respectively. Sensory evaluation (odor, taste and texture) of cooked mussels showed a good correlation with bacterial populations. On the basis of sensory analyses, a shelf-life of 12 days was obtained for vacuum-packaged mussels ozonated for 90 min as compared to a shelf-life of 9 days for the control sample.     

Inactivation of pectin methylesterase and stabilization of opalescence in orange juice by dynamic high pressure

The effect of dynamic high pressure homogenization (DHP) alone or in combination with pre-warming on pectin methylesterase (PME) activity and opalescence stability of orange juice was studied. DHP without heating reduced PME activity by 20%. Warming the juice (50 °C, 10 min) prior to homogenization significantly increased the effectiveness of DHP. PME inactivation was further increased by adjusting the pH downward prior to treatment. Accelerated shelf-life study at 30 °C revealed that opalescence stability can be increased by several days by DHP treatment, even in the presence of active PME. These results suggest that the opalescence stability of orange juice treated by DHP does not depend entirely on PME activity but also on particle size reduction and structural changes to pectin resulting from the treatment. The freshness attributes of orange juice treated by warming was improved by DHP treatment.     

Preparation and use of freshwater fish,rohu (Labeo rohita) protein dispersion in shelf-life extension of the fish steaks

A process to enhance shelf-life of freshwater fish, rohu, on ice using combination treatment of coating the fish steaks with gel dispersion from the same fish and low-dose gamma irradiation is described. Washed pieces of freshwater fish, rohu were converted into gel by dilute acetic acid treatment. The gel was homogenized in water to a dispersion having 29 g/L protein, apparent viscosity of 1.0 Pa s and pH 3.5. Coating of fresh rohu steaks by dipping in the dispersion for 1 h or gamma irradiation at 1 kGy gave a shelf-life of 32 days in ice, in comparison to 20 days for the untreated steaks. Irradiation at 1 kGy of the dispersion-coated steaks enhanced their shelf-life to 42 days. Bleaching of the pink colour of the steaks by the treatment was prevented when one of either butylated hydroxy anisole or ascorbic acid was incorporated at 5 g/kg (w/v) in the dispersion.     

Phytochemical,antioxidant and pigment stability of açai (Euterpe oleracea Mart.) as affected by clarification,ascorbic acid fortification and storage

Açai juice at two clarity stages (semi-clarified and clarified) was compared to 100% açai pulp following ascorbic acid fortification to evaluate phytochemical and antioxidant changes during storage at 4 and 20 °C. Cyanidin-3-rutinoside (202 ± 5.8 mg/L) and cyanidin-3-glucoside (75 ± 4.8 mg/L) were the predominant anthocyanins in açai while 11 non-anthocyanin polyphenolics were detected in concentrations from 1.1 to 55 mg/L of açai pulp. Clarification of açai pulp resulted in a 27% loss in total polyphenolics (197 ± 6.9 mg gallic acid/100 mL) and in a 20% reduction in both total anthocyanins (729 ± 3.4 mg/L) and antioxidant capacity (54 ± 1.7 μmol Trolox equivalents/mL). Anthocyanin degradation followed first order kinetics, with half-lives ranging from 9.4 to 43 days for cyanidin-3-glucoside and from 18 to 82 days for cyanidin-3-rutinoside. Fortification with ascorbic acid accelerated anthocyanin degradation in clarified juice at both storage temperatures, likely due to the loss of polymeric anthocyanin forms (21%) during clarification. Although clarification enhanced the amount of monomeric anthocyanins present in açai juice which relates positively to the aesthetic quality, processing and handling regimes must be optimized to achieve maximum retention of their functional properties during storage.