Gellan gum films as carriers of l-(+)-ascorbic acid

Edible gellan films were evaluated as carriers for stabilizing l-(+)-ascorbic acid (AA) for nutritional purposes and antioxidant effect on foods. AA retention during film casting (initial value), as well as stability and non-enzymic browning (NEB) development along film storage (25 °C) at 33.3%, 54.7% or 75.2%-relative humidity (RH) were assessed. Initial AA retention was around 100%, and half-lives were 36, 26 and 11 days, respectively. AA destruction followed a pseudo-first order kinetics in gellan matrices. A water activity map was built for AA losses and NEB. AA and NEB kinetics were attributed to the restricted mobility of water molecules.     

Quantitative modelling approaches for ascorbic acid degradation and non-enzymatic browning of orange juice during ultrasound processing

The objective of this study was to develop a deterministic modelling approach for non-enzymatic browning (NEB) and ascorbic acid (AA) degradation in orange juice during ultrasound processing. Freshly squeezed orange juice was sonicated using a 1500 W ultrasonic processor at a constant frequency of 20 kHz and processing variables of amplitude level (24.4–61.0 μm), temperature (5–30 °C) and time (0–10 min). The rate constants of the NEB and AA were estimated by a primary model (zero and first order) while their relationship with respect to the processing factors was tested for a number of models, i.e., second order polynomial, different types of Ratkowsky-type model, and an Arrhenius-type model. The non-monotonic behaviour of NEB has been described more accurately by the use of a polynomial model. The rate constants of AA were described by a similar type of model having a monotonic behaviour. A synergistic effect of temperature for different amplitudes on the rate constant of both NEB and AA was observed, while an antagonistic effect of amplitude on the rate of NEB was evident. The models with the best fit were integrated to produce contour plots for the combined amplitude and temperature. The constructed contour plots illustrate that low temperatures and intermediate amplitudes, i.e., 42.7 μm, result in lower NEB and AA deterioration and consequently better quality orange juice. The overall developed modelling approaches exploit quality data in order to identify the optimal processing regions for eliminating quality deterioration of orange juice during ultrasound processing which is of high importance to the food industry.     

Formation of 4(5)‐Methylimidazole in Aqueous d‐Glucose‐Amino Acids Model System

The International Agency for Research on Cancer (IRAC) has classified 4(5)‐methylimidazole (4‐MeI) as a group 2B possible human carcinogen. Thus, how 4‐MeI forms in a d ‐glucose (Glu) amino acids (AA) model system is important, as it is how browning is affected. An aqueous solution of Glu was mixed individually in equimolar amounts at 3 concentrations (0.05, 0.1, and 0.15 M) with aqueous solutions of l ‐Alanine (Ala), l ‐Arginine (Arg), Glycine (Gly), l ‐Lysine (Lys), and l ‐Serine (Ser). The Glu‐AA mixtures were reacted at 60, 120, and 160 °C for 1 h. The 4‐MeI levels were measured by gas chromatography‐mass spectrometry after derivatization with isobutylchloroformate. No 4‐MeI was formed at 60 °C for any treatment combination; however, at 120 °C and 0.05 M, Glu‐Arg and Glu‐Lys produced 0.13 and 0.14 mg/kg of 4‐MeI. At 160 °C and 0.05 M all treatment combinations formed 4‐MeI. At 160 °C and 0.15 M, the observed levels of Glu‐Ala, Glu‐Arg, Glu‐Gly, Glu‐Lys, and Glu‐Ser were 0.21, 1.00, 0.15, 0.22, and 0.16 mg/kg. The AA type, reactant concentrations, and temperature significantly affected (P < 0.001) formation of 4‐MeI as well as browning. Glu‐Lys treatment in all combinations produced the most browning, but Glu‐Arg produced the most 4‐MeI. This method showed that foods processed using low temperatures may have reduced levels of 4‐MeI.     

OSMOTIC DEHYDRATION OF MUSKMELON (CUCUMIS MELO): INFLUENCE OF BLANCHING AND SYRUP CONCENTRATION

The influence of blanching and syrup concentration on the quality parameters of osmo‐air‐dried muskmelon product was investigated. Fruit samples were dehydrated with sucrose solutions at 40, 50 and 60°Brix and the resulting products were analyzed for browning degree, ascorbic acid (AA) concentration and water activity. The values for all three parameters decreased as the syrup concentration increased. Blanching treatment before the osmotic processing had no effect on browning but caused a decrease in AA concentration. Osmotically dehydrated fruits showed no browning increase for at least 4 weeks at 2C. A decrease of about 60% in AA concentration was observed within the first 2 weeks at 10C. In contrast, AA loss was only observed after 2 weeks at 2C. The influence of storage time and temperature on AA retention was investigated by 2² factorial design. Statistical analysis of results showed that the two factors have a significant effect on AA retention. Osmotic dehydration may be an interesting alternative for processing of muskmelon as a pretreatment followed by cold storage or drying.     

Influence of System Composition on Ascorbic Acid Destruction at Processing Temperatures

The anaerobic L -ascorbic acid (AAs) destruction in glucose aqueous model systems (water activity, a_w, 0·94) of pH 3·5, 4·1 and 5·0 was studied. The AAs degraded as a function of time and temperature (70, 80 and 90°C) with a behaviour that, in general, could be described by first order kinetics except for AAs in the system containing L -lysine, in which the results adjusted to zero order. The increment of pH from 3·5 to 5·0 accelerated AAs destruction and browning reactions. The addition of tin(II) or lysine to the glucose medium, increased AAs loss and browning. No difference was observed in AAs degradation and colour intensity when sorbic or propionic acid were used as antimycotics, at pH 3·5. Packaging the glucose system of acid pH with an air chamber, produced a faster destruction of AAs and browning of the solution than the one observed for the same system in anaerobic condition. In aerobic condition, the presence of glucose produced a lesser degradation of AAs than the one observed in the system without humectants. © 1997 SCI     

Biochemical changes of fresh-cut pineapple slices treated with antibrowning agents

The effectiveness of ascorbic acid (AA), isoascorbic acid (IAA) and N‐acetyl‐cysteine (AC) in inhibiting browning of fresh‐cut pineapple slices that were stored for up to 14 days at 10 °C, were studied. Slices treated with IAA and AA maintained higher levels of sugars and vitamin C than AC and controls. A low reduction of total phenolic content in treated slices was correlated with a lower polyphenol oxidase activity. IAA and AA slowed the degradation rates of sugars, vitamin C, and phenolic content, whereas AC was less effective in affecting these processes. A higher content of AA and IAA was associated with better compositional quality parameters and appearance of the pineapple slices during the storage period.     

POLYPHENOLOXIDASE ACTIVITY OF MINIMALLY PROCESSED 'JONAGORED' APPLES (MALUS DOMESTICA)

The influence of three chemical dips using ascorbic acid (AA), citric acid (CA) and calcium chloride (CC) on the polyphenoloxidase (PPO) activity and on the total phenolic content of minimally processed (MP) apple (Malus domestica, cv. Jonagored) during cold storage was evaluated and a potential relationship with enzymatic browning was investigated. An ascorbic acid dip (42.6 mM) of 5 min duration was the most efficient chemical treatment in reducing the PPO activity of apple cubes. A 92% inhibition was achieved after 7 days of storage at 4C. All treatments were advantageous in comparison to the control in reducing color changes. Color changes, determined by absorbance at 420 nm (soluble pigments) and lightness (L) (insoluble pigments) of apple cubes treated with ascorbic acid were correlated with total phenolic content. No correlation was observed between PPO activity and tristimulus color parameters, browning index or total phenolic content of AA‐treated apple cubes.     

Changes in selected quality characteristics of minimally processed carambola (Averrhoa carambola L.) when treated with ascorbic acid

‘B 10’ carambola of ripening stage (RS) 3 and 4 were minimally processed (MP) and then dipped in 0, 15 and 30 mg L^?1 ascorbic acid (AA). The 1‐cm‐thick slices were then dried, packed into cling‐wrapped‐foam tray and stored at 7 °C for 0, 3 and 5 days. Skin colour (L*, C* and h°), flesh firmness, soluble solids concentration, vitamin C content, titratable acidity, pH, degree of browning, polyphenoloxidase (PPO) activity and sensory attributes of MP carambola treated with AA were determined. AA treatment had significant effect in decreasing cut surface browning degree but no significant effect on all the selected quality characteristics of the MP carambola. In the sensory evaluation, flesh colour, sweetness, flavour and overall taste were significantly affected by AA treatment especially at 15 mg L^?1. The RS of fruit significantly affected skin colour (C* and h°), pH and sensory attributes of colour and flavour of the MP carambola. As storage day (SD) progressed, skin colour (C* and h°), flesh firmness and vitamin C content, cut surface browning, PPO activity and all the sensory attributes of MP carambola decreased significantly. Flesh firmness of the MP carambola was affected by the interaction between AA × SD. Sensory attributes of MP carambola were affected significantly by AA × RS. All the sensory attributes of MP carambola positively correlated to each other but negatively correlated with browning degree. PPO activity positively correlated with browning degree. Copyright © 2007 Society of Chemical Industry     

A factorial approach to identify reactive constituents and their interactions in multicomponent highly acidic model systems simulating lime juice concentrate (32°B)

The non-enzymic browning mechanism in a multicomponent food product such as lime juice concentrate (32°B) was investigated using synthetic model systems. A 2⁵ factorial experiment was designed and the statistically significant main effects and interactions isolated. Four interactions: (1) citric acid + ascorbic acid, (2) citric acid + fructose, (3) fructose + ascorbic acid and (4) citric acid + fructose + ascorbic acid; and three main effects: (1) citric acid, (2) fructose and (3) ascorbic acid, were found to be statistically significant at the 0·05 level. These are interpreted in the light of available literature on non-enzymic browning reactions.     

Degradation kinetics of tomato juice quality parameters by ozonation

Tomato juice samples were ozonated with control variables of ozone concentration (1.6–7.8 %w/w) and treatment time (0–10 min). Effects of ozone processing variables on quality parameters of pH, ^oBrix, titratable acidity (TA), cloud value, non-enzymatic browning, colour values ( L *, a *, and b *) and ascorbic acid (AA) content were determined. No significant changes ( P  > 0.05) in pH, ^oBrix, TA, cloud value and Non enzymatic browning (NEB) ( P  ≤ 0.05) were found with ozonation. L *, a * and b * colour values were significantly affected by ozone concentration and treatment time. A significant reduction of AA (96 %) was observed at an ozone concentration of 7.8%w/w and a treatment time of 10 min. Results presented in this study indicate that visual colour and nutritional quality is significantly affected during ozone processing. Thus, the effects of ozonation on the nutritional properties of tomato juice should be considered by processors prior to its adoption as a preservation technique.     

Enzymatic Browning in Apple Pulps

Enzymatic browning in Golden Delicious apple pulp was studied as related to degree of ripeness and temperature (3.5–31°C). Green apple pulp showed the highest rate of browning. This was attributable to differences in ascorbic acid (AA) content and polyphenoloxidase activity in young fruits. The rate of browning determined by CIE L* measurements followed complex temperature dependent kinetics, represented by a multiple linear effects with log time. Equal changes in L* parameter yielded straight lines in a log temperature vs log time plot. Inhibition with AA caused an initial slow rate of browning and a well defined break point associated with exhaustion of antioxidant properties of the AA. The greater the AA concentration the longer the initial period.     

Heated Ascorbic/Citric Acid Solution as Browning Inhibitor for Pre-Peeled Potatoes

Treatment of pre-peeled potatoes with heated ascorbic acid (AA)/citric acid (CA) solution to extend shelf-life was investigated. Potatoes were abrasion or high pressure steam peeled, heated for 5–20 min in 1% AA + 2% CA at 45–55°C cooled, and then dipped for 5 min in browning inhibitor (BI) solution containing 4% AA +1% CA +1% sodium acid pyrophosphate. Combined treatment inhibited potato discoloration for 14 days at 4°C compared to 3–6 days with BI treatment alone. Raw material and treatment conditions were selected to minimize graying and textural abnormalities encountered with some treatments. Treatment with heated AA/CA may be an alternative to use of sulfites to control browning in pre-peeled potatoes.     

Effect of sonication on orange juice quality parameters during storage

Freshly squeezed orange juice was sonicated at various amplitude levels (40%, 70%, 100%), treatment times (2, 6 and 10 min) at a constant frequency of 20 kHz. Samples were stored for periods of up to 30 days at 10 °C. The combined effect of amplitude level, treatment time and storage period on pH, ^oBrix, titratable acidity, colour values ( L* , a* , b* ), non-enzymatic browning (NEB), cloud value and ascorbic acid content were investigated. Second order polynomial models were employed to investigate the effect of independent variables. No significant differences ( P <  0.05) in ^oBrix and titratable acidity were observed. Significant changes were observed in juice pH and colour values. During storage NEB increased while both cloud value and ascorbic acid content decreased. Predictive models developed for colour values, cloud value, NEB and ascorbic acid content were highly significant and were closely correlated to experimental data. Degradation mechanisms are proposed for the key quality parameters.     

Effects of initial low oxygen and perforated film package on quality of fresh‐cut cabbages

The effects of perforated film packages (PFP) with different oxygen partial pressures (5, 8 and 10 kPa) and a barrier package (BP) at 21 kPa of O₂ on the quality of fresh‐cut cabbages were studied at 5 and 20 °C. The microbial growth, appearance, flavor, ascorbic acid content and polyphenol oxidase activity were determined during storage. The results indicated that fresh‐cut cabbages had better color retention and quality in PFP. Oxidation of ascorbic acid (AA) and browning of fresh‐cut cabbage were inhibited effectively using a PFP and an initial oxygen partial pressure equal to 5 kPa. Analysis of microbial growth also showed that the total count on fresh‐cut cabbage was relative lower in PFP with an initial low O₂ content. Loss of total ascorbic acid was much lower in PFP than that in BP by suppressing AA oxidation. The results of sensory evaluation showed that flavor and appearance were maintained effectively at 5 °C and significant differences in flavor were found between PFP and BP both at 5 and 20 °C, while significant differences in appearance were found between PFP and BP only at 20 °C. Copyright © 2007 Society of Chemical Industry     

Changes in browning‐related components of apple slices during different stages of instant controlled pressure drop‐assisted hot air drying (AD‐DIC)

The effect of instant controlled pressure drop‐assisted hot air drying (AD‐DIC) on browning‐related components in apple slices was studied. Results showed the AD temperature had no significant effect on colour index of final apple slices. The aspartic acid, glutamic acid, lysine, histidine, arginine, sucrose and dehydroascorbic acid (DHAA) in apple slices increased firstly during the AD process and then decreased during DIC process. The fructose, glucose, reduced ascorbic acid and major phenolic compounds reduced with the abrupt increase of 5‐hydroxymethylfurfural (5‐HMF) during AD‐DIC. There were significant correlations (P < 0.05) among moisture content (w.b.), water activity (a_w), water state, reduced ascorbic acid, DHAA, chlorogenic acid, procyanidin B₁, (+)‐catechin, (?)‐epicatechin and phlorizin during AD‐DIC. The colour difference showed that the major browning reaction of apple slices during the predrying process was enzymatic browning, while nonenzymatic browning played a crucial role on green‐red value (CIE a* value) during DIC.     

Kinetics of aseptic concentrated orange juice quality changes during commercial processing and storage

Aseptically concentrated orange juice (COJ) was processed commercially at three holding temperatures (84, 87 and 90°C, 72 s) and stored for up to 7 weeks at 32°C and 15 weeks at 22°C. No differences were found in nonenzymic browning (NEB), vitamin C, sucrose, fructose and glucose, furfural, HMF (5-hydroxymethyl furfural), and DMHF (2,5-dimethyl-4-hydroxy-3(2H)-furanon) concentrations due to the different thermal treatment. the dominating factors affecting vitamin C retention and NEB were time and storage temperature. A lag-time was observed in NEB formation and its length depended on storage temperature. Furfural concentration was below 1 ppm. HMF reached c. 11 ppm after 7 weeks at 32°C. DMHF concentration decreased throughout the storage period. Sensory evaluation showed a nonsignificant preference for COJ processed at the lower temperature.     

Integrated effects of ascorbic acid,flavonoids and sugars on thermal degradation of anthocyanins in blood orange juice

This study aimed to elucidate how the major intrinsic factors, such as ascorbic acid (AA), flavonoids and sugars affected the thermal degradation of blood orange anthocyanins. The results in our study indicated that AA and sugars significantly accelerated anthocyanins degradation while flavonoids had a protective effect on degradation of anthocyanins. Flavonoids and AA could reduce the influence of temperature on anthocyanins degradation rate. However, the promoting effects of sugars on anthocyanins degradation correlated with the temperature. Moreover, the degradation of anthocyanins in the presence of sugars followed complex reaction kinetics when temperature was above 70 °C, and the promoting effects of sugars on anthocyanins degradation were glucose < sucrose < fructose. The results also indicated that flavonoids had a protective effect against either AA or sugars accelerated the degradation of anthocyanins, and this protective effect played a more important role in the degradation of anthocyanins comparing to the negative effect of AA or sugars. In addition, AA and sugars showed a synergistic effect on the degradation of anthocyanins at all our investigation temperatures except 90 °C.     

Application of edible coatings in minimally processed sweet potatoes (Ipomoea batatas L.) to prevent enzymatic browning

To control browning phenomenon, an edible coating of cassava starch along with ascorbic acid (AA) (combined treatment) was applied to minimally processed sweet potatoes var cv. ‘Blanca Correntina’. The samples were stored at 4 °C for 16 days, and the activities of polyphenol oxidase, peroxidase and phenylalanine ammonia lyase were studied; also, surface colour, antioxidant capacity, ascorbic acid, chlorogenic acid content were evaluated. The combined treatment showed a beneficial impact on the quality of the product, avoiding browning when compared with untreated samples and individual treatments (coating without AA or immersion in AA solution). The improvements were evidenced by the absence of changes in hue, minor changes in a* parameter and a major inhibitory effect of AA on the activity of the three enzymes. Ascorbic acid content and antioxidant capacity increased (P < 0.05). The combined treatment not only was effective in preventing enzymatic browning but also retained freshness and improved nutritional value.     

Prevention of enzymatic browning of apple cylinders using different solutions

Inhibition of enzymatic browning and decay on cut surfaces of Golden Delicious apple using ascorbic acid, cysteine, sodium chloride, calcium chloride, citric acid and sodium ascorbate alone or in combinations was investigated at 4 and 10 °C for a storage period of 0, 7 and 14 days, in an attempt to find the most effective treatment. Apple segments immersed in ascorbic acid and citric acid alone showed visual traces of browning after 7 days storage at 4 °C. After 14 days storage, only ascorbic acid and ascorbic acid plus sodium chloride had moderate browning, while all other treatments were severely affected. However, at 10 °C, only ascorbic acid was effective in reducing the level of browning, although its effect was minimal after 14 days storage. Browning was more severe at 10 °C than 4 °C in all solutions. The browning measurement (a* value) became increasingly positive from 7‐ to 14‐day storage. Microbial decay was absent in all treatments within 7 days at 4 and 10 °C. However, three test solutions showed microbial decay after 14 days storage at 10 °C in addition to the control solution, which showed decay at both 4 and 10 °C storage temperatures.     

Biochemical Changes and Sensory Quality of Shredded and MA-Packaged Iceberg Lettuce

Cultivars of shredded iceberg lettuce (Lactuca sativu L.) ‘Saladin’, ‘Santis’, ‘Telda’ and ‘Roxette’ responded in a parallel way to four modified atmosphere (MA) packaging treatments. Moderate vacuum packaging (mvp) in 80 μm polyethylene (PE) inhibited enzymatic browning over 10-day storage at 5°C. When lettuce was packaged in 80% O₂, 20% CO₂ (80/20), more browning occured in SL3-bags (59 μm multilayer coextruded film) than in PE-bags. Polyphenol oxidase activity declined during storage in all 4 atmospheres, with lowest activity in PE-80/20. Endogenous ascorbic acid (AA) did not act as an efficient antioxidant in delaying browning. Total carbohydrate content (TC) declined slightly during storage. Tristimulus color measurements correlated highly with visual ratings.