Effect of different moisture equilibration process on the quality of apple chips dried by instant controlled pressure drop (dic)‐assisted hot air drying

Moisture equilibration process (MEP) is an important process before controlled pressure drop (DIC) drying to obtain greater products quality and avoid producing bubbles. The aim of this work was to study the effect of MEP on the quality of apple chips dried by instant controlled pressure drop‐assisted hot air drying (DIC‐AD). After predrying by AD, four types of moisture equilibration solutions were applied to equilibrate the moisture of apple chips before DIC. The quality of apple chips equilibrated in water for 10 min was superior to those for 30 and 60 min with better color, brittleness, hardness, puffing degree (PD), and microstructure. Sugar solutions showed positive effect on brittleness and hardness, PD, and soluble solids of apple chips. In addition, calcium chloride was beneficial to the color of apple chips, and the product showed good rehydration and PD possibly due to the reaction between pectin and calcium ions.

Practical applications

Instant controlled pressure drop (DIC) was a new sort of united drying method that can combine with other drying technology, such as hot air drying and freezing drying. In practical production, apple slices are usually dried to low moisture content for long time storage and regained appropriate moisture content before drying. After predrying, moisture equilibration process (MEP) is an important process before DIC drying which made water homogenous distributed in the sample to obtain greater products quality and avoid producing bubbles during DIC drying. In this study, MEP with different solutions including water, fructose syrup, maltitol, and calcium chloride were performed before DIC drying, and the changes of physiochemical properties of dried products were studied. Based on the analysis of experimental results, predried apple slice equilibrated in water for 10 min, 10% fructose syrup and 30% maltitol solution might produce apple chips with better quality.     

Effects of 1‐methylcyclopropene and post‐controlled atmosphere air storage treatments on fresh‐cut Ambrosia apple slices

BACKGROUND: The effect of 1‐methylcyclopropene (1‐MCP) treatment and two different post‐controlled atmosphere air storage (PCAAS) durations on the quality and chemistry of fresh‐cut Ambrosia apple slices was studied. RESULTS: PCAAS for 1 or 2 weeks prior to slicing had an overall positive effect on the resultant quality of fresh‐cut apple slices. The most significant responses to PCAAS were the suppression of both phenolic and o‐quinone accumulation in slices, and this was related to the significantly lower browning potential values obtained for slices from PCAAS‐treated apples. Polyphenol oxidase (PPO), peroxidase (POX) and ascorbate peroxidase (APOX) activities were not affected by 1‐MCP or PCAAS treatments. PPO and POX activities were almost completely inhibited by a 50 g L^?1 calcium ascorbate anti‐browning dip of apple slices from all treatments. CONCLUSION: The most dramatic effect of the PCAAS treatments was to reduce the accumulation of soluble phenolics, which is likely the reason that o‐quinone accumulation was also inhibited in treated fruits. The consequent reduction in browning potential may be the explanation as to why PCAAS treatment has been shown to reduce fresh apple slice browning in previous work. Copyright © 2012 Society of Chemical Industry     

Effect of plant polyphenols and ascorbic acid on lipid oxidation,residual nitrite and N‐nitrosamines formation in dry‐cured sausage

The effects of green tea,grape seed polyphenols and ascorbic acid on pH, water activity (a_w), microbiological counts, TBARS, residual nitrite and N‐nitrosamines were determined in dry‐cured sausages during the ripening period. Results showed that TBARS increased gradually during ripening (P < 0.05), but were significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Green tea polyphenol (GTP) was most effective (P < 0.05) in reducing TBARS. Plant polyphenols and ascorbic acid significantly decreased residual nitrite, ascorbic acid being most effective (P < 0.05). The amount of N‐nitrosamines increased during ripening, but was significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Plant polyphenols had no significant effects on moisture content, a_w, pH or microbiological counts in dry‐cured sausage during ripening (P > 0.05). It was concluded that plant polyphenols and ascorbic acid were effective in maintaining the quality and safety of dry‐cured sausages.     

A Potent Antibrowning Agent from Pine Needles of Cedrus deodara: 2R,3R‐Dihydromyricetin

This article focuses on finding the novel antibrowning agents from the pine needles of Cedrus deodara and studying its antibrowning effect. By bioassay guide of tyrosinase inhibitory activity, the main active compound was isolated and purified from 50% methanol extract of pine needles of C. deodara through macroporous resin Diaion HP‐20 column chromatography and high‐performance liquid chromatography. Based on mass and nuclear magnetic resonance data, the active compound was identified as 2R,3R‐dihydromyricetin, which showed the potent monophenolase and diphenolase inhibitory activities. Moreover, 2R,3R‐dihydromyricetin exhibited a strong ABTS radical scavenging activity with a dose‐dependent manner. The antibrowning efficacy of 2R,3R‐dihydromyricetin was evaluated by monitoring the changes of L*, a*, and b* values and total color difference (△E) on fresh‐cut apple slices. It was found that 2R,3R‐dihydromyricetin was effective in inhibiting the browning of apple slices treated with a concentration as low as 0.05% at 25 °C for 24 h. Its antibrowning effect was significantly better than ascorbic acid (0.5%) alone. Furthermore, 2R,3R‐dihydromyricetin showed a good synergistic antibrowning effect with ascorbic acid. This is the first report that 2R,3R‐dihydromyricetin from pine needles of C. deodara may be used as a potential antibrowning agent in protecting against food browning.     

Stability of fructooligosaccharides,sugars and colour of yacon (Smallanthus sonchifolius) roots during blanching and drying

Yacon (Smallanthus sonchifolius) root is an important source of fructooligosaccharides (FOS). This study evaluated the influence of the blanching and drying processes on the sugars, FOS and colour of the obtained flour. Blanching in boiling water of 5 mm slices for 6 min allowed to inactivate 95% of polyphenol oxidase and peroxidase activity. Blanching solutions containing ascorbic, citric and lactic acid were detrimental in terms of FOS retention (68.2–87.4%) due to hydrolysis mainly of GF3, GF4 and GF5 FOS, and also important losses of reducing sugars (RS) were observed (69.5–87.4% retention). Blanching treatments that included ascorbic acid/CaCl₂ prevented RS and FOS losses and improved colour of the obtained flour. The drying tested temperatures of 50–80 °C did not affect the RS retention and FOS losses associated to hydrolysis and the use of 80 °C rapidly reduced the water content and minimised browning reactions yielding flours with excellent colour characteristics with high FOS content that can be derived to the elaboration of prebiotic containing functional foods or for the extraction and purification of FOS.     

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.     

Kinetic model of apple juice enzymatic browning in the presence of cyclodextrins: The use of maltosyl-β-cyclodextrin as secondary antioxidant

Enzymatic browning reactions limit the commercial shelf life of apple juice, so that colour preservation during storage is one of the main objectives of fruit processors. In this paper, the colour of fresh apple juice was evaluated in the presence of different types of cyclodextrins (CDs) (α-CD, β-CD, γ-CD and maltosyl-β-CD), compounds that bind or complex polyphenol oxidase substrates. The effectiveness of CDs as browning inhibitors was determined as the difference between the colours observed in the CD-treated sample and the controls, using the colour space CIE-L^∗, a^∗, b^∗ system. Although the effect of CDs on apple juice enzymatic browning has been studied, the action mechanism involved remains a subject of controversy. In this work, we have kinetically modelled apple juice enzymatic browning in the absence and presence of maltosyl-β-CD. The complexation constant between the mixtures of diphenols present in apple juice and maltosyl-β-CD was calculated (K_c = 4.09 mM⁻¹). Different concentrations of maltosyl-β-CD modified the evolution of lightness (L^∗), total colour (ΔE^∗) and hue angle (H^∗) because of the higher affinity constant it shows for the compounds responsible for apple juice browning than do α-CD, β-CD and γ-CD. Moreover, in this paper we show that maltosyl-β-CD can enhance the ability of ascorbic acid to prevent the enzymatic browning due to the protective effect of maltosyl-β-CD against ascorbic acid oxidation. Hence, maltosyl-β-CD seems to act as a “secondary antioxidant”, reducing apple juice browning and enhancing the naturally occurring antioxidant capacity of a food.     

EFFECT OF PE/AG2O NANO‐PACKAGING ON THE QUALITY OF APPLE SLICES

ABSTRACT

Effects of low‐density polyethylene (LDPE) packaging and nano‐structured silver‐polyethylene (PE/Ag₂O) packaging on the overall sensory quality, color, weight and solute loss of fresh‐cut apples stored at 5 and 15C were studied in this research. Results showed that, compared with normal LDPE packaging, the PE/Ag₂O packaging helped to maintain the freshness of apple slices. Nano‐structured PE/Ag₂O bag delayed apple browning and decreased the weight loss of apple slices during storage. In addition, it can also prevent apple slices from microbial spoilage. As a result, the quality of apple slices saved at 5C in PE/Ag₂O bag was acceptable in 12 days, while those held in LDPE bag showed some deterioration in 6 days. Furthermore, considering the potential health risk resulting from silver leak, the safety of PE/Ag₂O bag was evaluated, and the result indicated an acceptable safety for food packaging.

PRACTICAL APPLICATIONS

Types of nano‐structured bags are recently commercialized for food packaging in many countries, but few documents report their performance in quality maintenance. This study indicates that nano‐structured PE/Ag₂O bag is effective in maintaining the freshness of apple slices with extended shelf‐life. Results of this work may be useful for promoting the acceptance and application of similar nano‐packaging in the quality maintenance of fresh‐cut products.     

Postharvest performance of fresh‐cut ‘Big Top’ nectarine as affected by dipping in chemical preservatives and packaging in modified atmosphere

Fresh‐cut ‘Big Top’ nectarines were dipped in 2% (w/v) ascorbic acid–1% (w/v) calcium lactate and stored at 4 °C for up to 12 days in 10 kPa O₂‐ and 10 kPa CO₂‐modified atmosphere packaging (MAP). The used microperforated plastic film allowed O₂ and CO₂ concentrations to reach steady values from the fifth day in storage onwards. Samples stored in MAP after chemical dipping showed the highest visual quality score, slight browning symptoms, increment in firmness and very low ethanol and acetaldehyde content. The chemical dipping also increased antioxidant capacity, probably due to the effect of ascorbic acid. The results suggested that the control of yeasts was mainly exerted by MAP, whereas only a slight effect was achieved by the chemical dipping. Therefore, MAP plus ascorbic acid/calcium lactate dipping was the best combination to preserve phytochemical content, antioxidant capacity and microbiological safety of fresh‐cut nectarines during storage.     

Chitosan nanoparticle coatings reduce microbial growth on fresh‐cut apples while not affecting quality attributes

This study addressed the effects of chitosan‐based nanoparticles on microbiological quality, colour, polyphenol oxidase (PPO) and peroxidase (POD) and firmness of fresh‐cut ‘Gala’ apple slices during storage at 5 °C for 10 days. The treatments carried out were as follows: (i) slices pulverised with 110‐nm chitosan nanoparticles, (ii) slices pulverised with 300‐nm chitosan nanoparticles, (iii) 2 g L^?1 chitosan dissolved in 2% citric acid and (iv) noncoated samples. There was an increase in chroma and a proportional decrease in hue angle and lightness. Browning of the slices coated with conventional chitosan and control was slightly intense than those coated with chitosan nanoparticles of 110 and 300 nm. The PPO and PDO activities increased with time for all samples, with irrelevant difference among the treatments. Flesh firmness did not change for any treatment and period. Coatings with chitosan nanoparticles of 110 nm showed higher antimicrobial activity against moulds and yeasts, and mesophilic and psychrotrophic bacteria than the other treatments. No Salmonella, and total and faecal coliforms were detected. This investigation supports the potential use of chitosan nanoparticles as edible coatings in controlling microbial activity in fresh‐cut apples.     

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     

Antibrowning and Antimicrobial Properties of Sodium Acid Sulfate in Apple Slices

ABSTRACT: There are few available compounds that can both control browning and enhance microbial safety of fresh‐cut fruits. In the present study, the antibrowning ability of sodium acid sulfate (SAS) on “Granny Smith” apple slices was first investigated in terms of optimum concentration and treatment time. In a separate experiment, the apple slices were treated with water or 3% of SAS, calcium ascorbate, citric acid, or acidified calcium sulfate for 5 min. Total plate count, color, firmness, and tissue damage were assessed during a 21‐d storage at 4 °C. Results showed that the efficacy of SAS in inhibiting browning of apple slices increased with increasing concentration. A minimum 3% of SAS was needed to achieve 14 d of shelf life. Firmness was not significantly affected by SAS at 3% or lower concentrations. Antibrowning potential of SAS was similar for all treatment times ranging from 2 to 10 min. However, SAS caused some skin discoloration of apple slices. When cut surface of apple slices were stained with a fluorescein diacetate solution, tissue damage could be observed under a microscope even though visual damage was not evident. Among the antibrowning agents tested, SAS was the most effective in inhibiting browning and microbial growth for the first 14 d. Total plate count of samples treated with 3% SAS was significantly lower than those treated with calcium ascorbate, a commonly used antibrowning agent. Our results suggested that it is possible to use SAS to control browning while inhibiting the growth of microorganisms on the apple slices if the skin damage can be minimized. Practical Application: Fresh‐cut apples have emerged as one of the popular products in restaurants, schools, and food service establishments as more consumers demand fresh, convenient, and nutritious foods. Processing of fresh‐cut apples induces mechanical damage to the fruit and exposes apple tissue to air, resulting in the development of undesirable tissue browning. The fresh‐cut industry currently uses antibrowning agents to prevent discoloration. However, the antibrowning solutions can become contaminated with human pathogens such as Listeria monocytogenes, and washing of apple slices with the contaminated solutions can result in the transfer of pathogens to the product. It would be ideal if an antibrowning compound prevented the proliferation of human pathogens in solutions and minimized the growth of pathogens during storage. The study was conducted to investigate antibrowning and antimicrobial properties of sodium acid sulfate (SAS) in comparison with other common antibrowning agents on Granny Smith apples. Results showed that among the antimicrobial agents we tested, SAS was the most effective in inhibiting browning and microbial growth for 14 d at 4 °C. However, SAS caused some skin discoloration of apple slices. Overall, SAS can potentially be used to inhibit tissue browning while reducing the microbial growth on apple slices. The information is useful for the fresh‐cut produce industry to enhance microbial safety of fresh‐cut apples while minimizing browning, thus increasing the consumption of the health benefiting fresh fruit.     

Quality of Fresh-cut Apple Slices as Affected by Low-dose Ionizing Radiation and Calcium Ascorbate Treatment

ABSTRACT: Although ionizing radiation effectively inactivates food-borne bacterial pathogens in fresh-cut fruits and vegetables, it may adversely affect product quality. In this study, the effects of calcium ascorbate (CaA) and ionizing radiation on quality of 'Gala' apple slices under modified atmosphere packaging were investigated. 'Gala' apple slices, treated with water or 7% CaA followed by either nonirradiation (0 kGy) or irradiation at 0.5 and 1.0 kGy, were stored at 10°C for up to 3 wk. The titratable acidity, pH, firmness, ascorbic acid content, color, and microflora population were measured weekly throughout storage. Irradiation did not affect titratable acidity and pH of sliced apples. Fruit slices softened during irradiation and storage, but this decrease in firmness during storage was reduced by the CaA treatment. Although the ascorbic acid content of apple slices treated with CaA decreased rapidly during storage, the ascorbic acid content was always higher in those treated samples than in the apple slices treated with water. Irradiation decreased both L * and hue values of apple slices. Hue values decreased during the entire storage period while L * increased during the 1st wk of storage, then decreased between 1 to 3 wk of storage. CaA increased L * and hue values of apple slices, suggesting CaA reduced browning, even in irradiated samples. The microflora population of apples slices was not affected by CaA, and CaA treatment did not alter the reduction in microflora by irradiation. The combination of CaA and irradiation enhanced microbial food safety while maintaining quality of fresh-cut apple slices.     

Protective effect of cysteine—HCl on vitamin C in dehydrated pickled/candied pineapples and guava

Dehydrated pickled/candied guava and pineapples pretreated with 0.24 g kg^?1 cysteine hydrochloride (cys-HCl) had increased ascorbic acid retention and reduced colour change during storage. Dehydrated pineapples pretreated with cys-HCl had two to three times the ascorbic acid content of control or metabisulphite-treated products. The rate of ascorbic acid loss for all products stored at room temperature were similar, showing that cys-HCl was only protective towards ascorbic acid during the preparation and dehydration process. Candied dehydrated guava showed less colour change and higher ascorbic acid retention (about 57%) than pickled guava (ascorbic acid retention about 30%). Cys-HCl was quite effective in reducing browning of candied pineapples but not pickled pineapples. Sensory evaluation showed that candied guava pretreated with 0.24 g kg^?1 cys-HCl was generally preferred over the other dehydrated guava products. Cys-HCl-treated candied pineapples had the best flavour compared with all other dehydrated pineapple products. Cys-HCl appeared to favour conversion of glucose to fructose during storage of dehydrated pineapples.     

Kinetics of colour change of bamboo shoot slices during microwave drying

The effect of microwave power on colour change kinetics of bamboo shoot slices was investigated during microwave drying. Colour changes were quantified by tri‐stimulus Hunter L (whiteness/darkness), a (redness/greenness), and b (yellowness/blueness) system. These values were also used for calculation of total colour change (ΔE), chroma, hue angle, and browning index (BI). Microwave drying as expected changed colour parameters because of browning. The values of L and b decreased, while values of a and ΔE increased during drying. Mathematical modelling of colour change kinetics indicated that L, b, chroma and BI could be defined using a first‐order kinetic model, while a, ΔE and hue angle could be defined using a zero‐order kinetic model. Considering together colour deterioration and quality of dried bamboo shoot slices at higher power reveals the need of process standardisation for getting good quality product.     

Kinetic models of non‐enzymatic browning in apple puree

The effects of thermal treatments on 11 °Brix apple puree were studied at temperatures from 80 to 98 °C. Colour changes (measured by reflectance spectroscopy, colour difference, L*, a* and b* and the evolution of 5‐hydroxymethylfurfural (HMF) and sugars (hexoses and sucrose) were used to evaluate non‐enzymatic browning. A kinetic model based on a two‐stage mechanism was applied to the evolution of colour difference and a*. A first‐order kinetic model was applied to L* evolution, while the evolution of absorbance at 420 nm (A₄₂₀) of the liquid fraction was described using a zero‐order kinetic model. Thermally treated samples became more reddish and suffered a slight loss of yellow hues. The effect of temperature on the kinetic constants was described by an Arrhenius‐type equation. The presence of pulp in the samples led to activation energies for A₄₂₀ and sucrose which were lower than those found previously for clarified juices with the same soluble solids content. © 2000 Society of Chemical Industry     

Physiological and biochemical changes of different fresh-cut mango cultivars stored at 5 °C

Treatments to inhibit browning, decay and to extend shelf life of ‘Keitt’, ‘Kent’ and ‘Ataulfo’ mango cultivars as a fresh‐cut produce were investigated. Combinations of calcium chloride (CaCl₂), antioxidants [ascorbic acid (AA), citric acid (CA)] and two commercial film coatings resulted in a reduction of browning and deterioration of fresh‐cut mangoes stored at 5 °C, especially for the Ataulfo cultivar. The use of CaCl₂ + AA + CA significantly reduced colour deterioration, loss of firmness and did not affect sensory characteristics of fresh‐cut mango, with a larger effect in the Ataulfo cultivar. In general, these treatments prevented loss of sugar and vitamin C of cubes during storage at 5 °C. Shelf life of this cultivar was 21 days, while that of Keitt and Kent was only 9 and 12 days, respectively. There is a correlation between carotene and vitamin C content of Ataulfo mango and its longer shelf life compared with the other cultivars.     

Effect of storage on non‐enzymatic browning of liquid infant milk formulae

Furfural, hydroxymethylfurfural (HMF), furosine, lactulose, ascorbic acid and absorbance at 284 and 420 nm (A₂₈₄ and A₄₂₀) were all determined in two types of liquid infant formula prepared with different processing protocols. These browning indicators were used to assess the effects of storage and modified atmosphere on the shelf‐life of infant formulae. The study was carried out at 20 and 55 °C for 15, 30 and 90 days. At 20 °C, slight browning was observed and could be evaluated by furosine, furfural and total HMF indicators. At 55 °C, formula type A (pasteurised, spray‐dried and reconstituted) showed more browning in nitrogen storage conditions than did type B. Furfural, HMF, lactulose, A₂₈₄ and A₄₂₀ are useful indicators to control the extent of browning reactions in adverse storage conditions. © 2002 Society of Chemical Industry     

Non-enzymatic browning in clarified cashew apple juice during thermal treatment: Kinetics and process control

The effect of thermal treatment on clarified cashew apple juice was studied at temperatures from 88 to 121 °C. Changes in colour measured with colorimetric parameters (reflectance spectra, colour difference and CIELAB), and the variation in ascorbic acid, 5-hydroxymethylfurfural (5-HMF) and sugar content were used to evaluate non-enzymatic browning. Kinetic models were applied to the changes in reflectance spectra, ascorbic acid and 5-HMF. The effect of temperature on kinetic constants was described by an Arrhenius type equation. The sugar content remained constant during thermal treatment and did not affect non-enzymatic browning, which was mainly affected by degradation of ascorbic acid. The kinetic models were used to optimise and control the thermal treatment for clarified cashew apple juice.     

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.