Antioxidant and functional properties of a high dietary fibre powder from carambola (Averrhoa carambola L.) pomace

The use of carambola pomace as a raw material for the production of a high dietary fibre powder (HDFP) was investigated. A face‐centred design was used to study the effects of extraction conditions, namely water‐to‐pomace ratio, time and temperature, on both reducing sugars (RS) and total extractable polyphenols (EPP) contents of fibre concentrate. RS content decreased by increasing extraction times and water‐to‐pomace ratios, while EPP tend to diminish by increasing temperature and contact time (P < 0.01). Selected HDFPs showed an EPP content in the range of 5.0–6.1 g GAE 100 g^?1 dry basis (db), with antioxidant activities between 386.2–443.9 and 204.7–228.6 μmol Trolox equivalents g^?1 db according to FRAP and ABTS assays, respectively. HDFP obtained at 55 °C, 5 min and 2:1 water‐to‐pomace ratio exhibited the highest EPP content, total dietary fibre (84.0% db) and dietary indigestible fraction (61.3% db). This product can be considered as a potential valuable food ingredient considering their oil retention and swelling capacities.     

Sensorial and physicochemical quality responses of pears (cv Rocha) to long‐term storage under controlled atmospheres

Pears (cv Rocha) kept under controlled atmospheres (CA) and air were evaluated after long‐term storage in terms of sensory attributes and physicochemical parameters, namely colour, firmness, polyphenoloxidase (PPO) activity and concentration of hydroxycinnamic compounds. The CA conditions were all combinations of 2 and 4% (v/v) O₂ with 0.5 and 1.5% (v/v) CO₂. Storage under CA conditions produced a beneficial effect on ‘Rocha’ pears in maintaining their quality and, consequently, in extending their shelf life and acceptability. Clear differences in sensorial attributes, colour parameters and PPO activity were found between CA‐ and air‐stored pears. The effect provided by the CA conditions persisted throughout the time of exposure to the open air. The 2% O₂ concentration produced a more beneficial effect than its 4% counterpart on the sensorial and physical characteristics of the pears. The former concentration of O₂ prevented yellowing and allowed regular softening, hence keeping a high flavour quality. No clear effects could be associated with CO₂ levels. Empirical models were developed that describe the effects of O₂ and CO₂ concentrations, as well as time at room temperature on physicochemical parameters pertaining to ‘Rocha’ pears. Copyright © 2004 Society of Chemical Industry     

Effect of cut‐type on quality of minimally processed papaya

BACKGROUND: This research was undertaken to study the effects of different cut‐types (cube, parallelepiped, cylinder and sphere) on the quality and shelf‐life of papaya cv. Sunrise Solo. Physicochemical analyses were carried out during 10 days of storage at 4 °C to determine colour, firmness, pH, titratable acidity, total soluble solids, weight loss and vitamin C content. Microbiological analysis and sensory evaluation were also performed. RESULTS: Papaya spheres (1.55 cm radius) presented the most favourable physicochemical and microbiological properties (smaller changes in colour parameters L*, a*, b*, chroma and hue angle, firmer texture, lower increase in pH, higher titratable acidity, almost constant total soluble solids, reduced weight loss, high vitamin C content and lower microbial loads) and sensory characteristics on day 10, while papaya cubes (1.4 cm side) proved to be the least acceptable. CONCLUSION: The results of physicochemical, microbiological and sensory analyses performed on different cut‐types of papaya indicated acceptable fresh‐cut produce during 10 days of storage at 4 °C. The potential shelf‐life at 4 °C is therefore 10 days, provided that no contamination occurs in the postharvest period and during minimal processing operations. Copyright © 2008 Society of Chemical Industry     

Changes of quality characteristics of pepino fruit (Solanum muricatum Ait) during convective drying

Quality assessment of pepino fruit preserved through convective dehydration was investigated in this work. The effect of process temperature (50, 60, 70, 80 and 90 °C) on physicochemical properties, colour, non‐enzymatic browning, vitamin C, total phenolic content, antioxidant activity and firmness of the fruit were considered. When comparing the fresh with the corresponding dehydrated pepino samples, it was shown that the drying conditions resulted in important reductions of proteins and crude fibres. Discoloration of fruit was noticeable for all treatments due to effects of non‐enzymatic browning and changes in chromatic coordinates leading to a modification of the original colour. Regarding vitamin C and total phenolic content, an increase of drying temperature resulted in a considerable reduction of both initial compounds contents. Antioxidant activity showed an important decrease especially at low temperatures (e.g. 50 °C). Softening of the dried product was observed for all the treatments indicating structural modifications of the fruit due to thermal process.     

Thermal inactivation kinetics parameters of browning enzymes in starfruit (Averrhoa carambola L.) juice

This study aimed to evaluate the thermal inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in starfruit juice. It followed the Malaysia Food Regulations 1985 and CODEX STAN 247-2005. Glucose, fructose and sucrose were the main sugars in starfruit juice. The total soluble solids, pH, titratable acidity, and total phenolics content of the starfruit juice produced were 8.13 ± 0.25 °Brix, 3.80 ± 0.05, 0.43% ± 0.02% malic acid, and 93.67 ± 4.96 mg GAEL⁻¹, respectively. Thermal inactivation kinetics of PPO and POD followed the first-order kinetic model. The decimal reduction time at 83.6 °C (D_83.6) of PPO and POD was 198.48 and 98.4 s, respectively, while the thermal resistance constant (z value) of PPO and POD was 12.8 and 5.4 °C, respectively. In conclusion, PPO might be a suitable signal for thermal processing on starfruit juice since it has higher heat resistance than POD.     

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.     

Hot air dehydration of figs (Ficus carica L.): drying kinetics and quality loss

The dehydration of fruit from fig trees is normally achieved by sun drying. There is concern about the safety of the end product, mainly because there is a risk of the development of aflatoxins. These concerns can be overcome by artificial drying (oven dehydration). Fig fruits of a local cultivar, which were either pre‐treated by blanching or blanching plus sulphuring or not treated at all, underwent hot air dehydration under mild processing conditions in a pilot airflow cabinet dryer. Sampling was carried out at regular intervals to calculate the rate of dehydration and assess quality changes. Microbiological counts and nonenzymatic browning were also monitored. Pretreatments resulted in a shorter processing time, compared with control fruits. In general, a falling dehydration rate period was observed. A dramatic loss of ascorbic acid was recorded, while an informal sensorial assay of the dried fruits gave a positive assessment.     

Volatile composition and sensory quality of Spanish pomegranates (Punica granatum L.)

BACKGROUND: Pomegranate is highly valued for its health‐promoting effects. Fruits of nine pomegranate cultivars were analysed for volatile compounds, antioxidant activity and quality parameters, including maturity index and CIEL*a*b* colour. Volatile compounds were isolated from fresh juices using hydrodistillation; extracts were analysed using gas chromatography/mass spectrometry. Fruit colour was influenced by cultivar and grouping of cultivars according to their taste (sweet, sour‐sweet or sour), with sweet fruits having more intense red colour and higher lightness values. RESULTS: A total of 18 compounds were found in pomegranate aroma profiles, including monoterpenes, aldehydes, alcohols, monoterpenoids and linear hydrocarbons. The most abundant compound were trans‐2‐hexenal, 3‐carene, α‐terpinene and α‐terpineol. The total concentration of volatiles ranged from 1.7 to 10.9 g kg^?1. Overall consumer liking of pomegranate juices was associated with the presence of monoterpenes such as α‐pinene, β‐pinene, β‐myrcene, limonene and γ‐terpinene. The presence of aldehydes such as hexanol, hexanal and cis‐3‐hexenol was correlated with poor overall consumer liking. CONCLUSION: Fruits from the cultivar Mollar de Elche 2 were those most suited for juice processing because they had the highest total concentration of volatiles, which was related to high overall consumer liking, intense and acceptable fresh pomegranate odour and flavour (high scores of satisfaction degree), medium intensity of red colour and low sourness. Copyright © 2010 Society of Chemical Industry     

Radiation processing of minimally processed sprouts (dew gram and chick pea): effect on sensory,nutritional and microbiological quality

Sprouts have become an important part of the diet because of their nutritive value and low‐calorie content. The effect of radiation processing (1 and 2 kGy dose) on minimally processed dew gram and chick pea sprouts with respect to different quality parameters was studied over a storage period of 16 days at 8 °C. Radiation treatment and storage period did not have any significant effect on the sensory as well as nutritional qualities of irradiated dew gram and chick pea sprout. No significant change (P > 0.05) was observed in the colour and firmness of irradiated sprouts as compared to control samples. However, radiation processing resulted in significant reduction in aerobic plate counts (APC), coliform counts (CC), yeast and mould count (YMC) and staphylococci counts (SC). Radiation processing of dew gram and chick pea sprouts at 1 and 2 kGy extends the shelf life without affecting sensory and nutritional qualities.     

Quality of minimally processed red chicory (Cichorium intybus L.) evaluated by anthocyanin content,radical scavenging activity,sensory descriptors and microbial indices

Changes in the quality of minimally processed red chicory (Cichorium intybus L.) were studied during storage in a polyvinyl chloride (PVC) film and in a mono‐oriented polypropylene (OPP) film at 4 °C. The maximum limit of 5 × 10⁷ CFU g^?1 for mesophilic aerobic bacterial count was attained after 4 days using the PVC film and after 4.5 days using the OPP film. The loss of fruity aroma occurred after 3 days in the products stored in PVC but not in those stored in OPP. In spite of microbial growth, no off‐odour was perceived by trained panellists. Storage in PVC slightly decreased the contents of cyanidin 3‐O‐malonyl glucoside, total phenolics and antioxidant activity, whereas these parameters increased upon storage in OPP. When red chicory heads subjected to mild stress in the field were minimally processed, OPP packaging decreased the microbial growth with respect to PVC, but antioxidants were degraded in both conditions.     

Ascorbate oxidase from starfruit (Averrhoa carambola): preparation and its application in the determination of ascorbic acid from fruit juices

A study was conducted to utilize ascorbate oxidase (AAO) from very immature starfruit for the enzymatic determination of ascorbic acid (AsA) in colored samples. The enzyme preparation was carried out by a combination of (NH₄)₂SO₄ fractionation, DEAE-Toyopearl 650 M and ultrafiltration. A calibration curve for AsA was constructed by plotting the amount of AsA oxidized by the enzyme at a specified reaction time against the absorbance. The curve showed a linear relationship in the range of 0–100 μg ml⁻¹ AsA used. Using the plot, the values of AsA in juice samples were determined and compared with the conventional 2,6-dichloroindophenol method.     

Effect of washing with citric acid and antioxidants on the colour and microbiological quality of whole mushrooms (Agaricus bisporus L.)

The effect of washing with citric acid followed by anti‐browning treatment involving rinsing with sodium d ‐isoascorbate or sodium l ‐ascorbate on the colour, microbiological quality and bacterial blotch of whole mushrooms when stored at 5 °C for up to 13 days at 80% RH was evaluated. Washing with 1% citric acid reduced Pseudomonas counts avoiding bacterial blotch, but caused an important deterioration of colour. When washing with citric acid was followed by an anti‐browning treatment, mushrooms colour was improved, at the same time as bacterial blotch was reduced, although the decrease of Pseudomonas counts was smaller than in mushrooms washed only with citric acid. The most effective treatment was washing with 1% citric acid followed by anti‐browning treatment with 1.5% sodium l ‐ascorbate.     

Phytochemicals and quality characteristics of candied paprika (Capsicum annuum L.) during storage

In this study, we prepared candied paprika from various coloured fresh paprika and compared the changes in phytochemicals and quality for 42 days by analysing carotenoids, ascorbic acids and total phenolic content, and by assessing sensory and instrumental qualities. We identified five types of carotenoids from candied red paprika (CRP) and three from candied orange paprika (COP) and candied yellow paprika (CYP). At 0‐day storage, capsanthin and β‐carotene in CRP were quantitatively analysed to 26.96 μg g^?1 fw and 3.81 μg g^?1 fw, zeaxanthin and β‐carotene in COP were 9.35 μg g^?1 fw and 4.16 μg g^?1 fw, and lutein and β‐carotene in CYP were 0.27 μg 100 g^?1 fw and 0.70 μg 100 g^?1 fw, respectively. After 42‐days storage, CRP retained approximately 68.6% carotenoids, COP retained 40%, and CYP retained 33%. Ascorbic acid and total phenolic content decreased during storage as carotenoids did. However, rates of decrease were different in different coloured paprika, especially, ascorbic acid in COP and phenolic acid in CRP were considerably conserved for 42 days. Hardness, springiness and chewiness in all samples were significantly increased by 14‐days storage and maintained until 42‐days storage, and all the sensory parameters, including colour, appearance, odour, texture, paprika flavour and overall consumer preference showed no differences until 28 days.     

Physical changes and physiological characteristics of red and green peel during nectarine (cv. Hu018) maturation

BACKGROUND: The aim of this study was to determine physical changes in nectarine and distinctive physiological characteristics related to red and green peel under stresses occurring during fruit maturation, information on which is currently not available. RESULTS: Fruit firmness increased from 4 to 6 weeks after blooming (WAB) then decreased from 6 WAB until ripening. Anthocyanins in red and green peel during nectarine maturation were identified by high‐performance liquid chromatography as cyanidin 3‐glucoside together and, at a much lower level, cyanidin 3‐rutinoside. Cyanidins in red and green peel decreased from 4 to 8 WAB then increased from 8 to 12 WAB. Anthocyanin contents were positively correlated with PAL, POD, A*, MDA and O$_{2}^{\bullet-}$ values and inversely correlated with L* and B* values. Red and green peel during maturation could be separated by hierarchical cluster analysis of the tested data. CONCLUSION: This study has provided an overview of red and green peel characteristics during nectarine (cv. Hu018) maturation. Values of A*, anthocyanins, O$_{2}^{\bullet-}$ , MDA, PAL, PPO and POD in red peel were higher than those in green peel, while values of L*, B* and chroma in red peel were lower than those in green peel throughout fruit maturation. Copyright © 2011 Society of Chemical Industry     

The effects of cooking method on selected quality traits of broccoli and green asparagus

Broccoli and green asparagus were cooked using boiling water, steam, microwave oven and combi oven with overheated steam and combination of hot air with overheated steam (only broccoli). Vegetables were analysed for chlorophylls a and b, carotenoids, total polyphenols, antioxidant activity, colour parameters and sensory properties. Cooking in the combi oven with overheated steam was an effective method to achieve the highest levels of polyphenols and antioxidant activity, but it negatively influenced the contents of chlorophylls in both vegetables and carotenoids in asparagus. Boiling and cooking in the combi oven with overheated steam or hot air and steam ensured the best and comparable sensory properties of broccoli. Asparagus showed a lower susceptibility to heat treatments than broccoli as none of the treatments applied caused significant differences in colour redness and yellowness, polyphenol content and sensory properties of this vegetable.