Batch drying of banana pieces — effect of stepwise change in drying air temperature on drying kinetics and product colour

Slices of banana were dried in a two-stage heat pump dryer capable of producing stepwise control of the inlet drying air temperature while keeping absolute humidity constant. Two stepwise air temperature profiles were tested. The incremental temperature step change in temperature of the drying air about the mean air temperature of 30°C was 5°C. The total drying time for each temperature-time profile was 240 min. The drying kinetics and temporal colour change of the products dried under these stepwise variation of the inlet air temperature were measured and compared with constant air temperature drying. The effects of the profile starting temperature and cycle time on both drying kinetics and product quality were also studied. It was observed that by employing stepwise-varying drying air temperature with appropriate starting temperature and cycle time, it was possible to reduce significantly the drying time to reach the desired moisture content with improved product colour.     

Design of apple snacks – A study of the impact of calcium impregnation method on physicochemical properties and structure of apple tissues during convective drying

Calcium impregnation methods (at atmospheric pressure, AI, or under vacuum, VI) followed by air drying at 60 °C were used for producing healthy apple snacks. This study compared the effect of the impregnation method on the ultrastructure features and physicochemical properties (desorption isotherm, density, porosity and shrinkage, thermal transitions, rheological behaviour, colour) of fortified apples along convective drying. Calcium concentration in AI and VI dried apples were ≈ 3600 and ≈ 5200 ppm respectively, which implied, considering a portion of dried apple of 50 g, 18% and 26% of the recommended intake for adults. Calcium incorporation did not affect the desorption behaviour but induced browning of apple tissues. Drying resulted in a great increase in porosity of AI samples and a noticeable compaction of the VI tissues. Impregnated tissues at a_w ≤ 0.47 exhibited distinctive mechanical properties: AI apples were characterized by very high stiffness and lower resistance to rupture, while VI apples appeared stronger and moderately stiff.Industrial relevance textThis study will help to develop large-scale commercial production of calcium fortified apple snacks with distinctive characteristics. High quality and content of nutrients, easy industrialization and storage and a long shelf life are important aspects of these healthy snacks. They constitute a valuable functional shelf-stable product, that also can help feeding the population during natural disasters and wars, as well as reducing food insecurity in vulnerable groups as part of the diet. On the other hand, the use of apples not meeting the organoleptic requirements for direct consumption, or not processed into juice, drink, or cider as raw material, looks of particular interest for diversifying the production within the framework of sustainable production.     

Effect of thermal and high pressure processing on antioxidant activity and instrumental colour of tomato and carrot purées

Total antioxidant activity, levels of bio-active compound groups and instrumental colour of tomato and carrot purée subjected to high pressure treatment (400–600 MPa/15 min/20 °C) and thermal treatments (70 °C/2 min) were measured. Antioxidant activity in tomato and carrot purée was significantly higher (p < 0.05) than in untreated or thermally processed samples. High pressure treatments at 600 MPa retained more than 90% of ascorbic acid as compared to thermal processing in tomato purées. Heat treatments caused a rapid decrease in ascorbic acid (p < 0.05). Phenolic contents were in general un-affected by thermal or high pressure treatments. Colour parameters were significantly affected (p < 0.05) by thermal and high pressure processing. Principal component analysis (PCA) revealed that the first two components represented 97% and 92% of the total variability in instrumental colour parameters with respect to processing for tomatoes and carrots respectively.Industrial relevanceThis research paper provides scientific evidence of the potential benefits of high pressure processing in comparison to thermal treatments in retaining important bioactive compounds. Antioxidant activity (ARP), ascorbic acid, and carotenoids after exposure to high pressure treatments (400–600 MPa) were well retained. Our results also show that redness and colour intensity of purées were better preserved by high pressure processing than conventional thermal treatment. It would appear from a nutritional prospective, high pressure processing is an excellent food processing technology which has the potential to retain compounds with health properties in foods. Therefore high pressure processed foods could be sold at a premium over their thermally processed counterparts as they will have retained their fresh-like properties.     

Effects of heating method and temperature in combination with hypoxic treatment on γ-aminobutyric acid,phenolics content and antioxidant activity of germinated rice

Heat and hypoxic treatments were combined with soaking to enhance γ-aminobutyric acid (GABA) production in germinated paddy (GP). Effects of heating temperature, heating techniques, that is, impinging stream drying (ISD) and tray drying (TD), and germination time on the GABA content, phenolics content and antioxidant activity were also investigated. Heating temperature had a significant effect on the GABA content; both ISD and TD helped increase the GABA content when the post-treatment grain temperature was 38–40.5 °C. Within this grain temperature range, soaking in combination with heat and hypoxic treatments (S-ISD-H and S-TD-H) yielded GP with higher GABA content than soaking (S) and soaking in combination with hypoxic treatment (S-H). However, ISD was noted to be more suitable than TD. Phenolics content and antioxidant activity of GP prepared by S-ISD-H at different heating temperatures and S-H were not significantly different but were higher than those of the GP prepared by S.     

Changes in colour,antioxidant activities and carotenoids (lycopene, β-carotene,lutein) of marigold flower (Tagetes erecta L.) resulting from different drying processes

Marigold (Tagetes erecta L.) flower has long been used as a food colourant and ingredient in human food and animal feed. Drying is one of the most important processes for producing marigold powder. Therefore the effects of different drying processes, namely freeze drying (FD), hot air drying (HA) and combined far-infrared radiation with hot air convection (FIR-HA), on the colour, carotenoids (lycopene, β-carotene and lutein) and phenolic compounds of marigold flowers were evaluated. The results indicate that colour changes were less for FIR-HA dried marigold than after FD and HA drying. Different drying methods resulted in changes in the content of individual bioactive compounds. HA gave the highest content of β-carotene (15.5 mg/100 g dry weight (DW)), while FIR-HA and FD provided the highest levels of lutein and lycopene. The predominant phenolic acids in all samples of marigold are p-coumaric acid, ferulic acid and sinapic acid. Gallic, protocatechuic, caffeic, syringic, p-coumaric and ferulic acid showed the highest content in marigold after FIR-HA drying. These results demonstrate that FIR-HA should be considered as a suitable drying method for marigold with respect to preserving its colour, antioxidant properties and bioactive compounds and provided useful information for industrial production of marigold powder.     

The effect of α-tocopherol and butylated hydroxyanisole on the colour properties and lipid oxidation of kavurma, a cooked meat product

Kavurma is a cooked meat product and is consumed sliced. The amount of animal fat in kavurma (30-40%) is higher than in other meat products; therefore, lipid oxidation and colour defects are a major problem during storage and in the market place. To preserve the quality characteristics of kavurma in markets antioxidants must be added and the product must be packaged and stored at low temperature. In this study, the effects of α-tocopherol and butylated hydroxyanisole (BHA) levels on lipid oxidation and colour deterioration of sliced and vacuum-packaged kavurma were investigated. Kavurma was made from beef meat and melted beef fat in 5 groups: No-added antioxidant, 50mg/kg BHA, 100mg/kg BHA, 50mg/kg α-tocopherol and 100mg/kg α-tocopherol. The kavurma produced was sliced (3-4-cm thick) and vacuum packed and stored at 4°C for 300 days, and thiobarbituric acid reactive substance, pH, moisture, lightness, redness and yellowness values of sliced product were determined during storage. The use of antioxidants in kavurma production caused a significant (P<0.01) decrease in the thiobarbituric acid reactive substances (TBARS) values. The lipid oxidative stability effect of the antioxidants was in following order: 100mg/kg BHA>100mg/kg α-tocopherol>50mg/kg BHA=50mg/kg α-tocopherol>no-added antioxidant group. Also, TBARS values did not differ significantly (P>0.05) between 0 and 300 days in the 100mg/kg BHA and 100mg/kg α-tocopherol groups. In addition, the no-added antioxidant group had lower lightness and yellowness values than all the antioxidant groups. Sliced and vacuum-packaged kavurma with added antioxidant showed greater colour and lipid oxidative stability during storage than kavurma to which no antioxidant was added.     

Effect of cocoa in diabetes: the potential of the pancreas and liver as key target organs,more than an antioxidant effect?

Increasingly, type 2 diabetes mellitus is being linked to metabolic abnormalities within the liver and pancreas, associated with fat deposition and oxidative stress. Cocoa and chocolate have been seen to improve oxidative stress and enhance insulin sensitivity. Recent in vitro and animal model studies have begun to investigate the potential of cocoa and cocoa extracts in modulating fatty liver and pancreatic function. Evidence from these studies has highlighted a number of mechanisms, which facilitate insulin secretion and enhanced survival in pancreatic beta cells. Whilst in liver, improved effect of insulin was observed with some improvements in fatty infiltration. However, what was seen as a common effect was an increase in endogenous antioxidant capability. The potential of cocoa products in the management of fatty liver and supporting pancreatic function in humans is likely to be limited by their macronutrient and energy profile or palatability, unless taken as cocoa extract supplements.     

Effect of pH on betalain–anthocyanin mixture in bayberry juice: influences on pigments,colour, and antioxidant capacity

Betalains (mainly betanin, isobetanin, and phyllocactin) extracted from red–purple pitaya were blended with Chinese bayberry juice (rich in anthocyanins) to explore variation trends of two natural pigments in one system. The mixture showed higher anthocyanin contents at pH 4, 4.5, and 5. In this process, redness and colour saturation were also maintained to a greater extent compared to the control. The coexisting betalains and anthocyanins increased colour acceptability of the juice matrix and expanded the pH tolerance range. Interestingly, colour change (ΔE) showed the opposite trend. Besides, betalains showed the function of improving the antioxidant activity of juice matrix at pH 3, 4, and 4.5, which confirmed their biological activity. Betalain-added bayberry juice obtained a satisfactory ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging capacity for 62.52% at pH 5.     

Effect of high-pressure processing on flavonoids,hydroxycinnamic acids,dihydrochalcones and antioxidant activity of apple ‘Golden Delicious’ from different geographical origin

The influence of high-pressure processing (HPP) (400, 500 and 600 MPa at 35 °C for 5 min) on different classes of phenolic compounds and antioxidant activity (AA) of ‘Golden Delicious’ apple from two different growing regions, northeastern of Spain (lowland climate) (S-apples) and north of Italy (mid-mountain climate) (I-apples) was investigated. Total hydroxycinnamic acids, total dihydrochalcones and total flavan-3-ols content were higher in S-apple (untreated and HPP-treated) than in I-apples and total flavonols content was higher in I-apples. HPP affected phenolic compounds and AA depending on the apple geographical origin. 400 MPa/35 °C/5 min increased total flavonols (30%) and maintained total phenolic compounds determined by HPLC (TP-HPLC) in S-apples. The higher increase of TP-HPLC (54%) was achieved when I-apple was treated at 600 MPa. Untreated and HPP-treated I-apples displayed higher AA than S-apples. HPP (400 and 600 MPa) increased AA in I-apple. Positive correlations were found between TP-HPLC and AA (TP-FC, DPPH^·, ABTS^·+ and FRAP) in both Italian and Spanish apples.Industrial relevanceThe apples of cultivar ‘Golden Delicious’ are one of the most consumed fruits in the UE. High-pressure processing (HPP) of these fruits acquires great importance to obtain ingredients and apple functional foods highly demanded by consumers. For this, it is necessary to know the process variables and plant material that favor greater extraction of phenolic compounds and antioxidant activity characteristics. This paper provides useful results to help fruit processor to select the appropriate HPP conditions and the geographical origin of ‘Golden Delicious’ apple to obtain apple-based products with high content on different classes of phenolic compounds with beneficial health effects.     

A review of the structure,function, and application of plant-based protein–phenolic conjugates and complexes

Interactions between plant-based proteins (PP) and phenolic compounds (PC) occur naturally in many food products. Recently, special attention has been paid to the fabrication of PP–PC conjugates or complexes in model systems with a focus on their effects on their structure, functionality, and health benefits. Conjugates are held together by covalent bonds, whereas complexes are held together by noncovalent ones. This review highlights the nature of protein–phenolic interactions involving PP. The interactions of these PC with the PP in model systems are discussed, as well as their impact on the structural, functional, and health-promoting properties of PP. The PP in conjugates and complexes tend to be more unfolded than in their native state, which often improves their functional attributes. PP–PC conjugates and complexes often exhibit improved in vitro digestibility, antioxidant activity, and potential allergy-reducing activities. Consequently, they may be used as antioxidant emulsifiers, edible film additives, nanoparticles, and hydrogels in the food industry. However, studies focusing on the application of PP–PC conjugates and complexes in real foods are still scarce. Further research is therefore required to determine the structure–function relationships of PP–PC conjugates and complexes that may influence their application as functional ingredients in the food industry.     

About the oxidative coupling of catechins – crystal and molecular structure of a 6′,8-dehydro-dicatechin

9a . The biological activity of the oligomeric dehydro-catechins is discussed. Received: 7 September 1999     

Low temperature,continuous wine ‐ making by immobilized cells: A comparative study of the effect of temperature on volatile by ‐ products

Abstract

A comparison study concerning the formation of methanol, ethylacetate, propanol‐1, isobutanol and amyl alcohols (mixture of 2‐ methylbutanol‐1 and 3‐methylbutanol‐1) in continuous wine‐making by γ‐alumina, kissiris and alginates supported biocatalysts is performed in this investigation. The effect of temperature was also examined. Methanol content was not affected by the support, process and temperature, but the concentrations of the other above compounds were reduced by the reduction of the temperature in all studied supports. The percentage content of ethyl acetate in the total volatile determined plus methanol was higher in the case of immobilized cells than in free cells. Kissiris supported biocatalyst increased this parameter but the other and free cells decreased it. Propanol‐1, isobutyl‐alcohol and amyl alcohols as percentage on total volatiles determined plus methanol were less than those of free cells for all supports and temperatures studied. The effect of the improvement of the formation of volatiles on quality of the wine was examined by a taste test.     

Isolation and identification of new compound, 2,7″-phloroglucinol-6,6′-bieckol from brown algae,Ecklonia cava and its antioxidant effect

Brown algae, Ecklonia cava has been regarded as a useful material in the prevention or treatment of several human diseases in Jeju Island, Korea. In this study, we investigated its antioxidant activity, and isolated a new antioxidative compound, which was identified as 2,7″-phloroglucinol-6,6′-bieckol (PHB) on the basis of LC/MS, as well as ¹H and ¹³C NMR spectroscopy results. The antioxidant activity of PHB was evaluated via several in vitro assays, such as radical scavenging activities using electron spin resonance spectrometry, intracellular reactive oxygen species scavenging activity, and DNA damage assays. PHB evidenced profound scavenging activities on DPPH, alkyl, hydroxyl, and superoxide radicals (IC₅₀: 0.51, 2.07, 75.64 and 57.19 μM for DPPH, alkyl, hydroxyl and superoxide radicals, respectively). The antioxidant activity of PHB was higher than that of ascorbic acid. Furthermore, PHB effectively inhibited H₂O₂-induced DNA damage. The results of this study indicate that PHB may prove useful as a novel natural marine antioxidant.     

Extraction optimisation,antioxidant activity and inhibition on α-amylase and pancreatic lipase of polyphenols from the seeds of Syzygium cumini

The objectives of this study were to determine the optimal extraction conditions of polyphenols from Syzygium cumini seeds by response surface methodology and investigate their antioxidant activity and inhibition on α-amylase and pancreatic lipase. As results, the optimal extraction conditions in the ultrasonic extraction process which maximised total polyphenols content, minimised the IC₅₀ values of α-amylase and pancreatic lipase were determined as follows: extraction time 60 min, ethanol concentration 63% and solvent/solid ratio 44 mL g⁻¹. The main phenolic compounds in partially purified fraction of Syzygium cumini seeds were catechin, epicatechin, kaempferol, gallic, 5-caffeoylquinic, caffeic and ferulic acids. In addition, the partially purified fraction inhibited 87.66 ± 5.55 and 86.61 ± 3.15% of α-amylase and pancreatic lipase, respectively. The results suggested that Syzygium cumini seeds could be explored as a natural antioxidant and could be used as a source of highly antidiabetic and anti-obesity bioactive compounds.