Quantification of gallic acid and ellagic acid from longan (Dimocarpus longan Lour.) seed and mango (Mangifera indica L.) kernel and their effects on antioxidant activity

Gallic acid (GA) and ellagic acid (EA) have been identified in longan seed and mango kernel by the use of reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with photodiode array detection (DAD). The ethanolic extract of longan seed contained 23.3 and 156 mg/100 seeds of GA and EA, respectively. The ethanolic extracts of mango kernel contained approximately 87% more GA than the longan seed ethanolic extracts but about 32% less EA. After heat treatment and acid hydrolysis, mango kernel had higher concentrations of GA and EA, contributing to more potent antioxidant activity. The results demonstrated rich sources of GA and EA in longan seed and mango kernel which might provide a novel source of these natural antioxidants.     

Antioxidant and antiproliferative activities of mango (Mangifera indica L.) flesh and peel

The antioxidant and antiproliferative properties of flesh and peel of mango (Mangifera indica L.) were investigated. The cytoprotective effect of mango flesh and peel extracts on oxidative damage induced by H₂O₂ in a human hepatoma cell line, HepG2, were determined, and the underlying mechanism was examined by a single-cell electrophoresis assay (comet assay). Treatment of HepG2 cell with mango peel extract prior to oxidative stress was found to inhibit DNA damage. The free radical scavenging activities of mango flesh and peel extracts were evaluated by electron spin resonance (ESR). The mango peel extract exhibited stronger free radical scavenging ability on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and alkyl radicals than mango flesh extract, regardless of ripeness. Similarly, peel extract exhibited significant antiproliferative effect against all tested cancer cell lines, compared to that of flesh extract, in a dose-dependent manner. The result also showed that the antiproliferative activity of mango flesh and peel extracts correlated with their phenolic and flavonoid contents. Thus, mango peel, a major by-product obtained during the processing of mango product, exhibited good antioxidant activity and may serve as a potential source of phenolics with anticancer activity.     

Physico-chemical and antioxidant properties of four mango (Mangifera indica L.) cultivars in China

Four principal mango cultivars (Tainong No.1, Irwin, JinHwang and Keitt) grown in southern China were selected, and their physico-chemical and antioxidant properties were characterized and compared. Of all the four cultivars, Tainong No.1 had highest content of total phenols, ρ-coumaric acid, sinapic acid, quercetin, titratable acidity, citric acid, malic acid, fructose, higher antioxidant activities (DPPH, FRAP) and L^∗, lower pH, PPO activity and individual weight. Keitt mangoes showed significantly (p < 0.05) higher contents of β-carotene, ρ-hydroxybenzoic acid, sucrose, total sugar, total soluble solid, catechin, succinic acid and higher PPO activity. JinHwang mangoes exhibited significantly (p < 0.05) higher individual weight and PPO activity, but had lower content of total phenols, β-carotene and lower antioxidant activity. Principal component analysis (PCA) allowed the four mango cultivars to be differentiated clearly based on all these physico-chemical and antioxidant properties determined in the study.     

Antioxidant phytochemical and quality changes associated with hot water immersion treatment of mangoes (Mangifera indica L.)

Mangoes are an important tropical fruit crop worldwide and are best noted for their vibrant flesh colour, juicy texture, and sweet flavour, along with important nutrient contributions from their phytochemical constituents. Mangoes imported to the US must be exposed to thermal quarantine treatments, such as irradiation and hot water treatment (HWT), to eradicate invasive pests, yet limited data exist regarding polyphenolic changes to the fruit following hot water immersion treatment. Although the water temperature remains constant, the duration of treatment depends on fruit size. Therefore, these investigations focused on polyphenolic and antioxidant changes to mature, green mangoes following varying times of HWT and their changes during short-term storage. Experimentally, fruit were immersed in 46.1 °C water from 70 to 110 min; half evaluated within 2 h of treatment, while the remainder was evaluated after 4 days of storage at 25 °C for changes in polyphenolics, antioxidant capacity and fruit quality. Free gallic acid and four gallotannins were tentatively identified as the major polyphenolics present by HPLC analysis against authentic standards. Two major polyphenolics in mango, gallic acid and gallotannins, as well as total soluble phenolics, decreased as a result of prolonged HWT, while the antioxidant capacity remained unchanged in all heat-treated mangoes immediately after HWT. However, during 4 days storage, only minor changes were observed in gallic acid and gallotannin concentrations whereas total soluble phenolics and antioxidant capacity in all hot water-treated fruits decreased. The optimum hot water immersion times did not affect the external quality and polyphenolics of mangoes but all heat treatments reduced total soluble phenolics and antioxidant capacity, regardless of the duration of treatment times, during 4 days storage.     

Antioxidant phytochemical and fruit quality changes in mango (Mangifera indica L.) following hot water immersion and controlled atmosphere storage

Tropical fruits such as mangoes destined for import into the United States are commonly required to have a thermal treatment against invasive pests, which could be combined with controlled atmosphere (CA) storage to prolong shelf life and preserve fruit quality. Changes in antioxidant phytochemicals and resultant quality during storage and ripening were investigated in fresh mangoes, as influenced by application of CA in combination with a hot water immersion quarantine treatment (46 °C for 75 min). Mature-green mangoes with or without a hot water treatment, were held in air, 3% O₂ + 97% N₂, or 3% O₂ + 10% CO₂ + 87% N₂ and evaluated for external quality and phytochemical differences after storage for 2 weeks at 10 °C and after subsequent ripening in air at 25 °C. Visible appearance of anthracnose during ripening was effectively inhibited by the hot water treatments combined with CA. Concentrations of gallic acid and numerous hydrolysable tannins and their resultant antioxidant capacity were unaffected by the hot water treatment, while total polyphenolics naturally decreased throughout fruit ripening, regardless of hot water treatment or storage atmosphere. However, the overall decline in polyphenolic concentration was inhibited by the CA treatments, as a result of delayed ripening. Quality parameters such as flesh colour and titratable acidity provided supporting evidence that the CA conditions helped to delay fruit ripening.     

Structural properties and gelatinisation characteristics of potato and cassava starches and mutants thereof

The molecular size of amylopectin (AP) and amylose (AM), AP chain length distribution, crystallinity and granular structure (morphology and granule size distribution) of five wild type potato starches (wtps), five AM free potato starches (amfps), four high-AM potato starches (haps), one wild type cassava starch (wtcs) and one AM free cassava starch (amfcs) were investigated and related to their gelatinisation characteristics. Starches with higher levels of short chains [degree of polymerisation (DP) 6–9 and DP 10–14)] had lower gelatinisation onset (T_o), peak (T_p) and conclusion (T_c) temperatures, whereas higher contents of longer chains (DP 18–25 and DP 25–80) led to higher gelatinisation temperatures. Gelatinisation enthalpies (ΔH) increased with degree of crystallinity. The granules of wtps were larger than those of amfps and haps, respectively. No differences in morphology were observed between wtps and amfps granules, but the haps granules had more irregular surfaces and showed multi-lobed granules.     

Maintaining mango (Mangifera indica L.) fruit quality during the export chain

Mangoes are tropical/sub tropical fruit with a highly significant economic importance. Preferable quality attributes include freedom from external damages such as bruises, latex or sap injury and decay, uniform weight, colour, aroma, firmness (with little give away, not soft), shape and size. The fruit is rich in antioxidants and recommended to be included in the daily diet due to its health benefits such as reduced risk of cardiac disease, anti cancer, and anti viral activities. Maintenance of mango fruit quality during the supply chain depends on many aspects including adequate orchard management practices, harvesting practices, packing operation, postharvest treatments, temperature management, transportation and storage conditions, and ripening at destination. Postharvest losses are high during the supply chain due to harvesting fruit at improper maturity, mechanical damage during the whole chain, sap burn, spongy tissue, lenticels discolouration, fruit softening, decay, chilling injury, and disease and pest damage. The aim of postharvest treatments and management practices in the supply chain is to create suitable conditions or environments to extend the storage life and retain the quality attributes, nutritional and functional compositions. This review summarises the available research findings to retain the overall mango fruit quality and to reduce postharvest losses during supply chain by adopting suitable postharvest novel technologies.     

Chemometric profiling of pre-climacteric Sri Lankan mango fruit (Mangifera indica L.)

There is no published information on the genotypic variation of major biochemical constituents in mango fruit endemic to Sri Lanka. Accordingly, non-structural carbohydrates, non-volatile organic acids and total phenolics were determined from the peel and pulp of pre-climacteric Sri Lankan mango cultivars (viz. Willard, Karutha Colomban, Vellai Colomban, Ampalavi, and Malgova) at three different maturity stages. Principal components analysis revealed distinct clustering of samples according to their biochemical profiles of peel and pulp at three maturity stages. Sugar concentrations generally declined with maturity in both peel and pulp except for cv. Willard. Fructose was the predominant sugar in both peel (56.2–106 mg/g dry weight (DW)) and pulp (67.4–141 mg/g DW), followed by glucose and sucrose. Starch concentration increased with maturity and was higher in pulp (26.0–55.0% DW) than peel (18.2–38.9% DW) at full mature stage. Dry matter as a proportion of fresh weight (FW) increased with maturity.     

Purification and characterisation of multiple forms of polygalacturonase from mango (Mangifera indica cv. Dashehari) fruit

Three multiple forms of polygalacturonase (PG) namely PGI, PGII and PGIII were isolated, purified and characterized from ripe mango (Mangifera indica cv. Dashehari) fruit. Native molecular weights of PGI, PGII and PGIII were found to be 120, 105 and 65 kDa, respectively. On SDS–PAGE analysis, PGI was found to be a homodimer of subunit size 60 kDa each while those of PGII and PGIII were found to be heterodimers of 70, 35 and 38, 27 kDa subunit size each, respectively. Three isoforms of PG differed with respect to the effect of pH, metals, reducing agents and their susceptibility towards heat. PG isoforms also differed with respect to the effect of substrate concentration on enzyme activity. PGI and PGIII exhibited inhibition at high substrate concentration while PGII did not. Km for polygalacturonic acid was found to be 0.02% for PGI.     

Utilisation of mango seed kernel (Mangifera indica) as a source of oil

Fat extracted from mango seed kernel (Mangifera indica) was analysed for its chemical and physical constants, triglycerides, fatty acids and phospholipids; and these were compared with those of cotton seed oil, cocoa butter and two of its substitutes, namely, Croklaan Special 555 and Wesco Special E. The effects of incorporation of mango seed kernel oil in butterscotch toffee on its organoleptic properties were also studied. It was found that mango kernel oil and cocoa butter were almost identical in several of their constants, triglycerides, fatty acids and effects on taste, odour and texture of the toffee.     

Steam blanching effect on polyphenoloxidase,peroxidase and colour of mango (Mangifera indica L.) slices

The heat stability of peroxidase (POD) and polyphenoloxidase (PPO) was investigated in mango (Mangifera indica L.) slices, and the relative colour was studied after different steam blanching times. There was complete inactivation after 5 min for POD and 7 min for PPO. Steam blanching of 3 min gave residual activity of 2.85% and 8.33% for PPO and POD, respectively, and when compared with samples blanched for 5 min had no effect on colour over 20 days of storage. Correlation was found between activities of PPO, POD and colour change over 20 days. After 7 min steam blanching the browning index was stable but less than at 3 and 5 min because non-enzymic browning had occurred. This research suggests that yellowness (b) and lightness (L) values contribute positively to the browning index (BI), compared to redness (a).     

Optimisation of freeze drying conditions for purified serine protease from mango (Mangifera indicaCv. Chokanan) peel

This study investigated the possible relationship between the encapsulation variables, namely serine protease content (9–50 mg/ml, X₁), Arabic gum (0.2–10% (w/w), X₂), maltodextrin (2–5% (w/w), X₃) and calcium chloride (1.3–5.5% (w/w), X₄) on the enzymatic properties of encapsulated serine protease. The study demonstrated that Arabic gum, maltodextrin and calcium chloride, as coating agents, protected serine protease from activity loss during freeze-drying. The overall optimum region resulted in a suitable freeze drying condition with a yield of 92% for the encapsulated serine protease, were obtained using 29.5 mg/ml serine protease content, 5.1% (w/w) Arabic gum, 3.5% (w/w) maltodextrin and 3.4% (w/w) calcium chloride. It was found that the interaction effect of Arabic gum and calcium chloride improved the serine protease activity, and Arabic gum was the most effective amongst the examined coating agents. Thus, Arabic gum should be considered as potential protection in freeze drying of serine protease.     

Effects of different drying treatments on the stability of carotenoids in Taiwanese mango (Mangifera indica L.)

The stability of carotenoids in Taiwanese mango as affected by different drying treatments was studied. Mangoes were soaked in 1% sodium hydrogen sulfite solution or 1% ascorbic acid solution, prior to hot-air drying and freeze-drying. Results showed that in most cases, the highest yield of the epoxy-containing carotenoids was achieved by freeze-drying plus soaking in 1% sodium hydrogen sulfite solution. However, freeze-drying plus soaking in 1% ascorbic acid solution resulted in the highest retention of all-trans-β-carotene and its cis isomers, all-trans-zeaxanthin and its cis isomers, as well as cis-lutein. Nevertheless, for hot-air drying, with or without soaking, a mango product of deep orange colour was produced. On freeze-drying, mango could generate yellow colour, while a lighter color was observed when soaked in antioxidants.     

Phase transition of cross-linked and hydroxypropylated corn (Zea mays L.) starches

The thermal behaviors of three chemically modified starches (cross-linked waxy corn, hydroxypropylated regular corn, and hydroxypropylated and oxidized waxy corn) were studied using light microscopy, SEM, DSC, XRD, and HPSEC. During the gelatinization process, molecular and crystalline order losses occurred independently from each other. Oxidation treatment altered the effects of hydroxypropylation on starch gelatinization. Both cross-linking and hydroxypropylation tended to preserve granular crystalline order during initial stages of gelatinization. The crystallinities and X-ray patterns of each starch remained essentially unchanged prior to phase transition.     

Structural and some nutritional characteristics of Velvet bean (Mucuna pruriens) and Lima bean (Phaseolus lunatus) starches

Velvet bean (Mucuna pruriens) and lima bean (Phaseolus lunatus) starches were isolated from seeds and their structural characteristics evaluated using XRD, size‐exclusion chromatography and light scattering analyzes. Total starch, available starch, RS and in vitro digestibility were also determined. Structural and nutritional characteristics of Velvet bean and Lima bean starches were compared to those of commercial corn starch. The legumes starches presented a C‐type XRD pattern and crystallite sizes of 43.1 Å for velvet bean and 48.3 Å for lima bean. Lima bean starch average molar mass (4.9 × 10⁶ g/mol) was slightly higher than the velvet bean starch (3.04 × 10⁶ g/mol). Size‐exclusion chromatography indicated structural similarity between the lima bean and corn starches which differed from that of the velvet bean starch. Hydrodynamic radius (R_H) for the velvet bean and lima bean starches was 45.5 and 55 nm, respectively, and their radius of gyration (R_G) was 67.7 and 82.5 nm, respectively. Total starch content in all three starches was greater than 98%. Their complex crystalline structure provided the legume starches lower in vitro digestibility values than the corn starch. RS content in both the velvet bean starch (7.72%) and lima bean starch (5.66%) was higher than in the corn starch, essentially qualifying these polysaccharides as natural dietary fiber sources, with the associated physiologic advantages.     

Rheological characteristics of tamarind (Tamarindus indica L.) juice concentrates

The steady-shear and small-amplitude oscillatory rheological properties of tamarind (Tamarindus indica L.) juice concentrate (TJC) were studied in the temperature range of 10-90 °C using a controlled-stress rheometer. Under steady-shear deformation tests, shear stress-shear rate data were adequately fitted to the Herschel-Bulkley and Casson model at lower (10-30 °C) and higher (50−90 °C) temperature range, respectively. The Carreau model was applied to describe the shear-thinning behaviour of the concentrate, and the model parameters estimated empirically showed temperature dependence. Oscillatory shear data of TJC revealed predominating viscous behaviour (G″>G′) at lower frequency range while the elastic modulus predominating over the viscous one (G′>G″) at higher frequency range. The Cox-Merz rule that relates steady shear and dynamic material functions was tested and not followed by most of the temperatures. The specific heat of TJC increased with temperature and the glass transition temperature of the product was found to be −70.74 °C.     

Response surface optimization and characteristics of rambutan (Nephelium lappaceum L.) kernel fat by hexane extraction

Response surface methodology (RSM) was used to study the effect of moisture content (1.59-18.41 g/100 g), extraction time (2.3-10.7 h) and particle size (0.09-2.11 mm) on the fat yield from rambutan kernels using hexane extraction. The physical and chemical characteristics of rambutan fat were also determined. The optimum conditions obtained from response surface analysis was 4.99 g/100 g moisture, 1.05 mm particle size and 9.2 h extraction time. Under these optimum conditions, the maximum fat yield was 37.35 g/100 g. The extracted fat was a white solid at room temperature. The physical and chemical characteristics of the extracted fat compared well with those of conventional fats. The high level of arachidic acid (∼ 34.3 g/100 g fat) and low iodine value in rambutan kernel fat permits the use of the fat, especially where oxidation may be a concern, without its being subjected to hydrogenation.     

Multiple forms of polygalacturonase from mango (Mangifera indica L. cv Alphonso) fruit

Polygalacturonase (PG) from mango pulp revealed three isoforms (I, II, III) upon ion exchange and gel filtration chromatography, each having an abundance of 68%, 6% and 26%, and molecular weights (M_r) 40, 51 and 45 kDa, respectively. The pH optimum for the isoforms was between 3 and 4. PG-I was stable over a wide pH range (4–7.5) unlike PG II and III, which were stable at pH 4 and 5, respectively. The optimum temperature was around 40 °C for all the three isoforms. Their apparent K_m for pectic acid was in the range 0.22–0.25 mg ml⁻¹. The V_max for PG I, II and III was 5.7, 3.6 and 4.4 μmol GalA equivalent h⁻¹, respectively. Cd²⁺, Cu²⁺ and Fe²⁺ and EDTA inhibited whereas GalA, Gal, Fuc, Rha and Ara stimulated PG-I activity, in particular. The major endogenous substrates for mango PG were identified to be two rhamnogalacturonans varying in their sugar ratio. These results are discussed in the light of pectin dissolution in vivo in ripening mango.