Kinetic study of the activation of banana juice enzymatic browning by the addition of maltosyl-beta-cyclodextrin

In recent years, the use of cyclodextrins (CDs) as antibrowning agents in fruit juices has received growning attention. However, there has been no detailed study of the behavior of these molecules as substances, which can lead to the darkening of foods. In this paper, when the color of fresh banana juice was evaluated in the presence of different CDs, the evolution of several color parameters was the opposite of that observed in other fruit juices. Moreover, a kinetic model based on the complexation by CDs of the natural browning inhibitors present in banana is developed for the first time to clarify the enzymatic browning activation of banana juice. Finally, the apparent complexation constant between the natural polyphenoloxidase inhibitors present in banana juice and maltosyl-beta-CD was calculated (Kci = 27.026 +/- 0.212 mM (-1)).     

Characterization of resistant starch type III from banana (Musa acuminata)

Banana starch (Musa acuminata var. Nandigobe) was evaluated for its use in generating resistant starch (RS) type III. Structural, physicochemical, and biological properties of these products were analyzed. The investigated process includes debranching of the native starch and retrogradation under different storage temperatures and starch concentrations. After enzymatic debranching, a high amount of low-molecular-weight polymers with a degree of polymerization between 10 and 35 glucose units beside a higher molecular weight fraction were found. The resulting products comprised RS contents of about 50%. After heat-moisture treatment, the RS yield increased up to 84%. Peak temperatures of about 145 degrees C found in DSC measurements pointed to a high thermal stability of the RS products. In vitro fermentations of the RS products, carried out with intestinal microflora of healthy humans, resulted in a molar ratio of acetate:propionate:butyrate of about 49:17:34. The established method allowed the production of a high-quality RS with prebiotic properties for health preventing applications.     

Use of natural and modified cyclodextrins as inhibiting agents of peach juice enzymatic browning

Although cyclodextrins (CDs) have been successfully used as antibrowning agents in different fruit juices, no research has studied the effect of these compounds on enzymatic browning in peach juice. In this paper, the color of fresh peach juice was evaluated in the presence of two types of natural (alpha-CD and beta-CD) and a modified (maltosyl-beta-CD) CD, and the effectiveness of these compounds as browning inhibitors was determined using the color space CIELAB system. Moreover, to clarify the mechanism by which CDs inhibit peach juice enzymatic browning, the process was kinetically modeled in the absence and presence of CDs using a colorimetric method; the apparent complexation constants between the mixtures of diphenols present in peach juice and some types of CD were calculated. The results show that the highest affinity constant was presented by alpha-CD (Kc = 18.31 mM-1) followed by maltosyl-beta-CD (Kc = 11.17 mM-1), whereas beta-CD was incapable of inhibiting peach juice enzymatic browning. Keywords: Cyclodextrin; browning; peach; juice; color; polyphenol oxidase.     

Physicochemical and digestibility properties of double-modified banana ( Musa paradisiaca L.) starches

Banana starch was chemically modified using single (esterification or cross-linking) and dual modification (esterification-cross-linking and cross-linking-esterification), with the objective to increase the slowly digestible starch (SDS) and resistant starch (RS) concentrations. Physicochemical properties and in vitro digestibility were analyzed. The degree of substitution of the esterified samples ranged from 0.006 to 0.020. The X-ray diffraction pattern of the modified samples did not show change; however, an increase in crystallinity level was determined (from 23.79 to 32.76%). The ungelatinized samples had low rapidly digestible starch (RDS) (4.23-9.19%), whereas the modified starches showed an increase in SDS (from 10.79 to 16.79%) and had high RS content (74.07-85.07%). In the cooked samples, the esterified starch increased the SDS content (21.32%), followed by cross-linked starch (15.13%). Dual modified starch (cross-linked-esterified) had the lowest SDS content, but the highest RS amount. The esterified and cross-linked-esterified samples had higher peak viscosity than cross-linked and esterified-cross-linked. This characteristic is due to the fact that in dual modification, the groups introduced in the first modification are replaced by the functional group of the second modification. Temperature and enthalpy of gelatinization decreased in modified starches (from 75.37 to 74.02 °C and from 10.42 to 8.68 J/g, respectively), compared with their unmodified starch (76.15 °C and 11.05 J/g). Cross-linked-esterified starch showed the lowest enthalpy of gelatinization (8.68 J/g). Retrogradation temperature decreased in modified starches compared with unmodified (59.04-57.47 °C), but no significant differences were found among the modified samples.     

Production potential of cavendish cultivars (Musa spp. AAA) under greenhouse and field conditions in subtropical areas of Turkey

The objective of this study was to evaluate the production potential of banana cultivars, ‘Grand Nain’, ‘Petit Nain’, ‘Poyo’, ‘Williams’ and ‘Basrai’, as alternatives to the ‘Dwarf Cavendish’ for open-field and greenhouse cultivation in subtropical conditions. Stem circumference, stem height, total leaf number, bunch stalk circumference, days from shooting to harvest, number of hands per bunch, number of fingers per bunch, finger circumference, finger length and bunch weight were measured in open-field and greenhouse cultivation. Cultivars ‘Williams’ and ‘Grand Nain’ were superior to ‘Dwarf Cavendish’ in greenhouse cultivation, while these two cultivars and ‘Petit Nain’ and ‘Basrai’ were superior to ‘Dwarf Cavendish’ in open-field cultivation. ‘Poyo’ was not suitable for greenhouse cultivation because of its excessive height and for open-field cultivation due to its sensitivity to wind damage. Greenhouse cultivation of bananas was superior to open-field cultivation for all cultivars with increases in yield of 19 to 28% according to the cultivar.     

Purification and characterization of polyphenol oxidase from banana (Musa sapientum L.) pulp

Polyphenol oxidase (EC 1.10.3.1, PPO) in the pulp of banana (Musa sapientum L.) was purified to 636-fold with a recovery of 3.0%, using dopamine as substrate. The purified enzyme exhibited a clear single band on polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The molecular weight of the enzyme was estimated to be about 41000 and 42000 by gel filtration and SDS-PAGE, respectively. The enzyme quickly oxidized dopamine, and its K(m) value for dopamine was 2.8 mM. The optimum pH was at 6.5, and the enzyme activity was stable in the range of pH 5-11 at 5 degrees C for 48 h. The enzyme had an optimum temperature of 30 degrees C and was stable even after a heat treatment at 70 degrees C for 30 min. The enzyme activity was completely inhibited by L-ascorbic acid, cysteine, sodium diethyldithiocarbamate, and potassium cyanide. Under a low buffer capacity, the enzyme was also strongly inhibited by citric acid and acetic acid at 10 mM.     

In vitro propagation of banana (Musa spp.) using thidiazuron and activated charcoal

Abstract

Rapid clonal propagation potential of banana was investigated by using excised shoot tips of Musa spp. Shoot tips isolated from young suckers of ‘Anamur 2’, ‘Dwarf Cavendish’, and ‘Gazipasa 6'genotypes were used. Excised shoot tips were transferred immediately to Murashige and Skoog (MS) medium with different concentrations of 6-benzylaminopurine (BAP) and thidiazuron (TDZ) either alone or with indoleacetic acid (IAA). Rooting was achieved with indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) in the presence or absence of activated charcoal (AC). The results showed that shoot proliferation rate was statistically affected by cytokinin types and their concentration. The responses to TDZ were better than to BAP. BAP or TDZ with IAA increased shoot elongation compared with BAP or TDZ alone. An increase in plant height, root numbers and average number of roots per explant was obtained using AC. Hence, for multiplication of ‘Dwarf Cavendish’, the use of MS medium with 2.5 µM TDZ with 1 µM IAA followed by rooting with AC only is recommended. For multiplication of banana genotypes ‘Anamur 2’ and ‘Gazipasa 6’, the use of MS medium with 1 µM TDZ and 1 µM IAA followed by rooting with AC only is recommended.     

Synergistic effect of root-associated bacteria on plant growth and certain physiological parameters of banana plant (Musa acuminata)

Fifty strains of bacteria isolated from banana roots were studied for their plant growth promoting (PGP) activities. Indole -3- acetic acid (IAA) production by root-associated bacteria ranged from 20 to 302 µg ml^?1. Seventeen isolates (34%) were positive for siderophore production and 18 isolates (36%) showed phosphate solubilization. None of the isolates showed potassium solubilization. All the isolates showed growth on nitrogen free Jensen medium. Identification of the bacteria based on 16S rRNA gene sequencing revealed that the isolates belonged to genus Bacillus sp, Klebsiella sp, Microbacterium sp and Enterobacter sp. A pot experiment in a greenhouse was conducted to investigate the effect PGP bacteria on banana plant growth and enzyme activities. The results demonstrated a significant (P < 0.05) increase in plant growth, chlorophyll, total phenolics, proline, catalase and ascorbic acid oxidase in banana plants treated with PGP bacteria as compared to control. However, the plant-growth response was variable and dependent on the bacterial strains, enzyme activity, and growth parameter observed. The present study revealed that bacteria showing multiple PGP activity could be used as biostimulants in enhancing banana production.     

Partial purification and characterization of polyphenol oxidase from banana (Musa sapientum L.) peel

Polyphenol oxidase (EC 1.10.3.1, o-diphenol: oxygen oxidoreductase, PPO) of banana (Musa sapientum L.) peel was partially purified about 460-fold with a recovery of 2.2% using dopamine as substrate. The enzyme showed a single peak on Toyopearl HW55-S chromatography. However, two bands were detected by staining with Coomassie brilliant blue on PAGE: one was very clear, and the other was faint. Molecular weight for purified PPO was estimated to be about 41 000 by gel filtration. The enzyme quickly oxidized dopamine, and its Km value (Michaelis constant) for dopamine was 3.9 mM. Optimum pH was 6.5 and the PPO activity was quite stable in the range of pH 5-11 for 48 h. The enzyme had an optimum temperature at 30 degrees C and was stable up to 60 degrees C after heat treatment for 30 min. The enzyme activity was strongly inhibited by sodium diethyldithiocarbamate, potassium cyanide, L-ascorbic acid, and cysteine at 1 mM. Under a low buffer capacity, the enzyme was also strongly inhibited by citric acid and acetic acid at 10 mM.     

影响根癌农杆菌介导的香蕉遗传转化因素研究

以香蕉（Musa spp.)的横切薄层切片（transverse thin cell layer,tTCL)外植体作为转化受体，通过对外植体GUS基因瞬时表达率的研究以及受体材料对抗生素的敏感性实验，找出了较适合的外植体转化条件和培养条件。研究表明：用低代香蕉无菌苗为材料，横切薄层切片芽再生率高，有较高的GUS基因瞬时表达率；香蕉对头孢霉素（Cefotaxime)和羧苄霉素（Carbenicillin)不敏感，而对潮霉素（Hygromycin)很敏感；菌液的预处理是影响香蕉转化的主要因子，重悬液中的蔗糖浓度也是影响转化的因素之一，对遗传转化有明显的促进作用。     

Inhibition of acetate ester biosynthesis in banana (Musa sapientum L.) fruit pulp under anaerobic conditions

The effect of anaerobic conditions on acetate ester biosynthesis in ripened banana pulp was investigated. Incubation of the pulp in less than 1% O(2) resulted in a significant reduction in the formation of ethyl acetate. Regardless of the presence of a large amount of endogenous ethanol and the remaining exogenous isobutyl alcohol after complete anaerobic incubation with the pulp, the production of acetate ester decreased. The effect of addition of pyruvate, isobutyl alcohol, acetate, and methyl hexanoate on acetate ester formation in 100% N(2) was also investigated. The addition of pyruvate and isobutyl alcohol to the pulp gave lower acetate esters in N(2) than in air, whereas the pulp incubated with acetate and isobutyl alcohol produced more acetate ester in both conditions. Therefore, the lack of acetyl CoA, or more precisely acetate, in the tissue is the main reason for the inhibition of acetate ester formation under anaerobic conditions. The activity of beta-oxidation measured by incubation with methyl hexanoate was detected only in the samples incubated in air. The formation of acetyl CoA, derived from pyruvate through mitochondria and through beta-oxidation, was inhibited by anaerobic conditions, which suggests that mitochondrial activity and/or beta-oxidation are essential for ester biosynthesis.     

Maillard reaction and enzymatic browning affect the allergenicity of Pru av 1, the major allergen from cherry (Prunus avium)

The influence of thermal processing and nonenymatic as well as polyphenoloxidase-catalyzed browning reaction on the allergenicity of the major cherry allergen Pru av 1 was investigated. After thermal treatment of the recombinant protein rPru av 1 in the absence or presence of carbohydrates, SDS-PAGE, enzyme allergosorbent tests, and inhibition assays revealed that thermal treatment of rPru av 1 alone did not show any influence on the IgE-binding activity of the protein at least for 30 min, thus correlating well with the refolding of the allergen in buffer solution as demonstrated by CD spectroscopic experiments. Incubation of the protein with starch and maltose also showed no effect on IgE-binding activity, whereas reaction with glucose and ribose and, even more pronounced, with the carbohydrate breakdown products glyceraldehyde and glyoxal induced a strong decrease of the IgE-binding capacity of rPru av 1. In the second part of the study, the effect of polyphenoloxidase-catalyzed oxidation of polyphenols on food allergen activity was investigated. Incubation of rPru av 1 with epicatechin in the presence of tyrosinase led to a drastic decrease in IgE-binding activity of the protein. Variations of the phenolic compound revealed caffeic acid and epicatechin as the most active inhibitors of the IgE-binding activity of rPru av 1, followed by catechin and gallic acid, and, finally, by quercetin and rutin, showing significantly lower activity. On the basis of these data, reactive intermediates formed during thermal carbohydrate degradation as well as during enzymatic polyphenol oxidation are suggested as the active chemical species responsible for modifying nucleophilic amino acid side chains of proteins, thus inducing an irreversible change in the tertiary structure of the protein and resulting in a loss of conformational epitopes of the allergen.     

离子交换和吸附相结合抑制浓缩酥梨汁褐变的研究

该文研究离子交换和吸附相结合技术在降低、控制浓缩砀山酥梨汁褐变中的应用。将20 °Brix砀山酥梨汁依次经FPC-21阳离子交换树脂和XAD-16大孔吸附树脂处理后,减压浓缩至70 °Brix,贮存,检测褐变指数等指标的变化。结果显示,阳离子树脂处理可降低酥梨汁的pH值、氨基态氮和褐变指数;降低pH值可提高吸附树脂对酥梨汁的脱色能力;降低pH值、氨基态氮可控制70 °Brix浓缩酥梨汁贮存中褐变速度。采用阳离子树脂处理将酥梨汁的pH值降低为4.05,再经吸附树脂将色值提高为85%,浓缩至70 °Brix的酥梨汁在37℃下贮存35 d后,色值仍大于45%,符合出口要求。     

Characterization of sinapyl derivatives in pineapple (Ananas comosus [L.] Merill) juice.

Three previously unidentified phenolic compounds were found in pineapple (Ananas comosus [L.] Merill) juice in substantial concentrations and were isolated by semipreparative reverse phase HPLC. The structures were elucidated from UV spectra, acid hydrolysis, and subsequent amino acid analysis, mass spectrometry, and two-dimensional NMR spectroscopy. The compounds are identified as S-sinapyl-L-cysteine, N-L-gamma-glutamyl-S-sinapyl-L-cysteine, and S-sinapylglutathione.     

Honeys from different floral sources as inhibitors of enzymatic browning in fruit and vegetable homogenates

Honeys from different floral sources were evaluated for their antioxidant content and for their ability to inhibit enzymatic browning in fruits and vegetables. Antioxidant contents of honeys vary widely from different floral sources, as do their abilities to protect against enzymatic browning. Polyphenol oxidase (PPO) activity was reduced over a range of approximately 2-45% in fruit and vegetable homogenates, corresponding to a reduction in browning index by 2.5-12 units. Soy honey was particularly effective when compared to clover honey, which had a similar antioxidant content. When compared to commercial inhibitors of browning, honeys were less effective; however, in combination they added to the effectiveness of metabisulfite and ascorbic acid. Honey has great potential to be used as a natural source of antioxidants to reduce the negative effects of PPO browning in fruit and vegetable processing.     

Aromatic profile of aqueous banana essence and banana fruit by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O)

Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to determine the aromatic composition and aroma active components of commercial banana essence and fresh banana fruit paste. Totals of 43 and 26 compounds were quantified in commercial banana essence and fresh banana fruit paste, respectively. Five new components in commercial banana essence were identified as methyl butyrate, 2,3-butanediol diacetate, 2-hydroxy-3-methylethylbutyrate, 1-methylbutyl isobutyrate, and ethyl 3-hydroxyhexanoate. A total of 42 components appear to contribute to the aromatic profile in banana. Isoamyl acetate, 2-pentanol acetate, 2-methyl-1-propanol, 3-methyl-1-butanol, 3-methylbutanal, acetal, isobutyl acetate, hexanal, ethyl butyrate, 2-heptanol, and butyl butyrate had high concentrations and were most detected by GC-O panelists in the commercial banana essence. Volatile components found only in fresh banana fruit paste that were detected by aroma panelists include E-2-hexenal, limonene, and eugenol.     

Control of enzymatic browning in potato (Solanum tuberosum L.) by sense and antisense RNA from tomato polyphenol oxidase

Polyphenol oxidase (PPO) activity of Russet Burbank potato was inhibited by sense and antisense PPO RNAs expressed from a tomato PPO cDNA under the control of the 35S promoter from the cauliflower mosaic virus. Transgenic Russet Burbank potato plants from 37 different lines were grown in the field. PPO activity and the level of enzymatic browning were measured in the tubers harvested from the field. Of the tubers from 28 transgenic lines that were sampled, tubers from 5 lines exhibited reduced browning. The level of PPO activity correlated with the reduction in enzymatic browning in these lines. These results indicate that expression of tomato PPO RNA in sense or antisense orientation inhibits PPO activity and enzymatic browning in the major commercial potato cultivar. Expression of tomato PPO RNA in sense orientation led to the greatest decrease in PPO activity and enzymatic browning, possibly due to cosuppression. These results suggest that expression of closely related heterologous genes can be used to prevent enzymatic browning in a wide variety of food crops without the application of various food additives.     

The role of “effective microorganisms” in the composting of banana (Musa ssp.) residues

“Effective microorganisms” (EM) are a poorly defined mixture of supposedly beneficial microorganisms that are claimed to enhance microbial turnover in compost and soil. In Costa Rica, EM are used to produce organic compost (bokashi) from banana residues (Musa ssp.). Given the scarcity of scientific data about the effects of EM on the mineralization of plant residues, this study aimed at investigating the effects of EM addition on the decomposition of banana residues during Bokashi production. To this end, the following non‐EM treatments were compared to EM Bokashi: Bokashi produced with water (W), with molasses (M) as an EM additive, and with sterilized EM (EMst). Subsequently, the effects of the resulting Bokashi treatments on the growth of young banana plants were evaluated. Compared with non‐EM controls, the effect of EM on the mineralization of banana material was negligible. Dry‐matter losses of the composts with different EM treatments were similar, with about 78% over 5 weeks. Ergosterol concentration was highest in EM Bokashi (77 µg (g dry soil)^–1) and lowest in EMst Bokashi (29 µg (g dry soil)^–1). Microbial biomass carbon (C_mic) and microbial biomass nitrogen (N_mic) were both lowest in EM (C_mic = 3121 µg g^–1; N_mic = 449 µg g^–1), while C_mic was highest in Bokashi produced with molasses (3892 µg g^–1) and N_mic was highest in EMst (615 µg g^–1). Treatment effects on adenylate concentrations and adenylate energy charge were negligible. Application of all Bokashi variants to young banana plants significantly increased shoot growth under greenhouse conditions compared to plants grown in a control soil without amendments. However, these effects were similar for all Bokashi treatments, even if EM Bokashi increased the K concentrations in banana leaves significantly compared to Bokashi produced with EMst and the control. Bokashi produced with only molasses and EM Bokashi decreased the number of root nematodes under greenhouse conditions compared to the control. Overall, the results confirmed the expected influence of composting on the degradation of organic material and the effect of compost application on plant growth. Hower, under the conditions of this study, EM showed no special effects in this, except for increasing the K concentrations in the leaves of young banana plants.     

Detection of nifH Sequences in Sugarcane (Saccharum officinarum L.) and Pineapple (Ananas comosus [L.] Merr.)

To detect N₂-fixing bacteria in a plant without using culture methods, nifH gene segments were amplified with degenerate primers from DNA extracted from stems of sugarcane ( Saccharum officinarum L.) and leaves of pineapple ( Ananas comosus [L.] Merr.). Sequences of the nifH clones were homologous to those of bacteria in the genera Bradyrhizobium, Serratia , and Klebsiella. The bacteria with nifH sequences homologous to those of the three genera may be promising candidates for predominant endophytic diazotrophs in sugarcane and pineapple, because these sequences were commonly detected in samples from different host plants, which were collected at different locations. On the other hand, no nifH sequence related to Gluconacetobacter diazotrophicus , which is an endophytic N₂-fixing bacterium and had been previously isolated from sugarcane, was detected in sugarcane. This indicates the absence or the presence of few G. diazotrophicus in the stems of the sugarcane plants used in the current study.