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Effect of steam explosion on nutritional composition and antioxidative activities of okra seed and its application in gluten-free cookies.

ABSTRACT: Health-conscious consumers are increasingly interested in gluten-free (GF) foods. Raw okra seed (ROS) flour and steam-exploded okra seed (SEOS) flour were explored for developing GF cookies with high nutritional values and in vitro enzymatic digestion. Results indicated that the steam explosion exhibited significant effects on enhancing the release of dietary fibers and lipids in okra seed flour at moderate explosion pressure. Although steam explosion caused the loss of flavonoid compounds, moderate high explosion pressure enhanced the release of total phenolics ranged from 294.57 to 619.07 mg GAE/100 g DM with significantly improved DPPH• radical scavenging activity (from 18.78% to 67.34%) and ferric reducing antioxidant power (from 13.37% to 149.04%). The rapidly digestible starch (RDS) content in GF cookies decreased with increasing steam explosion severity, whereas slowly digestible starch (SDS) and resistant starch (RS) contents significantly increased from 36.91% to 40.92% and from 2.50% to 9.06%, respectively. Steam explosion is an effective technique for enhancing the release of nutrients like dietary fiber and total phenolics, and okra seed flour, especially SEOS flour, can be alternative choices to provide food functional materials for developing various GF food products.

SUBMITTER: Hu L

PROVIDER: S-EPMC7455944 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Effect of steam explosion on nutritional composition and antioxidative activities of okra seed and its application in gluten-free cookies.

Hu Lei L Guo Jiamin J Zhu Xiwei X Liu Rui R Wu Tao T Sui Wenjie W Zhang Min M

Food science & nutrition 20200630 8

Health-conscious consumers are increasingly interested in gluten-free (GF) foods. Raw okra seed (ROS) flour and steam-exploded okra seed (SEOS) flour were explored for developing GF cookies with high nutritional values and in vitro enzymatic digestion. Results indicated that the steam explosion exhibited significant effects on enhancing the release of dietary fibers and lipids in okra seed flour at moderate explosion pressure. Although steam explosion caused the loss of flavonoid compounds, mode ...[more]

PMID: 32884721

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Project description:BackgroundAcetylated galactoglucomannan (AcGGM) is a complex hemicellulose found in softwoods such as Norway spruce (Picea abies). AcGGM has a large potential as a biorefinery feedstock and source of oligosaccharides for high-value industrial applications. Steam explosion is an effective method for extraction of carbohydrates from plant biomass. Increasing the reaction pH reduces the combined severity ( R 0 ' ) of treatment, affecting yields and properties of extracted oligosaccharides. In this study, steam explosion was used to extract oligosaccharides from Norway spruce wood chips soaked with sodium citrate and potassium phosphate buffers with pH of 4.0-7.0. Yields, monosaccharide composition of released oligosaccharides and biomass residue, their acetate content and composition of their lignin fraction were examined to determine the impact of steam explosion buffering on the extraction of softwood hemicellulose.ResultsReducing the severity of steam explosion resulted in lower yields, although the extracted oligosaccharides had a higher degree of polymerization. Higher buffering pH also resulted in a higher fraction of xylan in the extracted oligos. Oligosaccharides extracted in buffers of pH?>?5.0 were deacetylated. Buffering leads to a removal of acetylations from both the extracted oligosaccharides and the hemicellulose in the residual biomass. Treatment of the residual biomass with a GH5 family mannanase from Aspergillus nidulans was not able to improve the AcGGM yields. No hydroxymethylfurfural formation, a decomposition product from hexoses, was observed in samples soaked with buffers at pH higher than 4.0.ConclusionsBuffering the steam explosion reactions proved to be an effective way to reduce the combined severity ( R 0 ' ) and produce a wide range of products from the same feedstock at the same physical conditions. The results highlight the impact of chemical autohydrolysis of hemicellulose by acetic acid released from the biomass in hydrothermal pretreatments. Lower combined severity results in products with a lower degree of acetylation of both the extracted oligosaccharides and residual biomass. Decrease in severity appears not to be the result of reduced acetate release, but rather a result of inhibited autohydrolysis by the released acetate. Based on the results presented, the optimal soaking pH for fine-tuning properties of extracted AcGGM is below 5.0.

Project description:Background Lignocellulosic biomass is considered as a potential source for sustainable biofuels. In the conversion process, a pretreatment step is necessary in order to overcome the biomass recalcitrance and allow for sufficient fermentable sugar yields in enzymatic hydrolysis. Steam explosion is a well known pretreatment method working without additional chemicals and allowing for efficient particle size reduction. However, it is not effective for the pretreatment of softwood and the harsh conditions necessary to achieve a highly digestible cellulose fraction lead to the partial degradation of the hemicellulosic sugars. Previous studies showed that the autohydrolysis pretreatreatment of softwood can benefit from the addition of 2-naphthol. This carbocation scavenger prevents lignin repolymerisation leading to an enhanced glucose yield in the subsequent enzymatic hydrolysis.Results In order to prevent the degradation of the hemicellulose, we investigated in this study a two-stage 2-naphthol steam explosion pretreatment. In the first stage, spruce wood is pretreated at a severity which is optimal for the autocatalytic hydrolysis of the hemicellulose. The hydrolyzate containing the solubilized sugars is withdrawn from the reactor and the remaining solids are pretreated with different amounts of 2-naphthol in a second stage at a severity that allows for high glucose yields in enzymatic hydrolysis. The pretreated spruce was subjected to enzymatic hydrolysis and to simultaneous saccharification and fermentation (SSF). In the first stage, the maximal yield of hemicellulosic sugars was 47.5% at a pretreatment severity of log R0 = 3.75 at 180 °C. In the second stage, a 2-naphthol dosage of 0.205 mol/mol lignin C9-unit increased the ethanol yield in SSF with a cellulose loading of 1% using the whole second stage pretreatment slurry by 17% from 73.6% for the control without 2-naphthol to 90.4%. At a higher solid loading corresponding to 5% w/w cellulose, the yields decreased due to higher concentrations of residual 2-naphthol in the biomass and the pretreatment liquor, but also due to higher concentrations of potential inhibitors like HMF, furfural and acetic acid. Experiments with washed solids, vacuum filtered solids and the whole slurry showed that residual 2-naphthol can inhibit the fermentation as a single inhibitor but also synergistically together with HMF, furfural and acetic acid.Conclusions This work shows that a two-stage pretreatment greatly enhances the recovery of hemicellulosic sugars from spruce wood. The presence of 2-naphthol in the second pretreatment stage can enhance the ethanol yield in SSF of steam explosion pretreated softwood at low cellulose concentrations of 1% w/w. However, with higher solid loadings of 5% w/w cellulose, the ethanol yields were in general lower due to the solid effect and a synergistic inhibition of HMF, furfural, acetic acid with residual 2-naphthol. The concentration of residual 2-naphthol tolerated by the yeast decreased with increasing concentrations of HMF, furfural, and acetic acid.

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Effect of steam explosion on nutritional composition and antioxidative activities of okra seed and its application in gluten-free cookies.

Publications

Effect of steam explosion on nutritional composition and antioxidative activities of okra seed and its application in gluten-free cookies.

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