Sweet Potato Residue Research Articles

Structure, physicochemical properties and effects on nutrients digestion of modified soluble dietary fiber extracted from sweet potato residue

Alkaline hydrogen peroxide (AHP) modification increased the yield and the content of soluble dietary fiber extracted from sweet potato residue. As compared to the original sweet potato dietary fiber (O-SPDF), AHP modified SPDF (A-SPDF) had a smaller molecular weight of 69073.59 Da and a lower zeta-potential of −27 mV. Monosaccharide composition analysis revealed that A-SPDF had a higher proportion of pectin polysaccharides with homogalacturonan (HG) and rhamnogalacturonan-Ⅰ (RG-Ⅰ) backbones. Fourier transformed infrared (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were employed to determine the structural differences between A-SPDF and O-SPDF. Characterization of their rheological properties showed that A-SPDF exhibited higher viscosity than O-SPDF at concentrations of 2%, 4% and 6%, respectively. Additionally, A-SPDF had a more gel-like behavior than O-SPDF in the presence of Ca2+, supporting the better functional properties of A-SPDF as determined by water holding capacities (WHC), oil holding capacities (OHC), and water swelling capacities (WSC). Furthermore, A-SPDF performed significantly better in inhibiting starch hydrolysis and reducing the glucose diffusion rate using an Infogest simulated digestion model. However, SPDFs had no impact on the digestion rate of protein. Our results suggested that A-SPDF has the potential to serve as a novel food additive and functional hydrocolloid to attenuate nutrients digestion related disorders, which forms the scientific basis for the better utilization of sweet potato residue and further develop sweet potato dietary fiber (SPDF) as a functional food and/or additive in the food industry.

Orange fleshed sweet potato technology toolkit catalog. TAAT Clearinghouse technical report series 005

Orange fleshed sweet potato technology toolkit catalog. TAAT Clearinghouse technical report series 005

Integrated Efforts for the Valorization of Sweet Potato By-Products within a Circular Economy Concept: Biocomposites for Packaging Applications Close the Loop

With the aim to fully exploit the by-products obtained after the industrial extraction of starch from sweet potatoes, a cascading approach was developed to extract high-value molecules, such as proteins and pectins, and to valorize the solid fraction, rich in starch and fibrous components. This fraction was used to prepare new biocomposites designed for food packaging applications. The sweet potato residue was added to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in various amounts up to 40 wt % by melt mixing, without any previous treatment. The composites are semicrystalline materials, characterized by thermal stability up to 260 °C. For the composites containing up to 10 wt % of residue, the tensile strength remains over 30 MPa and the strain stays over 3.2%. A homogeneous dispersion of the sweet potato waste into the bio-polymeric matrix was achieved but, despite the presence of hydrogen bond interactions between the components, a poor interfacial adhesion was detected. Considering the significant percentage of sweet potato waste used, the biocomposites obtained show a low economic and environmental impact, resulting in an interesting bio-alternative to the materials commonly used in the packaging industry. Thus, according to the principles of a circular economy, the preparation of the biocomposites closes the loop of the complete valorization of sweet potato products and by-products.

Dose-dependent Effect of Biochar as Soil Amendment on Reducing Copper Phytotoxicity and Mobility

Using biochar to remediate metal-contaminated agricultural soil has attracted increasing attention due to it is relatively low cost and high efficiency. In this study chemical speciation, greenhouse experiments, and column leaching study were conducted to understand the mechanisms of copper (Cu) immobilization by pine needle biochar (PNB) and sweet potato residue biochar (SPRB) to evaluate the effect of biochar amendment rate for remediation Cu contaminated soils. The results showed that both PNB and SPRB amendment effectively raised soil pH and converted Cu into more stable chemical forms. 1% (W/W) SPRB was adequate for reducing exchangeable Cu fractions from 43.3 to 9.9 mg kg−1 in the contaminated soils. 1% (W/W) SPRB and 5% (W/W) PNB treatments show the best result to promote sweet potato growth. Over liming caused by 5% (W/W) SPRB resulted in inhibition of plant growth. 5% (W/W) PNB treatment also shows the best result for reducing Cu mobility: the cumulative amount of Cu in the leachate after 9 leaching events was reduced from 7.0 to 1.0 mg kg−1. However, 5% (W/W) SPRB amendment is a little effective for reducing Cu mobility. Although the biochar amendment can provide additional sorption sites for metal pollution remediation, soil pH after an amendment is also a critical factor to estimate optimal biochar application dosage for promoting plant growth and reduce metal leachability.

Effect of high hydrostatic pressure-assisted pectinase modification on the Pb2+ adsorption capacity of pectin isolated from sweet potato residue

Novel pectin derived from sweet potato residue was modified by high hydrostatic pressure (HHP)-assisted pectinase and then used for Pb2+ removal from aqueous solutions. The removal characteristics and mechanisms were also investigated. Results showed that modified sweet potato pectin exhibited greater adsorption performances for Pb2+ than that of natural ones, and showed excellent eco-friendly properties and good potential for adsorption of some other heavy metals (such as Cu2+). The adsorption curves were much more conformed to Langmuir model, and the highest capacity for Pb2+ adsorption was 263.15 mg/g with 1.00% pectin at pH 7. Chemical adsorption process of pectin for Pb2+ absorption involved O-containing functional groups (O–H, COO-), cation exchange, and along with electrostatic interactions. Overall, the results in this study indicated that sweet potato pectin modified with HHP-assisted pectinase had the potential to become an environmentally friendly coagulant-flocculant agent for the heavy metal adsorption, especially for Pb2+.

Structural, physicochemical and emulsifying properties of sweet potato pectin treated by high hydrostatic pressure and/or pectinase: a comparative study.

Sweet potato (Ipomoea batatas L.) is the sixth most important food crop in the world, and China is the largest producer. Large amounts of sweet potato residues are generated during starch extraction, leading to environmental pollution and resource waste. However, these residues can be used as a viable source for pectin extraction. As a natural biopolymer with high molecular weight and complex structure, the usefulness of pectin has been limited, and it needs to be modified in order to improve its physicochemical properties, thus expanding its applications in the food industry. Therefore, the reported study was conducted to modify sweet potato pectin (SPP) using high hydrostatic pressure (HHP) and/or pectinase treatment, and to determine the effects of such treatment on structural, physicochemical and emulsifying properties. The results demonstrated that the molecular weight of SPP decreased following HHP and pectinase treatment, which was evidenced using scanning electron microscopy and atomic force microscopy. The degree of esterification was also decreased, confirmed by decreased intensity of the peak at 1739 cm-1 in the Fourier transform infrared spectrum and decreased peaks at 3.6 and 3.8 ppm in the 1 H NMR spectrum. Moreover, the content of monosaccharides and uronic acids increased and emulsifying properties improved after HHP and pectinase treatment. HHP-assisted pectinase treatment could be used as novel technique for the modification of pectin to give better emulsifying properties with great potential for application in the food industry. © 2020 Society of Chemical Industry.

Modification of sweet potato (Ipomoea batatas Lam.) residues soluble dietary fiber following twin-screw extrusion

Effect of twin-screw extrusion on soluble dietary fiber (SDF) from sweet potato residues (SPRs) were investigated using optimized conditions, at screw speed of 180 rpm, feed rate at 17 Hz, feed moisture at 40% and extrusion temperature at 150 °C. Extruded SDF, showed higher SDF levels (9.63%–29.25%), cholesterol and sodiumcholate adsorption capacity, radical scavenging capacity, and inhibition of digestive enzymes. Moreover, extrusion effectively reduced particle size and molecularweight of SDF, modulated monosaccharide ratios, and increased water retention capacity (WRC), oil retention capacity (ORC), swelling capacity (SC) and glucose absorption capacity (GAC). Additionally, scanning electron microscopy (SEM) demonstrated decomposition of macromolecules of SDF to smaller fractions and formation of a porous morphology following extrusion. Furthermore, the extruded SDF increased thermal stability as determined by differential scanning calorimetry (DSC). Overall, the SDF from SPRs with improved functional and physiochemical properties could be used as a functional additive in diverse food products.

Characterization of Pickering emulsions stabilized by OSA-modified sweet potato residue cellulose: Effect of degree of substitute and concentration

The aims of the present study were to modify the native sweet potato residue cellulose (NSPRC) with octenyl succinic anhydride (OSA) using DMAc/LiCl reaction system and to evaluate the formation and stability of Pickering emulsion stabilized by this modified cellulose with different degree of substitute (DS) and concentration. The results showed that the molecular structure, crystal character, contact angle and surface texture of OSA-modified sweet potato residue cellulose (OSA-SPRC) were remarkably changed compared to NSPRC. In conclusion, the hydroxyl of the NSPRC was successfully replaced by the carboxyl group of OSA. Moreover, the emulsifying ability and stability of OSA-SPRC were both higher than that of Tween 80 at the same concentration and storage time. Compared with low DS (0.0017 ± 0.0003) OSA-SPRC, the emulsions stabilized by high DS (0.0063 ± 0.0005) OSA-SPRC displayed better creaming index, lower particle size, uniform droplets distribution, higher apparent viscosity, and emulsion stability after storing for 15 d. Similar findings were obtained with the concentration of OSA-SPRC from 0.25% to 1.75%. The improvement in the emulsion properties was likely due to the formation of oil-OSA-SPRC particles network and the saturated adsorption of OSA-SPRC particles at the O/W interface, thereby limiting the aggregation of oil droplets. Overall, the Pickering emulsions stabilized by OSA-SPRC exhibited benign stability against coalescence. The emulsions were found to be responsive to the DS and concentration of OSA-SPRC. This research revealed the formation mechanism of the Pickering emulsion stabilized by OSA-SPRC and its main affecting factors.

Optimization of Pectin Extraction from Sweet Potato Peels Using Citric Acid and its Emulsifying Properties.

Pectin is a natural polysaccharide that has been used widely as a stabilizer in food emulsion system. This study aimed to optimize the yield of pectin extracted from sweet potato residue and investigate its emulsifying properties. Response surface methodology (RSM) has been utilized to investigate the pectin extracted from sweet potato peels using citric acid as the extracting solvent. Investigation of the effect of different extraction conditions namely temperature (°C), time (min) and solution pH on pectin yield (%) were conducted. A Box-Benhken design with three levels of variation was used to optimize the extraction conditions. The optimal conditions determined were temperature 76°C, time 64 min and pH 1.2 with 65.2% yield of pectin. The degree of esterification (DE) of the sweet potato pectin was determined using Fourier Transform Infrared (FTIR) Spectroscopy. The pectin is high-methoxyl pectin with DE of 58.5%. Emulsifying properties of sweet potato pectin were investigated by measuring the zeta-potential, particle size and creaming index with addition of 0.4 and 1.0 wt % pectin to the emulsion. Extraction using citric acid could improve the pectin yield. Improved emulsion stability was observed with the addition of the sweet potato pectin.

Optimization of sweet potato pectin extraction using hydrochloric acid

Pectin has been used widely as thickener, stabilizer and gelling agent. However, the sources of pectin industrially are still limited. This study aims to optimize the extraction of pectin from sweet potato residue using hydrochloric acid. In this study, proximate analysis of the sweet potato residues were performed and the extraction of pectin from sweet potato residues using hydrochloric acid was optimized to maximize its yield using response surface methodology (RSM). Three parameters were manipulated and optimized which were temperature (°C), pH and extraction time (min). The extracted pectin was further analyzed for its degree of esterification (DE) using Fourier Transform Infrared Spectroscopy (FTIR). The sweet potato residue sample obtained moisture content of 79.7±1.7%, ash content of 1.08±0.09% and carbohydrate content of 34.3±2.7%. The optimum condition to extract pectin from sweet potato residues using hydrochloric acid was at extraction temperature 60 °C, pH 1 and extraction time 60 min with 23.48 % pectin yield. The pectin has 57.48% of DE which indicates high methoxyl pectin. The results show that hydrochloric acid can be used as one of the solvents to extract pectin from sweet potato.

Yeast population dynamics on air exposure in total mixed ration silage with sweet potato residue.

To investigate the yeast population dynamics during air exposure in total mixed ration (TMR) silage containing sweet potato residue. TMR were ensiled in laboratory silos (1kg) with or without two lactic acid bacteria strains, Lactobacillus plantarum (LP), and Lactobacillus amylovorus (LA). Fermentation characteristics were measured and yeast population was investigated by ITS1 region gene sequencing using Illumina MiSeq platform. All treatments were well ensiled, and L. amylovorus improved aerobic stability. During aerobic exposure, Pichia kudriavzevii was detected with increased relative abundance in all treatments and more relative abundant in LP. Pichia fermentans was more relative abundant in control. Higher relative abundance of Pichia anomala was detected in deteriorating LP. The relative abundance of Pichia ohmeri increased during later aerobic exposure in the control and LA, with a significant increase in the count of yeast population. Despite Cryptococcus was detected more relative abundant during early stage of aerobic exposure, the yeast population was below the detection limit. Aerobic deterioration was characterized by an increase in operational taxonomic units of Pichia. High relative abundance of P. anomala and P. kudriavzevii made aerobic deterioration easier. Inhibition of P. fermentans might be an effective strategy for improving the aerobic stability to some instance.

Dietary fiber isolated from sweet potato residues promotes a healthy gut microbiome profile.

This study investigated the impact of dietary fiber from sweet potato residue (SPDF) on the diversity of the gut microbiota. An in vitro batch culture system simulating the human gut was used to understand the prebiotic role of SPDF. The results showed that SPDF mediated a significant increase in the concentrations of Bifidobacterium and Lactobacillus, whereas induced a significant decrease of Enterobacillus, Clostridium perfringens and Bacteroides. The prebiotic index and Bifidobacterium/Enterobacillus value were also significantly increased in SPDF groups compared to those of the control group, suggesting that SPDF had prebiotic effects. Furthermore, to investigate the effects of SPDF on the intestinal microecosystem, diets containing different concentrations of SPDF were used to feed Wistar rats for 4 weeks. 16S rRNA gene sequencing, short chain fatty acid quantification and physiochemical property analysis in the rat feces were then conducted. The results showed that SPDF significantly increased the Bacteroidetes to Firmicutes ratio at the phylum level and the amount of Akkermansia was also increased at the genus level, which was confirmed by qRT-PCR. The production of propionate and butyrate in the rat feces of both 3% and 15% SPDF groups was higher than that in the control group, which was further confirmed by the decrease of pH. Additionally, SPDF supplementation in this study resulted in a higher villus height to fossa depth ratio, which indicated improved digestion and absorption in the GI tract. Our findings support the utilization of SPDF from sweet potato residue in the development of potentially prebiotic food products for improving intestinal health.

Effects of steam explosion pretreatment and Lactobacillus buchneri inoculation on fungal community of unensiled and ensiled total mixed ration containing wheat straw during air exposure.

To compare the effects of steam explosion and Lactobacillus buchneri inoculation on fungal community in ensiled total mixed ration (TMR) during aerobic exposure. The TMRs were prepared using wheat straw with or without steam explosion, sweet potato residue, lucerne hay, maize meal and soybean meal, and ensiled with or without L. buchneri inoculation. Fungal communities were detected by high-throughput sequencing. All ensiled TMRs were well ensiled and steam explosion has a major effect on improving aerobic stability. The fungal species, such as Xeromyces bisporus and Cryptococcus victoriae, that dominated in the TMR decreased after ensiling, with a concomitant increase in Candida humilis, Pichia kudriavzevii, Aspergillus flavus and Phanerochaete chrysosporium. Most mould species decreased, with C. humilis and P. kudriavzevii dominating during aerobic exposure. Steam explosion could improve the aerobic stability in ensiled TMR by inhibition of C. humilis. High-throughput sequencing used in this study provides insight into the fungal community in ensiled TMR during aerobic exposure, which could contribute towards elucidating the mechanism by which aerobic deterioration develops.

Synergism of cellulase, pectinase and xylanase on hydrolyzing differently pretreated sweet potato residues

The synergism of cellulase (C), pectinase (P), and xylanase (X) for the saccharification of sweet potato residues (SPR) was investigated. The removal of starch from SPR was easily achieved by using amylase, but the cellulose conversion of de-starched SPR was relatively low, thus dilute H2SO4, NaOH, and H2O2 pretreatment was conducted to improve the enzymatic digestibility. The lignin content of NaOH pretreated SPR was the lowest, whereas H2SO4 pretreatment resulted in the lowest contents of hemicellulose and pectin. The combination of C, P, and X exhibited different sugar production patterns, C–P displayed synergistic action on glucose and galactose production from each type of SPR, C–X also exhibited synergistic effect on glucose production except when H2SO4 pretreated SPR was used, whereas no synergism between P–X on monosaccharide production was observed. The presence of synergism between cellulase and mixed accessory enzymes [C–(PX)] on glucose formation was determined by C–X, and the degree of synergism between C–P and C–(PX) on glucose production had a positive relationship with pectin content. The highest cellulose conversion of 96.2% was obtained from NaOH pretreated SPR using mixed enzymes comprising C, P, and X with the ratio of 8:1:1.

Preferential Alternatives to Returning All Crop Residues as Biochar to the Crop Field? A Three-Source 13C and 14C Partitioning Study.

The simultaneous effects of biochar on soil organic matter (SOM, C4) and sweet potato (SP) residue (Ipomoea batatas, C3) mineralization were studied over 180 days via 13C and 14C isotopic label partitioning. Upon concomitant SP residue addition, biochar mineralization decreased by 11% of the total added biochar-C. Compared to positive priming effects induced by biochar amendment alone on SOM (0.46 mg C g-1 soil) at 180 days, amendment solely with SP residues induced significantly larger effects (1.5 mg C g-1 soil). Combination biochar and SP residue addition reduced SOM mineralization by 20.5% and increased SP residue mineralization by 10.1%. Biochar addition caused preferential uptake of SP residues over SOM by microbes. Thus, the lower priming effects on SOM and CO2 emission induced by biochar amendment with or without SP residues compared to that from SP residue addition alone may result in crop residues being partly pyrolyzed to biochar in the cropland.

Optimization of DHEA Extraction from Sweet Potato Pomace by Ultrasonic-Microwave Synergistic Employing Response Surface Methodology.

Background: A lot of sweet potato residues (SPR) were discarded and wasted. Objective: To make full use of the SPR. Methods: Ultrasonic microwave synergistic (UMS) extraction method was used to extract dehydroepiandrosterone (DHEA) in SPR. The extraction conditions were optimized by response surface methodology based on single factors. Results: The optimum extraction conditions were 1:25 (solid-liquid ratio), 300 W (microwave power), 30 min (extraction time), and 30°C (extraction temperature). The extraction yield of DHEA from SPR reached 117.25 μg/100 g. Conclusions: The advantage of UMS extraction technology is to make full use of the synergistic effect of ultrasound and microwave to improve extraction efficiency. Highlights: The technology provides an effective way to improve the DHEA extraction yield from the SPR in industrial production.

Co-liquefaction of low-lipid microalgae and starch-rich biomass waste: The interaction effect on product distribution and composition

The co-hydrothermal liquefaction (HTL) of low-lipid microalgae (MA) mixed with starch-rich biomass waste (sweet potato residue, SPR) was performed. To explore the interaction effect at different mass ratios of MA/SPR, the distribution and composition of HTL products were analyzed. Results showed that although the addition of SPR did not obviously promote the formation of bio-crude by Maillard reaction between starch and protein, the generation of bio-char was boosted. On the other hand, the experimental higher heating values of both bio-crude and bio-char derived from co-liquefaction were greater than the theoretical calculated values. Meanwhile, the N content of bio-crude exhibited a declining tendency with higher dosage of SPR. For MA/SPR ratio of 3/1, the experimental energy recovery (70.8%) was greater than the theoretical calculated value (66.96%), suggesting the synergistic effect on reaction efficiency. Furthermore, GC/MS analysis of bio-crude showed a lower relative percentage of alkylamides but higher hydrocarbons with MA/SPR ratios ranging from 5/1 to 3/1, indicating the positive interaction effect between MA and SPR.

Antimicrobial Activity of Dehydroepiandrosterone in Sweet Potato Residue

To study the antibacterial activity of Dehydroepiandrosterone(DHEA)in sweet potato residue,the antibacterial activity of DHEA was tested with Kluyveromyces marxianus,Saccharomyces cerevisiae,L. rhamnosus,E.coli,Bacillus subtilis,Bacillus anthraci,Salmonella,Staphylococcus aureus. Bacillus subtilis,Salmonella,Staphylococcus aureus and Bifidobacterium as the indicator bacteria. The antimicrobial activity of dehydroepiandrosterone was studied by turbidimetry,minimal inhibitory concentration(MIC),minimum bactericidal concentration(MBC),growth curve and scanning electron microscopy. The results showed that the bacteriostatic effect of DHEA on the tested bacteria was as follows:Kluyveromyces marxianus>Escherichia coli>Staphylococcus aureus>Bacillus anthracis>Salmonella>Bacillus subtilis>Saccharomyces cerevisiae>Lactobacillus rhamnosus. The minimum bactericidal concentration were as follows:Kluyveromyces marxianus 5.67 mg/mL,Escherichia coli 9.82 mg/mL,Staphylococcus aureus 13.52 mg/mL,Bacillus anthracis 16.46 mg/mL,Salmonella 17.68 mg/mL,Bacillus subtilis 17.87 mg/mL,Saccharomyces cerevisiae 20.82 mg/mL,Lactobacillus rhamnosus had no significant inhibitory effect. DHEA shortened the growth cycle of the test bacteria and reduced the cell concentration. Scanning electron microscopy showed that the morphology of the cells was changed after DHEA treatment,the cell wall ruptured and the cell contents were partially eluted. The research showed that DHEA in sweet potato residue had inhibitory effects on most bacteria.

Sweet potato and potato residual flours as potential nutritional and healthy food material

In this study, the proximate composition, mineral content and amino acid composition of starch processing residues from 10 cultivars of sweet potato and 10 cultivars of potato were determined, and the nutritional and health-related values of these residues were investigated. The residual flours contained 20.63–31.48 g and 17.14–28.57 g rich dietary fiber per 100 g dry weight for sweet potato and potato, respectively, as well as mineral elements, including potassium, ferrum, zinc and copper. The highest limiting amino acid score (AAS) of the almost balanced amino acid composition were observed to be 71.07 and 57.96 for sweet potato and potato residues, respectively. A grey relational analysis showed that the nutritional values of Jishu 4 at 0.7519 and LT-5 at 0.7281 were the highest among the sweet potato and potato residues, respectively. The evaluation of the sweet potato/potato residues, the by-products of the starch industry, based on recommended daily intake (RDI) standards, indicated that the residues have potential nutritional and health-related food values.

Hydrophilic modification of cellulose nanocrystals improves the physicochemical properties of cassava starch-based nanocomposite films

Carboxymethyl cellulose nanocrystals (N-CMCs) were produced by carboxymethylation of cellulose nanocrystals (CNCs) that derived from sweet potato residue. Transmission electron microscopy showed that the N-CMCs which had a porous surface structure were more loosely packed and slightly larger with a uniform diameter ranging from 30 nm to 50 nm. N-CMCs with low viscosity (<25 mPa s) and nano-sized scale were used as reinforcement for preparing cassava starch-based films. Effect of N-CMCs varying 0.2 g/100 mL −0.5 g/100 mL was studied on physicochemical properties of N-CMCs/cassava starch films. N-CMCs/cassava starch film with 0.4 g/100 mL N-CMCs exhibited a 554% increase in tensile strength, 41% increase in elongation at break, and 123% increase in water solubility compared with the CNCs/cassava starch film. Moreover, the water vapor permeability and moisture absorption of the N-CMCs/cassava starch film decreased by 42.7% and 15.9%, respectively. Better mechanical properties, water barrier properties and water solubility was achieved for the N-CMCs/cassava starch film than for the CNC/cassava starch film, indicating N-CMCs after carboxymethylation were beneficial for reinforcement of cassava starch-based films. The moisture absorption abilities of both cassava starch nanocomposite films were comparable. The results may be applied to the development of water-soluble and biodegradable edible films for food packaging.