Purple-fleshed Sweet Potato Research Articles

Effects of different foliar iron applications on activity of ferric chelate reductase and concentration of iron in sweet potato (Ipomoea batatas)

We studied the relative efficacy of different forms of foliar iron (Fe) fertilisation on leaf re-greening in Fe-deficient, purple-fleshed sweet potato (Ipomoea batatas (L.) Lam.) varieties xuzi8 and xuzi6. Activities of ferric chelate reductase (FCR) and concentrations of Fe were measured in the leaves and roots at intervals over 5 days to quantify recovery from leaf chlorosis. Freshly expanded and chlorotic leaves were immersed in one of three different fertiliser compounds containing 9 mm Fe: FeSO4, Fe2(SO4)3, Fe(III)-EDTA. An Fe-sufficient treatment and an Fe-deficient control were included. The experiment had a completely randomised block design with five replications per treatment and was conducted in a sunlit glasshouse. For variety xuzi8, leaf FCR activity in the Fe2(SO4)3 treatment was highest at 1 h after application, and higher than all other treatments, whereas FeSO4 and Fe(III)-EDTA treatments showed their highest FCR at day 5 after application, both significantly higher than the Fe2(SO4)3 and control treatments. Furthermore, leaf Fe concentration reached a maximum in the FeSO4 treatment at day 1, and in the Fe2(SO4)3 treatment at day 3. By contrast, root Fe concentration was relatively constant and lower in the foliar Fe treatments than the Fe-sufficient and -deficient treatments. For variety xuzi6, leaf SPAD was higher with the Fe2(SO4)3 than the FeSO4 treatment at day 5 after application. In general, FCR activity and Fe concentrations in roots and leaves of xuzi6 were higher than those of xuzi8. Variations in leaf Fe concentrations were similar for both the FeSO4 and Fe2(SO4)3 treatments of the two varieties. Maximum leaf Fe levels in xuzi6 were ~4-fold those in xuzi8. The results of the study suggest that foliar-applied Fe2(SO4)3 was the most effective compound at correcting Fe-deficiency symptoms. The higher leaf and root FCR activity and Fe concentration in xuzi6 might explain its higher tolerance to Fe deficiency and better re-greening than xuzi8.

Comparison of the in vitro gastrointestinal bioavailability of acylated and non-acylated anthocyanins: Purple-fleshed sweet potato vs red wine

Acylated anthocyanins from purple-fleshed sweet potato (PFSP) have been reported to have multiple benefits to human health. Although, the bioavailability of these anthocyanins remains unknown. In the present study, a characterization of the gastrointestinal bioavailability of PFSP anthocyanins was assayed and compared with the bioavailability of Red Wine anthocyanins. Acylated anthocyanins showed higher resistance to overall simulated digestions when compared to less complex anthocyanins from Red wine, with degradation at the intestinal level of about 30% and 45%, respectively. Transport rates of absorption of acylated anthocyanins were not dependent on the cell type. However, a higher transport efficiency was observed in gastric cells (8%) when compared to the intestinal cells (5%). Glucose and proteins, but not starch, decreased the transport efficiency of anthocyanins in about 3–7% in gastric cells and 2–3% in intestinal cells. These results bring new insights and lay the groundwork for further research on acylated anthocyanins bioavailability.

Processing effects on anthocyanins, phenolic acids, antioxidant activity, and physical characteristics of Vietnamese purple-fleshed sweet potato flours

Abstract Effects of thermal processes on bioactive compounds and properties of purple-fleshed sweet potato (PFSP) flours were studied. “Nhật tím” sweet potato cultivar grown in Vietnam was processed into flours by different techniques including hot air drying (HA), freeze drying (FD), microwave vacuum drying (MVD), drum drying (DD), and extrusion cooking (ECD), respectively. Anthocyanins (cyanidin and peonidin), phenolic acids (chlorogenic acid, caffeic acid, ferulic acid, and p-Hydroxybenzoic acid), antioxidant activity, and physical characteristics of PFSP flours were evaluated. PFSP flours prepared by MVD process contained highest cyanidin (157.56 µg/g dw), peonidin (610.40 µg/g dw), and antioxidant activity, while HA process preserved highest chlorogenic acid content (582.13 µg/g dw) and FD technique yielded PFSP flours with highest p-Hydroxybenzoic acid content (161.46 µg/g dw). According to the overall results, MVD was the most efficient process for producing PFSP flours since it could preserve the most anthocyanins and phenolic compounds with highest antioxidant activity. Practical applications PFSP is a good source of anthocyanin pigments and phenolic compounds. Therefore, conversion of fresh PFSP roots into flours through appropriate techniques is quite important to preserve the bioactive compounds and antioxidant activity contained in the raw material. Conventional drying processes in comparison with novel thermal techniques for PFSP flour preparation and characterization were investigated. The results of the study demonstrated the effective approaches to enhance the quality of PFSP flours. The outcome of this study will lead to the industrial drying and flour production of sweet potatoes in Vietnam. PFSP flours can be used in a wide variety of healthy food products such as bakeries, desserts, soups, snacks, beverages, confectioneries, and noodles.

In vitro and in vivo hypoglycemic effects of cyanidin 3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucoside, an anthocyanin isolated from purple-fleshed sweet potato

Anthocyanins are major components of purple sweet potatoes (PSP) with antioxidant, anti-obesity, and antidiabetic activity. In this study, we evaluated the hypoglycemic effects of 12 individual anthocyanins purified from PSP (Korean variety Shinzami). We separated the anthocyanins using liquid chromatography with diode array detection and electrospray ionization/mass spectrometry (LC-DAD-ESI/MS). Three anthocyanins were selected through a radical scavenging activity test. We examined whether individual anthocyanins inhibited glucose secretion in HepG2 cells (hepatic gluconeogenesis). Additionally, we determined the effect of each anthocyanin on fasting blood glucose levels in 6-week-old male C57BL/6J mice fed a 60% high-fat diet for 14 weeks. Mice were evaluated at 0, 1, 2, and 4 h after oral administration of anthocyanins (80 mg/kg), an anthocyanin-rich-fraction (80 mg/kg), positive control (metformin, 80 mg/kg), and distilled water (control). Cyanidin 3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucoside (PEAK9) was the main PSP anthocyanin that inhibited hepatic glucose secretion and reduced blood glucose.

Quantifying cultivation technique and growth dynamics of purple-fleshed sweetpotato (Ipomoea batatas L.) in China

The cultivation technique and growth dynamics of purple-fleshed sweetpotato (Ipomoea batatas [L.] Lam) have not been extensively addressed. The objectives of the present study were to explore the optimum cultivation conditions and growth characteristics of purple-fleshed sweetpotato Xuzishu 3, which is a new cultivar with high anthocyanin content, good germination and nice agronomic traits. Through the analysis of orthogonal experiments L9(34), the use of 300 kg/ha of K fertilizer, the planting 50,250 plants per hectare, and the growth for 120 DAT were regarded as optimum conditions for Xuzishu 3. The agronomic traits, qualitative characteristics and biomass accumulation of Xuzishu 3 during the six growth periods were measured to discuss the dynamic changes of its essential characteristics and yield accumulation. The main traits of Xuzishu 3 revealed sigmoidal or linear patterns during these growth periods. Most of the traits appeared as peak values after 90 DAT, except for anthocyanin, soluble sugar and protein content. Extremely significant positive correlations were found between dry matter rates of the up-ground parts (including leaf petioles, leaves and stems). Meanwhile, each of these had extremely significant positive correlations in terms of reducing sugar content and storage root weight per plant, respectively. Furthermore, the assimilated product distributed more in the stems and leaves than in storage roots before 90 DAT. Subsequently, the partition of assimilates to the storage roots rapidly increased and peaked at 135 DAT, even though the photosynthetic capacity and net assimilation rate decreased. The data and inferences in the present study not only improved the yield and quality of Xuzishu 3, but also provided a method to more precisely optimize the cultivation of purple-fleshed sweetpotato.

Mathematical modelling of adsorption isotherms of Malaysian variety of purple flesh sweet potato at different temperatures

Purple flesh sweet potato or Ipomea batatas is one of the most important crops in Malaysia. Currently the crop is exclusively consumed and marketed in a dried form as traditional snacks and chips. So, understanding the moisture sorption isotherms of this crop is imperative for determining its storability and optimal shelf life of the dried product. Thus, the objective of this study was to determine the adsorption isotherms of purple flesh sweet potato experimentally and the data obtained were used to model the process at different temperatures by employing several mathematical models using non-linear regression analysis. Several mathematical models (GAB, BET, Oswin, Chung and Pfost, Peleg, Henderson, Langmuir, Caurie and Halsey) were tested and compared with the experimental data. The best fitting mathematical model for all temperatures was Caurie’s equation with highest R2 value within the range of 0.9919 and 0.9949 and lowest chi square (λ2) values of 0.0000151–0.0000229. The monolayer moisture content for optimum moisture level for safe storage can be obtained from BET, GAB and Caurie equations. The monolayer moisture content from the GAB equation were found to be 0.1314, 0.1253 and 0.1182 kgw/kgDM and from Caurie’s equation, the values were 0.071, 0.0707 and 0.0692 kgw/kgDM. Both at 25 °C, 50 °C and 60 °C respectively.

Enhancement of water removing and the quality of fried purple-fleshed sweet potato in the vacuum frying by combined power ultrasound and microwave technology

The combination of ultrasound and microwave in vacuum frying system was investigated to achieve higher drying efficiency and quality attributes of fried products. Purple-fleshed potato were used as test specimen and different power levels of microwave (0 W, 600 W, 800 W) and ultrasound (0 W, 300 W, 600 W) during vacuum frying. Drying kinetics, dielectric properties, moisture state variation and quality attributes of fried samples were measured in a vacuum frying (VF), and an innovatively designed ultrasound and microwave assisted vacuum frying (USMVF) equipment. The USMVF process markedly increased the moisture evaporation rate and effective moisture diffusivity compared to VF process. The oil uptake was reduced by about 16–34%, the water activity and the shrinkage was lowered, the texture (crispness) and the color of fried samples were greatly improved. The higher ultrasound and microwave power level in USMVF made a greater improvement. The total anthocyanin levels and retention of fried purple-fleshed potato chips was the highest (123.52 mg/100 g solids and 79.51% retention, respectively) among all treatments in US600M800VF process. The SEM analysis revealed a more porous and disruption microstructure in USMVF sample.

Effects of Cooking Methods on the Changes of Total Anthocyanins, Phenolics Content and Physical Characteristics of Purple-Fleshed Sweet Potato (Ipomoea batatas L.) Grown in Vietnam

Total anthocyanin content (TAC) and total phenolics in “Nhật tim” purple-fleshed sweet potato (PFSP) variety were analyzed as affected by four cooking methods: steaming, baking, roasting, and frying. Moisture content (%), core flesh temperature (oC) and color characteristics of cooked PFSP were evaluated. TAC in steamed, fried (skin-on), roasted, baked, and fried (skin-off) PFSP were 234.18; 217.14; 208.11; 195.25; 173.68 mg/100g dry weight (DW), respectively. Under the same cooking time, steaming was good for the retention of total phenolics and anthocyanins as compared with baking. Cooking by steaming, roasting, baking, skin-on or skin-off frying produced significant increase (P ≤ 0.05) of TAC and total phenolics as compared to the respective fresh samples. Steaming resulted in the greatest increase of TAC whereas skin-on frying showed a good cooking method to retain high total phenolics (826.47 mg GAE/100g DW) in shred PFSP.

Effect of pretreatment on purple-fleshed sweet potato flour for cake making

The purple-fleshed sweet-potato (PFSP) flour was produced by varying pretreatment of washed chips: dipping in 0.5 and 1.0% (w/v) citric acid solution for 30 min, dipping in 0.5 and 1.0% (w/v) citric acid solution for 30 min and followed by steam blanching for 5 min. The pretreatment effect on cake quality was investigated. The results showed that PFSP flour produced from pretreatment with dipping in 0.5% citric acid for 30 min followed by steam blanching for 5 min had higher lightness (L*) value and lower browning index, higher hedonic value of color and aroma and baking expansion. The specific volume of cake from pretreated flour, untreated flour and wheat flour were 44.87, 43.83, and 50.43cm3/g, respectively. The sensory evaluation of cake indicated that cake from pretreated PFSP flour was acceptable compare to those of cake from wheat flour.

Comparative transcriptome analysis of purple-fleshed sweet potato provides insights into the molecular mechanism of anthocyanin biosynthesis

Sweet potato, <i>Ipomoea batatas</i>, is a globally important food crop. The purple-fleshed sweet potato, rich in anthocyanins, has great potential for both nutritional and pharmaceutical uses. In this study, we characterized the root transcriptomes of the purple-fleshed sweet potato cv. Jingshu 6 and its mutant JS6-5 with high anthocyanin content by high-throughput RNA sequencing. A total of 22873364 and 27955097 high quality reads were obtained from Jingshu 6 and JS6-5, respectively, and assembled into 35592 unigenes. In all, we obtained 1566 differentially expressed genes (DEGs). Among them, 994 were upregulated and 572 were downregulated in JS6-5 compared to the expression in Jingshu 6. A total of 1436 DEGs were annotated, in which 847 DEGs had gene ontology (GO) terms and 329 DEGs were assigned to 84 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Most importantly, 23 differentially expressed genes and 24 transcription factors were identified as candidate genes involved in anthocyanin biosynthesis. In addition, 2349 SSRs were detected. This study not only provides the candidate genes but also provides insights into the molecular mechanism of anthocyanin biosynthesis in sweet potato.

The effect and evidence of ethanol content on the stability of anthocyanins from purple‐fleshed sweet potato

This study aimed to evaluate and understand the water–ethanol system effect on the stability of purple-fleshed sweet potato anthocyanins (PSPa). The stability of the PSPa in the model ethanol–water solutions (0–80%, vol/vol, pH 3.5) during storage (60 hr) at room temperature was monitored by UV-vis. The frontier molecular orbital theory was used to interpret the hydration reaction rate of the PSPa in both ethanol–water and aqueous solutions. In all of the model ethanol–water solutions, the degradation of the PSPa followed first-order kinetics during storage, and the degradation rates increased with increased ethanol concentration. Theory calculation results showed that an increase in ethanol concentration decreased the LUMO energy of anthocyanins, and accelerated nucleophilic attack from water, thus, resulting in lower stability. These findings could provide valuable evidence of the solvent effect on the stability of anthocyanins. Practical applications Fruit wines that contain anthocyanins are among the common alcoholic beverages. The stability of the anthocyanins is responsible for wine quality and may also affect the nutritional properties. Thus, investigating the effect of ethanol on the stability of anthocyanins is particularly valuable. The results of this research have important implications for the models developed so far to explain the degradation mechanism of anthocyanins in different media. In this context, examining the effect of different media on the degradation of anthocyanins would be useful to provide improved anthocyanin ability in the food and beverage industry.

Potential of Hyperspectral Imaging for Rapid Prediction of Anthocyanin Content of Purple-Fleshed Sweet Potato Slices During Drying Process

This study aimed to investigate the potential of hyperspectral imaging technique in tandem with chemometrics analysis for rapid and nondestructive determination of anthocyanin content within purple-fleshed sweet potato (PFSP) during drying process. Hyperspectral images of PFSP in the spectral range of 371–1023 nm were obtained during contact ultrasound-assisted hot air drying (CUHAD) process, and the reference anthocyanin contents of PFSP were measured by a traditional method. Partial least square regression (PLSR) and least-square support vector machine (LS-SVM) were applied to establish the calibration models based on raw extracted spectrum and spectrum preprocessed by four different methods. In order to simplify the calibration model, three algorithms including PLSR, LS-SVM, and multiple linear regression (MLR) were used to build models based on ten optimal wavelengths selected by regression coefficients (RC) method. The results showed that the RC-MLR yielded best results with the coefficient of determination for calibration ( $$ {R}_C^2 $$ ) of 0.868 and coefficient of determination for prediction ( $$ {R}_P^2 $$ ) of 0.866. Finally, distribution maps were developed based on an image processing algorithm to visualize anthocyanin content of PFSP at different drying periods which cannot be achieved by conventional methods. The overall results demonstrated that hyperspectral imaging technique is a useful tool for rapid and nondestructive determination of the anthocyanin content during drying process.

Profiling of anthocyanins in transgenic purple-fleshed sweet potatoes by HPLC-MS/MS.

Anthocyanins in purple-fleshed sweet potato (PSP) are beneficial to human health. The leaf color (Lc) gene is a transcription factor involved in regulating anthocyanin biosynthesis. The anthocyanin profiles of wild-type PSP of Ayamurasaki and its three Lc-transgenic lines were investigated by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). In vitro antioxidant activities of wild-type and Lc-transgenic lines, including reducing power activity, DPPH radical scavenging activity, hydroxyl radical scavenging activity, linoleic acid autoxidation inhibition activity, ABTS free radical scavenging activity and oxygen radical absorbance capacity activity, were measured. The results showed that the total anthocyanin contents increased 1.5-1.9 times in three transgenic lines compared with that in wild-type PSP. Seventeen anthocyanins were found in wild-type PSP, while 19 in Lc-transgenic lines including cyanidin-based, peonidin-based and pelargonidin-based anthocyanins. Three pelargonidin-based anthocyanins were detected in three Lc-transgenic lines. Among them, the relative contents of cyanidin-based and pelargonidin-based anthocyanins increased 1.9-2.0 and 3.4-4.5 times respectively, while peonidin-based anthocyanins decreased 1.8-1.9 times in Lc-transgenic lines, compared with wild-type PSP. PSP from wild-type Ayamurasaki and three Lc-transgenic lines exhibited potent antioxidant activities, whereas there was no distinct difference among them. The transgene Lc significantly increased the content of total anthocyanins and remarkably changed the anthocyanin profiles in Ayamurasaki. Such novel and high content of anthocyanins obtained in the Lc-transgenic lines with potent antioxidant activities may provide unique functional products with potential helpful for human health. © 2017 Society of Chemical Industry.

A Root-Preferential DFR-Like Gene Encoding Dihydrokaempferol Reductase Involved in Anthocyanin Biosynthesis of Purple-Fleshed Sweet Potato.

Purple-fleshed sweet potato is good for health due to rich anthocyanins in tubers. Although the anthocyanin biosynthetic pathway is well understood in up-ground organs of plants, the knowledge on anthocyanin biosynthesis in underground tubers is limited. In the present study, we isolated and functionally characterized a root-preferential gene encoding dihydrokaempferol reductase (IbDHKR) from purple-fleshed sweet potato. IbDHKR showed highly similarity with the reported dihydroflavonol reductases in other plant species at the sequence levels and the NADPH-binding motif and the substrate-binding domain were also found in IbDHKR. The tissue profile showed that IbDHKR was expressed in all the tested organs, but with much higher level in tuber roots. The expression level of IbDHKR was consistent with the anthocyanin content in sweet potato organs, suggesting that tuber roots were the main organs to synthesize anthocyanins. The recombinant 44 kD IbDHKR was purified and fed by three different dihydroflavonol substrates including dihydrokaempferol (DHK), dihydroquerctin, and dihydromyrecetin. The substrate feeding assay indicated that only DHK could be accepted as substrate by IbDHKR, which was reduced to leucopelargonidin confirmed by LC-MS. Finally, IbDHKR was overexpressed in transgenic tobacco. The IbDHKR-overexpression tobacco corolla was more highly pigmented and contained higher level of anthocyanins than the wild-type tobacco corolla. In summary, IbDHKR was a root-preferential gene involved in anthocyanin biosynthesis and its encoding protein, specifically catalyzing DHK reduction to yield leucopelargonidin, was a candidate gene for engineering anthocyanin biosynthetic pathway.

A Modified Method for the Determination of Acylated Anthocyanins in Purple-fleshed Sweet Potato (&lt;i&gt;Ipomoea batatas&lt;/i&gt; (L).) Tubers by High-performance Liquid Chromatography with Visible Absorption

A Modified Method for the Determination of Acylated Anthocyanins in Purple-fleshed Sweet Potato (&lt;i&gt;Ipomoea batatas&lt;/i&gt; (L).) Tubers by High-performance Liquid Chromatography with Visible Absorption

Non-Destructive Prediction of Moisture Content and Freezable Water Content of Purple-Fleshed Sweet Potato Slices during Drying Process Using Hyperspectral Imaging Technique

The aim of this study was to investigate the feasibility of hyperspectral imaging in measuring moisture content and freezable water content during drying process. Hyperspectral images were acquired for purple-fleshed sweet potato (PFSP) slices during contact ultrasound assisted hot drying (CUHAD) process, and the corresponding mean reflectance spectra from regions of interest in visible and near infrared (371–1023 nm) regions were extracted. Moving average, Savitzky-Golay smoothing filter (S_G filter) and multiplicative scatter correction (MSC) were investigated to preprocess the raw spectra and partial least square regression (PLSR) calibration model was established to analyze the relationship between the extracted spectral data and measured quality attributes. Comparing the performance of model based on different preprocessing methods, the PLSR model with MSC pre-treatment presented better results with coefficients of determination for prediction ( $$ {R}_P^2 $$ ) of 0.9837 and 0.9323 for moisture content and freezable water content, respectively. Instead of selecting full range spectra data, optimal wavelengths were identified based on the regression coefficients (RC) method. Then two linear calibration algorithms named PLSR and multiple linear regression (MLR), and a non-linear calibration algorithm named backpropagation (BP) neural network were used to establish models to predict quality attributes of samples simultaneously. The results showed that the RC-MLR with $$ {R}_P^2 $$ of 0.9359 and 0.8592 was considered as the best for determining moisture content and freezable water content of PFSP slices. Therefore, the study demonstrates the potential of using hyperspectral imaging in tandem with chemometrics analysis as an objective, fast and non-destructive method for predicting the moisture content and freezable water content at different dehydrated times.

Double-blind, placebo-controlled pilot trial of anthocyanin-rich purple sweet potato beverage on serum hepatic biomarker levels in healthy Caucasians with borderline hepatitis.

The objective is to evaluate the efficacy of anthocyanin-rich purple-fleshed sweet potato (PSP) beverage on the serum levels of gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in healthy Caucasians with borderline hepatitis. Forty healthy Caucasians (41-69 years) consumed three bottles of the PSP beverage (177 mg anthocyanins per 125-ml bottle) or placebo (1.3 mg) per day for 8 weeks. Thirty-nine subjects completed the study and two subjects were excluded from statistical analysis. GGT levels in the PSP group on days 15 and 43 were lower (P=0.077 and 0.038, respectively), AST levels in the PSP group on days 29 and 43 were lower (P=0.010 and 0.045, respectively) and ALT level in the PSP group on day 43 was lower (P=0.037) than in the placebo group. The PSP beverage did not induce clinically relevant changes in other blood and clinical chemistry parameters.

Cloning and characterization of the cDNA and promoter of UDP-glucose:flavonoid 3-O-glucosyltransferase gene from a purple-fleshed sweet potato

UDP-glucose:flavonoid 3-O-glucosyltransferase (UF3GT) catalyses the transfer of the glucosyl moiety from UDP-glucose to the 3-hydroxyl group of anthocyanidins to produce the first stable intermediate in the anthocyanin biosynthesis pathway. A full-length UF3GT cDNA (designated IbUF3GT) was isolated and characterized from a purple-fleshed sweet potato (Ipomoea batatas cv. Yamakawamurasaki). The cDNA was 1541bp in length and contained a 1359bp open reading frame encoding 452 amino acids with a calculated molecular mass of 48.8kDa and an isoelectric point of 5.64. Bioinformatics analyses revealed that IbUF3GT had high homology with UFGTs from other plant species. To verify the function of IbUF3GT, the gene was introduced into the UF3GT T-DNA insert mutant of Arabidopsis thaliana. Transformed Arabidopsis plants were obtained with purple cotyledon, hypocotyl and stems. A comparison of the anthocyanin contents of transgenic lines with the Arabidopsis mutants indicated that IbUF3GT encoded a functional protein for anthocyanin biosynthesis. The gene expression and anthocyanin accumulation analyses revealed that the IbUF3GT gene expression pattern matched the accumulation pattern of anthocyanins in different tissues and cultivars and in different developmental stages of the sweet potato root, suggesting that IbUF3GT was a key enzyme involved in anthocyanin accumulation in the purple-fleshed sweet potato. Furthermore, the IbUF3GT promoter sequence (designated pIbUF3GT; 758bp in length) was cloned from the purple-fleshed sweet potato cv. Yamakawamurasaki. Structural analysis of pIbUF3GT suggested that the IbUF3GT transcript level might be regulated by the transcription factors MYB and MYC, responsive factors to light, salicylic acid (SA) and gibberellic acid (GA). Tobacco leaves transiently expressing full-length and four 5′-deletions of pIbUF3GT fused with GUS indicated that pIbUF3GT had promoter activity and that the key elements related to promoter activity were located in the region from −758bp to −633bp in pIbUF3GT.

Hot air drying of purple-fleshed sweet potato with contact ultrasound assistance

ABSTRACTA drying technique using a combination of a contact ultrasound apparatus and a hot air dryer is developed to investigate the strengthening effect of contact ultrasound on hot air drying. The effects of drying parameters such as ultrasound power and drying temperature on drying characteristics, effective moisture diffusivity (Deff), microstructure, glass transition temperature (Tg), rehydration ratio, and color difference are discussed. The results show that the application of contact ultrasound causes a significant acceleration of internal mass transfer, and higher ultrasound power applied leads to faster drying rate. The effect of ultrasound power on drying rate decreases along with the reduction of moisture content during drying process. The increase in drying temperature significantly reduces drying time but has a little negative influence on the strengthening effect of ultrasound. Deff values range from 1.0578 × 10−10 to 5.4713 × 10−10 m2/s in contact ultrasound-assisted hot air drying of purple-fleshed sweet potato and increase significantly with an increase in drying temperature as well as ultrasound power. The microstructure of purple-fleshed sweet potato is greatly different at different ultrasound powers during contact ultrasound-assisted hot air drying and shows more microchannels and dilated intercellular spaces in the cross-section of purple-fleshed sweet potato micrographs at higher ultrasound power. Contact ultrasound application during hot air drying could improve the mobility of water and consequently reduce glass transition temperature. Lower color difference and higher rehydration ratio could be achieved as drying temperature decreases and ultrasound power increases. The increase in contact ultrasound power could reduce energy consumption of drying process up to 34.60%. Therefore, contact ultrasound assistance is a promising method to enhance hot air drying process.

Functional fabric treatment using tannic acid and extract from purple-fleshed sweet potato

Purple-fleshed sweet potato (PSP) has a reddish purple color with high amounts of anthocyanins and phenolic acids, both of which have various health-promoting effects. The acylated anthocyanins present in PSP are more heat-resistant than the nonacylated types found in other plants. Therefore, PSP extract was considered as a natural pigment and functional agent for textile dyeing and/or finishing processes. Here, wool and cotton fabrics are pretreated by a tannic acid aqueous solution to increase their dyeability and then dyed by PSP extract. The dyed fabrics are then investigated by various analysis techniques. The results revealed that wool and cotton fabrics can be dyed bluish red through the pretreatment and dyeing process. The wool and cotton fabrics also showed antibacterial and antioxidant characteristics.