Impact of cultivar types and thermal processing methods on sweet potato metabolome, a comparative analysis via a multiplex approach of NIR and GC-MS based metabolomics coupled with chemometrics.

This study comprehensively analyzes the primary metabolites of sweet potato peels and pulps from four cultivars and assesses the impact of four different processing methods on pulp metabolome using a multiplex metabolomics approach of GC-MS and NIR. A total of 69 metabolites were identified. Beauregard cv. showed the highest sugar content (387.85 mg/g), whereas Sahrawy cv. was higher in alcohols (24.63 mg/g) and organic acids (2.98 mg/g). The chemometric analysis identified key markers that distinguished each cv. represented by its pulp, peel, and processed pulp. KEGG enrichment analysis pinpointed key metabolic pathways leading to the metabolic discrepancy of the specimens. Sugars were the most altered class by processing as manifested by a 5 to 11-fold increase, notably in the air-fried pulp. Air-frying also increased alcohol and organic acid contents. NIR analysis revealed that air-frying was the preferred method of processing, preserving the majority of pulp's metabolites, including ß-carotene and phenolics.

In vitro simulated digestion of different heat treatments sweet potato polysaccharides and effects on human intestinal flora.

The aim of this study was to investigate the changes of untreated and steamed (100 °C, 20 min), fried (150 °C, 10 min), and baked (200 °C, 30 min) sweet potato polysaccharides during in vitro digestion and their effects on the intestinal flora. The results showed that the reducing sugar content of all four sweet potato polysaccharides increased significantly during digestion. During in vitro fecal fermentation, the content of reducing sugars and total carbohydrates decreased significantly. It indicated that all four polysaccharides showed degradation of polysaccharides during fermentation. Compared to the blank group, the total SCFAs content of the four polysaccharide sample groups was significantly increased. It was worth noting that sweet potato polysaccharides increased the percentage of Bacteroidetes and decreased the percentage of Proteobacteria in the intestinal flora. The findings provide evidence that sweet potato polysaccharides regulate intestinal flora and maintain intestinal health through interactions with intestinal flora.

Preparation of chitosan/polyvinyl alcohol antibacterial indicator composite film loaded with AgNPs and purple sweet potato anthocyanins and its application in strawberry preservation.

This study incorporated purple sweet potato anthocyanin (PSPA) and silver-nanoparticles (AgNPs) into the chitosan/polyvinyl alcohol film matrix (PVA/CS) to successfully prepare a composite film, which effectively inhibited bacterial growth and indicated product freshness. The addition of AgNPs and PSPA led to a dense structure of the film, which effectively enhanced its physical properties, barrier properties and functional properties. The incorporation of PSPA made the composite film highly pH-sensitive, which exhibited distinct color changes in varying pH solutions. The PVA/CS-AgNPs-PSPA10 composite film with PSPA and AgNPs resulted the shelf life of strawberries to 13 days at 4 °C, which effectively reduced strawberry breathing during storage. Additionally, such composite film changed color from purple to yellow-purple, indicating the deterioration of strawberries. It also showed an antibacterial indication through its excellent antibacterial property and freshness indication performance, which demonstrated its significance in developing antibacterial indicator composite packaging materials for fruits and vegetables preservation.

Preparation of a colorimetric hydrogel indicator reinforced with modified aramid nanofiber employing natural anthocyanin to monitor shrimp freshness.

The pH-responsive hydrogels have potential applications in food visualization detection, but their fragile mechanical properties limit their applicability. The excellent mechanical properties and thermal stability of aramid nanofibers (ANFs) can improve the structural stability of hydrogels. In this study, the surface properties of ANFs were enhanced through modification to improve their surface activity. The modified ANFs, designated as ANF-SN, were produced following treatment with a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3), which led to increased reactivity and dispersibility of the ANFs due to the proliferation of active groups on their nanofiber surface. The preferred anthocyanin extract from purple sweet potatoes (purple sweet potato extract [PSPE]) had significant color responses to pH (2-12) and ammonia vapor. A stable dual-network colorimetric hydrogel was fabricated by combining ANF-SN, polyvinyl alcohol/sodium alginate (PVA/SA), and PSPE through a two-step method (freeze-thawing and staining). Characterization analysis showed that the strong acid modification of ANFs effectively improved their chemical reactivity. ANF-SN was better than ANF in promoting the formation of hydrogen bond networks, enhancing hydrogel network structures, and improving the viscoelasticity of hydrogels. The optimal hydrogel indicator PVA/SA/ANF-SN/PSPE had good color responsiveness and sensitivity to ammonia. It can also be used to further determine shrimp freshness value using a smartphone and RGB color-picking software.

The mechanism of purple sweet potato anthocyanin extract to reduce the digestion rate and improve the starch digestion characteristics based on dough system.

Current studies have predominantly focused on the in vitro interactions between starch and anthocyanins, neglecting the complexity of actual food composition systems. In this study, purple sweet potato anthocyanin extract (PSPAE)-dough mixture was constructed with the aim of refining the mechanism by which anthocyanins improved starch digestive properties. Animal experiments demonstrated that the dough containing PSPAE (250 mg/kg) significantly reduced peak blood glucose levels in mice by 39.69 %. Further analysis of the dough mixture properties-including texture, particle size, pasting characteristics, microstructure, infrared spectrum, and crystallinity-helped elucidate how PSPAE impedes starch digestion. The incorporation of 600 mg of PSPAE into the dough led to a 40.45 % reduction in the volume mean diameter compared to the blank dough. Textural and microstructural examinations suggested that PSPAE obstruct the interaction forces between starch molecules by filling gluten protein pores or wrapping starch molecules. This denser microstructure likely contributes to enhanced starch resistance. Additionally, alterations in dough crystallinity revealed that PSPAE encourages the reorganization of linear starch molecules, boosting the content of resistant starch and thereby reducing starch digestibility. This study enriches the mechanism of PSPAE in ameliorating diabetes symptoms and provides theoretical insights for the development of functional foods aimed at diabetes management.

Biochemical mechanism of chlorine dioxide fumigation in inhibiting Ceratocystis fimbriata and black rot in postharvest sweetpotato.

The inhibitory properties and underlying mechanism of chlorine dioxide (ClO2) fumigation on the pathogen Ceratocystis fimbriata (C. fimbriata) and resultant sweetpotato black rot were investigated in vitro and in vivo. Results revealed that the ClO2 fumigation effectively inhibited fungal growth and induced obvious morphological variation of C. fimbriata mycelia. Furthermore, the mycelial membrane suffered damage, as evidenced by a significant increase in malondialdehyde content and the leakage of protein and nucleic acid from mycelia cells, accompanied by a marked decrease in ergosterol content. Additionally, ClO2 fumigation caused spores cell membrane damage, a notable decrease in spore viability, and induced cell apoptosis as indicated by reductions in spore germination rate, two fluorescence staining observations, and flow cytometry analysis. Moreover, the decay diameter of sweetpotato black rot lesions decreased significantly after ClO2 fumigation, and the growth of C. fimbriata was also inhibited. These findings present a novel and effective technology for inhibiting the progression of sweetpotato black rot.

Advances in valorization of sweet potato peels: A comprehensive review on the nutritional compositions, phytochemical profiles, nutraceutical properties, and potential industrial applications.

During food production, food processing, and supply chain, large amounts of food byproducts are generated and thrown away as waste, which to a great extent brings about adverse consequences on the environment and economic development. The sweet potato (Ipomoea batatas L.) is cultivated and consumed in many countries. Sweet potato peels (SPPs) are the main byproducts generated by the tuber processing. These residues contain abundant nutrition elements, bioactive compounds, and other high value-added substances; therefore, the reutilization of SPP holds significance in improving their overall added value. SPPs contain abundant phenolic compounds and carotenoids, which might contribute significantly to their nutraceutical properties, including antioxidant, antimicrobial, anticancer, prebiotic, anti-inflammatory, wound-healing, and lipid-lowering effects. It has been demonstrated that SPP could be promisingly revalorized into food industry, including: (1) applications in diverse food products; (2) applications in food packaging; and (3) applications in the recovery of pectin and cellulose nanocrystals. Furthermore, SPP could be used as promising feedstocks for the bioconversion of diverse value-added bioproducts through biological processing.

Impacts of poultry manure and biochar amendments on the nutrients in sweet potato leaves and the minerals in the storage roots.

Poultry manure (PM) has demonstrated its potential to enhance crop nutritional quality. Nevertheless, there remains a dearth of knowledge regarding its synergistic effects when combined with wood biochar (B) on the nutrient concentrations in sweet potato leaves (Ipomoea batatas L.) and the mineral content stored in sweet potato storage roots. Hence, a two-year field trial was undertaken during the 2019 and 2020 cropping seasons in southwestern Nigeria, spanning two locations (Owo-site A and Obasooto-site B), to jointly apply poultry manure and wood biochar as soil amendments aimed at enhancing the nutritional quality of sweet potato crop. Each year, the experiment involved different combinations of poultry manure at rates of 0, 5.0, and 10.0 t ha-1 and biochar at rates of 0, 10.0, 20.0, and 30.0 t ha-1, organized in a 3 × 4 factorial layout. The results of the present study demonstrated that the individual application of poultry manure (PM), biochar (B), or their combination had a significant positive impact on the nutrient composition of sweet potato leaves and minerals stored in the sweet potato storage roots, with notable synergistic effects between poultry manure and biochar (PM × B) in enhancing these parameters. This highlights the potential of biochar to enhance the efficiency of poultry manure utilization and improve nutrient utilization from poultry manure. The highest application rate of poultry manure at 10.0 t ha-1 and biochar at 30.0 t ha-1 (PM10 + B30), resulted in the highest leaf nutrient concentrations and mineral composition compared to other treatments at both sites. Averaged over two years, the highest application rate of poultry manure at 10.0 t ha-1 and biochar at 30.0 t ha-1 (PM10 + B30) significantly increased sweet potato leaf nutrient concentrations: nitrogen by 88.2%, phosphorus by 416.7%, potassium by 123.8%, calcium by 927.3%, and magnesium by 333.3%, compared to those in the control (PM0 + B0). The same treatment increased the concentration of sweet potato root storage minerals: phosphorus by 152.5%, potassium by 77.4%, calcium by 205.5%, magnesium by 294.6%, iron by 268.4%, zinc by 228.6%, and sodium by 433.3%, compared to the control. The highest application rate of poultry manure at 10.0 t ha-1 and biochar at 30.0 t ha-1 yielded the highest economic profitability in terms of gross margin (44,034 US$ ha-1), net return (30,038 US$ ha-1) and return rate or value-to-cost ratio (VCR) (263). The results suggested that the application of poultry manure at 10 t ha-1 and biochar at 30 t ha-1 is economically profitable in the study areas and under similar agroecological zones and soil conditions.

Trends in acrylamide content in selected potato/sweet potato products on the Canadian market.

Processed plant-based foods, particularly high carbohydrate-containing foods, are among the greatest contributors to dietary acrylamide, a probable human carcinogen, uptake. Between 2009 and 2020, five surveys were conducted to determine acrylamide in high carbohydrate-containing foods in Canada. These surveys included sampling of potato and sweet potato chips, French fries, and frozen potato/sweet potato products, as a follow-up to our earlier surveys from 2002 - 2008. Samples were analyzed using isotope dilution (13C3-acrylamide) with LC-MS/MS. The highest mean acrylamide levels were found in sweet potato chips. Among potato chips (57 to 4660 ng g-1), one brand consistently showed the highest concentrations with wide variability. Acrylamide concentrations decreased over time in ready-to-eat French fries (from 480 to 358 ng g-1), and one brand showed a clear reduction temporally. Wide variations were observed among brands, among lots/outlets of same brands, and among different food chains. Acrylamide levels in potato chips decreased between 2009 and 2016 (504.3 ng g-1) relative to the period 2002 - 2008 (1096.9 ng g-1). The acrylamide trends observed in the products measured in the latest study indicate that food producers may have adopted mitigation strategies.

Effect of different pre-treatment on acrylamide content, nutrition value, starch digestibility and anthocyanin bioaccessibility of purple sweet potato (Ipomoea batata) deep-fried chips.

Veggie chips have gained popularity in the European market. These are considered healthier than potato chips by consumers. However, few works evaluate their nutritional and digestibility. The current work aimed to evaluate the effect of four pre-frying treatments (soaking, blanching, pulsed electric field (PEF) and PEF + blanching combination (PEFB)) on the chemical composition, anthocyanins, acrylamide, and digestive behavior (starch hydrolysis and anthocyanins bioaccessibility) of purple sweet potato deep-fried chips. In total 15 independent batches were made, three for each studied treatment (also a control without pretreatment was developed). The studied pretreatments impacted on fat and starch content, especially blanching and PEFB, which caused an increase in fat absorption and break starch, generating maltodextrins. Nineteen anthocyanins were detected, mainly cyanidin and peonidin derivatives, but a drastic loss was observed in blanched, PEF-treated and PEF-B-Treated chips. Acrylamide values ranged from 504.11 to 6350.0- µg/kg, with the highest values reported by untreated chips and the lowest by PEF-B-treated chips (p < 0.05). The anthocyanin's bioaccessibility ranged between 66.57 and 92.88%, with soaked chips that showed the highest values.

Hot air treatment alleviates chilling injury of sweet potato tuberous roots by regulating osmoregulatory substances and inducing antioxidant defense system.

Sweet potato tuberous roots are susceptible to chilling injury (CI) when stored below 10 °C. In this study, we investigated the mitigating effects of hot air (HA) treatment on CI. Results showed that HA45°C-3h treatment delayed the CI and internal browning during cold storage. After HA45°C-3h treatment, the cells' structural integrity was maintained, malondialdehyde accumulation and ion leakage were inhibited. Additionally, the osmoregulatory substances, such as total soluble solids, proline were maintained, and soluble protein was enhanced. Higher activity of antioxidant enzymes including superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, and the antioxidant substances including ascorbic acid, glutathione, total phenols, and flavonoids were observed in sweet potato tuberous roots treated by HA45°C-3h than untreated group. Our study suggested that HA45°C-3h treatment could reduce CI and maintain a better quality of sweet potato tuberous roots following cold storage.

Stability of anthocyanin extracts from chokeberry, grape, hibiscus, and purple sweet potato in ω-3-fatty acid rich oil-in-water emulsions.

The food industry is actively investigating the stability of natural red pigments to replace artificial food colorants from all food applications in the near future. In this study, the stability of coloring extracts from chokeberry, grape, hibiscus, and purple sweet potato was investigated in ω-3 fatty acid-rich flaxseed oil-in-water emulsion during storage. The red color of the oil-in-water emulsions faded within 4 days, indicating that the anthocyanin extracts were susceptible to lipid oxidation reactions of the ω-3 fatty acids. The color stability varied between all used extract sources: The chokeberry (degradation constant k = 19.6 h-1) and grape (k = 15.2 h-1) extracts showed similar degradation kinetics, whereas purple sweet potato extract (k = 10.7 h-1) degraded significantly slower, and hibiscus extract (k = 110.2 h-1) significantly faster. The differences can be explained by the different anthocyanins contained in the plant extract, especially by the proportion of acylated anthocyanins.

Microbiome-metabolomics-based insight into the protective effects of dietary fiber from sweetpotato residues on the high-fat diet-induced intestinal integrity damage.

Dietary fibers have attracted much attention due to their multiple benefits on gut health. In this work, the protective mechanism of dietary fiber from sweetpotato residues (SRDF) on the high-fat diet (HFD)-induced intestinal barrier injury was investigated using microbiome-metabolomics-based approach. The physicochemical property analysis demonstrated a thermal stability below 200 °C and porous pectin-polysaccharide structure of SRDF with high in vitro functional activities. The biochemical analysis indicated that SRDF significantly ameliorated intestinal barrier function by improving intestinal morphology and permeability and inhibiting inflammatory response. Microbiome analysis demonstrated that SRDF significantly reversed the HFD-induced dysbacteriosis, decreased the ratio of Firmicutes/Bacteroides and enhanced the relative abundance of probiotics, such as Muribaculaceae and Bifidobacteriaceae. Metabolomics analysis showed that SRDF also significantly altered the metabolic profile in the colon, wherein the differential metabolites were mainly involved in amino acid metabolism (especially tryptophan). Pearson correlation coefficient identified the beneficial relationship between intestinal microbiome and metabolome induced by SRDF. The limitation of this study was that the mouse model may not fully replicate the human intestinal responses due to the difference between the standard environmental conditions and natural world. Generally, our results implied the great potential of SRDF as a functional food ingredient.

Effects of soluble dietary fiber from pomegranate peel on the physicochemical properties and in-vitro digestibility of sweet potato starch.

The effects of soluble dietary fiber (SDF) from pomegranate peel obtained through enzyme (E-SDF) and alkali (A-SDF) extractions on the structural, physicochemical properties, and in vitro digestibility of sweet potato starch (SPS) were investigated. The expansion degree of SPS granules, pasting viscosity, gel strength and hardness were decreased after adding E-SDF. The setback was accelerated in the presence of A-SDF but E-SDF delayed this effect during the cooling of the starch paste. However, the addition of A-SDF significantly reduced the breakdown of SPS and improved the freeze-thaw stability of starch gels, even at low concentrations (0.1 %), while E-SDF showed the opposite result. The structural characterization of SDF-SPS mixtures showed that A-SDF can help SPS form an enhanced microstructure compared with E-SDF, while polar groups such as hydroxyl group in E-SDF may bind to leached amylose through hydrogen bonding, leading to a decrease in SPS viscoelasticity. In addition, the results of in vitro digestion analysis indicated that A-SDF and E-SDF could decreased the digestibility of SPS and increased the content of resistant starch, especially when 0.5 % E-SDF was added. This study provides a new perspective on the application of SDF from pomegranate peel in improving starch-based foods processing and nutritional characteristics.

Effects of component ratios on the properties of sweet potato-oat composite dough and the quality of its steamed cake.

To enhance the value proposition of sweet potato and oat while broadening their applicability in further processing, this study systematically investigated the impact of oat flour incorporation ratios (5%-25% of sweet potato dry weight) on the quality attributes of sweet potato-oat composite dough and its resulting steamed cake products. The results showed that the addition of oat flour could promote the rheological, water retention, and thermomechanical properties of the composite dough and improve the internal microstructure, specific volume, texture, and other processing properties of the steamed cake products. The rheology, water retention, and protein stability of the dough were maximized when the proportion of oat flour was 25%. The textural properties of steamed cakes, hardness, elasticity, cohesion, adhesion, chewiness, and recovery significantly increased (p < 0.05) and viscosity significantly decreased (p < 0.05) with the addition of oat flour. It is noteworthy that thermodynamic properties, internal structure of the dough, and air holding capacity, which are critical for processing, showed the best results at 20% oat flour addition. Therefore, the addition of 20%-25% oats is recommended to produce composite doughs with optimal quality and processing characteristics. PRACTICAL APPLICATION: As living standards improve, traditional cereals may no longer able to meet people's health needs. Therefore, there is an urgent consumer demand for nutritious, tasty alternatives to staple foods. In this study, oat flour and sweet potato mash were mixed to make sweet potato-oat cake, and the effect of ingredient ratio on the performance and quality of composite dough containing sweet potato-oat flour was analyzed, thus proposing an innovative approach to the research, development, and industrial production of sweet potato and oat food products.

Machine learning methods in near infrared spectroscopy for predicting sensory traits in sweetpotatoes.

It has been established that near infrared (NIR) spectroscopy has the potential of estimating sensory traits given the direct spectral responses that these properties have in the NIR region. In sweetpotato, sensory and texture traits are key for improving acceptability of the crop for food security and nutrition. Studies have statistically modelled the levels of NIR spectroscopy sensory characteristics using partial least squares (PLS) regression methods. To improve prediction accuracy, there are many advanced techniques, which could enhance modelling of fresh (wet and un-processed) samples or nonlinear dependence relationships. Performance of different quantitative prediction models for sensory traits developed using different machine learning methods were compared. Overall, results show that linear methods; linear support vector machine (L-SVM), principal component regression (PCR) and PLS exhibited higher mean R2 values than other statistical methods. For all the 27 sensory traits, calibration models using L-SVM and PCR has slightly higher overall R2 (x¯ = 0.33) compared to PLS (x¯ = 0.32) and radial-based SVM (NL-SVM; x¯= 0.30). The levels of orange color intensity were the best predicted by all the calibration models (R2 = 0.87 - 0.89). The elastic net linear regression (ENR) and tree-based methods; extreme gradient boost (XGBoost) and random forest (RF) performed worse than would be expected but could possibly be improved with increased sample size. Lower average R2 values were observed for calibration models of ENR (x¯ = 0.26), XGBoost (x¯ = 0.26) and RF (x¯ = 0.22). The overall RMSE in calibration models was lower in PCR models (X = 0.82) compared to L-SVM (x¯ = 0.86) and PLS (x¯ = 0.90). ENR, XGBoost and RF also had higher RMSE (x¯ = 0.90 - 0.92). Effective wavelengths selection using the interval partial least-squares regression (iPLS), improved the performance of the models but did not perform as good as the PLS. SNV pre-treatment was useful in improving model performance.

Phenolic profile, cheminformatics, and antiplatelet aggregation activity of orange and purple sweet potato (Ipomoea batatas L.) storage roots.

Sweet potatoes are rich in cardioprotective phytochemicals with potential anti-platelet aggregation activity, although this benefit may vary among cultivars/genotypes. The phenolic profile [HPLC-ESI(-)-qTOF-MS2], cheminformatics (ADMET properties, affinity toward platelet proteins) and anti-PA activity of phenolic-rich hydroalcoholic extracts obtained from orange (OSP) and purple (PSP) sweet potato storage roots, was evaluated. The phenolic richness [Hydroxycinnamic acids> flavonoids> benzoic acids] was PSP > OSP. Their main chlorogenic acids could interact with platelet proteins (integrins/adhesins, kinases/metalloenzymes) but their bioavailability could be poor. Just OSP exhibited a dose-dependent anti-platelet aggregation activity [inductor (IC50, mg.ml-1): thrombin receptor activator peptide-6 (0.55) > Adenosine-5'-diphosphate (1.02) > collagen (1.56)] and reduced P-selectin expression (0.75-1.0 mg.ml-1) but not glycoprotein IIb/IIIa secretion. The explored anti-PA activity of OSP/PSP seems to be inversely related to their phenolic richness. The poor first-pass bioavailability of its chlorogenic acids (documented in silico) may represent a further obstacle for their anti-PA in vivo.

Gastroprotective effects of polysaccharides from purple sweet potato (Ipomoea batatas (L.) Lam) on an ethanol-induced gastric ulcer via regulating immunity and activating the PI3K/Akt/Rheb/mTOR pathway.

The study aimed to investigate the alleviation of an ethanol-induced gastric ulcer in mice by apolysaccharide (PSP) from purple sweet potato (Ipomoea batatas (L.) Lam) and explore the mechanism. The anti-ulcer activity was determined by histopathological evaluation, total gastric acidity, pepsin activity, gastric ulcer index and gastric ulcer inhibition rate. The expression levels of inflammatory factors were detected using ELISA. A special protein meter was used to detect the content of immunoglobulin lgM, immunoglobulin lgG, and complements C3 and C4 in the serum of mice. The expression of CD4+/CD8+ lymphocyte subsets of mice was detected using flow cytometry. Western blot analysis was used to examine the effect of PSP on the PI3K/Akt/Rheb/mTOR pathway. The results showed that PSP could effectively reduce the total gastric acidity, pepsin activity, and the index and inhibition rate of gastric ulcers. At the same time, PSP could significantly increase the levels of immunoglobulins (lgG and lgM) and complements (C3 and C4). It could also increase the activity of peritoneal macrophages in mice and the expression of CD4+/CD8+ in the spleen. ELISA analysis showed that the contents of TNF-α, IL-1ß and IL-6 were significantly decreased and the content of IL-10 was significantly increased in the PSP group. The western blot analysis showed that PSP could upregulate the relative protein expressions of MUC5AC, PI3K, p-Akt, Rheb and mTOR. These results indicate that PSP can activate the PI3K/Akt/Rheb/mTOR signaling pathway to improve the immunity of mice and maintain the balance of the immune system, thereby protecting the gastric mucosa and improving stress gastric ulcers.

Preparation of Steamed Purple Sweet Potato-Based Films Containing Mandarin Essential Oil for Smart Packaging.

Anthocyanin-rich steamed purple sweet potato (SPSP) is a suitable raw material to produce smart packaging films. However, the application of SPSP-based films is restricted by the low antimicrobial activity of anthocyanins. In this study, SPSP-based smart packaging films were produced by adding mandarin essential oil (MEO) as an antimicrobial agent. The impact of MEO content (3%, 6%, and 9%) on the structures, properties, and application of SPSP-based films was measured. The results showed that MEO created several pores within films and reduced the hydrogen bonding system and crystallinity of films. The dark purple color of the SPSP films was almost unchanged by MEO. MEO significantly decreased the light transmittance, water vapor permeability, and tensile strength of the films, but remarkably increased the oxygen permeability, thermal stability, and antioxidant and antimicrobial properties of the films. The SPSP-MEO films showed intuitive color changes at different acid-base conditions. The purple-colored SPSP-MEO films turned blue when chilled shrimp and pork were not fresh. The MEO content greatly influenced the structures, physical properties, and antioxidant and antimicrobial activities of the films. However, the MEO content had no impact on the color change ability of the films. The results suggested that SPSP-MEO films have potential in the smart packaging of protein-rich foods.

A comparative study on the structure, physical property and halochromic ability of shrimp freshness indicators produced from nine varieties of steamed purple sweet potato.

Nine varieties of purple sweet potato were steamed and used for the production of shrimp freshness indicators. The impact of purple sweet potato's variety on the structure, physical property and halochromic ability of indicators was determined. Results showed different varieties of purple sweet potato had different starch, crude fiber, pectin, protein, fat and total anthocyanin contents. The microstructure, crystallinity, moisture content, water vapor permeability, tensile strength and elongation at break of indicators were affected by crude fiber content in purple sweet potato. The color, transmission and halochromic ability of indicators was associated with the total anthocyanin content in purple sweet potato. Freshness indicators produced from Fuzi No. 1, Ganzi No. 6, Ningzi No. 2, Ningzi No. 4, Qining No. 2 and Qining No. 18 of purple sweet potato were suitable to indicate shrimp freshness. This study provides useful information on screening suitable varieties of purple sweet potato for intelligent packaging.