Characterisation of sweetpotato from Papua New Guinea and Australia: Physicochemical, pasting and gelatinisation properties

Effects of Steaming on Chemical Composition of Different Varieties of Purple-Fleshed Sweetpotato

Purple-fleshed sweetpotatoes (PFSPs) are rich in anthocyanins and are one of the health foods of interest. In this study, the effects of steaming on the anthocyanin, starch, soluble sugar, volatile organic compounds (VOCs) and pasting properties of nine PFSPs from China were investigated. The anthocyanin content of raw PFSP ranged from 9 to 185 mg/100 g. The total starch content decreased and soluble sugar content increased in all purple potatoes after steaming. Among the nine PFSPs varieties, Guangshu20 showed the greatest decrease in starch content (30.61%) and the greatest increase in soluble sugar content (31.12%). The pasting properties affected the taste of the PFSPs, with Shuangpihuang having the lowest peak viscosity (720.33 cP) and Guangzishu12 having the highest peak viscosity (2501.67 cP). Correlation studies showed that the anthocyanin content and pasting properties were negatively correlated with most of the sensory indicators, whereas the soluble sugar content of steamed PFSPs was significantly positively correlated with sweetness. A total of 54 VOCs were identified in this study, and aldehydes and terpenoids were the major VOCs in PFSPs. This study provides a theoretical basis for the processing of different PFSP varieties.

The Chemical, Rheological, and Sensorial Characteristics of Arabic Bread Prepared from Wheat-Orange Sweet Potatoes Flour or Peel

The current study investigates the feasibility of preparing Arabic bread from wheat flour, sweet potato flour, or peeled sweet potatoes based on the nutritional values, technological characteristics, and sensory properties of the final products. First, we analyzed the proximate, elemental, total and individual phytochemical compositions of the raw materials and bread samples. The analysis showed that potassium, calcium, and phosphorus were higher in peels than pulp, in the same manner to the total phenolics, flavonoids, and anti-radical scavenging activities. Phenolic acids and flavonols were quantified, where p-coumaric, feruloyl-D-glucose, eucomic, gallic, and ferulic acids were measured as major phenolic acids in either peels or pulp flours, and their quantities were higher in the peels. Furthermore, we evaluated the effects of wheat substitution on the properties of the dough blends and their final bakery. The results indicated that the fortified samples' nutritional and rheological properties were significantly improved, while their sensory qualities were comparable to those of the control. Thereby, the fortified dough blends presented higher dough stabilities, indicating a wider range of applications. Additionally, after the heat treatment, the fortified breads maintained significantly higher total phenolic, flavonoid, anthocyanin, and carotenoid contents, and total antioxidant activities, implying their accessibility for humans upon consumption.

Ozone exposure tunes the physicochemical properties of sweet potato starch by modifying its molecular structure

Ozonation is an efficient method for improving the technical performance of some starches, but the feasibility of its use for sweet potato starch remains unknown. The effects of aqueous ozonation on the multi-scale structure and physicochemical properties of sweet potato starch were explored. Structurally, ozonation did not generate significant alterations at the granular level (size, morphology, lamellar structure, and long-range and short-range ordered structures), but led to tremendous changes at the molecular level, including converting hydroxyl groups to carbonyl and carboxyl groups and depolymerizing starch molecules. These structural changes resulted in prominent alternations in the technological performance of sweet potato starch, such as increases in water solubility and paste clarity and decreases in water absorption capacity, paste viscosity, and paste viscoelasticity. For these traits, their amplitudes of variation elevated when the ozonation time was extended and peaked at the longest ozonation time (60 min). The greatest changes in paste setback (30 min), gel hardness (30 min), and the puffing capacity of the dried starch gel (45 min) were observed at moderate ozonation times. In summary, aqueous ozonation is a new method for fabricating sweet potato starch with improved functionality.

Resistant starch from sweet potatoes: Recent advancements and applications in the food sector

In tropical and subtropical areas, tuber and root crops are staple foods and a key source of energy. Sweet potato (SP) is currently regarded as one of the world's top ten foods because of its diverse sizes, shapes, color, and health benefits. The resistant starch (RS) content of SP is substantial. It is predicted to become the cheapest item in the food industry due to its extensive variety, food stability, emulsifier and fat substitution capabilities, and as filler. As a result, interest in SP-sourced RS has recently increased. Due to their unique nutritional and functional qualities, novelty has become a popular research focus in recent years. This review will summarize the current understanding of SP starch components and their impact on the technological and physicochemical properties of produced starch for commercial viability. The importance of sweet potato RS in addressing future RS demand sustainability is emphasized. SPs are a viable alternative to tubers as a sustainable raw material for RS production. It has an advantage over tubers because of its intrinsic nutritional value and climatic endurance. Thermal, chemical, and enzymatic treatments are effective RS manufacturing procedures. The adaptability of sweet potato RS allows for a wide range of food applications.

Sizes, Components, Crystalline Structure, and Thermal Properties of Starches from Sweet Potato Varieties Originating from Different Countries

Sweet potato is a root tuber crop and an important starch source. There are hundreds of sweet potato varieties planted widely in the world. Starches from varieties with different genotype types and originating from different countries have not been compared for their physicochemical properties. In the research, starches from 44 sweet potato varieties originating from 15 countries but planted in the same growing conditions were investigated for their physicochemical properties to reveal the similarities and differences in varieties. The results showed that the 44 starches had granule size (D[4,3]) from 8.01 to 15.30 μm. Starches had different iodine absorption properties with OD680 from 0.259 to 0.382 and OD620/550 from 1.142 to 1.237. The 44 starches had apparent amylose content from 19.2% to 29.2% and true amylose content from 14.2% to 20.2%. The starches exhibited A-, C_A-, C_C-, or C_B-type X-ray diffraction patterns. The thermograms of 44 starches exhibited one-, two-, or three-peak curves, leading to a significantly different gelatinization temperature range from 13.1 to 29.2 °C. The significantly different starch properties divide the 44 sweet potato varieties into different groups due to their different genotype backgrounds. The research offers references for the utilization of sweet potato germplasm.

Insights into the correlations between the size of starch at nano- to microscale and its functional properties based on asymmetrical flow field-flow fractionation

In this study, the starches were isolated from three botanical sources (i.e., rice, sweet potato, and lotus seed). The size distributions of starch granules and molecules were determined by asymmetrical flow field-flow fractionation (AF4), and compared with those measured from optical microscopy (OM) and dynamic light scattering (DLS). Furthermore, the starches were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). AF4 coupled online with UV-visible, multiangle light scattering (MALS), and differential refractive index (dRI) detectors (AF4-UV-MALS-dRI) was employed for the investigation of the digestion and retrogradation properties of starches. Meanwhile, the relationships between the size of starch at nano- to microscale and its functional properties (i.e., digestibility, retrogradation, and thermal properties) were studied by Pearson correlation analysis. AF4-UV-MALS-dRI was proved to be a rapid and gentle method for the separation and size characterization of starches at both micro- and nano-molecule levels. Moreover, it was demonstrated that AF4-UV-MALS-dRI is a useful tool for the monitoring of the digestion and retrogradation properties of starches. The results suggested that the sizes of starch granules and molecules were to some extent correlated with their thermal properties and digestibility, but not with retrogradation property.

Relationships between isolated sweetpotato starch properties and textural attributes of sweetpotato French fries

Sweetpotato French fry (SPFF) textures have been associated with dry matter and starch contents, but these do not fully account for all textural differences. This study investigated the relationships between the physicochemical properties of sweetpotato starch and textural attributes of sweetpotato fries. Starches from 16 sweetpotato genotypes that varied in dry matter content were isolated and analyzed. The amylose content, pasting temperatures and viscosities, and textural properties of equilibrated starch gels were measured. Correlational analysis was performed with the respective SPFF mechanical and sensory texture attributes. Sweetpotato starch amylose content ranged from 17.3% to 21.1%, and the pasting and gel textural properties varied significantly between starches. Starch from orange-fleshed sweetpotatoes had lower pasting temperatures than starches from yellow/cream-fleshed genotypes, 72.2 ± 2.0 and 75.5 ± 1.1 °C, respectively. Notable inverse correlations were observed between the starch pasting temperature and perceived moistness (r = -0.63) and fibrousness (r = -0.70) of fries, whereas SPFF denseness was positively associated with starch pasting viscosity (r = 0.60) and nonstarch alcohol-insoluble solids content. Fry textures were likely affected by cooked starch properties, which should be considered when selecting varieties for sweetpotato fries. PRACTICAL APPLICATION: Without the aid of a batter, sweetpotato French fries (SPFFs) tend to be soft and limp-undesirable attributes in a fried food. The physiochemical properties of starch, the most abundant component in sweetpotato fries, were further explored in this study to better understand the properties of sweetpotato starch that influence SPFF textures. These findings can be used by sweetpotato processors and breeders for developing new sweetpotato varieties that are designed for production of fried products with desirable textures.

Properties of South-Indian rice cultivars: physicochemical, functional, thermal and cooking characterisation

Physicochemical, functional, thermal, pasting and cooking properties of five Indian rice cultivars, ADT 36, 43, 39, IW PONNI and CR1009 were investigated. The starch, protein and fat contents varied from 1.321 to 2.489 mg/ml, 11.16-13.32% and 1.19-1.77% respectively, showing significant difference amongst the cultivars. ADT46 showed the highest amylose-amylopectin ratio. Water (103.55-132.48%) and oil (112.89-137.30%) absorption capacities also varied significantly. CR1009 showed highest swelling power at 60 °C, whereas IW PONNI exhibited the highest solubility (10.165%). The gel consistency of rice flours extended from 1.32 to 4.12 cm. The thermal properties of rice cultivars were found to be profoundly affected by amylopectin and showed correlation with amylose-amylopectin ratio. The pasting properties of rice flours also varied significantly, with peak viscosity and breakdown viscosity ranging between 2068.5-839 Cp and 1609.5-764.15 Cp respectively. The cooking time of the rice grains was found to be consistent with their shape and size. ADT43 and ADT46 showed the highest and least water uptake % on cooking. ADT46 showed the least cooking loss %, owing to the highest pasting viscosity. This study delivers the knowledge of the Indian rice cultivars, to be used for utilization of rice varieties for different products with relevance to the properties and enhance the post-harvest value chain improvement.

Effect of bleaching and variety on the physico-chemical, functional and rheological properties of three new Irish potatoes (Cipira, Pamela and Dosa) flours grown in the locality of Dschang (West region of Cameroon)

Enzymatic browning, which usually occurs during irish potato tuber processing, causes deterioration in the nutritional, functional, physical and acceptability quality of the products derived from this matrix. To fight against this phenomenon, several treatment methods have been developed, such as bleaching. This led us to investigate the effect of bleaching on the physico-chemical, functional and rheological properties of three irish potato varieties. To achieve our objective, blanched and unbleached irish potatoes flours of three varieties (Cipira, Dosa and Pamela) were produced. The physico-chemical, functional and rheological aspects of the flours were then studied according to standard and developped methods. It appears from this study that treatment and variety significantly influenced (P < 0.05) the nutritional composition of irish potatoes flours. The physical properties with the exception of titratable acidity were affected (P < 0.05) by the treatment and the varieties. Analysis of the functional properties revealed that unbleached flours had a higher swelling rate and water retention capacity than bleached flours. Rheological properties, such as final viscosity, are influenced by the treatment and variety. The main component analysis showed that bleaching affects the properties of the varieties Pamela and Cipira. In view of all this, we can therefore highlight the applicability of each of the flours in a specific industrial field.

Impacts of nitrogen fertilization rate on the root yield, starch yield and starch physicochemical properties of the sweet potato cultivar Jishu 25

In recent years, the sweet potato cultivar Jishu 25 has exhibited good characteristics for starch processing in northern China. The storage root dry matter yields of this cultivar can exceed one ton per mu (1/15 of a hectare) at nitrogen (N) rates of 60–90 kg ha^-1 based on soil nutrient content. However, the effect of N fertilizer on the physicochemical properties of starches isolated from this cultivar has not been reported. In order to evaluate these effects, three different N rates, 0 (control, N0), 75 (N1), and 150 kg ha^-1 (N2), were selected for a field experiment in 2017. The results showed that N1 exhibited the highest storage root yield and starch yield. Compared to the control group, N fertilizer significantly increased the total starch content while no significant difference was found in these between the N1 and N2 groups. The amylose (AM) content was highest in the N2 group and lowest in the N0 group. In addition, N fertilizer exhibited no significant effects on the values of [D(v, 0.9)], D [4, 3] and D [3, 2]. Compared to the control group, N1 demonstrated significantly higher setback viscosity (SV), while N2 showed significantly higher peak viscosity (PV), cold paste viscosity (CPV) and SV. However, there were no significant differences in the hot paste viscosity (HPV), peak time and pasting temperature between the N1 and N2 groups. For the thermal properties of starch, there were no significant differences in peak temperature (T_p), conclusion temperature (T_c) or gelatinization enthalpy (ΔH) between the N1 and N2 groups. Overall, for the starch samples of cultivar Jishu 25, N fertilizer exerts significant effects on the starch content, AM content and viscosity properties but little effect on the particle size distribution and ΔH. 75 kg N ha^-1 can easily lead to substantial planting benefits from the high storage root yield, dry matter yield and total starch content of this cultivar.

Physicochemical and functional properties of sweetpotato flour

BACKGROUND

Sweetpotato (Ipomoea batatas Lam.) is a major starchy crop with great agricultural significance in many countries. There is a need to assess more genetic resources for sweetpotato quality improvement. This study aims to analyze physicochemical properties of whole (unpeeled) root flours from seven New Zealand sweetpotato varieties with commercial significance. Using whole unpeeled plants for 'healthy' food formulations becomes more popular due to nutritional effects and environmental concerns.

RESULTS

Great variations were found in chemical composition, in vitro antioxidant activities, swelling power, water solubility index, in vitro digestibility, thermal, pasting and gel textural properties of the seven flours. The antioxidant activities and phenolic contents were higher in the color-fleshed samples. Correlation analysis showed that the swelling, pasting and texture properties were largely affected by the activity of the endogenous amylase. Principal component analysis was done in four aspects including chemical composition, mineral content, antioxidant activities and functional properties to analyze the similarity and difference among these seven sweetpotato varieties.

CONCLUSION

The seven sweetpotato flours showed a wide range of functionalities and will be useful for the formulations of diverse and 'healthy' sweetpotato-based products. © 2019 Society of Chemical Industry.

Evaluation of 10 genotypes of sweetpotato for fries

The potential use of selected genotypes of sweetpotato for fries was evaluated. Moisture, fat, browning index, and beta-carotene content of fries from 10 sweetpotato genotypes, Apomuden, Bohye, Nanungungu, Otoo, CIP442162, Patron, CIP440390, Obare, Dadanyuie, and Tu-Purple, were determined by standard methods. Sensorial properties of the fries were further evaluated by an in-house trained panel of eight members using standard methods. Fat content was highest in CIP442162 and low in Dadanyuie, while beta-carotene content decreased by 44.27% in Bohye and 13.20% in Nanungungu after frying. Browning index was highest in the orange-fleshed and purple genotypes, but this was mostly due to their flesh colors and not the frying conditions. Fries from orange-fleshed genotypes, Apomuden and Nanungungu, were considered to be sweeter than the other genotypes. Detection of caramel and starch (rawness sensation) was very low for all genotypes assessed. Oily mouthcoat, moistness, and sogginess were detected in mostly the orange-fleshed genotypes, particularly Apomuden and Nanungungu. Tu-Purple, Bohye, and CIP440390 produced moderately crunchy fries and had the highest score for desirable attributes compared with the other genotypes. Tu-Purple, Bohye, and CIP440390 could be explored in commercial production of fries for enhanced utilization of developed sweetpotato genotypes.

Effects of Different Isolation Media on Structural and Functional Properties of Starches from Root Tubers of Purple, Yellow and White Sweet Potatoes

Different-colored sweet potatoes have different contents of pigments and phenolic compounds in their root tubers, which influence the isolation of starch. It is important to justify the identification of the most suitable isolation medium of starch from different colored root tubers. In this study, starches were isolated from root tubers of purple, yellow and white sweet potatoes using four different extraction media, including H₂O, 0.5% Na₂S₂O₅, 0.2% NaOH, and both 0.5% Na₂S₂O₅ and 0.2% NaOH. Their structural and functional properties were investigated and compared among different extraction media. The results showed that the granule size, apparent amylose content, lamellar peak intensity, thermal properties, and pasting properties were different among different-colored sweet potatoes due to their different genotype backgrounds. The four extraction media had no significant effects on starch structural properties, including apparent amylose content, crystalline structure, ordered degree, and lamellar peak intensity, except that the NaOH and Na₂S₂O₅ treatment were able to increase the whiteness of purple and yellow sweet potato starches. The different extraction media had some effects on starch functional properties, including thermal properties, swelling power, water solubility, and pasting properties. The above results indicated that the H₂O was the most suitable extraction medium to simply and fast isolate starch from root tubers of different-colored sweet potatoes.

Variation in composition, protein and pasting characteristics of different pigmented and non pigmented rice (Oryza sativa L.) grown in Indian Himalayan region

This present study was aimed to evaluate proximate composition, antioxidant activity, amino and phenolic acids, protein profile and pasting characteristics of pigmented rice (PR) and non pigmented rice (NPR) landraces grown in Himalayan region. Higher antioxidant activity, total phenolic content, fat and protein content were observed for PR as compared to NPR. Histidine, iso-leucine, lysine, methionine, phenyl-alanine, valine and threonine were significantly higher for PR. Paste viscosities were higher for NPR (except IC568266) as compared to PR. IC568266 was observed to be waxy landrace. Higher free (gallic acid, catechin, caffeic acid, vanillic acid, sinapic acid and luteolin) and bound phenolics (ferulic acid, p-coumaric acid and quercetin) were observed in PR as compared to NPR. Majority of PR landraces showed higher accumulation of prolamines with low molecular weight polypeptides of 18, 20 and 29 kDa as compared to NPR. PR showed the higher essential amino acids, phenolic acids (p-coumaric acid, ferulic acid and quercetin) and antioxidant activity with improved nutritional value and showed potential for developing nutraceutical and functional foods.

Parallel evolution of storage roots in morning glories (Convolvulaceae)

BACKGROUND

Storage roots are an ecologically and agriculturally important plant trait that have evolved numerous times in angiosperms. Storage roots primarily function to store carbohydrates underground as reserves for perennial species. In morning glories, storage roots are well characterized in the crop species sweetpotato, where starch accumulates in storage roots. This starch-storage tissue proliferates, and roots thicken to accommodate the additional tissue. In morning glories, storage roots have evolved numerous times. The primary goal of this study is to understand whether this was through parallel evolution, where species use a common genetic mechanism to achieve storage root formation, or through convergent evolution, where storage roots in distantly related species are formed using a different set of genes. Pairs of species where one forms storage roots and the other does not were sampled from two tribes in the morning glory family, the Ipomoeeae and Merremieae. Root anatomy in storage roots and fine roots was examined. Furthermore, we sequenced total mRNA from storage roots and fine roots in these species and analyzed differential gene expression.

RESULTS

Anatomical results reveal that storage roots of species in the Ipomoeeae tribe, such as sweetpotato, accumulate starch similar to species in the Merremieae tribe but differ in vascular tissue organization. In both storage root forming species, more genes were found to be upregulated in storage roots compared to fine roots. Further, we find that fifty-seven orthologous genes were differentially expressed between storage roots and fine roots in both storage root forming species. These genes are primarily involved in starch biosynthesis, regulation of starch biosynthesis, and transcription factor activity.

CONCLUSIONS

Taken together, these results demonstrate that storage roots of species from both morning glory tribes are anatomically different but utilize a common core set of genes in storage root formation. This is consistent with a pattern of parallel evolution, thus highlighting the importance of examining anatomy together with gene expression to understand the evolutionary origins of ecologically and economically important plant traits.

Strategies to include sweet potato meal associated with the use of exogenous enzymes, in broiler chicken feed

SUMMARY This work evaluated the effect of including sweet potato meal (SPM), as an alternative to corn in broiler chicken diets, on performance, carcass yield, intestinal morphometry, organ biometry, meat quality and drumstick pigmentation. The study used 936 male Cobb-500 chicks. The experiment had a completely randomized, 3x2 factorial design, with three diet types. These included corn as the energetic ingredient in the standard diet (corn-soybean meal, CSM), and an increasing (ISP) and decreasing (DSP) inclusion of sweet potato meal as a corn substitute, in association with exogenous enzymes, for a total of six treatments with six repetitions and 26 birds per plot. During the period of 1 to 21 days, there was an interaction (P<0.05) for the weight gain (WG) variable; the CSM diets promoted greater WG in relation to the ISP and DSP groups, when supplemented with exogenous enzymes. There was an increase (P<0.05) in surface absorption of the jejunum villi and relative weight of the pancreas, and worse feed conversion (FC), for the ISP and DSP diets. With exception of the pancreas, for the entire period of 1 to 39 days the performance, yield of the carcass and cuts, meat quality, relative weight of the liver, and feet pigmentation variables were not affected (P>0.05) by the factors evaluated. Sweet potato meal, independent of the inclusion program (ISP/DSP) and enzyme supplementation, could partially substitute corn in broiler chicken feed, guaranteeing good performance, carcass yield and meat quality.

Conversion of sweet potato waste to solid fuel via hydrothermal carbonization

Hydrothermal carbonization (HTC) of sweet potato waste was performed to investigate the effect of process parameters including reaction temperature (180-300 °C) and residence time (0-120 min) on the characteristics of hydrochars. The results showed that the increase of reaction temperature and residence time both decreased the yield of hydrochars. With the increase of reaction temperature and residence time, the carbon content of hydrochars increased, while the hydrogen and oxygen contents decreased. The lower H/C and O/C ratios indicated that dehydration and decarboxylation reactions occurred during HTC. The occurrence of aromatization reaction was found in FTIR spectra. Thus, the fixed carbon content, higher heating value, and energy density of hydrochars increased. SEM analysis indicated that HTC developed rough surface with crack on the hydrochars. The thermogravimetric experiments displayed the increase trend in combustion ignition temperature, burnout temperature and activation energy as reaction temperature and time increase, which showed better combustion characteristics.

Effects of tempering (annealing), acid hydrolysis, low-citric acid substitution on chemical and physicochemical properties of starches of four yam (Dioscorea spp.) cultivars

The effects of tempering (annealing), acid hydrolysis and low-citric acid substitution on chemical and physicochemical properties of starches of four Nigerian yam cultivars were investigated. Crude fat and protein contents of the native starches decreased significantly after the modifications, while nitrogen-free extract increased significantly with acid hydrolysis and citric acid substitution. Acid hydrolysis and low-citric acid substitution reduced the least concentration for gel formation of the starches from 4 to 2% w/v, but tempering had no effect. Swelling power of the starches reduced significantly, and water solubility increased significantly at 75 and 85 °C, especially with acid hydrolysis and low-citric acid substitution. However, tempering significantly reduced starch solubility in the four cultivars. Paste clarity of starches of white (29.17%), water (18.90%), yellow (30.90%) and bitter (10.57%) yams reduced significantly with tempering to 14.43, 11.83, 16.93 and 7.27%, but increased significantly with acid hydrolysis to 41.40, 35.37, 28.77 and 32.33%, and low-citric acid substitution to 36.60, 44.17, 50.67 and 14.33%, respectively. Pasting properties such as peak, trough, breakdown, final, and setback viscosities and peak time of native starches reduced significantly with acid hydrolysis and low-citric acid substitution, however, tempering significantly increased their pasting temperature, peak time, setback and final viscosities.

Rapid quantitative determination of maltose and total sugars in sweet potato (Ipomoea batatas L. [Lam.]) varieties using HPTLC

When a raw sweet potato root is analysed, only sucrose, glucose and fructose are present but during cooking, starch is hydrolysed into maltose giving the sweet flavour to cooked roots. This study aimed at developing an HPTLC protocol for the rapid quantitative determination of maltose and total sugars in four commercial varieties and to compare them to 243 hybrids grouped by flesh colour (white, orange, purple). In commercial varieties, mean maltose content varied from 10.26 to 15.60% and total sugars from 17.83 to 27.77% on fresh weight basis. Hybrids showed significant variation in maltose content within each group, with means ranging from 7.65% for white-fleshed, to 8.53% in orange- and 11.98% in purple-fleshed. Total mean sugars content was 20.24, 22.11 and 26.84% respectively for white, orange and purple flesh hybrids. No significant correlations were detected between individual sugars but maltose and total sugars content were highly correlated. Compared to the best commercial variety (Baby), 25 hybrids (10.3%) presented a higher maltose content and 40 (16.5%) showed a higher total sugars content. HPTLC was observed as an attractive, cost efficient, high-throughput technique for quantitating maltose and total sugars in sweet potatoes. Perspectives for improving sweet potato quality for consumers' requirements are also discussed.

Nutrient utilisation in grower pigs fed a protein concentrate blended with sweet potato roots either boiled or ensiled with or without vines

Blending sweet potato (Ipomoea batatas L. (Lam)) with a protein concentrate for pig feed is a common strategy used by small-scale livestock farmers across Africa, Asia and the Pacific. However, high dietary fibre in sweet potato (SP) forage may reduce nutrient utilisation and energy metabolism and reduce the growth rate of young pigs. A 32-day metabolic trial with grower pigs using a 4 × 4 Latin square design tested the hypothesis that there would be no difference in apparent total tract digestibility (ATTD) of nutrients, energy and nitrogen (N) balance in 25 kg grower pigs (Large White × Landrace × Duroc) fed diets based on a blend of 43–40% protein supplement with 57–60% of DM as SP roots either boiled (BR43) or ensiled alone (ER43) or ensiled with vines (ERV40). Blended SP diets provided ~14–15% crude protein (CP), 16.1–16.3 MJ digestible energy (DE)/kg DM and 0.54–0.58 g lysine/MJ DE. The control diet (STD) contained 16.5% CP, 14.8 MJ DE/kg DM, 0.58 g lysine/MJ DE. The major findings were as follows: (1) DM intake was higher (P &lt; 0.05) for BR43 than ER43, ERV40 and STD diets, which were similar; (2) DM ATTD and energy utilisation were higher (P &lt; 0.05) in pigs fed SP diets; (3) carbohydrate (N-free extracts) ATTD was higher (P &lt; 0.05) in pigs fed BR43 and ER43 diets, while CP ATTD of both these diets was similar to that of STD and higher than that of ERV40; (4) ATTD of fats (ether extracts), CP, carbohydrates (N-free extracts) and total phosphorus was lower (P &lt; 0.05) on ERV40, but fibre ATTD was higher; (5) N intake and N retained were similar (P &gt; 0.05) for pigs fed BR43, ER43 and STD diets but lower for ERV40 (P &lt; 0.05). Boiled or ensiled SP roots provided high nutrient and energy utilisation in growing pigs, but the inclusion of SP vines lowered ATTD, energy utilisation and N retained from the mixed diet (ERV40). It is concluded that boiled or ensiled SP root are equally valuable as blended feed for grower pigs. However, at 30%DM, ensiled SP vine in blended feed led to reduced grower-pig performance.

Chemical constituents and health effects of sweet potato

Sweet potatoes are becoming a research focus in recent years due to their unique nutritional and functional properties. Bioactive carbohydrates, proteins, lipids, carotenoids, anthocyanins, conjugated phenolic acids, and minerals represent versatile nutrients in different parts (tubers, leaves, stems, and stalks) of sweet potato. The unique composition of sweet potato contributes to their various health benefits, such as antioxidative, hepatoprotective, antiinflammatory, antitumor, antidiabetic, antimicrobial, antiobesity, antiaging effects. Factors affecting the nutritional composition and bio-functions of sweet potato include the varieties, plant parts, extraction time and solvents, postharvest storage, and processing. The assays for bio-function evaluation also contribute to the variations among different studies. This review summarizes the current knowledge of the chemical composition of sweet potato, and their bio-functions studied in vitro and in vivo. Leaves, stems, and stalks of sweet potato remain much underutilized on commercial levels. Sweet potato can be further developed as a sustainable crop for diverse nutritionally enhanced and value-added food products to promote human health.

Physical, functional, and pasting properties of flours from corms of two Cocoyam (Colocasia esculenta and Xanthosoma sagittifolium) cultivars

Physical, functional and physicochemical properties of flours of five cocoyam (Colocasia spp and Xanthosoma spp) cultivars were evaluated. Colour (L*a*b*) parameters of corms and flours, pasting and functional properties of the flours were determined. Xanthosoma spp showed significantly higher length (95.16-151.46), width (75.29-78.03) and weight (179.20-605.94) than the Colocasia spp., but the parameters did not vary significantly within either Xanthosoma and Colocasia spp. Generally, colour of peeled corms [L* (72.08-78.93); a* (+1.06 - +3.5); b* (+17.65 - +35.80)] was lighter than the flours [L* (69.35-84.97); a* (+0.30 - + 4.76); b* (+4.44 - +23.48)]. The NXs001 showed significantly higher peak (201.71RVU), trough (186.75 RVU), final (289.75 RVU) and setback (103 RVU) viscosities that the other cultivars. Pasting profiles of the cocoyam flours showed similar trend with the NXs001 showing a steeper curve. Pasting temperature and peak time ranged from 87.33 to 92.53 °C and 5.17-6.34 min, respectively. Water absorption capacity, gelling point, pH, foam capacity, bulk density and swelling power varied from 32-69 %, 6.56-7.59, 58.5-72.5 °C, 7.19-14.72 %, 0.94-1.01 g/mL and 3.18-7.36, respectively.