Effect of home preparation practices on the content of provitamin A carotenoids in coloured sweet potato varieties (Ipomoea batatas Lam.) from Kenya

The content of β-carotene was determined in raw peeled, boiled peeled and roasted peeled roots of six orange- and yellow-fleshed sweet potato varieties from Kenya to evaluate their vitamin A potential before and after household preparation. The boiling and roasting procedures were similar to traditional methods used in Kenya. Dried products, chips and flour, of the variety Zapallo were also analysed. The varieties differed in dry matter and β-carotene content (1240–10,800 μg/100 g fresh weight (FW)) and thus in vitamin A content (100–830 RE/100 g FW). As sweet potato roots are consumed after heating, the loss of all-trans-β-carotene during preparation should be taken into account. Boiling of roots of the selected varieties seemed to result in a higher true retention (TR) of all-trans-β-carotene than roasting and TR of all-trans-β-carotene seemed to be dependent on the variety (42–128%). Preparation of chips by drying resulted in a significant reduction of the all-trans-β-carotene content of approximately 21%, which was further reduced when flour was produced from chips. The varieties Tainung and SPK-004 can be recommended for consumption especially after boiling in order to enhance the vitamin A intake in Kenya. Both varieties have a high content of vitamin A, the losses after boiling are rather low and both varieties have high consumer acceptability.Industrial relevanceThe content and stability of β-carotene in sweet potato is an issue that is particularly important for developing countries with high prevalence of vitamin A deficiency. In order to prolong the shelf life of sweet potato, it is necessary to implement and develop industrial or small scale processing methods so that it is possible to produce sweet potato products with highest possible vitamin A values in these countries. In developed countries, focus is on innovation of new products with a good taste and a high health value. Consequently, sweet potato and sweet potato products might have a future as healthy foods in developed countries, and therefore there is a need to build up an industry that can provide the people in these countries with high quality sweet potato foods.     

β-carotene content in sweet potato varieties from China and the effect of preparation on β-carotene retention in the Yanshu No. 5

To compare the β-carotene contents in different Chinese sweet potato (SP) varieties and to choose a variety of SP rich in β-carotene for the study of the effect of processing methods on β-carotene retention, β-carotene in thirteen varieties of sweet potato from China was measured by HPLC. The results showed that β-carotene contents were significantly correlated with SP flesh colours, with the orange-red fleshed SP varieties being higher in β-carotene.β-carotene contents in SP were affected by many factors, and this was demonstrated using the variety of Yanshu No.5, showing that the β-carotene contents in SP grown in different farming sites in the same area ranged from 53.2 to 84.3 mg kg^− 1 fresh weight. Moreover, β-carotene distributes unevenly in one SP root, with highest concentrations in the core. The β-carotene content was positively related to the root size.Five processing methods including boiling, steaming, microwave cooking, frying, and post steam-drying were simulated in the study to check their effects on the true retention of β-carotene in SP. Compared to boiling, steaming resulted in much more loss of β-carotene and microwave cooking resulted in the biggest loss of β-carotene among the five processing methods.

Industrial relevance

Orange-fleshed sweet potato can be prepared for sale and consumption, using methods that protect the β-carotene content. This can aid in promoting sweet potato as a staple food as well as a snack food for supplying vitamin A for both rural and urban populations. Prepared orange-fleshed sweet potato can contribute to alleviating vitamin A deficiency in China as well as other low-income countries.     

The potential contribution of bread buns fortified with beta-carotene-rich sweet potato in Central Mozambique

BACKGROUND: Orange-fleshed sweet potato is an efficacious source of vitamin A. Substituting wheat flour with orange-fleshed sweet potato in processed products could reduce foreign exchange outlays, create new markets for producers, and result in increased vitamin A consumption among consumers provided there is adequate retention of beta-carotene during processing. OBJECTIVE: To explore whether substituting 38% of wheat flour (by weight) in bread buns ("golden bread") with boiled and mashed orange-fleshed sweet potato from fresh roots or rehydrated chips would produce economically viable beta-carotene-rich products acceptable to Mozambican rural consumers. METHODS: Modified local recipes maximized sweet potato content within the limits of consumer acceptability. Sensitivity analysis determined parameters underlying economic viability. Two samples each of buns from five varieties of orange-fleshed sweet potato were analyzed for beta-carotene content. Processed products with at least 15 microg/g product of trans-beta-carotene were considered good sources of vitamin A. RESULTS: Golden bread made from fresh roots of medium-intensity orange-fleshed sweet potato varieties met the good source criterion, but bread from lighter-intensity sweet potato varieties did not. Bread from rehydrated dried chips was not economically viable. Consumers strongly preferred golden bread over pure wheat flour bread because of its heavier texture and attractive appearance. The ratio of the price of wheat flour to that of raw sweet potato root varied from 3.1 to 3.5 among the bakers, whose increase in profit margins ranged from 54% to 92%. CONCLUSIONS: Golden bread is a good source of beta-carotene and is economically viable when the price ratio of wheat flour to raw orange-fleshed sweet potato root is at least 1.5. Widespread adoption during sweet potato harvesting periods is feasible; year-round availability requires storage.     

Comparison of functional components in various sweet potato leaves and stalks

The functional components of leaves and stalks from 14 sweet potato cultivars were investigated by determining lutein, β-carotene, chlorophyll, tannin and phenolic acid contents. It was found that the contents of the functional components in different cultivars differ significantly (p<0.05). Lutein, β-carotene and total chlorophyll contents were high in leaves and ranged from 19.01–28.85, 35.21–52.01 and 440.9–712.2 mg/100 g, respectively. The tannin and total phenolic acid contents of sweet potato leaves ranged from 2,280–4,460 and 2,640.2–4,200.9 mg/100 g, respectively. Significant correlations have been observed among cultivar, lutein, β-carotene, chlorophyll, and other antioxidants. The leaves of Healthymi cultivar contained the highest level of lutein, β-carotene and total chlorophyll, and Geonpungmi cultivar contained the highest level of the other antioxidant, among the all cultivars examined. Sweet potato leaves and stalks contain abundant functional components that make them potentially useful as fresh vegetables or processed foods.     

PACKAGING PRESERVATION OF β-CAROTENE IN SWEET POTATO FLAKES USING FLEXIBLE FILM AND AN OXYGEN ABSORBER

Sweet potato flakes are potentially an affordable, shelf-stable source of provitamin A β-carotene. Because β-carotene is susceptible to oxidative degradation, particularly in dehydrated food materials exposed to atmospheric oxygen, several packaging conditions were evaluated for enhancement of β-carotene retention in sweet potato flakes during storage. The flakes were packaged in either a polypropylene film (high oxygen permeability) with air headspace or a nylon laminate film (low oxygen permeability) with air headspace, under vacuum, or with an Ageless oxygen absorber sachet enclosed. Packaged flakes were stored in the dark at ambient laboratory temperature (～23C), and β-carotene content was determined at intervals from 0 to 210 day storage using reversed-phase liquid chromatography. Among the packaging conditions tested, β-carotene retention was enhanced incrementally as the apparent availability of oxygen was reduced (nylon > polypropylene; oxygen absorber > vacuum > air headspace). The combined use of oxygen absorbers and flexible oxygen barrier film gave excellent retention of β-carotene during the 210 day trial.     

Antioxidant Capacity and Antioxidant Content in Roots of 4 Sweetpotato Varieties

Abstract: The antioxidant contents (β-carotene, chlorogenic acid, and vitamin C) as well as the antioxidant capacity (ORAC, FRAP, and ABTS) of 4 sweetpotato varieties were measured in this study. The sweetpotato varieties were cultivated under different water regimes and also subjected to thermal processing. The results show that the 2 orange-fleshed varieties (Resisto and W-119) contain significant more β-carotene, chlorogenic acid, and vitamin C than the 2 cream-fleshed varieties (Bosbok and Ndou). Thermal processing decreased the carotenoid and vitamin C content of all the varieties but increased the chlorogenic acid content and antioxidant capacity. Drought stress appears to increase the β-carotene, vitamin C, and chlorogenic acid contents as well as the antioxidant capacity of some of the sweetpotato varieties, especially W-119.     

Improving food security through agricultural research and development in Timor-Leste: a country emerging from conflict

Timor-Leste is a small, poor and predominantly-agricultural nation of less than 1 million people. Most families suffer from chronic food insecurity practising food rationing 1–6 months of the year. The small size of Timor-Leste, its recent birth as a nation and conflict history, together with little previous research on staple crops make it a unique crucible to test the effect of a major post-conflict initiative of agriculture research on national food security. Research started in 2000 with the introduction of germplasm of staple crops (maize, peanut, rice, cassava and sweet potato). Replicated trials confirmed by extensive evaluation in farmer-managed trials revealed significant yield advantages over the local cultivar in maize of 53%, in peanut of 31%, in rice of 23% and in sweet potato of 80%, accompanied by improvements in size and eating quality. Cultivars of maize (2), peanut (1), rice (1) and sweet potato (3) were released in 2007. One year later an early adoption study of 544 farmers involved in on-farm trials showed that 73% had re-grown new cultivars. Cultivar adoption not only increased household food security but often produced surpluses for sale in the market—sometimes for the first time. The project is planning to increase seed production and dissemination to move from a highly positive pilot-scale impact in six Districts to impact food security nationally.     

Use of Multi-response Modelling to Investigate Mechanisms of β-Carotene Degradation in Dried Orange-Fleshed Sweet Potato During Storage: from Carotenoids to Aroma Compounds

In order to give insight into β-carotene degradation mechanism during the storage of dried orange-fleshed sweet potato, and particularly into the role of isomers and norisoprenoids formation, multi-response kinetic modelling was applied. Determination of degradation compounds were carried out by HPLD-DAD and SPME-GC-MS as a function of time between 10 and 40 °C and at four water activities from 0.13 to 0.76. Kinetic modelling was developed assuming first-order reactions and by using mass balance. Eight compounds, namely, two isomers (9-cis- and 13-cis-β-carotene), two β-carotene epoxides (β-carotene 5,6 and 5,8 epoxide) and four volatile compounds (β-cyclocitral, β-ionone, 5,6-epoxy-β-ionone and dihydroactinidiolide), were integrated into two theoretical reaction schemes. The different models were discriminated according to goodness of fit to experimental data. This work showed that: (1) the formation of cis-isomers from β-carotene preceded oxidation, (2) β-cyclocitral arose directly from β-carotene scission while the other norisoprenoids resulted from β-carotene epoxide degradation, (3) cis-isomers were high reactive compounds. Temperature had a major influence on reaction rates k while water activities only impacted k at values under 0.51. Therefore, multi-response modelling is not only a tool to predict β-carotene degradation but a interesting way to select the appropriate degradation scheme based on the different options presented in literature.     

Retinol and beta carotene content of indigenous raw and home-prepared foods in Northeast Thailand

Retinol and β-carotene contents of raw and home-prepared indigenous foods in Northeast Thailand were studied. The criteria used to select the vitamin A-rich foods were high retinol or β-carotene contents of the individual food items, the amount and frequency of consumption, preference of consumption and food availability. Items selected were chicken liver, chicken egg, ivy gourd, amaranth, swamp cabbage (Chinese), Chinese cabbage, pumpkin, yellow sweet potato and two traditional menu items, kang-nho-mai and om-kruang-nai-kai. Raw food items were purchased from the local market; the traditional cooking procedures of the community were duplicated in the laboratory. Retinol and β-carotene contents were determined prior to and following cooking using HPLC methodology. The results indicated that boiling intact chicken liver resulted in 5% loss of retinol; boiling with cutting into small pieces and grilling resulted in losses of 8 and 16%, respectively. Greater losses (43%) were observed for egg omelet compared to hard-boiled egg (11%). For vegetables, blanching resulted in 7–11% loss of β-carotene, while steaming, frying and boiling showed losses of 15, 18 and 43%, respectively. Traditional foods such as bambooshoot soup (Kang-nho-mai) and chicken organ soup (Om-kruang-nai-kai) exhibited β-carotene losses ranging from 6–21%.     

Potential impacts of bioprocessing of sweet potato: Review

Sweet potato (Ipomoea batatas L.) is among the major food crops in the world and is cultivated in all tropical and subtropical regions particularly in Asia, Africa, and the Pacific. Asia and Africa regions account for 95% of the world's production. Among the root and tuber crops grown in the world, sweet potato ranks second after cassava. In previous decades, sweet potato represented food and feed security, now it offers income generation possibilities, through bioprocessing products. Bioprocessing of sweet potato offers novel opportunities to commercialize this crop by developing a number of functional foods and beverages such as sour starch, lacto-pickle, lacto-juice, soy sauce, acidophilus milk, sweet potato curd and yogurt, and alcoholic drinks through either solid state or submerged fermentation. Sweet potato tops, especially leaves are preserved as hay or silage. Sweet potato flour and bagassae are used as substrates for production of microbial protein, enzymes, organic acids, monosodium glutamate, chitosan, etc. Additionally, sweet potato is a promising candidate for production of bioethanol. This review deals with the development of various products from sweet potato by application of bioprocessing technology. To the best of our knowledge, there is no review paper on the potential impacts of the sweet potato bioprocessing.     

Effects of cooking methods on the β-carotene levels of selected plant food materials

In the present study, the β-carotene contents of 14 plant food materials prepared by boiling, steaming, or baking or when they are raw were analyzed and compared. After boiling three pulse species, namely, peas, kidney beans, and dried mung beans, β-carotene contents of peas and kidney beans increased significantly, whereas that of mung beans (dried material) decreased. True retention factors of β-carotene contents in the cooked kidney beans, peas, and mung beans after boiling were 174.2, 128.3, and 91.8%, respectively. After steaming, the β-carotene content of regular millets significantly decreased but that of taros increased, in which the true retention factors were observed with β-carotene contents of 72.4% in the steamed regular millets and 160.9% in the steamed taros. Moreover, β-carotene contents in yellow-fleshed sweet potato (raw: 896.2 μg/100 g) decreased by baking (786.4 μg/100 g) and steaming (steaming: 553.1 μg/100 g). These results suggest that β-carotene contents in the selected plant food materials markedly depend on the cooking method and plant food materials classification.     

Determination of cis- and trans- α- and β-carotenoids in Taiwanese sweet potatoes (Ipomoea batatas (L.) Lam.) harvested at various times

A HPLC method was improved to determine sweet potato carotenoids rapidly with good separation efficiency. A C30 column and a gradient solvent system consisting of methanol–acetonitrile–water (84/14/2, v/v/v, solvent A) and dichloromethane (solvent B) (a mixture of 80% A and 20% B was used initially, and then the mixing was programmed to 55% B within 15 min and kept to the end) were used for analysis. The flow rate was 1 ml/min and detection was at 450 nm. A total of 11 all-trans and cis forms of α- and β-carotene in Taiwanese sweet potato (Ipomoea batatas (L.) Lam.) could be resolved within 16 min. The orange-fleshed sweet potato (Tainung 66) had higher total carotenoid content than the yellow-fleshed one (Tainung 57) at the same harvest time. The total carotenoid levels in both crops harvested at various times were in the order: October > July > April > January.     

A simple UV-Vis spectrophotometric method for determination of β-carotene content in raw carrot, sweet potato and supplemented chicken meat nuggets

A simple, rapid and low cost analytical method for the determination of β-carotene content in four different food categories is developed and validated. This method is based on solvent extraction followed by UV-Vis spectrometric detection. Target compound was extracted with four different solvents, in which acetone appears to be an excellent extractant as recovery of the analyte at 1 μg/g concentration in spiked samples was in the range of 67.8-98.8%, with relative standard deviation (RSD) ranging between 4.8 and 6.6%. Intra- and inter-day assay precisions of the method at 0.1, 1.0 and 5.0 μg/g concentrations ranged in between 3.4 and 8.9%. The linearities for β- carotene in the pure acetone, raw carrot, sweet potato, and fortified raw and cooked chicken meat nuggets were 0.994, 0.995, 0.990, 0.984 and 0.984, respectively. For robustness, the analytical method was applied to 24 samples of four different food categories namely carrot, sweet potato and carrot and sweet potato supplemented chicken meat nuggets.     

Traditional and novel fermented foods and beverages from tropical root and tuber crops: review

Tropical root and tuber crops [cassava, sweet potato, yams, colocasia (taro), etc] are important staples for food security for about a fifth of the world population. Bulk of cassava in Africa and Latin America are processed into fermented foods and food additives such as organic (acetic, citric and lactic) acids, mono-sodium glutamate, etc. The fermented foods from cassava are gari , fufu , lafun , chickwanghe , agbelima , attieke and kivunde in Africa, tape in Asia and ' cheese ' bread , and ' coated peanut ' in Latin America. Lactic acid bacteria and yeasts are the major group of micro-organisms associated with cassava fermentation. Similarly, sweet potatoes can be fermented into soy sauce, vinegar, lacto-juices, lacto-pickles and sochu (an alcoholic drink produced in Japan), and yams into fermented flour. Most of these fermented food products are functional foods rich in phytochemicals, dietary fibres, anti-oxidant compounds (β-carotene, anthocyanin, etc) and probiotic components (lactic acid bacteria and yeasts).     

Altering pasting characteristics of sweet potato starches through amino acid additives

ABSTRACT:  This study assessed the effects of amino acid additives, aspartic acid, leucine, lysine, and methionine, on the pasting and thermal characteristics of white- and orange-fleshed Beauregard sweet potato starches. A rapid visco analyzer 3D was used to determine pasting properties. In comparing pasting characteristics, starch from orange-fleshed sweet potato was found to be easier to cook, had a lower potential for retrogradation, and was less stable during heating than the white-fleshed sweet potato starch. The RVA analysis showed that the charged amino acids, aspartic acid and lysine, altered pasting characteristics of the 2 starches more than the neutral amino acids, leucine and methionine. Aspartic acid had similar effects on both starches, making them less stable during cooking and lowering the potential for retrogradation. Lysine, when added to the orange-fleshed sweet potato starch, decreased the breakdown, allowing for more stability during cooking. This study showed that pasting properties of sweet potato starches can be altered by the addition of amino acids.     

Changes in the contents of carotenoids,phenolic compounds and vitamin C during technical processing and lyophilisation of red and yellow tomatoes

We present the results of the first study on the impact of thermal processing and lyophilisation on three major micronutrient families: carotenoids, total polyphenols and vitamin C in two different tomato cultivars: a red tomato (RT) and a yellow one (YT). Micronutrients were analysed in fresh tomatoes, tomato purée and lyophilised tomatoes. YT contained no lycopene, lower β-carotene, similar vitamin C and higher total polyphenol contents than RT. Processing did not affect the carotenoid content in RT, but significantly lowered β-carotene in YT and also the contents of total polyphenol and vitamin C in both cultivars. Lyophilisation lowered the carotenoid content in RT but not in YT; in contrast, the total polyphenol content was preserved in RT but lowered in YT, and the vitamin C content was not affected in both cultivars. These results provide new data on the effect of thermal processing and lyophilisation on the content of the three main families of micronutrients in red and yellow tomatoes.     

Analysis of carotenoids with emphasis on 9-cis β-carotene in vegetables and fruits commonly consumed in Israel

Recent epidemiological studies have directed the attention from the synthetic all-trans β-carotene to natural carotenoids predominant in fruits and vegetables as possible active ingredients for prevention of cancer and cardiovascular diseases. Seventeen fruits and 17 vegetables commonly consumed in Israel and the β-car-otene-rich alga, Dunaliella bardawil, were analysed for their content of carotenoids with emphasis on 9-cis β-carotene by reversed-phase, 3D photodiode array HPLC. Fourteen carotenoids were eluted in order of decreasing polarity, from polar oxycarotenoids to lipophilic hydrocarbons, and quantified in μg carotenoid per gram freeze-dried plant sample. The richest sources of total carotenoids (>100μg/g dry weight) in Israeli fruits were pittango, mango and papaya while, in vegetables, the predominant types were carrot, dill, parsley, tomato, lettuce, sweet potato and red pepper. Red fruits and vegetables contained mainly lycopene. Yellow and orange fruits and vegetables had high contents of hydrocarbon carotenes with substantial levels of cryptoxanthins and xanthophylls. The green vegetables had high contents of both xanthophylls and hydrocarbon carotenes. Relatively high ratios (9-cis to all-trans β-carotene) of above 0.2 g/g were noted in sweet potato, papaya, parsley, lettuce, dill, apricot, pepper, prune and pumpkin, compared to the high ratio of 9-cis to all-trans β-carotene in the alga Dunaliella (~ 1.0 g/g). The high content of 9-cis β-carotene in certain fruits and vegetables and the wide variety of carotenoids and stereoisomers of carotenoids in all plants should shift nutritional and medical attention from the synthetic all-trans β-carotene toward natural carotenoids as potential candidates for chemoprevention.     

EFFECT OF GAMMA IRRADIATION ON ISOMERIZATION OF β-CAROTENE IN SWEET POTATO1

Cured Georgia Reds, sweet potato roots, were irradiated using ⁶⁰Co source for 500 Krad dose. HPLC analyses of tissue extracts indicated that irradiation did not lead to isomerization of all-trans-β-carotene. Greater than 97% of the total β-carotene was in the all-trans form. Cis isomers of β-carotene have lower provitamin A activities than all-trans-β-carotene. Since they were not produced with γ-irradiation, this process did not decrease provitamin A due to isomerization. Thus, irradiation of sweet potatoes can be used without significant changes in the provitamin A content.     

Nutrition-sensitive agriculture – a South African perspective

As environmental and social sustainability becomes more urgent, and the resilience of the industrial food system is under threat, addressing nutrition through food systems must go hand in hand with restructuring these systems for greater resilience. South Africa is a middle-income country with a highly dualistic agro-food system, dealing with the burden of undernutrition, diet-related chronic diseases and widespread micronutrient malnutrition. In South Africa, agriculture must maintain national food security while contributing to improving household food security through employment and production for own consumption; and providing access to a more diverse range of safe and quality foods at affordable prices. Agricultural activities can contribute to improved nutrition, if implemented in conjunction with direct nutrition interventions. This study gives an overview of the nutritional status of the South African population, and the history and current operations of the agro-food system. It identifies entry points for nutrition-sensitive agriculture (NSA) to begin to address food and nutrition security challenges. Case studies were identified using grey literature. With few exceptions, these cases were not NSA initiatives per se, yet demonstrated efforts that could inform actions to strengthen the nutrition-sensitivity of the South African food system. NSA is not an all-encompassing solution to food and nutrition insecurity in South Africa, but offers a way of strengthening the nutrition-sensitivity of agricultural initiatives. Viable entry points include linking small scale production and nutrition education; combining low external input farming and nutrition education; strengthening alternative marketing channels and local food economies; monitoring food prices; and developing appropriate governance and institutional arrangements.     

Comparative study on chemical composition,polyphenols, flavonoids,carotenoids and antioxidant activities of various cultivars of sweet potato

Chemical composition, polyphenols, flavonoids, carotenoids and antioxidant activities of twenty-five cultivars of sweet potato were investigated. Starch, crude protein, crude fat, total dietary fibre, reducing sugar and ash contents ranged between 51.88–69.21, 2.36–7.79, 0.24–1.11, 5.02–14.35, 1.07–9.78 and 1.95–4.29 g per 100 g dry weight (DW), respectively. Cultivars of Longshu, Pushu 32 and Qinshu No.7 (Shanxi province) displayed the highest values in total polyphenol contents (9.38, 9.11 and 8.76 mg GAE per g DW, respectively), Huangmeigui showed higher flavonoids content (2.54 mg RE per g DW), Xiangshu presented higher anthocyanin content (1.02 mg per g DW), whereas Pushu 32 had the highest β-carotene content (208.11 μg per g DW). Strong significant positive correlations were presented between antioxidant activities and total polyphenol and flavonoid contents, indicating that polyphenols and flavonoids are essential antioxidants in sweet potatoes. Among all cultivars, Pushu 32 presented the highest grey relational grade (GRG) value (0.7811), suggesting its importance as a healthy diet.