| 1. |
- Carrasco, Cristhian, et al.
(författare)
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Steam pretreatment and fermentation of the straw material "Paja Brava" using simultaneous saccharification and co-fermentation.
- 2011
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Ingår i: Journal of Bioscience and Bioengineering. - : Elsevier BV. - 1347-4421 .- 1389-1723. ; 111, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- Pretreatment, enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) of the South American straw material Paja Brava were investigated. Suitable process conditions for an SO(2)-catalyzed steam pretreatment of the material were determined and assessed by enzymatic digestibility of obtained fiber slurries for 72h at a water insoluble solids (WIS) content of 2%. The best pretreatment conditions obtained (200°C, 5min holding time and 2.5% SO(2)) gave an overall glucose yield following enzymatic hydrolysis of more than 90%, and a xylose yield of about 70%. Simultaneous saccharification and co-fermentation of glucose and xylose (SSCF) of the pretreated material using the xylose-fermenting strain Saccharomyces cerevisiae TMB3400 was examined at WIS contents between 5% and 10%. In agreement with previous studies on other materials, the overall ethanol yield and also the xylose conversion decreased somewhat with increasing WIS content in the SSCF. In batch SSCF, the xylose conversion obtained was almost 100% at 5% WIS content, but decreased to 69% at 10% WIS. The highest ethanol concentration obtained for a WIS content of 10% was about 40g/L, corresponding to a yield of 0.41g/g in a fed-batch SSCF. The Paja Brava material has previously been found difficult to hydrolyze in a dilute-acid process. However, the SSCF results obtained here show that similar sugar yields and fermentation performance can be expected from Paja Brava as from materials such as wheat straw, corn stover or sugarcane bagasse.
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| 2. |
- Penarrieta, Mauricio, et al.
(författare)
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Changes in phenolic antioxidants during chuno production (traditional Andean freeze and sun-dried potato)
- 2011
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Ingår i: Journal of Food Composition and Analysis. - : Elsevier BV. - 0889-1575. ; 24:4-5, s. 580-587
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Tidskriftsartikel (refereegranskat)abstract
- Total antioxidant capacity (TAC), total phenolic compounds (TPH), total flavonoids (TF) and the amounts of individual phenolic compounds were assessed in Bolivian potato cultivars (various Solanum species) before, during and after the traditional freezing and sun-drying of potatoes known as chunos. The TAC of chunos ranged from 0.4 to 2.7 mu mol Trolox equivalents/g dry matter using 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and from 0.7 to 3.0 according to the ferric reduction antioxidant power (FRAP). The values of TAC obtained using FRAP were about 70% lower after freeze-drying while they remained essentially constant when measured using ABTS. High-performance liquid chromatography showed the presence of epicatechin, chlorogenic acid, gallic acid, syringaldehyde and protocatechuic acid in both potato and chuno samples although the values were lower in the churl samples. The results suggest that the antioxidant capacity and the content of individual phenolics are somewhat decreased but far from eliminated during the process. Chuno can therefore still be considered an important source of antioxidants in the diet. (C) 2010 Elsevier Inc. All rights reserved.
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| 3. |
- Tejeda, Leslie
(författare)
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Antioxidants in Andean food and meals
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract The constant need to improve health and to prevent disease in Bolivia, especially in the Andean region with its extreme environmental conditions (high altitude and lower temperatures), motivated us to extend studies of antioxidant sources in foods and plants, since antioxidants are believed to have major health benefits. Spectrophotometric methods, such as ABTS (2, 2’- azinobis-3-ethylbenzotiazoline-6-sulfonic acid) and FRAP (ferric reduction antioxidant power), were used to evaluate antioxidant activity. Total polyphenolic content was evaluated by Folin-Ciocalteau reagent. Individual polyphenolic compounds were identified and quantified by reverse-phase HPLC. The ABTS method showed high antioxidant activity and high polyphenol content in hydrophilic and hydrophobic parts of quinoa (Chenopodium quinoa), and in canihua (Chenopidium pallidicaule), another Andean grain. In qentu (Rumex acetosella), the highest antioxidant content and polyphenolic content was found in the hydrophilic and hydrophobic parts. In chilca (Baccharis papillosa subsp. papillosa), a medicinal Andean plant, four phenolic compounds were reported: ermannine, isokamferine, drupanine and 5,7,5’,4’-tetrahydroxy-3-methoxyflavone. Highest antioxidant activity was found in 5,7,5’,4’-tetrahydroxy-3-methoxyflavone, followed by drupanine and ermannine. When Andean tubers such as white potato and freeze- and sun-dried potato called chuño (Solanum tuberosum) were compared with colored potato (Solanum stenotomum), slightly higher antioxidant content was found in colored potatoes, but polyphenolic content was similar in both cases. A partial correlation was found between botanical classification, based on morphological identification, and polyphenol composition in colored potatoes. For the ‘Ñojchjachaya’ cultivar, a strong correlation was found, with high levels of anthocyanidins. However, a correlation could be found between the ans gene clades, levels of anthocyanidins, and other polyphenols. The correlation between color and antioxidants in colored potatoes was confirmed. Antioxidant activity in processed food and meals may increase or decrease depending on the combination of individual food items, as well as in the cooking process. In some meals, antioxidant content was slightly higher than in other processed food; this was associated with higher fiber content. Antioxidant activity was evaluated in approximately 80 samples, comprising individual foods and meals. Based on the results, the conclusion was that antioxidant activity in individual foods is overestimated in comparison with processed food.
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| 4. |
- Tejeda, Leslie, et al.
(författare)
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Chemical composition, antioxidant capacity and content of phenolic compounds in meals collected in hospitals in Bolivia and Sweden
- 2012
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Ingår i: Nutrición Hospitalaria. - 1699-5198. ; 27:4, s. 1009-1016
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Forskningsöversikt (refereegranskat)abstract
- The objective of this study was to evaluate the proximal composition, as well as Total Antioxidant Capacity (TAC) and Total Phenols (TPH) in meals that represent a complex food matrix, from different hospitals in Bolivia and Sweden. Protein, fat, ash, dietary fiber and carbohydrate contents were measured in 29 samples: 20 from two Bolivian hospitals and 9 from the university hospital in Lund, Sweden. The antioxidant capacity was measured by three spectrophotometric methods: the ferric reducing antioxidant power (FRAP) method, the 2, 2'- azinobis-3-ethylbenzotiazoline-6-sulfonic acid (ABTS) method and Total Phenolic Compounds (TPH) using the Folin-Ciocalteu reagent. The results show that fat, protein, carbohydrate and dietary fiber in Bolivian and Swedish hospital meals are following internationally established recommendations. Regarding the main courses, TPH contents in both countries were in the same range. However, TAC and dietary fiber content were higher in Swedish meals than in Bolivian meals and the TAC was far lower, in both cases, in comparison with the value obtained from individual food items reported from literature. The results show that antioxidant levels can be easily overestimated by considering only individual uncooked ingredients. An interesting consideration is, the fiber content in the meals, which can be an important source of antioxidants and non-extractable phenolic compounds. (Nutr Hosp. 2012;27:1009-1016) DOI:10.3305/nh.2012.27.4.5849
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| 5. |
- Tejeda, Leslie, et al.
(författare)
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Relating genes in the biosynthesis of the polyphenol composition of Andean colored potato collection.
- 2014
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Ingår i: Food Science & Nutrition. - : Wiley. - 2048-7177. ; 2:1, s. 46-57
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to evaluate total antioxidant capacity (TAC), total phenolic content (TPH), and the identification of anthocyanidin and polyphenolic compounds in 13 colored potatoes collected from the Andean region of Bolivia, and understand how the chemical composition correlated with the botanical classification and molecular characterization of genes, ans (anthocyanidin synthase) and stan1 (Solanum tuberosum anthocyanidin synthase), associated with the synthesis of anthocyanidins. The results show the existence of a limited correlation between botanical classification, based on morphological identification and polyphenol composition. No association between genetic grouping of the ans and stan genes and botanical classification was found. However, it was possible to identify a correlation between the ans gene clades and the levels of anthocyanidins as well as of other polyphenols. Thus, this result confirms the concept that potato color can be used in the search for high polyphenol potato cultivars.
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