Ana María Estévez

Cactus pear fruit: A new source for a natural sweetener

The use of cactus pear ( Opuntia ficus indica L.) to obtain a new natural liquid sweetener was studied. The juice of the fruit (16.5 ° Brix) was clarified with enzymes, treated with active carbon to take out the color and vacuum concentrated to obtain a 60 °Brix syrup or liquid sweetener. Physical and chemical characteristics determined included: aw; reducing sugars (as inverted sugar); glucose (%); ash content (%); sugar composition by TLC; OD (420 nm) and Y, x, y chromaticity coordinates; viscosity (cps) and density (g ml-1). Sensory analyses to determine the relative sweetness were also conducted. Cactus pear syrup contained 52.38% reducing sugar. The syrup had a pH of 4.31, a viscosity of 27.05 cps, an Aw of 0.83, a density of 1.2900 g ml-1, an acidity (as citric acid) of 0.74% and an ash content of 1.4%. Compared with traditional sweeteners such as fructose and glucose syrup, the acidity was greater than that of HFCS (high fructose corn syrup) of 0.035%, and the ash values were considered a little high compared to glucose syrup which is 1.0%; these disparities can be attributed to the different processing conditions employed. Sensory evaluation revealed the same relative sweetness for cactus pear syrup and glucose, but lower than fructose; cactus pear syrup had a relative sweetness value of 67 with respect to sucrose (100).

Effect of processing on some chemical and nutritional characteristics of pre-cooked and dehydrated legumes

The effect of processing on chemical composition and protein quality of three legumes was studied. The species analyzed were beans (Phaseolus vulgaris), Tórtola and Coscorrón varieties; lentils (Lens esculenta), Laird variety; and chick peas (Cicer arietinum), California-INIA variety. The legumes were soaked in a solution of Na2 EDTA at 0.03% for 16 h and cooked for a predetermined period for each species. They were dried in a tray drier with cross currents of air flowing at a speed of 10 m/min until the residual mositure content was 8%. The water activity in the resulting products ranged from 0.574 to 0.587, thus completely assurring no microbial activity. No important changes were observed in the legumes protein, fat, or fibre contents after processing. The soaking solution was effective in reducing the phytic acid content from 2.99 to 1.64 mg/100 g in the Tórtola beans, which had the highest acid value prior processing. In all the species the heat treatment reduced the activity of the trypsin inhibitors by at least 50%. Cooking and drying significantly increased protein digestibility in all the legumes studied, with chick peas showing the most dramatic increase: from 54.7% pre-processing to 94.9% post-processing. With regard to Net Protein Ratio (NPR), chick peas had a value of 4.03, followed by Tórtola beans (3.29), Coscorrón (3.09) and lentils (2.61). The NPR value for the casein diet was 4.20.

Cereal and nut bars, nutritional quality and storage stability

Six snack-type bars were manufactured, to contain oat and wheat germ and two different walnut levels, agglutinated with natural sweeteners and fats. Two bars also contained toasted amaranth with brown sugar cover and wheat extrudate, while two others, contained puffed instead of toasted amaranth. Water activity (Aw) and moisture were determined in the manufactured products. Quality and sensory evaluation and proximate analysis were carried out on the bars containing highest levels of walnuts (18%). The caloric contribution of the bars was computed by Atwater methods. The nutritional quality of the bars was determined by means of the Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR), and the results were used to obtain relative PER and relative NPR. Samples of the latter bars were kept under accelerated storage for 15 days at 37 °C and analyzed every 5 days to determine their Aw, moisture, peroxide and sensory acceptability. The drying time for the cereal — and walnut — based bars was 45 min at 120 °C. All bars presented a good fiber supply and the CN1 bar, containing only oat, wheat germ and walnut, had the greatest protein content. In the sensory evaluation, the walnut level with the greatest preference was 18%. PER and NPR values of the bars did not differ significantly showing values approximately 86% that of the casein value. During storage, the moisture and Aw decreased in all the bars. Peroxides remained within the acceptable ranges; acceptability based on sensory evaluation remained best in the bar with toasted amaranth. Walnuts can successfully be used in the manufacture of snack bars as these offer good nutritional and sensory quality and remain stable in storage.

Physical and rheological characterization of seeds of three legume trees

El algarrobo chileno (Prosopis chilensis (Mol) Stuntz), la tara (Caesalpinea spinosa (Mol) Kuntze) y la acacia de las tres espinas (Gleditsia triacanthos L) ofrecen un interesante potencial para promover el desarrollo de las zonas aridas. En el endosperma de sus semillas existe una goma del tipo galactomanano que posee propiedades viscosantes y estabilizadoras de emulsiones. Se realizo una investigacion para evaluar las caracteristicas fisicas de las vainas y semillas y las propiedades reologicas de las gomas de estas especies. Se estudiaron frutos de cinco ecotipos de algarrobo (Region de Coquimbo y Region Metropolitana), de tara (Region de Coquimbo) y de acacia de las tres espinas (Region Metropolitana). Se midieron las dimensiones de las vainas, numero de semillas/ vaina, peso de semillas, rendimiento y parametros de color de cotiledon y goma y las propiedades reologicas de las gomas extraidas. Las gomas se extrajeron manualmente y se secaron a 50 oQ En algarrobo, las semillas pesaron 0,04 g y el rendimiento de goma vario entre 25,5 y 31,5%. Las semillas de tara pesaron 0,14 g y las de acacia de las tres espinas 0,16 g, con un rendimiento de goma 31,0 y de 40,1% y respectivamente. Las gomas presentaron una alta luminosidad y contribucion del amarillo y baja contribucion de rojo. Las dispersiones, en todas las gomas estudiadas, presentaron un comportamiento no newtoniano del tipo Herschel-Bulkley, correspondiendo a un fluido inelastico, independiente del tiempo. La viscosidad aparente de la goma de algarrobo fluctuo entre 0,020 y 0,12, la de tara entre 0,06 y 1,3, y la de acacia de las tres espinas entre 0,034 y 0,08 Pa*s. Las gomas de estas especies tienen caracteristicas reologicas que permitirian su aplicacion en alimentos.

Cactus pear cladodes powders as a source of dietary fibre: purification and properties

Cactus pear cladodes of 2–3 years were used to obtain a natural purified dietary fibre and their physical, chemical and technological properties were determined. The effect of particle size and washing temperature on the technological properties was studied. Purification produces a decrease in green colour (a*) and an increase in total dietary fibre but reduces the total phenolic compounds, mainly when cladodes are washed at higher temperatures. Technological properties did not present changes in the water retention capacity (WRC), water adsorption capacity and cationic exchange capacity, but it did in swelling capacity (SC), oil absorption capacity, apparent density and setting density, which were influenced by the particle size of the cactus powders. The purified fibre shows a high WRC between 5.20 and 5.86 g g− 1 and a high SC (7.02–8.27 mL g− 1). Purified fibre with a particle size between 600 and 1200 μm, independent of the washing temperature had better insoluble to soluble dietary fibre ratio, total phenolic content and technological properties.

Optimization of secoisolariciresinol diglucoside extraction from flaxseed (Linum usitatissimum L.) and isolation by a simple HPLC-UV method

This research was conducted to develop and optimize a methodology to quantify the content of secoisolariciresinol diglucoside (SDG), the main vegetable lignan present in flaxseed. However, at the time of this work, commercial SDG was not available for standard use. Therefore, an effective method to obtain purified SDG from flaxseed was developed using chromatographic techniques. The SDG obtained was of approximately 97% purity. The methanol extraction time, alkali concentrations, and reaction temperature were optimized through a response surface methodology (RSM), and the optimal conditions established for the extractions were 47°C, 58 mmol L−1 sodium methoxide, and 24 h. This methodology was then applied to study the variation of SDG content in flaxseed from different cultivars. The SDG content in different varieties of flaxseed ranged from 10.8 to 17.9 mg g−1 in defatted flaxseed flour and from 6.0 to 10.9 mg g−1 in whole flaxseed.

Bioaccessibility of lignans from flaxseed (Linum usitatissimum L.) determined by single‐batch in vitro simulation of the digestive process

BACKGROUND Flaxseed is an important source of lignan secoisolariciresinol diglucoside (SDG) and its aglycone, secoisolariciresinol (SECO). These phenolic compounds can be metabolized to the mammalian lignans enterodiol (ED) and enterolactone (EL) by human intestinal microflora. Flaxseed lignans are known for their potential health benefits, which are attributed to their antioxidant and phytoestrogenic properties. The focus of this study was to determine the bioaccessibility of plant and mammalian lignans in whole flaxseed (WF) and flaxseed flour (FF) throughout the entire digestive process. Moreover, the metabolic activity of intestinal microflora was evaluated. RESULTS A single-batch in vitro simulation of the digestive process was performed, including fermentation by the intestinal microflora in the colon. Bioaccessibility was calculated as (free lignan)/(total lignan). In digested WF, the bioaccessibility values of SECO, ED and EL were 0.75%, 1.56% and 1.23%, respectively. Conversely, in digested FF, the bioaccessibility values of SDG, ED and EL were 2.06%, 2.72% and 1.04%, respectively. The anaerobic count and short-chain fatty acids indicate that bacteria survival and carbohydrate fermentation occurred. CONCLUSION The contents of both SDG and ED were significantly higher in digested FF than in digested WF. FF facilitated the action of intestinal bacteria to release SDG and metabolize ED.

Dietary fibre concentrate from Chilean algarrobo (Prosopis chilensis (Mol.) Stuntz) pods: Purification and characterization

Prosopis species are generally fast-growing, drought-resistant, nitrogen-fixing trees or shrubs. Fruits of Prosopis spp are indehiscent pods, where pericarp is formed by the epicarp, light brown in colour, and fibrous nature; the mesocarp known as pulp, which is rich in sugars; and the endocarp. The aim of this work was to obtain a fibre concentrate from the pods of Prosopis chilensis Mol. (Stuntz) and to determine the chemical, physical, and technological properties of the pod flour (PF) and of a fibre concentrate or pod purified flour (PPF). Acetone, ethanol, and water at different conditions of time and temperature were used in the purification process. PF showed 53.7 g/100 g of total sugar content, 4.2 g/100 g of reducing sugar content, 41.8 g/100 g of total dietary fibre, 35.8 g/100 g of insoluble fibre, and 6.0 g/100 g of soluble fibre content. The PPF has a total sugar content of 3.8 g/100 g, reducing sugar content of 2.2 g/100 g, total dietary fibre content of 80.8 g/100 g, insoluble fibre content of 75.1 g/100 g, and soluble fibre content of 5.7 g/100 g. The scanning electron microscopy analysis showed the existence of voids in the structure of PPF flour, which reveals the efficiency of the purification process with a high decrease in the total sugar content.