Processing Techniques to Reduce Toxicity and Antinutrients of Cassava for Use as a Staple Food

ABSTRACT: Cassava is a valuable source of food for developing countries, but it contains highly toxic cyanogen compounds and antinutrients. Cyanogens are found in 3 forms in cassava: cyanogenic glucoside (95% linamarin and 5% lotaustratin), cyanohydrins, and free cyanide. Different processing techniques exist to remove cyanogens and their effectiveness depends on the processing steps and the sequence utilized, and it often is time‐dependent. Pounding or crushing is the most effective for cyanogenic glucoside removal because it ruptures cell compartments, thus allowing direct contact between linamarin and the enzyme linamarase that catalyzes the hydrolytic breakdown. Crushing and sun‐drying cassava roots made into flour removes 96% to 99% of total cyanogens, whereas soaking and sun‐drying into lafun or fufu, or soaking and fermenting and roasting into gari or farina, removes about 98% of cyanogens. For cassava leaves, which have 10 times more cyanogens than roots, pounding and boiling in water is an efficient process to remove about 99% of cyanogens. Other strategies to reduce toxicity include development of low‐cyanogen cassava varieties and cassava transgenic lines with accelerated cyanogenesis during processing. Although phytate and polyphenols have antioxidant properties, they interfere with digestion and uptake of nutrients. Fermentation and oven‐drying are efficient processing methods to remove phytate (85.6%) and polyphenols (52%), respectively, from cassava roots. Sun‐drying the leaves, with or without prior steaming or shredding, removes about 60% phytate. Cassava is a nutritionally strategic famine crop for developing countries and, therefore, reducing its toxicity and improving its nutritional value is crucial.     

Physico‐functional and antioxidant properties of purple‐flesh sweet potato flours as affected by extrusion and drum‐drying treatments

Effects of extrusion and drum‐drying treatments on physico‐functional and antioxidant properties of flours prepared from purple‐flesh sweet potato were evaluated. Extrusion variables were feed moisture contents (MC; 10%, 13%, 16%) and screw speeds (SS; 250, 325, 400 r.p.m.), whereas drum‐drying was done at 120, 130 or 140 °C. Effects of MC were generally greater than SS on flour properties. Extruded flours showed higher water absorption and water solubility indices compared with control nonextruded flours. Regardless of SS, total phenolic content and antioxidant activities (DPPH and ABTS) of flours processed at 10% MC were significantly higher than those at 13% and 16%. Both extruded and drum‐dried flours exhibited no peak viscosity, indicating complete gelatinisation of starch. Maximum phenolic content and antioxidant activities of drum‐dried flours were obtained at 140 °C. Although drum‐dried flours had higher antioxidant capacity than extruded flours, both flours could potentially be used as food ingredients.     

Effect of Processing on Anti-nutritional Factors of Red Kidney Bean (Phaseolus vulgaris) Grains

The effect of different processing methods (soaking in water or solutions of sodium bicarbonate, citric acid, soaking plus cooking, and germination) on anti-nutritional factors (phytic acid, total polyphenols, tannins, and hydrocyanic acid) of red kidney bean was studied. The anti-nutritional factors were reduced significantly (P < 0.001) with processing techniques. Cyanide contents were most effectively (25%) reduced by cooking after soaking in sodium bicarbonate solution, followed by germination. The most drastic effect was noted on tannin contents. Cooking after soaking in either citric acid or sodium bicarbonate solutions almost eliminated it. However, simple soaking in water did not result in any reduction in tannin contents. Reduction in total polyphenols was 78.7% with cooking after soaking in sodium bicarbonate solution. Phytic acid contents were reduced only with germination treatment (42.6%), while the other treatments did not bring about any large reduction.     

Nutritional Quality of Drum-processed and Extruded Composite Supplementary Foods

ABSTRACT: This study was conducted to evaluate the nutritional quality of ready‐to‐eat composite foods intended for supplementary feeding of preschool age children in Tanzania. Four supplementary foods, namely, corn‐bean‐sardine meal (CBSM), bean meal (BM), sorghum‐bean‐sardine meal (SBSM), and rice‐bean‐sardine meal (RBSM) were formulated according to the FAO/WHO/UNU guidelines. The food mixtures were extruded, drum‐processed, and cooked conventionally in the traditional way. Cooking doneness was evaluated by percent starch gelatinization and residual urease activity; biological qualities—true protein digestibility and growth performance—were evaluated using Sprague Dawley weanling rats. Efficiency in destroying phytohemagglutinins and the antinutritional factors, trypsin, chymotrypsin, and α‐amylase inhibitors, were also evaluated. Results of the study showed that starch gelatinization and residual urease activity were not significantly different (P > 0.05) between the extruded and drum‐processed diets. Relative to conventional cooking, starch gelatinization was 95% to 100% in extruded and 90% to 100% in drum‐processed products. Inactivation of urease activity ranged from 93% to 100% in extruded and 83% to 100% in drum‐processed diets. The true protein digestibilities were significantly (P≥ 0.05) higher when extruded foods, compared with drum‐processed and conventionally cooked foods, were fed to experimental animals. Animals fed extruded products gained more weight relative to those fed drum‐processed and conventionally cooked foods. Destruction of phytohemagglutinins ranged between 91% to 97% in extruded and between 90% to 95% in the conventionally cooked and drum‐processed foods. Extrusion, drum processing, and conventional cooking also resulted in significant destruction of the antinutritional factors trypsin, chymotrypsin, and a‐amylase inhibitors. These results suggest that extrusion and drum processing of cereal‐bean‐sardine composite foods result in products meeting the required nutritional quality.     

Domestic processing effects on available carbohydrate content and starch digestibility of black grams (Vigna mungo) and chick peas (Cicer arietium)

Domestic processing effects on available carbohydrate contents and starch digestibility of black grams and chick peas were investigated. The food legumes were soaked in tap water and alkaline solution of sodium bicarbonate at 30 and 100 °C for 1–2 h before cooking under pressure. Total soluble sugars, reducing sugars and starch contents of black grams and chick peas were 9.64% and 9.83%, 0.78% and 0.83%, 43.0% and 44.3%, respectively. All these available carbohydrate contents of black grams and chick peas were reduced to various extents as a result of soaking and cooking. At 30 °C, 4.46% of total soluble sugars, 3.84% of reducing sugars and 6.86% of starch contents were reduced on soaking the black grams in tap water for 1 h. Available carbohydrate contents were further reduced when soaking time and temperature of the food legumes was increased before cooking. About 3.43–25.0% of total soluble sugars and 4.26–22.7% of starch contents were lost on soaking black grams and chick peas in tap water and sodium bicarbonate solution. Maximum amounts of total soluble sugars (28.5–59.6%) and starch contents (29.9–67.4%) were lost on cooking the water- and alkali-soaked food legumes. However, these losses were comparatively less with the water soaking process. Besides these losses, starch digestibilities of black grams and chick peas were markedly improved as a result of cooking. However, no appreciable improvement in the starch digestibility was observed after soaking these food legumes in water or alkaline solution.     

Effect of processing on available carbohydrate content and starch digestibility of kidney beans (Phaseolus vulgaris L.)

The effects of different soaking and cooking methods were investigated on available carbohydrate content and starch digestibility of red and white kidney beans. Total soluble sugars, reducing sugars, non-reducing sugars and starch contents of red and white kidney beans were 9.95 and 11.3%, 0.82 and 0.96%, 9.13 and 10.3%, and 44.4 and 47.8%, respectively. All these available carbohydrate components decreased to various extents as a result of soaking and cooking. From 2.51 to 13.6% and 7.03 to 28.0% of total soluble sugars were lost on soaking kidney beans in tap water and sodium bicarbonate solution, respectively. However, losses in total soluble sugars were maximum (19.9–60.9%) on cooking pre-soaked kidney beans. Losses in starch contents were 4.27 to 24.7% and 30.4 to 70.7% as a result of the soaking and cooking processes, respectively. Besides these losses, starch digestibility of kidney beans was also markedly improved as a result of cooking. However, no appreciable improvement in starch digestibility was observed after soaking kidney beans in water or alkaline solution.     

In vitro fermentability and antioxidant capacity of the indigestible fraction of cooked black beans (Phaseolus vulgaris L.), lentils (Lens culinaris L.) and chickpeas (Cicer arietinum L.)

BACKGROUND: Pulses represent an important source of protein, as well as digestible and indigestible carbohydrates. Little information is available on the indigestible carbohydrates and antioxidant capacity of legume seeds. The cooked seeds of three pulses (black bean, chickpea and lentil) were evaluated for their indigestible fraction (IF), polyphenols content, antioxidant capacity and in vitro fermentability, including short‐chain fatty acid production. RESULTS: The insoluble indigestible fraction (IIF) was higher than the soluble counterpart (soluble indigestible fraction, SIF). The SIF value was highest in black beans, while no difference was observed between chickpeas and lentils. Black beans and lentils had higher polyphenols content than chickpeas. The IF of black beans exhibited the lowest and chickpeas the highest associated polyphenols content. Condensed tannins were retained to some extent in the IF that exhibited significant antioxidant capacity. The total IF of the three pulses produced short chain fatty acids (SCFA) after 24 h of in vitro fermentation by human colonic microflora. IF from black bean and lentil were best substrates for the fermentative production of butyric acid. CONCLUSIONS: It is concluded that the IF of pulses might be an important source of bioactive compounds. Copyright © 2010 Society of Chemical Industry     

Oxidation of Starch by Thermochemical Processing

The oxidation of starches of different amylose content with several oxidants has been investigated to maximize carboxyl content, increase water solubility and give products with new and novel properties. Methods of preparation studied were ambient-batch, jet cooking, jet cooking-drum drying, and drum drying alone. Other variables evaluated were reaction pH, jet cooking temperature, and oxidant concentration. Hypochlorite was the most effective oxidant and gave the highest carboxyl content in all preparation methods. Oxidized starches prepared by jet cooking and/or drum drying were of low viscosity and water soluble. SEM's of commercial oxidized starch showed intact granular structure, whereas samples prepared by instantaneous high temperature procedures showed complete gelatinization. Gel permeation chromatography showed structural depolymerization of the starches when high temperature processing was used. Copper binding capacity was evaluated on selected samples.     

不同干燥工艺对鲜玉米粉品质及风味的影响

本文研究了煮后烘干、炒制和冻干加工对鲜玉米粉的基本成分、抗氧化性能和香气成分影响。结果表明:不同干燥工艺鲜玉米粉的淀粉、总糖、总黄酮和总酚含量差异显著(P<0.05),冷冻干燥鲜玉米粉总黄酮和总酚含量最高,分别为3.45和3.96 mg/g。冷冻干燥、煮后烘干的鲜玉米粉对DPPH自由基的清除率分别为60.5%、50.8%,对·OH的清除率分别为46.8%和39.6%。运用固相微萃取-气相色谱-质谱联用对鲜玉米粒和3种干燥工艺的鲜玉米粒的香气物质进行分析,共鉴定出79种挥发性物质,分别为醇类3种、醛类11种、酮类8种、烃类24种、酯类8种、杂环类25种。含苯环类芳香族化合物是鲜玉米的主体风味化合物。综合分析,冷冻干燥和煮后烘干的鲜玉米粒抗氧化能力较高,对于鲜玉米芳香族化合物也有较好保留。     

Effects of different cooking methods on some chemical and sensory properties of Galega kale

Kale (Brassica oleracea L. var. acephala) is rich in bioactive phytochemicals such as phenolic compounds and vitamins. However, cooking the plants can cause important changes in composition. The objective of this study was to investigate the effect of some domestic cooking processes (boiling, steaming, microwaving and pressure cooking) on several quality parameters of Galega kale. Boiling had the strongest effect on the antioxidant capacity (the IC₅₀ was four times higher than in the fresh sample), total phenolics (losses of 76.4–77.9%) and colour (ΔE = 17.79–19.12). Microwaving caused the greatest loss of soluble solids (80.8–82.2%). Steaming seems to be the best method for retaining the nutrient and antioxidant capacity of kale (100% ash, 71–77.5% soluble solids, 100% antioxidant capacity, 67–71% total phenolics, 62–71% chlorophyll). However, steamed kale was awarded the lowest sensory scores, indicating the difficulty in reconciling nutritional value and sensorial quality. Use of discriminant statistical techniques enabled the classification of 100% of samples.     

The impact of cooking method on the phenolic composition,total antioxidant activity and starch digestibility of rice (Oryza sativa L.)

This study investigated changes in the phenolic composition, total antioxidant activity (TAA) and starch digestibility in white and brown rice due to three different cooking procedures, and subsequent reheating of cooked rice after storage. Among the analyzed samples, brown rice showed the highest TAA and phenolic content (622.5 mg/kg DW). All cooking methods resulted in significant decrease of phenolic content and TAA of rice (p < 0.05). The greatest loss was observed after processing in rice cooker, which reduced phenolic content of both brown and polished rice by ～30% and ABTS radical‐scavenging activity by 20 and 28%, respectively. In general, the levels of polyphenols and TAA of cooked rice tended to further decline after storage and reheating, but to a much lesser extent when rice was prepared using microwaves. The application of in vitro digestion system disclosed that the microwave cooking resulted in the highest starch digestibility among cooking methods used.

Practical applications

Rice is one of the most commonly consumed staple foods worldwide. Scientific and epidemiological studies have showed that their phytochemicals exhibit antioxidant, anti‐inflammatory, antihypertensive and chemopreventive effects. Therefore, their high consumption, easy availability throughout the year and use as an additive to meat and high‐fat foods may make rice, especially in the form of whole grains, potentially important chemopreventive component of the diet. The appropriate cooking procedure of rice is crucial for preservation of bioactive compounds as well as digestion of starch and thus duration of the glycemic response. Preferably, this study is focused on the evaluation of the effect of cooking methods on the health‐related quality of rice. The results provide practical advice that the consumption of freshly cooked rice ensures its highest nutritional quality, while rice microwaving is recommended both when cooked rice will be reheated after storage (e.g., in restaurants) and accelerated starch digestion is in favor.     

EFFECT OF PROCESSING TREATMENTS ON NUTRITIONAL AND ANTINUTRITIONAL CONTENTS OF GREEN GRAM

High‐yielding varieties of green gram (Vigna radiata L.), namely Asha and MH1K‐25 contained a significant amount of antinutrients. Various processing and cooking methods, namely soaking, dehulling, ordinary cooking, pressure cooking and sprouting, decreased the level of antinutrients and improved in vitro digestibility of protein and in vitro availability of calcium, iron and zinc observed. The beneficial effect was more pronounced with pressure‐cooked and soaked seeds followed by ordinary cooking, sprouting (24 h), dehulling and soaking in both cultivars. A significant increase in in vitro protein digestibility (34–35%), in vitro availability of Ca (59–61%), Fe (52–56%) and Zn (62–67%) may be ascribed to the reduced content of phytic acid (35–39%), polyphenols (41–42%) and trypsin inhibitor activity (69–70%). Pressure cooking was the most effective treatment in improving the nutritional quality of green gram.     

Effect of variety and processing on nutrients and certain anti-nutrients in field peas (Pisum sativum)

The effect of variety and processing (soaking, cooking and dehulling) on nutrients and anti-nutrients in field peas (Pisum sativum) was investigated. Analysis of variance showed that variety had a significant effect on crude protein, starch, ash, soluble dietary fibre (SDF), insoluble dietary fibre (IDF), total dietary fibre (TDF), trypsin inhibitor activity (TIA), minerals, phytic acid, sucrose and oligosaccharides. Soaking and cooking increased protein content, IDF, TDF, Ca, Cu, Mn and P in peas whereas ash content, Fe, K, Mg, Zn, sucrose and oligosaccharides were reduced. TIA was increased by soaking but reduced by cooking. Cooking was more effective than soaking in reducing oligosaccharides. Dehulling increased crude protein, starch, K, P, phytic acid, stachyose and verbascose content but reduced SDF, IDF, TDF, Ca, Cu, Fe, Mg and Mn.     

Comparison of composition and antioxidant capacity of some cereals and pseudocereals

Polyphenols, phenolic acids, fibres and antioxidant capacity were determined in water, acetone and methanol extracts of buckwheat, rice, soybean, quinoa and 3 amaranth cultivars. Their antioxidant activities were comparatively assessed by total radical‐trapping antioxidative potential (TRAP), ferric ion‐reducing antioxidant power (FRAP), cupric‐reducing antioxidant capacity (CUPRAC) and nitric oxide (NO^?) assays, which comprised of contributions from polyphenols and phenolic acids (especially from the most abundant ferulic acid). The correlation coefficients between polyphenols and antioxidant activities of cereal and pseudocereal methanol extracts with FRAP, NO^?, CUPRAC and TRAP were 0.99, 0.97, 0.96 and 0.77, respectively. The weakest correlation was with dietary fibres, an average one exhibited with tannins and marked correlation was shown with the phenolics. All the applied methods have shown that pseudocereals have higher antioxidant activity than some cereals (rice and buckwheat) and can be successfully replaced by cereals in case of allergy.     

Bioaccessibility and antioxidant activity of phenolic compounds in cooked pulses

The aim of this study was to evaluate the bioaccessibility of polyphenols and antioxidant activity in cooked pulses and to study the effect of cooking on their total phenolic content (TPC) and antioxidant capacity. Cooked faba beans showed the highest TPC, followed by soybeans and lentils or peas. TPC ranged from 10.4 ± 0.2 to 52.9 ± 0.3 mg/100 g and was positively correlated with antioxidant activity. Cooking resulted in increased TPC and antioxidant activity of the methanolic extracts, caused by cell disruption and improved extraction of polyphenols. Although polyphenols were lost in the cooking water, boiled legumes had more polyphenols than those resulting cooking broths. In vitro gastrointestinal digestion resulted in increased TPC and antioxidant capacity of the extracts. Soybeans showed the highest amount of bioaccessible polyphenols. The release of phenolics from cooked legumes was mainly achieved during the intestinal phase. Literature data may underestimate the TPC and antioxidant capacity of pulses.     

樱桃番茄果脯糖煮液废水的回用工艺及其对果脯品质的影响

目的:研究樱桃番茄果脯糖煮液废水的降黏回用工艺及其对果脯品质的影响。方法:对比6种降黏剂,以运动黏度和浊度为指标,确定降黏条件,并对比回用液的渗糖速率,建立废水降黏回用工艺。测定不同糖煮液腌渍果脯的营养成分、抗氧化能力和感官风味,评价回用工艺对樱桃番茄果脯品质的影响。结果:糖煮液废水经真空浓缩后回用,对果脯的脂溶性营养物质、抗氧化能力和感官风味有显著影响。最终选择皂土(添加量0.12%)作为废液的降黏剂,确定降黏工艺;回用液腌渍果脯的水溶性营养物质、抗氧化能力、游离氨基酸含量(3.499%)、挥发性风味物质含量(1463.737μg/kg)、樱桃番茄特征挥发性物质含量(265.349μg/kg)和整体感官评价值(77.00)均比新鲜糖水(约50°Bx)组果脯更高(P<0.05),且其脂溶性营养物质间无显著性差异。结论:糖煮液废水的回用工艺可提高加工果脯的营养成分、抗氧化性和感官风味。     

The antioxidant capacity and polyphenol content of organic and conventional retail vegetables after domestic cooking

Vegetable consumption is associated with health benefits. Organic foods are thought to have higher contents of antioxidant substances. The objective of this work is to quantify soluble and hydrolyzable polyphenols, ascorbic acid, and the antioxidant capacity of fresh conventional and organic retail vegetables (potato, carrot, onion, broccoli, and white cabbage) while evaluating the effect of boiling, microwaving, and steaming on these parameters. The recovery rate for soluble and hydrolyzable polyphenols was variable according to the vegetable analyzed. However, soluble polyphenols resulted in lower recovery rates than did hydrolyzable phenolics after cooking. Organic vegetables showed higher sensitivity to heat processing than did conventionally grown vegetables. In general, cooking was found to lead to reductions in the antioxidant capacity for most vegetables, with small differences between the cooking methods applied. Even with the alterations in their content, polyphenols showed a positive correlation with antioxidant capacity in raw and cooked vegetables from both types of agriculture.     

Berry fruits-enriched pasta: effect of processing and in vitro digestion on phenolics and its antioxidant activity,bioaccessibility and potential bioavailability

Pasta samples were made by substituting wheat flour (2.5% and 7.5%) for lyophilised raspberry, boysenberry, and redcurrant and blackcurrant. Total polyphenol content showed minimum variation during processing while anthocyanins presented high degradation. In general, the first minutes of cooking showed the major detrimental effect on antioxidant activity. In vitro starch hydrolysis showed the lowest value with the addition of raspberries and boysenberries. During simulated digestion, polyphenols were released from pasta matrix reaching a 2.3- to 4.3-fold increase in bioaccessible polyphenols. Likewise, values observed for reducing power and free radical scavenging activity ranged from a 0.7- to 2.0-fold and 1.6- to 6.8-fold increase in relation to cooked pasta, respectively. In addition, ≈40% of dialysability was observed for scavenging activity. In conclusion, enrichment of pasta with fine fruits is an effective tool to obtain a product with enhanced antioxidant potential.     

Replacement of buckwheat by black sorghum flour on soba-type noodles

Incorporation of black sorghum flour containing high levels of polyphenols and slowly digestible starch could provide opportunity to enhance nutritional functionality of noodles. Soba-type noodles were prepared based on a typical wheat-buckwheat (65:35) formulation by replacement of buckwheat flour with black sorghum flour at 0%, 25%, 50%, 75% and 100%. Noodle colour, texture, total phenolics, antioxidant capacity, in vitro starch digestibility and sensory acceptability were evaluated. Increasing the addition of black sorghum flour significantly (P < 0.05) decreased the firmness (g) in noodles and imparted a darker colour but increased total polyphenolics and antioxidant capacity. Significantly (P < 0.05) lower rapidly digestible starch and higher resistant starch was found in noodles with >50% replacement with black sorghum flour. Overall acceptability of noodles showed preference for noodles containing 25%–75% black sorghum flour. This study demonstrates the potential of using black sorghum as a novel functional food ingredient in noodle manufacturing.     

Processing and cooking effects on chemical,nutritional and functional properties of pasta obtained from selected emmer genotypes

BACKGROUND: Emmer wheat (T. turgidum ssp. dicoccum Schrank) is an old Mediterranean crop grown for centuries and progressively replaced with durum wheat. Although most of its supposed nutritional properties have not yet been scientifically proven, emmer seems to be appreciated for its content of dietary fibre, resistant starch (RS) and antioxidant compounds. The aim of this work was to evaluate the profiles of dietary fibre, starch and antioxidant compounds in raw materials and in semolina of 13 selected emmer lines and their parents (a durum wheat cultivar and an old T. turgidum dicoccum population). Moreover, the cooking effect on functional properties and total antioxidant capacity (TAC) of pasta derived from emmer lines and the in vivo effect of pasta on postprandial glucose response were determined. RESULTS: Processing and cooking affected the dietary fibre content of pasta: the insoluble dietary fibre content was increased, while a slight loss of soluble dietary fibre was observed. Cooking also resulted in a noteworthy increase in amylose and RS content. The antioxidant compounds (i.e., tocols and carotenoids) as well as TAC decreased dramatically after cooking. Pasta obtained with an emmer line significantly lowered the glycaemic index, strengthening the concept of pasta product as a source of functional components in the habitual diet. CONCLUSIONS: The results showed that emmer semolina is suitable for the preparation of pasta with good organoleptic quality and represents a source of RS and fibre, but processing and cooking negatively affected the amount of antioxidant compounds detected in the wholemeal. Copyright © 2008 Society of Chemical Industry