Barriers impairing mineral bioaccessibility and bioavailability in plant-based foods and the perspectives for food processing

Abstract

Plant-based foods gain more importance since they play a key role in sustainable, low-meat and healthy diets. In developing countries, these food products, especially legumes and cereals, are important staple foods. Nevertheless, the question arises on how efficient they are to deliver minerals and if it is useful to encourage their consumption to reduce the prevalence of mineral deficiencies? This review paper focuses on the discrepancy between the mineral content and the amount of minerals that can be released and absorbed from plant-based foods during human digestion which can be attributed to several inherent factors such as the presence of mineral antinutrients (phytic acid, polyphenols and dietary fiber) and physical barriers (surrounding macronutrients and cell wall). Further, this review paper summarizes the effects of different processing techniques (milling, soaking, dehulling, fermentation, germination and thermal processing) on mineral bioaccessibility and bioavailability of plant-based foods. The positive impact of these techniques mostly relies on the fact that antinutrients levels are reduced due to removal of fractions rich in antinutrients and/or due to their leaching into the processing liquid. Although processing can have a positive effect, it also can induce leaching out of minerals and a reduced mineral bioaccessibility and bioavailability.     

Influence of germination on the nutritional quality of Phaseolus vulgaris and Cajanus cajan

Germination is a method that can modify the presence of nutrients and antinutrients in legume seeds. In this study, the changes in trypsin inhibitors activity (TIA), phytic acid, tannins, ascorbic acid, thiamine, protein digestibility and minerals in germinated black beans (Phaseolus vulgaris L.), white beans (Phaseolus vulgaris L.) and pigeon beans (Cajanus cajan L. Millsp) were evaluated. The ungerminated grains were analysed as control. A significant decrease in the content of TIA of pigeon beans (19.2%), white beans (52.5%) and black beans (25%) was observed. The reduction of phytic acid was more than 40% for the three grains germinated; for the tannins, the reduction was of 14.3% for pigeon beans, 19% for black beans and 36.2% for white beans. Germination increased the protein digestibility in a 2-4% range, and also increased the ascorbic acid by 300% for white beans, by 33% for black beans and by 208% for pigeon beans. The thiamine content increased more than 26.7%. Germination affected the mineral content erratically, depending more on the grain and the type of mineral. These variations in the content of nutrients and antinutrients of the germinated grains are attributed to the joint effect of the germination and previous soaking the grains were subjected to.     

Effect of cooking on the composition of beans (Phaseolus vulgaris L.) and chickpeas (Cicer arietinum L.)

The effect of cooking on levels of nutrients and anti-nutritional factors in beans and chickpeas was investigated. Significant (p < 0.05) variation existed among the beans and chickpeas with respect to their crude protein, starch, soluble dietary fiber (SDF), insoluble dietary fiber (IDF), total dietary fiber (TDF), resistant starch (RS), trypsin inhibitor activity (TIA), mineral, phytic acid, tannin, sucrose and oligosaccharide (raffinose, stachyose and verbascose) contents. Cooking beans and chickpeas in water significantly increased protein, starch, SDF, IDF, TDF, Mn and P contents (on a dry weight basis), whereas reduced ash, K, Mg, TIA, tannin, sucrose and oligosaccharide contents were observed. Colored beans (black, cranberry, dark red kidney, pinto and small red bean) contained tannins, whereas little tannin in white-colored beans (great northern and white pea bean) and chickpeas (Desi and Kabuli type) was detected.     

Technology of removal of unwanted components of dry beans

Dry beans are one of the inexpensive sources of reasonable quality proteins, carbohydrates, vitamins, minerals, and fiber. Their underutilization has been attributed to the presence of several factors, such as proteinase inhibitors, flatus factors, tannins, phytates, phytohemagglutinins, and the beany flavor. Removal of these unwanted components promises improved utilization of dry beans for human food purposes. The current methodology of removing these factors includes several food processing techniques such as soaking, dry and moist heat treatment, filtration, germination, and fermentation. The commercial feasibility of these processes will be discussed. The current lack of knowledge about deleterious effects of the residual components (remaining after processing) will be addressed and the needs for the future will be discussed.     

Folate content in processed legume foods commonly consumed in Egypt

Industrial food processing and household cooking are reported to affect folate content. This study examined the effects of industrial and household processing methods on folate content in traditional Egyptian foods from faba beans (Vicia faba) and chickpeas (Cicer arietinum). Overnight soaking increased folate content by ∼40–60%. Industrial canning including soaking, blanching and retorting did not affect folate content (p = 0.11) in faba beans, but resulted in losses of ∼24% (p = 0.0005) in chickpeas. Germination increased folate content 0.4–2.4-fold. Household preparation increased the folate content in germinated faba bean soup (nabet soup) one-fold and in bean stew (foul) by 20% (p < 0.0001). After deep-frying of falafel balls made from soaked faba bean paste, losses of 10% (p = 0.2932) compared with the raw faba beans were observed. The folate content (fresh weight) in the traditional Egyptian foods foul and falafel and in the beans in nabet soup was 30 ± 2, 45 ± 2 and 56 ± 6 μg/100 g, respectively. The traditional Egyptian foods foul, falafel and nabet soup are good folate sources and techniques like germination and soaking, which increase the folate content, can therefore be recommended.     

The impact of processing on phytic acid,in vitro soluble iron and Phy/Fe molar ratio of faba bean (Vicia faba L.)

BACKGROUND: Faba bean is one of the important legumes in Asian countries. It is also a major source of micronutrients in many rural areas. Unfortunately, the bioavailability of iron from faba bean is low because it is present as an insoluble complex with food components such as phytic acid. The influence of soaking, germination and fermentation with the expectation of increasing the bioavailability of iron was investigated. RESULTS: Fermentation treatments were most effective in decreasing phytic acid (48–84%), followed by soaking at 10 °C after preheating (36–51%). Steeping faba beans for 24 h at 25 °C had the least effect on the removal of phytic acid (9–24%). With increased germination time at 30 °C, phytic acid progressively decreased from 9 to 69%. Most wet processing procedures, except soaking after wet preheating, caused losses of dry matter and iron (8–15%). In vitro iron solubility, as a percentage of total iron in soaked faba bean after dry preheating, was significantly higher than in raw faba bean (P < 0.05). Fermentation and germination did not have significant effects on the solubility of iron. CONCLUSION: The expected improvement of iron bioavailability levels due to lower phytic acid was not confirmed by increasing levels of in vitro soluble iron. Soaking, germination and fermentation can decrease phytic acid in faba bean. However, results from in vitro solubility measurement of iron showed little improvement of iron bioavailability in fermented and germinated faba beans over untreated raw faba beans (P < 0.05). It seems that componets of dietary fibre other than phytic acid are more important in binding iron. Probably, a complex association between dietary fibre and iron is the reason for the poor bioavailability of iron in faba bean. Copyright © 2009 Society of Chemical Industry     

Effects of Blanching, Soaking, and Cooking on the HCN Yields, Nitrogen, Ash, and Minerals of Lima Beans (Phaseolus lunatus)

Blanching, soaking, and cooking two cultivars of lima bean reduced the HCN concentrations to a safe level. Beans soaked for 12 hr had lower HCN levels than those soaked for 6 hr. Traditional processing was also effective in reducing the HCN concentration in the beans. The treatment of the beans also resulted in a reduction in ash, and the concentration of some minerals.     

In vitro Extractability of Calcium, Iron, and Zinc in Finger Millet and Kidney Beans During Processing

ABSTRACT: Finger millet ( Eleusine coracana ) and kidney beans ( Phaseolus vulgaris ) were processed by soaking, germination, autoclaving, and fermentation for incorporation into a complementary food for children. Extract-ability of calcium, iron, and zinc were determined by in vitro HCl-Pepsin and Pepsin-Pancreatin methods after each processing step. Germination significantly increased the in vitro extractability of these minerals, while soaking, autoclaving and fermentation showed a smaller or insignificant effect. Iron extractability was low in germinated, autoclaved and fermented millet, as determined by the pepsin-pancreatin method, but increased 6.8 times with addition of vitamin C. Phytic acid was reduced by 85 and 66% in finger millet and kidney beans, respectively, during the overall processing. These results show that various processing methods, especially germination, increase mineral extractability. Addition of vitamin C and mango could be used to enhance mineral extractabilities, thereby helping to alleviate micronutrient deficiencies in populations subsisting on these foods.     

萌发对芸豆酚类物质及抗氧化活性的影响

研究了萌发过程对黑芸豆、奶花芸豆、紫花芸豆中多酚、黄酮含量及抗氧活性的影响,并对多酚、黄酮含量及抗氧化能力做了相关性分析。结果表明:三种芸豆萌发（0⁶ d）后多酚、黄酮含量及抗氧化活性较未萌发的均显著降低（p<0.05）。且浸泡损失的多酚、黄酮高于萌发期间;黑芸豆萌发6 d后多酚、黄酮含量可能由于内切酶的作用开始增加。萌发期间,三种芸豆的DPPH·清除能力（DPPH）、ABTS+·清除能力（ABTS）、铁离子还原抗氧化能力（FRAP）、氧化自由基吸收能力（ORAC）均有降低趋势。多酚、黄酮含量与抗氧化能力极显著相关（p<0.01）,且多酚与ABTS值的相关性最高（r=0.955）。此外,黑芸豆的抗氧化能力萌发4 d后开始增加,萌发6 d时黑芸豆和奶花芸豆的ORAC值高于0 d。合适的萌发条件能更好的保留芸豆的生物活性物质。      

Distribution of Phosphorus and Phytate in Some Nigerian Varieties of Legumes and Some Effects of Processing

Phytate anion, total phosphorus (P), phytate-P, inorganic and residual P contents were determined in different varieties of cowpeas, lima beans and soybeans. The dry seeds were subjected to different processing methods which included cooking, autoclaving, soaking and germination. Germination and soaking were most effective in decreasing phytate contents while cooking and autoclaving only slightly altered total P, phytate and phytate-P contents in all varieties. Germination increased inorganic P contents but effected the highest percentage loss in residual organic P. Soybean contained considerable amounts of phytate anion and despite the reduction through processing, phytate content still exceeded the amount present in all varieties of raw lima beans.     

The influence of germination on the nutritional value of wheat, mung beans and chickpeas

The changes in nutrients during the germination of wheat, mung beans and chickpeas were investigated. Germination was performed under conditions commonly used in the household. The amount of water taken up during 4 days of germination varied from 159 g/100 g (chickpeas) to 450 g/100 g (mung beans). For all three seeds losses of dry matter and carbohydrates were observed. In wheat and mung beans, phytic acid was partially hydrolyzed. In mung beans, the total fat content decreased. Increases in the content of polyunsaturated fatty acids in wheat and of dietary fibre in wheat and mung beans were noted. At a constant level of crude protein, a measurable rise in limiting amino acids was observed in wheat and mung beans. Frequent watering during germination caused losses of Fe, between 9% and 21%, K (27% in chickpeas) and Cu (17% in chickpeas). Except for vitamin B6 in both legumes and vitamin B1 in chickpeas, accumulation of the vitamins under investigation (B1, B2, B6, C, E) was noted. Owing to these changes during germination, the nutritional value of the three seeds has been improved to various extents, most distinctly in wheat and least noticeably in chickpeas. Compared with other vegetables, sprouted seeds can be considered a valuable addition to the diet.     

Influence of natural and controlled fermentations on α-galactosides, antinutrients and protein digestibility of beans (Phaseolus vulgaris L.)

The influence of natural fermentation (NF) and controlled fermentation (CF) in diminishing the content of antinutrients, α‐galactosides and increments in in vitro protein digestibility was investigated. The dry bean (Phaseolus vulgaris) flour was the substrate used in this research study. A decrease in raffinose oligosaccharide, antinutritional components and pH was observed in both types of fermentation. The natural lactic fermentation of ground beans produced significant increase (P < 0.05) in protein digestibility. For all varieties of beans, raffinose concentration reduced significantly to an undetectable level after 96 h of NF. CF did not have any significant effect on the reduction of the α‐galactosides content of the flours during fermentation. NF is an inexpensive method by which consumers can obtain good‐quality protein. Both types of fermentation diminish antinutrients and improve the nutritional value of the bean flour, and indicate the potential to use bean flour as an ingredient for fabricated foods.     

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     

Total phenolic content and antioxidant properties of eclipse black beans (Phaseolus vulgaris L.) as affected by processing methods

ABSTRACT:  The effects of soaking, boiling, and steaming processes on the phenolic components and antioxidant activity of black beans were investigated. All processed beans exhibited significantly ( P < 0.05) lower antioxidant activities than raw beans in total phenolic content (TPC), DPPH free radical scavenging activity (DPPH), and oxygen radical absorbing capacity (ORAC). Steaming processes resulted in a greater retention of TPC and ORAC values than the boiling processes. Pressure boiling shortened processing time compared to regular boiling, resulted in insignificant differences in TPC, but significantly increased in ORAC as compared to the regular boiling method. Pressure steaming resulted in significant decreases in TPC, DPPH, while significantly increased in ORAC compared to regular steaming. Greater TPC, DPPH, and ORAC values were detected in boiling water than in the soaking and steaming water. Mass balance analysis showed that boiling caused more dry solid loss than steaming. All of these results indicated that processing methods significantly changed contents and activities of antioxidant components of black beans. Steam processing exhibited several advantages in appearance and texture of the cooked product, shortening processing time, and in greater retention of TPC and antioxidant activities. Steam processing may be used to develop high-quality health-promoting black bean products.     

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.     

Electrical Conductivity,Water Absorption,Leaching, and Color Change of Chickpea (Cicer arietinum L.) during Soaking with Ultrasound Treatment

The properties of soaking water of some cereals under high temperature were determined, but limited information is available on chickpeas in the literature. Change in electrical conductivity, turbidity, color, and soluble solids content of soaking water of chickpeas were studied at 87, 92, and 97°C without ultrasound, and with 25 kHz frequency and different ultrasound powers (100–300 W) for 260 min. Water absorption and color values of chickpea seeds were also studied during soaking. All the properties of soaking water and chickpea seeds were significantly (P < 0.05) affected by temperature, ultrasound treatment, and power of ultrasounds indicating leaching of some nutritional and anti-nutritional compounds. The moisture absorption rate of chickpeas increased with the increase of temperature and power of ultrasound, while color of chickpeas changed inversely with soaking water. Results showed that leaching and reabsorption of some nutritional compounds occur simultaneously and ultrasounds can be used to enhance cooking operations.     

Effect of processing on antioxidant contents in selected dry beans (Phaseolus spp. L.)

Dry beans are rich sources of dietary fiber and phytochemicals such as flavonoids and phenolics. In the current study, we determined the effects of two processing methods (soaking and toasting) on total phenolics, flavonoids, proanthocyanidin and antioxidant potential by 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity and ferric reducing antioxidant potential (FRAP) in selected dry beans (red kidney beans (K), black-eyed peas (B), pinto beans (P) and soy beans (S)).Total phenolics (mg/g dwb) expressed as gallic acid equivalents (GAE), total flavonoids (mg/g dwb) as catechin equivalents (CE) and proanthocyanidin expressed as leucocyanidin equivalent (mg LE/g) ranged from 3.42 to 7.21, 0.61 to 0.84 and 0.51 to 3.13 in raw beans; 3.58 to 6.94, 0.19 to 0.99 and 0.43 to 3.13 in soaked beans and 4.55 to 9.52, 0.23 to1.00 and 0.20 to 3.25 in toasted beans, respectively.FRAP (μg/g) in raw, soaked and toasted dry beans ranged from 0.00097 to 0.00424 while DPPH_(T30) (%) ranged from 43.9 to 62.61.Our results indicate that processing methods (soaking and roasting) influenced total phenolic, flavonoid and antioxidant contents (DPPH, FRAP) in selected dry beans.     

Effects of dehulling,soaking and germination on chemical composition,mineral elements and protein patterns of faba beans (Vicia faba L.)

The effects of dehulling, soaking and germination on the changes in general chemical composition, nine mineral elements and the protein patterns of whole faba beans were studied. Such pretreatments had a significant effect on the changes in the chemical composition of whole beans. Dehulling of beans significantly increased the contents of copper, zinc and potassium, while it significantly decreased the amounts of iron, manganese, phosphorus, calcium, magnesium and sodium compared with whole beans. Whole beans soaked for 12 h, followed by dehulling, had higher amounts of iron, copper, zinc, calcium and sodium, and quite a lower level of potassium, than unsoaked dehulled beans. All of the mineral elements except zinc were significantly increased on germination. No obvious changes in the electrophoretic pattern of faba bean proteins were observed as the seeds were soaked for up to 12 h. Extending soaking time for a further 4 h led to the disappearance of one band at the region of MW 67 KD. Germination of seeds for 3 days initiated disappearance of some bands while other new bands were observed.     

The effect of popping,soaking, boiling and roasting processes on antinutritional factors in chickpeas and red kidney beans

This study was conducted to determine the effect that a popping head (like a rice cake machine), a low-shear and low-water processing technology, has on the concentration of antinutritional factors in chickpeas and red kidney beans. Seeds were popped under several parameters (popping time, sample format and equipment type) and analysed against soaking (1:5 w/v in reverse osmosis water for 24 h), roasting (100 g at 180 °C for 20 min) and boiling (1:5 w/v in reverse osmosis water at 100 ± 1 °C for 1 h) processes. Popping and roasting significantly reduced phytic acid content in chickpeas (6%–22%) and red kidney beans (16%–39%). In contrast, phytic acid content after soaking and boiling was not significantly different to raw seeds. Condensed tannins were significantly reduced in red kidney beans after soaking (74%), boiling (100%) and 4 s popping (28%–42%) treatments and increased in both pulses after roasting (137%) and 8 s popping (21%–47%). Further analysis showed that the soluble phenolic content increased with popping, but total and bound phenolic content was reduced. These results demonstrate that the high temperatures and pressures applied during the popping process effectively reduce antinutritional factors in pulses, compared to conventional processing methods.     

Oligosaccharides in raw and processed legumes

 Oligosaccharides from several types of raw and processed legume seeds consumed in Spain, e.g. lentils (Lens culinaris L.), chickpeas (Cicer arietinum L.), red kidney beans (Phaseolus vulgaris L.), white common beans (Phaseolus vulgaris L.), “Judiones de la Granja” great white beans (Phaseolus vulgaris L.) and faba beans (Vicia faba L.), were analysed by high performance liquid chromatography. The total sugar content ranged from 6.69% to 9.99%, and oligosaccharides represented 25–46% of the total sugar, in the various dry legumes. The main oligosaccharide in raw faba beans was verbascose (3.32%), and stachyose in the remaining legumes (2.21–3.23%). Different amounts of sucrose and traces of glucose, fructose and small amounts of inulin were present in raw samples of all the legumes. After soaking in tap water the loss of oligosaccharides was lowest in red beans (1.25%) and highest in common white beans (27.6%). Pressure cooking, without previous soaking, resulted in no oligosaccharide loss in common white beans but a loss of up to 32% in chickpeas. After pressure cooking of soaked legumes, the loss of stachyose ranged from 14.2% in red beans up to 35.9% for lentils. Substantial amounts of flatus-producing factors can be eliminated by common processing methods. Received: 12 May 1997 / Revised version: 17 July 1997