Relationship of Loss of Membrane Functionality and Hard-to-Cook Defect in Aged Beans

Microsomal membranes were prepared from fresh beans (Phaseolus vulgaris) and from samples kept 9 mo at various temperatures and humitidies. Increasing storage severity produced progressively hard-to-cook (HTC) beans as well as higher solids loss and lower water-holding capacity during soaking. Membrane phase transition temperature (PTT), calcuated from spin label electron paramagnetic resonance data, also increased and showed a highly significant (r = 0.997) correlation with cooked hardness. Fatty acid analysis of membrane lipids demonstrated higher PTT values were due to a significant increase in proportion of saturated fatty acids. These data reflect membrane deterioration during aging that could explain solids loss and water-holding capacity changes. Changes in the membrane may be the primary event in initiation of the HTC defect.     

Water-Holding Capacity in Hard-to-Cook Beans (Phaseolus vulgaris): Effect of pH and Ionic Strength

The effect of pH and ionic strength (IS) of soaking solution on the water holding capacity (WHC) of hard-to-cook (HTC) and control black beans (Phaseolus vulgaris) was evaluated. Beans were soaked 18 hr in solutions covering the pH range 1–7 at constant IS (1.0 M) or in solutions ranging in IS from 0.01 to 1.3M (prepared with either NaCl or CaCl₂) at pH 7. WHC was significantly reduced in the pH range 3.5 to 5.1 in control beans but the effect was not as pronounced with HTC samples which had a lower WHC at each pH. Solutions prepared with NaCl produced significantly lower WHC values than CaCl₂ solutions in the control but not in the HTC beans. WHC values in control beans tended to increase with higher IS, although this effect was not as apparent for HTC beans.     

Processing and fermentation of the african locust bean (Parkia filicoidea Welw.) to produce dawadawa

African locust beans (Parkia filicoidea Welw.) were processed and fermented to the traditional West African condiment dawadawa. The beans were transformed to ‘processed substrate’ by boiling and dehulling, and then fermented at 37°C in static fermenter units. The overall mass balance and the mass balances of several bean components (moisture, fat, protein, ash and carbohydrate) were studied. It was found that 1.0 kg of raw beans (6.4% moisture) yielded 1.3 kg of processed substrate (63% moisture) which in turn was converted to 1.2 kg of dawadawa (65% moisture). The loss of bean solids during processing was due to the removal of adhering pulp and testa as well as to solids extraction during boiling and washing. Overall, 57% of the bean dry weight, 85% of the carbohydrate, 48% of the ash, 40% of the protein and 1% of the fat were lost in the conversion of raw beans to dawadawa. The dawadawa had considerably higher fat and protein contents than the raw beans and was a pleasant tasting food whereas the raw beans were inedible. Some microbiological aspects of the fermentation were also investigated. Normally prepared fermentation substrate was compared with both sterilised and radappertised beans in terms of conversion to dawadawa, number of colony forming units present, and the development of pH and titratable acidity. The presence of microorganisms was found to be obligatory for the conversion to proceed. Simultaneous increases in both pH and titratable acidity were observed during the fermentation.     

Storage Induced Changes of Phenolic Acids and the Development of Hard-To-Cook in Dry Beans (Phaseolus vulgaris var. Seafarer)

Navy beans were stored for 9 months under three conditions (5°C/ 40% RH, 20°C/73% RH, and 35°C/80% RH) to produce different degrees of hard-to-cook (HTC) defect. Changes in free hydroxycinnamic acids, hexane soluble and methanol soluble hydroxycinnamic acids, cell wall bound hydroxycinnamic acids, and lignin content were determined. Storage induced HTC beans contained higher levels of hydroxycinnamic acids (especially ferulic acid) than the control beans in all fractions prepared from seed coats and cotyledons except for the methanol soluble and cell wall bound phenolic acid fractions from cotyledons. No significant changes in lignin content were detected among the treatments. Large increases in free hydroxycinnamic acid content associated with increased hardening, suggest a relationship between these two factors.     

Hard-to-cook phenomenon in beans: Changes in antinutrient factors and nitrogenous compounds during storage

Five different bean varieties (Phaseolus vulgaris) from Kenya, which were either freshly collected or stored for 5 years in tropical conditions (30–40°C; >75% humidity), were compared for their cooking characteristics. The beans under storage develop an irreversible phenomenon classified as ‘hard-to-cook’ (HTC) which results in undesirable characteristics limiting their acceptability. Our aims were to determine the effects of the HTC phenomenon on the proteins and antinutrient factors in these beans. Both fresh and HTC beans contained nutritionally significant amounts of lectins, trypsin and α-amylase inhibitors. HTC samples had higher lectin and lower α-amylase inhibitor contents, while the amounts of trypsin and chymotrypsin inhibitors were the same. Storage appeared to reduce water-extractable nitrogen. Fractionation with sodium dodecyl sulphate also showed that less protein may be available in HTC than fresh beans. We established that the undesirable changes in beans, such as increased cooking time, which often accompany the storage of harvested seeds under tropical conditions produce an overall decrease in soluble-N fractions, particularly proteins. The results can provide guidelines on how to utilise these seed(s) and their products. Furthermore, appropriate processing is needed to reduce their antinutrients for human nutrition.     

Effect of phytate and storage conditions on the development of the ‘hard‐to‐cook’ phenomenon in common beans

Postharvest storage of beans (Phaseolus vulgaris L.) can alter the color, texture, flavor and time required for cooking. These alterations have been associated with the ‘hard‐to‐cook’ phenomenon (HTC) and a reduction in the quality of the grains. HTC has been linked to the genotype, environment and/or storage conditions of the grains, but very few studies have shown the interrelationship between these factors. Therefore, the objective of this study was to analyze the effect of two genotypes, Paraiso and Peruano, grown under the same phosphorus levels, on the development of HTC. These genotypes were evaluated for phytate, protein, tannin and phosphorus contents, hydration time and cooking time when stored for 45, 90 and 135 days, at 29 °C and 5 °C at a relative humidity of 75%. HTC was observed in Peruano after 135 days, which correlated with a reduction in the phytate content. Paraiso did not show HTC even though there was a reduction of tannins during the storage period. The lower storage temperature appeared to control HTC for both genotypes. Overall, the content of phytate can be an indicative factor for the cookability of fresh beans when the relationship between genotype and storage conditions has been determined. Copyright © 2007 Society of Chemical Industry     

SEED COAT EFFECTS IN COOKED RECONSTITUTED BEAN TEXTURE

The contribution of seed coat to cooked reconstituted bean texture was assessed by measuring sensory and instrumental parameters of beans with and without coats and also seed coats alone. Experiments using white beans stored for one year under tropical conditions to induce the hard-to-cook (HTC) defect or temperate conditions both resulted in reductions in the order of 50% in puncture force and sensory properties of beans when the seed coat had been removed. HTC bean texture was influenced less by absence of the seed coat than texture of soft beans. Seed coats softened during cooking but those from HTC beans softened less than those from soft beans. It is possible that seed coats harden during tropical storage by a lignification-type mechanism. Beans with harder seed coats absorbed less water during soaking which may contribute further to bean hardness.     

Chemical and microstructural evaluation of ‘hard‐to‐cook’ phenomenon in legumes (pinto bean and small‐type lentil)

Some physicochemical and microstructural characteristics of hard‐to‐cook (HTC) and easy‐to‐cook (ETC) pinto beans and small‐type lentils were compared. The development of HTC seeds was monitored over 6 months for changes in physicochemical properties. Results indicated that hardness, extent of water absorption and solid loss of HTC legumes were, respectively, 21–97%, 7–72% and 62–236% higher than those of ETC legumes. In addition, darkening of HTC beans and lentils was significantly higher than those of ETC ones. Scanning electron microscope observations indicated deteriorations in cytoplasmic contents of cotyledon cells of hard seeds. Phytic acid and total phenolic contents were, respectively, decreased 36–61% and 43–61% during storage, whereas hardness of seeds was increased 3–6 times. The soaking of hard seeds in sodium solutions resulted in the improvement in legume texture.     

The effect of pod and seed positions on the physical and cooking properties of faba beans (Vicia faba)

The effect of pod location on plant (lower, middle and upper regions) and seed position inside the pods (nodular, middle and terminal) on certain characteristics of dry and stewed faba beans were studied. The weight, volume, relative density, seed coat (%), hydration and swelling coefficients were determined for dry seeds. Hydration and swelling coefficients, fractured beans (%), penetrometer readings and scores of colour, granulation and softness (by taste panel) were evaluated for stewed beans. The weight, volume, relative density, pH, and total and soluble solids content of the stewed liquor were also measured. Analysis of variance showed that the weight and volume of 1000 dry seeds were significantly (P<0.001) affected by pod location and seed position. Higher values were obtained for lower pods and terminal and middle seeds. Seeds from upper pods had the highest percentage of seed coat. Pod location showed a significant effect on the weight, volume, pH, soluble and insoluble solids of stewed liquor. No significant effect was found for pod location or seed positions on the characteristics of stewed beans, except the hydration coefficient which was significantly affected by pod location.     

Water sorption and cooking time of red kidney beans (Phaseolus vulgaris L.): part I – Effect of freezing and drying conditions on water sorption and cooking time

Water sorption and cooking time of kidney beans were determined. The beans were manually harvested at 19.2 ± 0.1% moisture content and stored at ?20 and ?10 °C for about half a year. The beans were further dried at 30, 40 and 50 °C inside a thin‐layer drier for 7.5 h or under room conditions for 4 week. The freezing storage temperature before the beans were dried did not influence their cooking time and water sorption. The saturated kernel volumes decreased approximately 7% after drying. The beans decreased their sphericity during water sorption and had a larger swelling ratio in the thickness direction than in other directions. Lower initial moisture content, especially with a higher drying temperature, decreased water sorptivity and resulted in higher percentage of uncooked kernels if the beans were not soaked before cooking. However, there was no relationship between initial moisture content and uncooked percentage if the beans were soaked before cooking. High drying temperature resulted in hard‐to‐cook (HTC) phenomenon.     

Sensory Evaluation of Tempeh Produced by Fermentation of Common Beans

A tempeh fermented product was prepared from fresh and hard-to-cook (HTC) common beans with the mold Rhizopus oligosporus. Fresh samples fermented for 0, 24 and 48 hr were used to prepare fried tempeh, atoles and cookies at various substitution levels. Atoles were also prepared with fermented hardened beans. A panel evaluated samples for the sensory variables: appearance, odor, color, flavor, texture, and acceptability. For fried tempeh, flavor and acceptability were the sensory variables most affected by fermentation. Atoles, supplemented with fermented fresh and HTC seeds, had significantly lower (P<0.05) flavor and color than controls, respectively. Interestingly, acceptability of atoles, from both fresh and HTC samples, and of cookies was not significantly different (P>0.05) from the controls.     

Protein Denaturation and Starch Gelatinization in Hard-To-Cook Beans

A study was undertaken to assess protein denaturation and starch gelatinization in ground samples of common black beans exhibiting the hard-to-cook (HTC) defect. Using differential scanning calorimetry, no significant differences in either gelatinization or denaturation temperatures were found between hard and soft beans but tropical storage conditions produced significant increases in gelatinization enthalpy and decreases in denaturation enthalpy. Endotherms of cooked samples showed as little as 34% of the protein had denatured in HTC beans as compared to over 85% in soft beans. Micrographs indicated the ground raw material was composed of clumps of cotyledon cells; cooking soft beans produced cell separation but this did not occur in HTC samples. These data supported the idea that bean hardening was accompanied by limited water availability inside cotyledon cells that could reduce cell swelling, starch gelatinization and protein denaturation, leading to textural toughness.     

UTILIZATION OF RAPESEED MEAL IN SAUCE PRODUCTION

A sauce produced by fermenting rapeseed meal (RM) and wheat with Aspergillus oryzae and/or Aspergillus soyae for 1 yr was found comparable in its acceptability to a commercial soy sauce. During the fermentation the soluble solids in the liquor increased rapidly during the first 10 wk from 22.5% to 35.5% and then remained unchanged until the 40th wk when it again increased sharply to 40% by the 45th wk. The pH of the substrate decreased slowly from 5.5 to 4.9 after 40 wk of fermentation. A comparable RM sauce was produced using the semichemical method with 1 month fermentation. In this process, the soluble solids increased rapidly from 29% to 40% during the first 4 wk, then slowly to 42% after 12 wk. pH dropped from 5.5 to 5.2 after 5 wk of fermentation. The study showed that rapeseed meal could be used successfully as a soybean substitute in the sauce production.     

Physico-chemical characterization of stored black beans (Phaseolus vulgaris L.)

Selected physical and chemical characteristics were studied on black beans (Phaseolus vulgaris L.) after 2 years of storage under refrigerated hypobaric conditions (RHC) and ambient conditions (AC). Black beans stored under RHC of 4.5°C, 50–60% relative humidity and atmospheric pressure of 125 mm Hg exhibited quality factors characteristic of fresh beans, such as shorter cooking time, smaller quantities of solids loss, electrolytes leached, and percentage of hardshell than beans stored at AC of 23–25°C and 30–50% relative humidity. Additionally, beans stored under RHC demonstrated greater germination rate (93%) than beans stored at AC (72%). Beans stored at AC exhibited quality factors characteristic of hard-to-cook (HTC) beans. Percentage water absorption indicated a faster initial hydration rate in beans stored under RHC compared to beans stored at AC until after 12 h of soaking, when both reached a similar hydration rate. Moisture content of beans stored under RHC was similar to that of beans prior to storage, while the moisture content of beans stored at AC was significantly lower. Crude protein, crude fat, and ash concentration of beans prior to storage and beans stored for 2 years under RHC or AC were not significantly different. The electrophoretic profile of the main protein of beans, globulin G1, was not altered by the storage conditions. The combined effect of refrigeration and hypobaric storage conditions demonstrated potential for maintaining the fresh quality of beans in storage for up to 2 years.     

Mechanistic insight into common bean pectic polysaccharide changes during storage,soaking and thermal treatment in relation to the hard-to-cook defect

Different mechanisms responsible for the development of the hard-to-cook defect in common beans during storage, their soaking behavior and softening during thermal treatment have been previously suggested. However, these mechanisms have not been sufficiently confirmed by direct molecular evidence. This research aimed at gaining a detailed mechanistic insight into changes occurring in Canadian wonder bean pectic polysaccharides during storage, soaking and/or thermal treatment in different brine solutions in relation to the development and manifestation of the hard-to-cook (HTC) defect. Both fresh or easy-to-cook (ETC) and stored (HTC) bean samples were either soaked or soaked and thermally treated in demineralized water, solutions of Na₂CO₃ and CaCl₂ salts followed by extraction of cell wall materials. Pectic polysaccharide properties examined included sugar composition, degree of methylesterification (DM), extractability and molar mass (MM). The DM of pectin from ETC and HTC beans was similar but low (< 50%). Upon (pre)treatment in a Na₂CO₃ solution, solubilization of pectic polysaccharides, especially the strongly bound chelator- (CEP) and Na₂CO₃- (NEP) extractable pectins was enhanced leading to increased amounts of water extractable pectin (WEP). Also, there was a decrease in high MM polymers paralleled by an increase in β-elimination degradation products. These observations are in line with the fast cooking behavior of beans (pre)treated in a Na₂CO₃ solution. In contrast, (pre)treatment in a CaCl₂ solution hindered softening leading to the failure of the beans to cook. The beans (pre)treated in a CaCl₂ solution showed increased high MM polymers and lack of cell wall separation. Therefore, it can be inferred that development of the hard-to-cook defect in Canadian wonder beans during storage and its manifestation during soaking and subsequent thermal treatment is largely reflected by the pectic polysaccharide properties in line with the pectin hypothesis. Our data suggest the release of Ca⁺⁺ leading to pectin cross-linking and the increase or decrease of β-elimination depolymerization. However, the relatively high amounts of neutral sugars and strongly bound NEP in HTC seeds do not allow to rule out the possible existence of non-Ca⁺⁺ based pectin cross-linking.     

Changes in the composition of aromatic compounds and other quality parameters of strawberries during freezing and thawing

Six strawberry cultivars were analysed, as fresh and as frozen and thawed fruit, for their content of anthocyanins, ascorbic acid, titratable acid, soluble solids and aromatic compounds. During freezing and thawing the content of titratable acid and soluble solids remained constant, whereas the content of anthocyanins and ascorbic acid decreased. The composition of aromatic compounds was also changed during freezing and thawing and greatest decreases were found fortrans-2-hexenal and hexanol. The content of volatile acids, linalool and methyl hexanoate was doubled after freezing and thawing, and, for all cultivars except from Pandora and Dania, ethyl butanoate and ethyl hexanoate increased strongly. This cultivar-dependent ethyl ester formation occurred during thawing rather than during freezing.     

Consistency,Polysaccharidase Activities and Non-Starch Polysaccharides Content of Soya Beans During Tempe Fermentation

The relation between consistency of soya beans, polysaccharidase activities and the non-starch polysaccharides (NSP) content of soya beans was investigated during tempe fermentation. The fermentations were carried out in a rotating drum reactor (RDR) as well as in the traditional stationary tempe process. The firmness of the soya beans decreased rapidly during the first day of incubation. At increased incubation temperatures the hardness of the beans decreased more rapidly. In the RDR glycosidase activities became significantly higher beyond 48 h of incubation compared with the traditional process. This might have resulted from (a) the better control of temperature and gas composition in the RDR, and/or (b) the agitation in the RDR. The content of arabinose, galactose and uronic acids in the water-unextractable solids of NSP decreased more rapidly than that of glucose, mannose, xylose and fucose. These results indicate that during enzymatic maceration of soya beans in tempe fermentation, the arabinogalactan and pectin fractions are preferentially solubilised. © 1997 SCI.     

Preparation and characterization of protein from heat-stabilized rice bran using hydrothermal cooking combined with amylase pretreatment

Hydrothermal cooking (HTC) combined with amylase pretreatment (AP) was used to improve protein extraction from heat-stabilized rice bran. The physicochemical and emulsifying properties of rice bran protein isolate (RPI) were evaluated. Depending on HTC temperature (120 and 150 °C), HTC alone significantly increased extraction yield, while protein purity was decreased. In contrast, HTC combined with AP significantly improved both extraction yield and protein purity (about 45-50% and 72-74%, respectively). The AP avoided the co-precipitation of gelatinized starch during the acidic precipitation. Electrophoresis and size exclusion chromatography profiles indicated that HTC led to the dissociation of insoluble protein aggregates in rice bran, with subsequent increase of soluble aggregates in RPI, linked by non-covalent (e.g., hydrophobic interaction) and covalent bonds (disulfide bond). This result was evidenced by the increased disulfide bond contents and surface hydrophobicity of RPI. In addition, HTC-prepared RPI exhibited excellent emulsifying property.     

Modelling variety‐dependent dynamics of soluble solids and water in berries of Vitis vinifera

Background and Aims: We modelled the dynamics of soluble solids, largely sugars, and water in 12 Vitis vinifera varieties. Emphasis was placed on maximum concentration of soluble solids (S_max) and time of maturity for their viticultural importance. Methods and Results: We measured the concentration of soluble solids and water at weekly intervals during berry ripening. The dynamics of concentration of soluble solids was characterised with a sigmoid model, whereas water concentration was characterised with a concentration–response type curve. Scaling exponents for soluble solids (α_s) and water (α_w) were calculated as the slope of the log–log regression between amount of soluble solids or water per berry and berry fresh mass. S_max ranged from 27.1% in Shiraz to 21.2% in Riesling, was associated with both α_w and α_s, and was largely unrelated to source size (leaf area, pruning weight, light interception), source activity (stomatal conductance), sink size (yield components) and source : sink ratios. The time of maturity ranged from 26 January in Verdelho to 27 February in Crimson Seedless, and was an inverse function of the rate of change in concentration of soluble solids, which was in turn a direct function of stomatal conductance. Conclusions: Traits related to carbon assimilation influenced time of maturity, but their link with maximum concentration of soluble solids in berries was not evident. Significance of the Study: Quantitative models of accumulation of soluble solids are presented that provide a baseline for comparisons among varieties.     

INFLUENCE OF VARIOUS SALTS IN THE COOKING WATER ON PECTIN LOSSES AND COOKED TEXTURE OF COWPEAS (VIGNA UNGUICULATA)

The effects of processing with solutions of calcium chloride, magnesium chloride, sodium bicarbonate and a local tenderizer known as ‘Kanwa’ (sodium sesquicarbonate) on pectin losses and cooked texture of cowpea seeds were investigated. For comparison, the cowpeas were processed in double distilled water and a local tap water. Analysis included total pectin, calcium and magnesium content, leached solids, texture and water absorption. The results show that CaCl₂, MgCl₂ and the local tap water increased firmness, Ca and Mg content in the cooked beans compared to distilled water; however, water absorption, leached solids and pectin solubilization were decreased by these salts. Kanwa and NaHCO₃ increased water absorption, leached solids and softness in the cooked beans and also increased pectin solubilization but decreased Ca and Mg when compared to distilled water or the other salts. These changes are discussed with respect to the effects of divalent and monovalent cations on the texture of the bean tissue.