Modifications to physicochemical and nutritional properties of hard-To-cook beans (Phaseolus vulgaris L.) by extrusion cooking.

The objective of this work was to evaluate extrusion cooking as a means to improve the nutritional properties of Phaseolus vulgaris L. that had been stored either at 42 degrees C and 80% relative humidity for 6 weeks or for periods >1 year in cereal stores in tropical conditions. Storage under these conditions resulted in an increase in cooking time increased (7.7- and 12-fold, respectively) as a result of development of the hard-to-cook (HTC) defect. Single-screw extrusion of the milled beans was carried out at four barrel temperatures and two moisture contents. The extrudate bulk density and water solubility index decreased with increasing temperature, whereas the water absorption index increased due to the higher proportion of gelatinized starch in the extruded samples. Both fresh and HTC beans contained nutritionally significant amounts of lectins, trypsin, and alpha-amylase inhibitors, which were mostly inactivated by extrusion. Extrusion also caused a considerable redistribution of insoluble dietary fiber to soluble, although the total dietary fiber content was not affected. Changes in solubility involved pectic polysaccharides, arabinose and uronic acids being the main sugars involved. Stored beans subjected to extrusion cooking showed physical and chemical characteristics similar to those of extrudates from fresh beans.     

Impact of the hard-to-cook phenomenon on phenolic antioxidants in dry beans (Phaseolus vulgaris)

Epidemiological studies have established a link between consumption of dry beans and lower incidence of degenerative diseases. This relationship is attributed in part to properties of natural antioxidants present in beans. The objective of this study was to determine if the hard-to-cook (HTC) phenomenon in beans had a negative effect on the content of free and bound phenolic antioxidants and antioxidant capacity. Folin-Ciocalteu, Trolox equivalent antioxidant capacity, and HPLC methods were used to quantify the content of phenolic acids and antioxidant capacity. Results showed that the HTC phenomenon did not equally affect the content and antioxidant capacity of phenolic acids in different bean cultivars. Black beans were most affected, the contents of free and acid hydrolyzable phenolic acids being reduced by 35 and 36%, respectively, and the antioxidant activity by 18 and 25%, respectively. This study showed that the HTC phenomenon affected a potential nutritive characteristic of dry beans.     

Solid‐State Bioprocessing with Cordyceps militaris Enhanced Antioxidant Activity and DNA Damage Protection of Red Beans (Phaseolus angularis)

In this study, red beans were bioprocessed by using a novel solid‐state fermentation (SSF) with an edible and medical filamentous fungus Cordyceps militaris . The effect of SSF on the total phenolic content (TPC), antioxidant activity, and DNA damage protection of red beans was determined. Furthermore, solvents with different polarities (80% methanol, 80% ethanol, 80% acetone, and deionized water) were used to extract antioxidant compounds from the red bean samples. The results indicated that SSF significantly enhanced TPC, 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt radical cation scavenging activity, reducing power, and chelating ability of red beans. Furthermore, this study also demonstrated that fermented red beans exhibited greater protection against oxidative DNA damage than nonfermented red beans. Besides, the water extract of fermented red beans showed the highest TPC, antioxidant activity, and DNA damage protection among the various extracts examined. For the specific phenolics profile, HPLC analysis was performed, which showed that gallic acid, chlorogenic acid, p‐hydroxybenzoic acid, syringic acid, ferulic acid, daidzein, quercetin, and genistein of red beans were increased during SSF. There was a positive correlation among phenolic compounds, antioxidant activity, and DNA damage protection. Thus, this study demonstrated that SSF with C. militaris is an effective method for the enhancement of phenolic compounds, antioxidant activity, and DNA damage protection of red beans.     

Diversity in Antioxidant Capacity,Phenolic Contents,and Flavonoid Contents of 42 Edible Beans from China

Edible beans are among the most important grain legumes consumed by humans. To provide new information on the antioxidant phenolics of edible beans, the antioxidant capacity, total phenolic content (TPC), and total flavonoid content (TFC) in both soluble and bound fractions of 42 edible beans from China were systematically evaluated, with main phenolic compounds identified and quantified in 10 beans possessing the highest TPC. Edible beans contained a wide range of total antioxidant capacity and TPC generally comparable with common grains, fruits, and vegetables, and their bound fractions had significant antioxidant capacity, TPC, and TFC. Red sword bean was found for the first time to show extremely high total antioxidant capacity (ferrous[II] at 235 ± 13.2 μmol/g and Trolox at 164 ± 10.5 μmol/g) and TPC (1767 ± 58.3 mg of GAE/100 g). Phenolic compounds such as catechin, ferulic acid, gallic acid, p‐coumaric acid, and protocatechuic acid were widely detected in selected beans. A positive correlation was found between antioxidant capacity (ferric‐reducing antioxidant power [FRAP] and Trolox equivalent antioxidant capacity [TEAC] values) and TPC, with correlation coefficient r = 0.974 (FRAP value versus TPC) and r = 0.914 (TEAC value versus TPC). Therefore, beans with high antioxidant capacity and phenolic content can be valuable sources of dietary natural antioxidants for the prevention of oxidative stress‐related chronic diseases.     

Heat-induced changes in myofibrillar protein structures and myowater of two pork qualities. A combined FT-IR spectroscopy and low-field NMR relaxometry study

Low-field NMR T(2) and Fourier transform infrared (FT-IR) measurements were performed on meat samples of two qualities (normal and high ultimate pH) during cooking from 28 degrees C to 81 degrees C. Pronounced changes in both T(2) relaxation data and FT-IR spectroscopic data were observed during cooking, revealing severe changes in the water properties and structural organization of proteins. The FT-IR data revealed major changes in bands in the amide I region (1700-1600 cm(-)(1)), and a tentative assignment of these is discussed. Distributed NMR T(2) relaxation data and FT-IR spectra were compared by partial least-squares regression. This revealed a correlation between the FT-IR peaks reflecting beta-sheet and alpha-helix structures and the NMR relaxation populations reflecting hydration water (T(2B) approximately 0-10 ms), myofibrillar water (T(21) approximately 35-50 ms), and also expelled "bulk" water (T(2) relaxation times >1000 ms). Accordingly, the present study demonstrates that definite structural changes in proteins during cooking of meat are associated with simultaneous alterations in the chemical-physical properties of the water within the meat.     

Effect of different soaking solutions on nutritive utilization of minerals (calcium,phosphorus, and magnesium) from cooked beans (Phaseolus vulgaris L.) in growing rats

The effects of the commonly used processing techniques of soaking (at different pH values) and cooking on the digestive and nutritive utilization of calcium, phosphorus, and magnesium from common beans (Phaseolus vulgaris L.) were studied. Before the cooking step, the beans were soaked in solutions of acid (2.6 and 5.3) or basic (8.4) pH. Chemical and biological methods were used to determine nutritional parameters in growing rats, and the fiber content of the beans was established. As the pH of the soaking solution increased, so did mineral absorption and the apparent digestibility coefficient, which reached suitable values for growing rats, due to the reduced losses of soluble minerals and the increased food intake. Metabolic utilization also improved with increased pH of the soaking solution, although the values were, in general, low as a result of urinary losses under the experimental conditions. For the experimental period of 10 days, the femur and the muscle seem to be good metabolic indicators for calcium, but not for phosphorus or magnesium. The increased amount of cellulose in the soaked seed did not have a negative effect on the digestive utilization of minerals.     

Effect of solvent, temperature, and solvent-to-solid ratio on the total phenolic content and antiradical activity of extracts from different components of grape pomace

Grape byproducts were subjected to an extraction process under various different experimental conditions (namely, solvent type, temperature, solvent-to-solid ratio, time contact, and raw material) in order to study the effect of these conditions on the yield of phenolic compounds and the corresponding antiradical activity of extracts. Although the order of decreasing capacity to extract soluble materials was ethanol > methanol > water, methanol was the most selective for extracting phenolic compounds. Temperature and solvent-to-solid ratio were found to have a critical role in extraction efficiency; values of 50 degrees C (between 25 and 50 degrees C) and 1:1 (between 1:1 and 5:1) maximized the antiradical activity of phenolic extracts. In addition, extracts from grape samples previously subjected to distillation reached higher antiradical values in comparison to those coming directly from pressing; in both cases, seed extracts showed better results than those of stem when ethanol or water was employed, whereas the opposite occurred in the case of methanol. These differences were attributed to the different phenolic compositions of the considered fractions.     

Effects of microwave cooking conditions on bioactive compounds present in broccoli inflorescences

Cooking as a domestic processing method has a great impact on food nutrients. Most Brassica (Brassicaceae, Cruciferae) vegetables are mainly consumed after being cooked, and cooking considerably affects their health-promoting compounds (specifically, glucosinolates, phenolic compunds, minerals, and vitamin C studied here). The microwave cooking process presents controversial results in the literature due to the different conditions that are employed (time, power, and added water). Therefore, the aim of this work was to study the influence of these conditions during microwave cooking on the human bioactive compounds of broccoli. The results show a general decrease in the levels of all the studied compounds except for mineral nutrients which were stable under all cooking conditions. Vitamin C showed the greatest losses mainly because of degradation and leaching, whereas losses for phenolic compounds and glucosinolates were mainly due to leaching into water. In general, the longest microwave cooking time and the higher volume of cooking water should be avoided to minimize losses of nutrients.     

Physicochemical, nutritional, and microstructural characteristics of chickpeas (Cicer arietinum L.) and common beans (Phaseolus vulgaris L.) following microwave cooking

Microwave cooking of legumes such as chickpeas and common beans was evaluated by assessing the cooking quality (cooking time, firmness, cooking losses, and water uptake) and the physicochemical, nutritional, and microstructural modifications in starch and nonstarch polysaccharides. Compared to conventional cooking, microwave cooking with sealed vessels enabled a drastic reduction in cooking time, from 110 to 11 min for chickpeas and from 55 to 9 min for common beans. The solid losses, released in the cooking water, were significantly less after microwave cooking than after conventional cooking (6.5 vs 10.6 g/100 g of dry seed in chickpeas and 4.5 vs 7.5 g/100 g of dry seed in common beans). Both cooking procedures produced a redistribution of the insoluble nonstarch polysaccharides to soluble fraction, although the total nonstarch polysaccharides were not affected. Increases in in vitro starch digestibility were similar after both cooking processes, since the level of resistant starch decreased from 27.2 and 32.5% of total starch in raw chickpeas and beans, respectively, to about 10% in cooked samples and the level of rapidly digestible starch increased from 35.6 and 27.5% to about 80%. SEM studies showed that the cotyledons maintained a regular structure although most of the cell wall was broken down and shattered by both cooking procedures. In addition, the ultrastructural modifications in the cotyledon's parenchima and cells are consistent with the chemical modifications in NSP and the increase in starch digestibility after cooking.     

Effect of Processing on Antinutrient Compounds in Pulses

Processing of pulses (peas, beans, lentils, chickpeas, and faba beans) is necessary to reduce or eliminate the antinutrient compounds. Conventional processing including soaking, dehulling, boiling, and pressure cooking as well as germination and fermentation reduce the levels of phytate, protease inhibitors, phenolics, condensed tannins, lectins, and saponins. Recent research has investigated how innovative processes such as extrusion, microwave heating, micronization, and irradiation affect the antinutrient content. Germination tends to be most effective at reducing phytate levels, regardless of pulse type. Mixed results on the effectiveness of extrusion, microwave heating, and micronization have been reported. More work is needed to understand how processing of consumer‐ready foods containing pulse ingredients affects levels of antinutrient compounds.     

L-tryptophan reacts with naturally occurring and food-occurring phenolic aldehydes to give phenolic tetrahydro-beta-carboline alkaloids: activity as antioxidants and free radical scavengers

The reaction between the essential amino acid l-tryptophan and flavoring or naturally occurring phenyl and phenolic aldehydes was studied, and the alkaloidal reaction products were characterized by NMR and HPLC-MS. Benzaldehyde, vanillin, syringaldehyde, salicylaldehyde, and anisaldehyde condensed with l-tryptophan in aqueous-acidic media affording the corresponding phenolic tetrahydro-beta-carboline-3-carboxylic acid as two diastereoisomers, 1S,3S-cis and 1R,3S-trans. With the exception of benzaldehyde, the rest of the aldehydes needed heating conditions (70 degrees C) to significantly form tetrahydro-beta-carbolines over time with the cyclization highly favored at low pH. This suggests a likely formation of these compounds under conditions that may occur in foods, food processing, or cooking. The new phenolic tetrahydro-beta-carboline alkaloids were assayed, for the first time, for their activity as free radical scavengers and antioxidants and showed good antioxidant properties with Trolox equivalent antioxidant capacity (TEAC) values much higher than those of ascorbic acid and the water soluble vitamin E analogue, Trolox, in the 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) assay.     

Use of specific peaks obtained by diffuse reflectance Fourier transform mid‐infrared spectroscopy to study the composition of organic matter in a Haplic Chernozem

This study assessed specific peaks obtained by diffuse reflectance Fourier transform mid‐infrared spectroscopy (DRIFTS) for characterizing the soil organic matter (SOM) composition of a Haplic Chernozem. Soils were collected from the Static Fertilization Experiment, Bad Lauchstädt, Germany, during 5 years from the farmyard manure (FYM), mineral fertilizer (NPK), combination (FYM + NPK) and no fertilizer (Control) treatments. Soils were extracted with hot water (HWE), and fractionated by size and density. Bulk soil and fractions were analysed by DRIFTS. Peak areas at 2930, 1620, 1530 and 1159 cm^?1 were selected as a range of organic functional groups (with limited mineral interference), integrated with a local baseline (corrected peak area) and each was divided by the summed area of the four peaks (relative peak area). Positive correlations between carbon (C) in fractions representing labile OM (<1.8 g cm^?3, 1.8–2.0 g cm^?3, C_HWE) and the corrected peak area at 2930 cm^?1 (3010–2800 cm^?1) in the bulk soil indicated that this aliphatic peak corresponded to the more labile C compounds. Negative correlations between the same fractions and the corrected area of the predominantly aromatic peak at 1620 cm^?1 (1660–1580 cm^?1) in the bulk soil suggested a relationship with more stable SOM compounds. All relative peak areas were significantly affected by fertilizer treatment, with an increasing relative peak area at 2930 cm^?1 in FYM compared with non‐FYM treatments. The ratio of the peaks at 1620 and 2930 cm^?1 was positively correlated with the ratio of stable C (sum of C in >1.8 g cm^?3 and clay fractions) to labile C (C content of <1.8 g cm^?3 fraction) and thus taken as an indicator of SOM stability. The DRIFTS peak area method reflected changes in SOM quality and composition under long‐term management as measured by size and density fractionation, indicating heterogeneous chemical composition of the latter. Further, the DRIFTS analysis of undiluted soil samples can be used to assess SOM composition in small sample sets if specular reflection and mineral interferences are considered.     

中国黑土上腐殖酸和腐殖物质的提取及其描述

Twenty-three progressive extractions were performed to study individual humic acids (HAs) and humin fractions from a typical black soil (Mollisol) in Heilongjiang Province, China using elemental analysis and spectroscopic techniques. After 23 HA extractions the residue was separated into high and low organic carbon humin fractions. HA yield was the highest for the first extraction and then gradually decreased with further extractions. Organic carbon (OC) of the humin fractions accounted for 58% of total OC even after 23 successive HA extractions. In addition, the atomic C/H ratio decreased during the course of extraction while C/O increased; the E4/E6 ratio from the UV analysis decreased with further extraction while E~/E3 increased; the band assigned to aliphatic carbon (2 930 cm-1) in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra gradually increased with progressive extraction; the calculated ratio of the sum of aromatic carbon peak heights to that of aliphatic carbon peak heights from DRIFTS spectra declined with extractions; and nuclear magnetic resonance (NMR) data suggested that HA aliphatic carbons increased with extractions while aromatic carbons decreased. Thus, hydrophobicity and aliphaticity of HAs increased with extractions while polarity and aromaticity decreased. These data showed substantial chemical, structural, and molecular differences among the 23 HAs and two humin fractions. Therefore, these results may help explain why soil and sediment humin fractions have high sorption capacity for organic contaminants.     

Phenolic compounds and antioxidant activity of extracts from ultrasonic treatment of Satsuma Mandarin (Citrus unshiu Marc.) peels

Ultrasound-assisted extraction (UAE) was used to extract phenolic compounds from Satsuma mandarin ( Citrus unshiu Marc.) peels (SMP), and maceration extraction (ME) was used as a control. The effects of ultrasonic time (10, 20, 30, 40, 50, and 60 min), temperature (15, 30, and 40 degrees C), and ultrasonic power (3.2, 8, 30, and 56 W) on phenolic compounds were investigated. High-performance liquid chromatography (HPLC) coupled with a photodiode array (PDA) detector was used for the analysis of phenolic acids after alkaline hydrolysis (bound phenolic acids) and flavanone glycosides. The contents of seven phenolic acids (caffeic acid, p-coumaric acid, ferulic acid, sinapic acid, protocatechuic acid, p-hydroxybenzoic acid, and vanillic acid) and two flavanone glycosides (narirutin and hesperidin) in extracts obtained by ultrasonic treatment were significantly higher than in extracts obtained by the maceration method. Moreover, the contents of extracts increased as both treatment time and temperature increased. Ultrasonic power had a positive effect on the contents of extracts. However, the phenolic acids may be degraded by ultrasound at higher temperature for a long time. For example, after ultrasonic treatment at 40 degrees C for 20 min, the contents of caffeic acid, p-coumaric acid, ferulic acid, and p-hydroxybenzoic acid decreased by 48.90, 44.20, 48.23, and 35.33%, respectively. The interaction of ultrasonic parameters probably has a complex effect on the extracts. A linear relationship was observed between Trolox equivalent antioxidant capacity (TEAC) values and total phenolic contents (TPC); the correlation coefficient, R(2), is 0.8288 at 15 degrees C, 0.7706 at 30 degrees C, and 0.8626 at 40 degrees C, respectively. The data indicated that SMPs were rich sources of antioxidants. Furthermore, UAE techniques should be carefully used to enhance the yields of phenolic acids from SMPs.     

Determination of free and bound phenolic compounds in buckwheat spaghetti by RP-HPLC-ESI-TOF-MS: effect of thermal processing from farm to fork

Nowadays there is considerable interest in the consumption of alternative crops as potential recipes for gluten-free products production. Therefore, the use of buckwheat for the production of gluten-free pasta has been investigated in the present study. RP-HPLC-ESI-TOF-MS has been applied for the separation and characterization of free and bound phenolic compounds in buckwheat flour and buckwheat spaghetti. Thus, 32 free and 24 bound phenolic compounds in buckwheat flour and spaghetti have been characterized and quantified. To the authors' knowledge, protochatechuic-4-O-glucoside acid and procyanidin A have been detected in buckwheat for the first time. The results have demonstrated a decrease of total free phenolic compounds from farm to fork (from flour to cooked spaghetti) of about 74.5%, with a range between 55.3 and 100%, for individual compounds. The decrease in bound phenols was 80.9%, with a range between 46.2 and 100%. The spaghetti-making process and the cooking caused losses of 46.1 and 49.4% of total phenolic compounds, respectively. Of the total phenolic compounds present in dried spaghetti, 11.6% were dissolved in water after cooking.     

Nutritional and sensory evaluation of akara made from blends of cowpea and hard-to-cook mottled brown dry beans

The effect of replacing cowpea with hard-to-cook beans on the nutritional and sensory properties of akara were evaluated. Cowpea (Vigna unguiculata), traditionally used for making akara, was substituted 0%, 25%, 50%, 75%, and 100% with hard-to-cook (HTC) mottled brown beans (Phaseolus vulgaris). Cowpea (CP) soaked for 60 min HTC beans soaked for 18 h were separately decorticated, ground to a paste, and mixed in the following CP:MBB ratios: 0:100, 25:75, 50:50, 75:25, and 100:0. The paste mixtures were each whipped and fried into akara. The samples were analyzed for bulk density, nutritional composition, carbohydrate and protein digestibility, alpha-amylase inhibitor and trypsin inhibitor activity, and sensory attributes. The bulk density of paste as well as of akara increased with the increasing content of HTC bean. Akara made from composite paste had a relatively better amino acid profile. Frying beyond 5 min destroyed the alpha-amylase inhibitors as well as the trypsin inhibitor activity. No significant difference was observed in the overall acceptability of akara made from cowpea substituted up to 50% with HTC beans. Hence, this approach permits the utilization of hard-to-cook beans.     

Effect of Presoaking on Textural,Thermal, and Digestive Properties of Cooked Brown Rice

Brown rice kernels (japonica type) were soaked in water at different temperatures (25 or 50°C) before cooking to a moisture content of 20 or 30%. Soaked brown rice was cooked in either the soaking water (SW) or in distilled water (DW) (rice solids to water ratio 1:1.4). Color, texture, and in vitro digestive properties of the cooked rice were examined. When the soaking temperature was higher (50°C vs. 25°C), water absorption and starch leaching were greater. To reach 20% moisture, the rice required 1 hr of soaking at 50°C but 2 hr of soaking at 25°C. Both the moisture content of the soaked rice and the soaking temperature affected the texture of the cooked brown rice. Rice that attained 20% moisture content during soaking was harder and less adhesive when cooked compared with rice that attained 30% moisture content. The rice soaked at 50°C was slightly softer but more adhesive when cooked than rice soaked at 25°C. The soaking temperature and moisture content of the rice kernels also affected the digestive properties of the cooked rice. The cooked brown rice that had attained 30% moisture before cooking was digested to a greater extent than rice that had attained 20% moisture. Even at equal moisture content, the rice soaked at the higher temperature (50°C) was digested more readily. It was assumed that the amount of soluble material leached during soaking differed according to the soaking temperature and moisture content, which subsequently affected the texture and digestive properties of the cooked brown rice. The rice cooked in its own soaking water was harder and more adhesive, had higher levels of resistant starch (RS), and exhibited smaller glycemic index (GI) values than its counterpart cooked with distilled water. This result indicated that the soluble material leached during soaking made the cooked rice harder and less digestible, perhaps due to interactions between these molecules and the gelatinized rice during cooking.     

Residue levels and storage responses of nectarines, apricots, and peaches after dip treatments with fludioxonil fungicide mixtures

Mature apricots (Prunus armeniaca), nectarines [Prunus persica var. nectarine (Ait.)], and peaches [P. persica (L.) Batsch.] were subjected to a 2 min dip treatment with warm water at 48 degrees C or with fludioxonil (FLU) at 100 mg L-1 and 20 degrees C or at 25 mg L-1 FLU and 48 degrees C and then stored at 5 degrees C and 90-95% relative humidity (RH) for 1 week plus 1 additional week at 18 degrees C and approximately 80% RH. Fruit residue uptake was determined as a function of fungicide concentration, dip temperature, treatment time (only on nectarines), and fruit storage conditions. FLU residue level was closely related to fungicide concentration and treatment temperatures and was dependent on fruit species. FLU residues showed great persistence over both storage and shelf life. Fruit dipping in water at 48 degrees C effectively reduced decay development in cvs. 'May Grand' nectarines and 'Pelese' apricots but was ineffective in cvs. 'Red Top' and 'Sun Crest' nectarines during 7 days of storage compared with nontreated fruit. Decay rates in cvs. 'Glo Haven' peaches and 'Fracasso' apricots were very low in fruit dipped in water at both 20 and 48 degrees C. Fungicide treatments at 20 and 48 degrees C resulted in the total or almost total suppression of decay in all cultivars. During shelf life, fruit became very prone to decay, averaging 25.7-100% depending on the cultivar. Fruit dipping in hot water effectively reduced decay in 'Pelese' and 'Fracasso' apricots, 'Sun Crest' peaches, and 'May Grand' nectarines as compared to control, but was ineffective in 'Glo Haven' and 'Red Top' peaches. Fungicide treatments at 20 degrees C were more effective than hot water in most cultivars. The combination of FLU with water at 48 degrees C further improved the fungicide performance. Indeed, reduced levels (a fourth) of active ingredient were required to achieve a control of decay comparable to that for treatment at 20 degrees C. Residue levels in fruit after treatment with 100 mg L-1 FLU at 20 degrees C or with 25 mg L-1 FLU at 48 degrees C averaged approximately 0.6-2 mg kg-1, which were notably lower than the maximum residue limit (5 mg kg-1) allowed in the United States for stone fruit.     

Influence of aging and salting on protein secondary structures and water distribution in uncooked and cooked pork. A combined FT-IR microspectroscopy and 1H NMR relaxometry study

Fourier transform infrared (FT-IR) microspectroscopy and low-field (LF) proton NMR transverse relaxation measurements were used to study the changes in protein secondary structure and water distribution as a consequence of aging (1 day and 14 days) followed by salting (3%, 6%, and 9% NaCl) and cooking (65 degrees C). An enhanced water uptake and increased proton NMR relaxation times after salting were observed in aged meat (14 days) compared with nonaged meat (1 day). FT-IR bands revealed that salting induced an increase in native beta-sheet structure while aging triggered an increase in native alpha-helical structure before cooking, which could explain the effects of aging and salting on water distribution and water uptake. Moreover, the decrease in T2 relaxation times and loss of water upon cooking were attributed to an increase in aggregated beta-sheet structures and a simultaneous decrease in native protein structures. Finally, aging increased the cooking loss and subsequently decreased the final yield, which corresponded to a further decrease in T2 relaxation times in aged meat upon cooking. However, salting weakened the effect of aging on the final yield, which is consistent with the increased T2 relaxation times upon salting for aged meat after cooking and the weaker effect of aging on protein secondary structural changes for samples treated with high salt concentration. The present study reveals that changes in water distribution during aging, salting, and cooking are not only due to the accepted causal connection, i.e., proteolytic degradation of myofibrillar structures, change in electrostatic repulsion, and dissolution and denaturation of proteins, but also dynamic changes in specific protein secondary structures.     

班豆在浸泡加工过程中吸水特性的模拟

在生产速食干豆过程中,主要包括浸泡、蒸煮和干燥等工序。浸泡的温度和时间直接影响到在浸泡过程中固性物的损失和最终产品的质量。该研究测定了班豆在浸泡过程中在不同温度和时间下的吸水和固性物的损失特性,同时利用数学模型预测了在变温情况下班豆的吸水特性。该研究结果将对生产高质量的速食班豆有一定的指导作用