Evaluation and standardisation of small‐scale canning methods for small white beans (Phaseolus vulgaris L.) canned in tomato sauce

Canning and evaluation procedures should be standardised to ensure that beans selected, based on canning quality, meet the requirements set by the market and processors. For the purpose of evaluating the canning qualities of small white beans in tomato sauce, three small‐scale canning techniques were evaluated, one of which was found to deliver a product with quality parameters similar to those of international standards. Using South African small white bean cultivars and the selected method, Teebus, the cultivar used by industry as the standard to indicate acceptable canning quality, displayed better visual appearance and less split beans than with the other two methods. The percentage washed drained weight and texture values of Teebus were also in agreement with international standards. The evaluation procedure for the small white beans after canning was also optimised, by comparing two procedures, which identified texture, visual appearance (scale 1 to 10), splits (scale 1 to 10), hydration coefficient, clumping, size and colour as the statistically most suitable quality parameters. With the aid of the developed method, it was possible to define standard values for South African ‘choice’ and ‘standard’ grade beans, which previously was based only on ‘visual inspection’ by a trained inspection panel. Copyright © 2006 Society of Chemical Industry     

Postharvest treatments with radio frequency for 10 and 20 kg batches of black beans (Phaseolus vulgaris L.)

Radio frequency (RF) heating has been considered an alternative to conventional postharvest disinfestation methods in stored agricultural products. RF treatments at pilot scale (12 kW, 27.12 MHz) were applied in black beans (batches of 10 and 20 kg), until reach the target temperature for weevil mortality (50 °C). Temperature was held by 1 min, and then beans were cooled by forced air. During the protocol, the temperatures were followed by thermal images. For the 10 kg batch, the average heating time was 2.72 min, while for the 20 kg batch, only 1.29 min were required to reach the target temperature of 50 °C. This reduction in heating time is due to dielectric heating provides rapid and volumetric heating. Average cooling time was 14.75 and 26.75 min for batches of 10 and 20 kg respectively. The heating uniformity index values (λ) were close to zero (0.025 for 10 kg batch and 0.023 for 20 kg), indicating even heating. Water absorption capacity, density and viability of beans were not affected by the RF treatments (P > 0.05). Due to volumetric heating, better results were obtained for 20 kg batch, demonstrating the feasibility of RF technology for disinfestation purposes in relatively large batches of black beans.     

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.     

Comparison of the canning quality of small white beans (Phaseolus vulgaris L.) canned in tomato sauce by a small‐scale and an industrial method

The use of laboratory canning techniques to predict the commercial canning quality of dry beans is widely accepted in bean breeding. The validation of laboratory canning procedures is determined by its relationship with commercial practices. Laboratory evaluation of the canning quality of industrially canned beans obtained from retailers stressed that canning quality standards for South African small white beans in tomato sauce need defining. Four small white bean cultivars were canned and evaluated according to laboratory procedures and the same cultivars were supplied to an industrial canner to be canned according to industrial procedures. Different canning parameters used in the laboratory (hydration coefficient, percentage washed drained weight, visual appearance, splits, size, texture and colour) and by industry (water uptake, percentage washed drained weight, splits, size) necessitated the use of multivariate analysis to compare the two sets of data. Canonical variate analyses showed the same groupings of cultivars according to canning quality for laboratory and industrial canning. Laboratory procedures were therefore as successful as industrial procedures in grouping cultivars according to canning quality. For bean breeding purposes, it was also shown that the laboratory canning and evaluation method is able to detect the same environmental and genetic effects on canning quality that also affect industrial canning. Copyright © 2006 Society of Chemical Industry     

Comparison of high-performance liquid chromatography and spectrofluorimetry for vitamin C analysis of green beans (Phaseolus vulgaris L.)

 A spectrofluorimetric method and a chromatographic method [high-performance liquid chromatography – ultraviolet (HPLC-UV) detection] were compared for vitamin C analysis of green beans. For HPLC-UV, the determination was performed before [ascorbic acid (AA)] and after reduction with dithiothreitol [AA + dehydroascorbic acid (DHAA)]; for spectrofluorimetry, DHAA was determined after oxidation with activated charcoal. The fluorimetric determination of DHAA before oxidation was also carried out, and showed good precision but poor accuracy (very high recovery percentages). HPLC-UV showed better linearity and sensitivity, while spectrofluorimetry was more precise. Both methods were suitable for green bean samples, and the choice of which one to use depends on the particular interest of the analysis: spectrofluorimetry may be preferable when the total content of vitamin C is required, but not for individual analysis of each form. HPLC-UV is more suitable when the interest of the analysis is the ascorbic acid form as a deterioration index of vegetable products. Received: 29 March 1999 / Revised version: 12 May 1999     

Use of low-temperature extrusion for reducing phytohemagglutinin activity (PHA) and oligosaccharides in beans (Phaseolus vulgaris L.) cv. Navy and Pinto

Bean (Phaseolus vulgaris L.) lectins and oligosaccharides are the anti-nutrients that limit dry bean consumption. The objective of this study was to study the effects of low temperature (85 °C) extrusion and steam-cooking (82 °C) on the fate of lectin, analysed as phytohemagglutinin activity (PHA), and the oligosaccharides, raffinose and stachyose. Both extrusion processing and steam-cooking significantly (p ? 0.05) reduced the lectin in bean flour by 85–95% over raw bean flours (control). The stachyose content in extruded navy bean flours was comparable to that in raw and steam-cooked flours while extruded pinto bean flour had significantly lower stachyose content than that found in raw and steam-cooked flour. The raffinose content of both navy and pinto extruded flours, though lower than raw bean flours, was significantly higher than that in steam-cooked flours. The results of this study demonstrated that extrusion processing at relatively lower temperature can be effective in eliminating lectins and reducing oligosaccharides.     

Thermal treatment of common beans (Phaseolus vulgaris L.): Factors determining cooking time and its consequences for sensory and nutritional quality

Over the past years, the shift toward plant-based foods has largely increased the global awareness of the nutritional importance of legumes (common beans (Phaseolus vulgaris L.) in particular) and their potential role in sustainable food systems. Nevertheless, the many benefits of bean consumption may not be realized in large parts of the world, since long cooking time (lack of convenience) limits their utilization. This review focuses on the current insights in the cooking behavior (cookability) of common beans and the variables that have a direct and/or indirect impact on cooking time. The review includes the various methods to evaluate textural changes and the effect of cooking on sensory attributes and nutritional quality of beans. In this review, it is revealed that the factors involved in cooking time of beans are diverse and complex and thus necessitate a careful consideration of the choice of (pre)processing conditions to conveniently achieve palatability while ensuring maximum nutrient retention in beans. In order to harness the full potential of beans, there is a need for a multisectoral collaboration between breeders, processors, and nutritionists.     

Multivariate assessment of canning quality,chemical characteristics and yield of small white canning beans (Phaseolus vulgaris L) in South Africa

The canning quality of small white dry beans produced in South Africa is subject to environmental effects, resulting in inconsistent quality. The aim of this study was to evaluate quality parameters and their genotype × environment interactions and to attain a better understanding of variates that discriminate between cultivars for canning quality, using multivariate analysis. Six small white cultivars were evaluated across 11 environments. The cultivars differed significantly over localities for eight of the characteristics. Significant genotype × environment interactions existed for protein, seed size, soaked bean mass, visual appearance, splits, texture and yield. Low linear correlation coefficients indicated that no single parameter could explain the variation in yield and canning quality attributes. Canonical correlation analysis was used to determine to what extent the variation in biochemical components was responsible for differences in canning quality. The differences between unacceptable, standard grade and choice grade cultivars were examined by means of canonical variate analysis. The differences between cultivars were mainly due to visual appearance and percentage K. The main differences between standard grade and choice grade beans were in seed size and percentage Ca. A model was computed for the objective characterisation of variation in canning quality attributes. © 2000 Society of Chemical Industry