Common beans are a leguminous plant of the genus Phaseolus. They are rich in protein, energy, and minerals. They confer a wide range of health benefits when consumed. Utilization of common bean has however been poor due to high antinutrient content that results in reduced nutrient digestibility and mineral bioavailability. Flatulence after consumption is also a huge deterrent to common bean consumption. Lactic acid fermentation is the most common form of food fermentation with the Lactobacilli spp dominating most spontaneous fermentations. The objective of this study was to determine the effect of lactic acid bacteria (LAB) on the antinutrient and flatulence causing oligosaccharide composition of red haricot bean. A factorial research design was used in the study. Red haricot beans were sorted and soaked for 15 h. The soaked beans were fermented in 2% salt-sugar solutions for 120 h. Experimental batch was inoculated with Lb. plantarum BFE 5092 (IF), and the control batch was spontaneously fermented (SF). Microbial growth and pH were monitored every 24 h during fermentation. After fermentation, the beans were dried and milled, and the flours were subjected to biochemical analysis. ANOVA was done using SPSS statistics 23. The pH decreased significantly (
The year 2016 was declared an international year of pulses by the United Nations (UN) to increase public awareness on the benefits of consuming pulses. Pulses are edible seeds of the legume family in which common beans belong. They are widely grown around the world, hence available and affordable. Common beans are a good source of protein, rich in lysine [
However, though beans are nutritionally rich, they are also high in antinutrients [
In a bid to lower the antinutrients and oligosaccharides in beans, researchers like Adewumi and Odunfa [
Raw red haricot beans (Wairimu) were acquired from the National Cereals and Produce Board (NCPB) Nairobi, Kenya.
The red haricot beans were hand sorted to remove dirt and defective grains. About 500 g of the beans was drawn as control sample, milled raw and stored in freezer awaiting biochemical analysis.
About 1.5 kg of the sorted red haricot beans was washed in distilled water, and all floats were removed. The beans were then soaked in distilled water at a ratio of 1 : 5 weight per volume (
Fermentation solution (2% salt-sugar solution) was prepared by dissolving 12 g of salt and sugar 1 : 1
A pure colony of
About 200 g of soaked beans, from above, was transferred to each fermentation bottle containing 600 ml of 2% salt-sugar fermentation solution prepared above. Exactly, 600
The fermentation bottles were then left on a sterile bench to ferment at
Approximately, 5 ml of the fermentation solution was drawn aseptically after every 24 h of fermentation for pH determination using a pH meter (HI 2211, Hanna Instruments, Japan).
Conventional microbiological methods were used for microbial enumeration. Spread plate method was used. Each analysis was carried out in triplicate. All bacterial and fungal counts were expressed as colony-forming units per millilitre (CFU/ml).
At the end of each fermentation, the fermentation solution was discarded, and the fermented red haricot bean (
Tannin content was determined using the Vanilin-HCL method of Price et al. (1978) using about 0.2 g of bean flour sample. The absorbance of the sample extracts and standard solutions were read at 500 nanometers using a UV-vis photospectrophotometer (UV mini 1240 model, Shimadzu, Japan).
Phytates were extracted using the method of Camire and Clydesdale. (2006) with modification. About 0.5 g of milled bean flours were extracted. Liquid chromatography-mass spectrophotometry (LC-MS) (Genevac, DNA-23050-A00, England) analysis was done using Shimadzu Refractive Index Detector (RID 6A). The mobile phase was 0.005 N sodium acetate in distilled water at a flowrate of 0.5
Quantification of raffinose and stachyose was done using the method of Antonio et al. [
Each analysis was done in triplicate and the experiments conducted three times. Data was presented as
The changes in pH of the fermentation solutions during the fermentation of soaked whole red haricot bean are presented in Figure
Effect of fermentation time on the pH during the fermentation of soaked whole red haricot bean presented as
The fermenting microorganisms were able to break down fermentable sugars in the beans [
The growth of total viable count during fermentation of soaked whole red haricot bean is presented in Table
Effect of soaked whole red haricot beans fermentation on microbial growth (CFU/ML).
Fermentation time | Spontaneous fermentation | |||||||
---|---|---|---|---|---|---|---|---|
LAB | TVC | Coliform | Fungi | LAB | TVC | Coliform | Fungi | |
0 h | ND | ND | ||||||
24 h | ND | ND | ||||||
72 h | ND | ND | ||||||
120 h | ND | ND | ||||||
<0.0001 | <0.0001 | <0.0001 | — | <0.0001 | <0.0001 | <0.0001 | — |
Values are means of triplicate determinations ± SEM. Means in the same column followed by the same superscript are not significantly different
LAB dominated the fermentation of soaked whole red haricot bean after 24 h of fermentation (Table
The LAB counts then decreased to log10 8.3 CFU/ml after 72 h of fermentation and remained unchanged by the end of 120 h of fermentation. In the SF batch, there was a significant increase (
At the start of fermentation, the coliform count was at log10 4 CFU/ml (Table
Fungi was not detected in all the inoculated and spontaneous fermentation batches. This observation is similar to the findings of Granito and Alvarez [
The tannin content in the raw red haricot bean (
Effect of soaking and fermentation on antinutrient content of whole red haricot bean.
Spontaneous fermentation | ||||
---|---|---|---|---|
Treatment | Tannins mg/100 g | Phytates mg/100 g | Tannins mg/100 g | Phytates mg/100 g |
Raw bean | ||||
Soaked | ||||
24 h fermentation | ||||
72 h fermentation | ||||
120 h fermentation | ||||
<0.0001 | <0.0001 | <0.0001 | <0.0001 |
Values are
Fermentation resulted in a decrease in tannin content in all the fermentation batches. In the IF batch, the tannin content reduced from 306.82 mg/100 g in the soaked whole bean to 283.41 mg/100 g after 24 h of fermentation. Higher tannin reduction in the IF batches occurred between 72 h and 120 h of fermentation. At the end of fermentation, the tannin content in the IF batch was 109.50 mg/100 g. In the SF batch, higher tannin losses occurred compared to the batches inoculated with
The phytate content in raw red haricot bean was 482.99 mg/100 g as presented in Table
The concentration of raffinose in the raw red haricot bean (
Fermentation resulted in a decrease in raffinose concentration in both the fermentation batches (Table
Effect of soaking and fermentation on oligosaccharide content of whole red haricot bean.
Spontaneous fermentation | ||||||||
---|---|---|---|---|---|---|---|---|
Treatment | Raffinose mg/100 g | % loss | Stachyose mg/100 g | % loss | Raffinose mg/100 g | % loss | Stachyose mg/100 g | % loss |
Raw bean | 0.00 | 0.00 | 0.00 | 0.00 | ||||
Soaked | 22.64 | 1.37 | 22.64 | 1.37 | ||||
24 h fermentation | 9.52 | 29.97 | 10.16 | 26.91 | ||||
72 h fermentation | 11.21 | 11.68 | 13.75 | 39.95 | ||||
120 h fermentation | 26.85 | 23.08 | 24.78 | 14.59 | ||||
<0.0001 | — | <0.0001 | — | <0.0001 | — | <0.0001 | — |
Values are
The stachyose content of raw red haricot bean was 1264.45 mg/100 g (Table
In the SF batch, stachyose concentration decreased by 26.91% from 1247.17 mg/100 g to 911.61 mg/100 g after 24 h of fermentation. Further decrease of 39.95% and 14.59% in stachyose concentration occurred after 72 h and 120 h of fermentation (Table
Although soaking of red haricot bean lowers tannins, phytate, and raffinose content significantly, it has no significant effect on the stachyose. Yet this is the most abundant oligosaccharide in the bean. Fermentation of soaked whole red haricot beans results in increased significant reduction of tannin, phytate, raffinose, and stachyose concentrations. Fermentation of soaked red haricot bean lowers antinutrient and oligosaccharide content significantly. However, spontaneous fermentation of soaked whole red haricot bean results in significantly higher antinutrient losses. The highest antinutrient and oligosaccharide losses occur between 24 and 72 h of fermentation.
The analyzed data used to support the findings of this study are included within the article.
The authors declare no conflict as a result of publication of this paper.
The research was funded by