by Okafor D. C., Onuegbu N. C., Odimegwu N. E., Ibeabuchi J. C., Njoku N. E, Agunwa I. M., Ofoedu C. E and Adirieje B.C.
Original Research
Four species of oyster mushroom(Pleurotus ostreatus, Pleurotus sajor-caju, Pleurotus pulmonarius and Pleurotus populinus) were evaluated for their antimicrobial and antioxidant capacity (total antioxidant activity). The total antioxidant activity differed significantly. Mean total antioxidant activities were (P.ostreatus = 35.36±0.01mm,P.sajor-caju = 32.26±0.02mm,P.pulmonarius = 28.86±0.01mm,P.populinus = 26.65±0.01mm). Antimicrobial activities of the extracts against Bacillus cereus,Streptococcus agalactiae,Agrobacterium vitis, Pseudomonasaeruginosa, Escherichia coli andShigella dysenteriae were investigated. Antimicrobial activities of the oyster mushroom extracts against Bacillus cereus,Streptococcus agalactiae,Agrobacterium, Pseudomonasaeruginosa, Escherichia coli andShigella dysenteriae were examined by agar well diffusion method and zones of inhibition varied for different organisms but zones of inhibition were highest inP.ostreatus and P.sajor-caju for all tested organisms except inE.coli and S.dysentriae whereP.pulmonarius and P.populinus had higher zones. P.ostreatus andP.sajor-caju were not significantly different against all tested microorganisms but were found to be significantly different (p ≥ 0.05) fromP.pulmonarius and P.populinusagainst B.cereus, E.coli andS.dysenteriae. P.pulmonarius andP.populinus were not significantly different in their inhibition against all tested microorganisms.
American Journal of Food Science and Technology. 2017, 5(2), 64-69. DOI: 10.12691/ajfst-5-2-6
Pub. Date: May 10, 2017
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by T.G.G. Uthpala and R.A.U.J. Marapana
Original Research
Gherkin (Cucumis sativus L.) is an important cucurbitaceous vegetable. The pickling type gherkins are produced in Sri Lanka since 1988 for export market and it expanded over several agrological regions. Locally grown two gherkin varieties (Ajax and Vlasset) were tested for proximate composition (moisture, dry matter, ash, mineral, protein, fat, dietary fibre and carbohydrate) of raw fruits (AOAC methods) and within 6 month of brine fermentation, firmness measurements (FTA) were recorded and varieties were evaluated. Vlasset and Ajax varieties contained 96.30% and 95.54% moisture, respectively. The ash, protein and fat were higher (p<0.05) and dietary fibre, carbohydrate lower in Ajax. Mg, K and Zn content were higher (p<0.05) in Ajax noted as 16.60 ± 1.47, 194.0± 7.80 and 14.69± 0.40 respectively while Vlasset was noted lower values. Ca (10.62± 0.59 ) and Na (13.46 ±0.43) were greater in Vlasset while Ajax was given lower values. Both varieties showed K to be highest followed by Zn, Na and Ca while Mg amount was secondly highest in Ajax and lowest in Vlasset. Firmness variation of both exocarp and mesocarp of Vlasset has shown same pattern while giving maximum reading in the 2nd month after fermentation. Firmness variation of exocarp and mesocarp of Ajax was not followed same pattern while maximum value was recorded in 5th and 2nd month respectively. These findings indicated that Sri Lankan gherkins have similar nutrient values as cucumber. Even initial moisture content is higher in Vlasset than Ajax variety the better textural quality is apparent in Vlasset supported by physicochemical properties of higher dietary fibre, carbohydrate, minerals (Ca, Na) and having higher firmness in mesocarp tissue than exocarp.
American Journal of Food Science and Technology. 2017, 5(2), 61-63. DOI: 10.12691/ajfst-5-2-5
Pub. Date: April 18, 2017
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by Pierre Nobosse, Edith N. Fombang and Carl M F. Mbofung
Original Research
The antioxidant activity of plant materials is affected by post-harvest treatments. The present study was undertaken to evaluate the effects of steam blanching and two (solar and electric) drying methods on physicochemical composition, antioxidant activity (AOA) and rehydration properties of Moringa oleifera leaves. Fresh and blanched leaves ofM. oleifera were dried by indirect solar-drying (≈35 ± 3°C, 12 h) and hot air electric drying (50°C, 5 h), and milled into flour (particle size ≤ 500 µm). Fresh, blanched and dried leaves were analyzed for their nutrient and phytochemical contents, antioxidant activity (Total Reducing Power (TRP) and 2,2-diphenyl-2-picryl hydrazyl (DPPH) scavenging activity) as well as rehydration properties (water absorption capacity (WAC) and water solubility index (WSI). Macronutrients content of M. oleiferaleaves were unaffected by blanching and drying. Irrespective of drying method, drying had a significant negative effect (p < 0.05) on phytochemical contents, TRP and DPPH scavenging activity ofM. oleifera leaves. Blanching prior to drying, however, dimmed the negative effect of the latter. Blanched leaves exhibited higher carotenoids content, TRP and WAC compared to unblanched leaves; whereas blanching caused a decrease in DPPH scavenging activity, vitamin C and WSI. This study highlights that fresh and blanched Moringa oleifera leaves are more suiTableas a source of dietary antioxidants than dry leaves.
American Journal of Food Science and Technology. 2017, 5(2), 53-60. DOI: 10.12691/ajfst-5-2-4
Pub. Date: February 20, 2017
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by Magda S. Sharara
Original Research
The present study aimed at utilization of copigmentation phenomenon to increase the stability of anthocyanin in roselle extract during storage at 10°C for 60 days by the addition of some phenolic acids (ferulic, cinnamic and coumaric) as a copigments and investigate the possibility of using copigmented extracts as a natural food colorants instead of harmful synthetic ones. The data obtained confirmed that addition of the aforementioned phenolic acids to roselle anthocyanin extracts resulted in an increment of anthocyanin and color stability during storage comparing with the control extract. At the end of storage period, the reduction in anthocyanin content were 31.53, 20.48, 9.31 and 5.52% for control and extracts copigmented with ferulic, cinnamic coumaric acids respectively. Addition of phenolic acids to roselle extract also attributed to a hyperchromic effect and bathochromic shift in visible absorption spectra of copigmented extracts compared to the control. Roselle anthocyanin extracts treated with phenolic acids showed a noticeable antioxidant and antimicrobial activities compared with control extract. Marshmallow prepared from studied copigmented roselle extracts as a natural colorants was highly accepted by panelists.
American Journal of Food Science and Technology. 2017, 5(2), 45-52. DOI: 10.12691/ajfst-5-2-3
Pub. Date: February 15, 2017
16196 Views3396 Downloads
by Onwordi C.T., Olanrewaju A.J., Wusu A.D. and Oguntade B.K.
Original Research
Residual sulphite as sulphur dioxide causes severe systemic reaction characterised by difficulty in breathing and cardiovascular collapse. Few studies have described exposure of humans to excessive preservatives from food and beverage products in Nigeria. Little is also known about the levels of preservatives such as benzoate, sorbates, sulphur (IV) oxide, sorbic acid and ascorbic acid in carbonated drink (CD) ,fruit juices (FJ), sport drinks(SD) and dairy drinks. Commonly consumed carbonated drinks (14), fruit juices (14), sport drinks (2) and dairy drinks (3) purchased in various markets in Lagos metropolis were analysed for the preservative contents using standard methods. Residual sulphite levels expressed as sulphur (IV) oxide in CD ranged from 4.0 ¨C 15.2 mg/L, FD ranged from ND-13.6 mg/L. SD ranged from 3.6-13.6 mg/L while in DD it ranged from ND ¨C 4.7 mg/L. Benzoic and citric acid contents for CD, FJ, SD and DD ranged from 222-702 mg/L & 0.38-0.89% m/v ; 168-799 mg/L & 0.26-0.89% m/v; 451-494 mg/L & 0.24-0.32% m/v; 132-318 mg/L & 0.36-0.7%m/v, respectively. The pH of the drinks ranged from 2.46-5.58. 55% of the samples analysed have benzoic acid content below the regulatory limit. Values of pH, ascorbic acid and sulphur (IV) oxide for all samples were in conformity with standards. Benzoic acid and ascorbic acid concentration was higher in Sport drinks than other samples while levels of sulphur (IV) oxide and citric acid were more in carbonated drinks. The citric acid values of about 21% of the samples analysed had value above required limit of 0.5%m/v. The sum total of the preservatives levels are within the regulatory limit, however, 71.4% of the carbonated and 100% of the fruit drinks have benzoic acid level above the national permitted level of 250 and 150 mg/L respectively.
American Journal of Food Science and Technology. 2017, 5(2), 38-44. DOI: 10.12691/ajfst-5-2-2
Pub. Date: February 13, 2017
16620 Views3659 Downloads
by David Adu-Poku and Jacob K. Agbenorhevi
Original Research
The effect of microstructure and temperature on the mechanism of potassium diffusion through and out of potato was studied at 15-120°C by means of the scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and leaching experiments. Tissues from different regions of the same tuber differed in their microstructural architecture and response to heat. The water-rich perimedullary region showed a regular and more defined arrangement of cells with larger vacuoles than the cortex which had irregularly arranged cells with densely packed starch granules. Granule morphology remained visibly unchanged at temperatures below 50°C. The gelatinization temperatures and range were significantly higher in the perimedullary. In addition, the average transition enthalpy was about 3 J/g lower in the perimedullary. The different microstructural architecture and thermal properties of tissues from different regions of the same tuber were linked with different membrane permeabilities and solubility with implications for the rate and mechanism of potassium transport through and out of potatoes.
American Journal of Food Science and Technology. 2017, 5(2), 31-37. DOI: 10.12691/ajfst-5-2-1
Pub. Date: February 10, 2017
13813 Views3369 Downloads3 Likes