The effect of ageing temperature on the physicochemical properties, phytochemical profile and α-glucosidase inhibition of Hibiscus sabdariffa (roselle) wine

The effect of temperature (6, 15 and 30 °C) during ageing on the colour, phytochemical composition and bioactivity of roselle wine was investigated over 12 months. At the end of ageing, wines stored at 6 °C had the highest colour density and lowest polymeric anthocyanins. The initial concentration of most of the individual phenolic compounds decreased during ageing, with reduction of monomeric anthocyanins contributing to the formation of anthocyanin-derivatives (pyranoanthocyanins), eight of which were identified tentatively and reported here for the first time in roselle wine. The decrease in individual phenolic compounds did not affect inhibition of α-glucosidase (maltase) activity, which remained relatively low but stable throughout ageing. Diethyl succinate was the only volatile clearly influenced by ageing temperature, with the most pronounced effect at 30 °C (∼256 fold increase). In summary, the final concentrations of anthocyanins and diethyl succinate were the major compounds influenced by ageing temperature

Genetic diversity of provitamin-A cassava (Manihot esculenta Crantz) in Sierra Leone

Open Access Article; Published online: 04 Mar 2020Understanding the genetic diversity among accessions and germplasm is an important requirement for crop development as it allows for the selection of diverse parental combinations for enhancing genetic gain in varietal selection, advancement and release. The study aimed to characterize 183 provitamin A cassava (Manihot esculenta Crantz) accessions and five Sierra Leonean varieties using morphological traits, total carotenoid content and SNP markers to develop a collection for conservation and further use in the cassava breeding program. Both morphological parameters and 5634 SNP markers were used to assess the diversity among the provitamin-A cassava accessions and varieties. Significant differences were observed among the accessions for most of the traits measured. The first five PCs together accounted for 70.44% of the total phenotypic variation based on yield and yield components among the 183 provitamin-A cassava accessions and five Sierra Leonean varieties. The present study showed that provitamin-A cassava accessions in Sierra Leone have moderate to high diversity based on morphological and molecular assessment studies. The similarity index among the 187 and 185 cassava accessions grouped them into 6 and 9 distinct clusters based on morphological and molecular analyses, respectively. A significant positive, but low correlation (r = 0.104; p\0.034), was observed between the two dendrograms. The results obtained will serve as a guide and basis of germplasm management and improvement for total carotenoid content, yield and African cassava mosaic disease resistance in Sierra Leone

Foam-Mat Freeze-Drying of Blueberry Juice by Using Trehalose-β-Lactoglobulin and Trehalose-Bovine Serum Albumin as Matrices

This study aimed to evaluate the effect of pure protein compounds and trehalose incorporated into blueberry juice for foam-mat freeze-drying on the foam and powder properties. Foam-mat freeze-drying (FMFD) of blueberry juice was tested at − 55 °C for 24 h. Matrices used were trehalose + β-lactoglobulin (T3BL1) and trehalose + bovine serum albumin (T3A1) and compared with maltodextrin + whey protein isolate (M3W1). Physicochemical properties of foam and powder, e.g., foam stability, foam density, moisture, rehydration time, color, particle morphology, total phenolic, and anthocyanins (total and individuals), were investigated. T3BL1 and T3A1 had more stable foam than M3W1. However, overrun of T3BL1 and T3A1 foamed were inferior to the M3W1 sample. The M3W1 sample recovered 79% powder (dry weight) and was superior to others. Rehydration time of powdered T3BL1 and T3A1, with bulk densities of 0.55–0.60 g cm−3, was the fastest (34–36 s). The blueberry powders of M3W1 showed more irregular particle size and shape, while the samples with trehalose and pure proteins generated particles of more uniform size with obvious pores. T3BL1 and T3A1 showed less redness (a*) values than the M3W1 product. All samples were considered pure red due to hue values < 90. M3W1 was superior in total phenolic content (TPC) and total monomeric anthocyanins (TMA) compared with both samples made with trehalose + β-lactoglobulin and trehalose+bovine serum albumin. Delphinidin-3-glucoside (Del3Gl) concentration was found to be higher in M3W1. Also, M3W1 had higher cyanidin-3-glucoside (Cyn3Gl) and malvidin-3-glucoside (Mal3Gl) concentration. M3W1 also prevented the degradation of these bioactive compounds better than the other FMFD samples. The use of pure proteins and trehalose as matrices in the FMFD process had little advantage compared with maltodextrin/whey protein isolate. Thus, maltodextrin/whey protein isolate seems an ideal matrix for the manufacture of FMFD blueberry

Evaluation of total monomeric anthocyanin, total phenolic content and individual anthocyanins of foam-mat freeze-dried and spray-dried blueberry powder

Anthocyanins in blueberries have generated considerable interest in the scientific community owing to their pleiotropic health benefits against cardiovascular diseases, diabetes and cancer. However, anthocyanins are labile in nature due to their sensitivity to temperature, light, pH, and oxidation and final concentrations in blueberry products is influenced by the processing technique employed. This study evaluated the effect of foam-mat freeze-drying (FMFD) and spray-drying (SD) using a feed rate of 180 and 360 mL/h on the total monomeric anthocyanin (TMA), total phenolic content and contents of individual anthocyanins cyanidin-3-glucoside (Cyn3Gl), delphinidin-3-glucoside (Del3Gl) and malvidin-3-glucoside (Mal3Gl) in blueberry powders. The protective effect of mixtures of encapsulating agents namely: maltodextrin (MD), trehalose, whey protein isolate (WPI), bovine serum albumin (BSA) and β-lactoglobulin on anthocyanins and phenolic content was also investigated. Anthocyanin content was measured using the pH differential and HPLC methods, while total phenolic content was evaluated using the Folin’s assay. The outcome of the study revealed that concentrations of TMA and individual anthocyanins were higher with FMFD (7.11–8.09 mg/g: TMA) compared to SD samples (4.34–5.69 mg/g: TMA). Furthermore, Del3Gl, Cyn3Gl and Mal3Gl retentions were greater, in the order: FMFD > SD 180 = SD 360. Retention of total phenolic ranged from 68 to 76% and 48–72% in FMFD and SD samples respectively and the choice of the matrix MD/WPI as encapsulating agent was the most effective in protecting blueberry anthocyanins. FMFD is therefore recommended for developing blueberry powders with good retention of anthocyanins

Assessment of aflatoxin and heavy metals levels in maize and poultry feeds from Delta State, Nigeria

The aim of this study was to determine the concentration of total aflatoxin and heavy metals (lead cadmium, chromium and copper) in poultry feed and ingredients from two regions (north and central) in Delta State, Nigeria. A total of 120 samples collected (comprising of maize, soybean meal, layers mash and broiler finisher) directly from poultry farms, feed mills and poultry feed dealers were analysed for moisture content, total aflatoxin and heavy metals (lead, cadmium, chromium and copper) concentrations. Moisture content was analysed using standard Association of Official Agricultural Chemists method, while total aflatoxin and heavy metals concentrations were determined by enzyme-linked immunosorbent assay and atomic absorption spectrometry, respectively. Total aflatoxins concentrations ranged from 12.0 to 20 µg/kg and 21 to 31 µg/kg in samples from north and central region, respectively. Apart from maize, aflatoxin content in other samples from the north was marginally lower (18–20 µg/kg) than permitted levels. On the other hand, aflatoxin levels in samples from the central were all above tolerable limits. Copper content in samples was less than permissible limit, while 44.4, 29.1 and 21% of samples had concentrations of lead, cadmium and chromium, respectively, above permissible limit. The presence of aflatoxin and lead in poultry feeds above permissible limits of 20 µg/kg and 5 mg/kg, respectively, may pose a risk for animal productivity and human health

Inhibition of human α-amylase by dietary polyphenols

Functional foods offer the possibility to modulate the absorption of sugars, leading to benefits for diabetics and those with metabolic syndrome. As part of the characterisation of such foods, inhibition of α-amylase is used to assess components for their potential ability to modify the post-prandial glycaemic response. Many publications on phenolics as potential inhibitors report widely varying assay conditions leading to variable estimates of inhibition. On this basis, we have optimised the in vitro α-amylase inhibition assay and, in particular, we show the importance of removing certain polyphenols after the enzymic reaction when using 3,5-dinitrosalicylic acid since they interfere with this reagent. There was a substantial ~5-fold effect on acarbose IC50 values when working just outside optimal conditions. This shows that inappropriate assay conditions, such as excess enzyme, greatly influence IC50 values and could explain some discrepancies in the existing literature