Exploring metabolic responses of potato tissue induced by electric pulses

In this study, we investigated the metabolic responses of potato tissue induced by pulsed electric field (PEF). Potato tissue was subjected to field strengths ranging from 30 to 500 V/cm, with a single rectangular pulse of 10 μs, 100 μs, or 1 ms. Metabolic responses were monitored using isothermal calorimetry, changes on electrical resistance during the delivery of the pulse, as well as impedance measurements. Our results show that the metabolic response involves oxygen consuming pathways as well as other unidentified events that are shown to be insensitive to metabolic inhibitors such as KCN and sodium azide. The metabolic response is strongly dependent on pulsing conditions and is independent of the total permeabilization achieved by the pulse. Evidence shows that calorimetry is a simple and powerful method for exploring conditions for metabolic stimulation, providing information on metabolic responses that can not be obtained from electrical measurements. This study set the basis for further investigations on defense-related consequences of PEF-induced stress.Sparbanksstiftelsen Färs & Frosta (Sweden).Fundação para a Ciência e a Tecnologia (FCT).Lund University (Sweden).Department of Cell and Organism Biology; Department of Plant Biochemistry

Quality evaluation of beverage produced from pre-treated tigernut (Cyperus esculentus)

Tigernut seeds were subjected to various pre-treatments before processing into beverage. Beverage samples from pretreated and untreated tigernut were evaluated for physical and chemical properties. Sensory evaluation of the beverage samples were carried out and the best preferred tigernutbeverage was compared with a popularly consumed beverage, soymilk. All the pre-treatments, except germination, yielded beverage samples with enhanced total solids and corresponding increase in sediment height, while soluble solids were increased with germination and pregelatinization. Roasting and pre-gelatinization of the seeds resulted in non significant reduction in pH when compared with the untreated sample. Sensory properties of beverage produced from the untreated tigernut were comparable to those of soymilk in almost all the quality attributesevaluated. This observation suggests that tigernut beverage could serve as a good alternative to local beverages in Nigeria

Optimization of important production factors of a non-alcoholic beverage from roselle calyx, sorghum stem sheath and local spices

RSM was used to optimize the important processing variables for a non-alcoholic beverage (NAB) from roselle calyx, sorghum stem sheath and two local spices. A CCRD consisting of six variables reduced to five for mathematical convenience [Roselle Calyx/Sorghum Stem Sheath, (RC/SSS, 0-75/25-100 g), ginger (0-1.50 g/100ml), Alligator Pepper (AP, 0-1.50 g/100ml), Extraction Temperature (ET, 80-100oC) and Time of Extraction (TOE, 20-40 min)] with five coded levels (-2,-1, 0, +1, +2) were studied with two replications, making 54 experiments. Mathematical models were developed for the responses [Vitamin C (VC), Total Carotenoids (TC), 1, 1 -Diphenyl-2-picrylhydrazyl (DPPH), Total Phenols (TP), pH, Total Titratable Acidity (TTA)] for making a prediction during NAB production. Storage stability indices [pH, VC, TTA, Total Viable (TVC) and coliform counts] of the beverage were monitored for 28 days. The optimum processing variables were RC/SSS, 66.67 g/33.33 g; ginger, 0.375 g/100ml; AP, 0.375 g/100ml; ET, 85°C; and TOE, 35 min, yielding actual values of 15.33, 1757.2, 0.306 (mg/100ml), 89.21% for VC, TC, TP and DPPH respectively. The developed mathematical models for the measured responses could be successfully used for their prediction during non-alcoholic beverage production with a correlation coefficient (R2) ranging from 0.84-0.99. Reduction in pH (4.98-2.66) and VC (15.33 -12.69 mg/100 ml) were observed while TTA increased (1.70-5.02%) during storage. There was no coliform growth throughout the storage period, however, after 7 days, TVC was 7x102 CFU/ml

QUALITY EVALUATION OF HARD DOUGH BISCUIT PRODUCED FROM FERMENTED BAMBARA GROUNDNUT TEMPEH AND WHEAT FLOUR MIXES

There is growing interest in fortifying wheat flour with high lysine material, such as bambara groundnut flour, to improve the essential amino acid balance of baked food products. Bambara groundnut is not adequately utilized in Nigeria. In this study, wheat flour in a standard biscuit formulation was partially or fully substituted with fermented bambara groundnut tempeh flour at six levels: 0%, 5%, 10%, 25%, 40% and 100%. The composite flours were analyzed for physic-chemical properties such as pH, water absorption capacity, bulk density, pasting characteristics and reconstitution index. Biscuit samples were them evaluated for chemical composition, texture, microbial characteristics and sensory properties. Increasing levels of fermented bambara tempeh flour in the mix resulted in changed flour characteristics. Incorporation of fermented bambara tempeh flour exerted positive influence on the nutritional status of the resultant biscuit products based on the level of substitution. Sensory evaluation tests revealed that biscuit sample prepared form wheat flour substituted with 5% fermented bambara groundnut tempeh flour consistently had the highest rating in terms of all the quality attributes assessed. Biscuit that closely followed this was that from pure wheat flour while rating for other samples gradually decreased with increasing level of substitution with bambara groundnut tempeh flour. All the biscuit samples were however acceptable though at varying degrees depending on the level of bambara flour incorporation