Influence of fertilizer application on biomass yield and nutritional quality of Mustard Spinach (Florida) Broadleaf in South Africa

K.A. Seetseng¹, A.S. Gerrano¹*, S. Mavengahama², H.T. Araya¹ and C.P. Du Plooy¹

¹Agricultural Research Council, Vegetable and Ornamental Plants, Private Bag X293, Pretoria 0001, South Africa
²Crop Science Department and Food Security and Safety Research Group, Faculty of Natural and Agricultural Sciences, North-West University P/Bag X2046, Mmabatho 2735, South Africa
*Correspondence: agerrano@arc.agric.za

Abstract:

Mustard Spinach (Florida Broadleaf) is an indigenized leafy vegetable grown in Southern Africa. It is a good source of vitamins and mineral nutrients. An understanding of its response to fertilizer application is important in developing cultural practices for improved yield of the crop. Furthermore, improving fertilizer use efficiency such as nitrogen (N), phosphorus (P) and potassium (K) would result in improving cropping system. Therefore, a field experiment was conducted in 2010 and 2011 winter cropping season to determine the influence of NPK applications and their interactions on biomass yield and nutritional values of Mustard spinach. A randomized complete block design replicated four times were used for the experiment. ANOVA showed significant variation among the treatments. The values for total fresh biomass yield ranged from 252–4,510 and 820–4,982 kg ha^-1 in 2010 and 2011 cropping seasons, respectively. Omission of P had 4,510 kg ha^-1 of total fresh biomass yield, while omission of K had 4,506 kg ha^-1 in the first season. The lowest N content (2.63%) was recorded when nitrogen fertilizer was omitted. Full NPK application increased the content of N and K on the leaf tissues of Mustard Spinach. The highest percentage of dietary fiber was observed when K was omitted. The values recorded for ascorbic acid content varied from 126.94 and 117.42 mg 100g^-1, respectively for both seasons. Iron was more concentrated on the treatments, where K was omitted. Mustard Spinach responded to fertilizer application and the results validated that application of NPK had a beneficial effect on increased production and productivity of the crop tested for small scale farmers.

Key words:

Investigation of extruded cereals enriched with plant by-products and their use in fermented beverage production

D. Konrade¹, I. Lidums¹*, D. Klava¹, E. Ence² and A. Kirse-Ozolina¹

¹Latvia University of Life Sciences and Technologies, Faculty of Food Technology, Department of Food Technology, 22 Rigas street, LV-3001 Jelgava, Latvia
²Milzu Ltd., "Miķeļi", Rumba parish, Kuldiga county, Latvia
*Correspondence: ivo@ilm.lv

Abstract:

The aim of the study was to analyse the quality of extruded cereals enriched with plant by-products and to obtain fermented drinks from production rejects. Extrusion was performed with co-rotating twin-screw extruder (compression ratio 8:1) at MILZU Ltd. from rye and oat flour (80:20, control samples) with addition of apple (ABF), carrot (CBF) and pumpkin (PBF) by-product flour in various amounts (10%, 15% and 20%). Naturally fermented kvass production process was used for non-alcoholic fermented beverage production. Total dietary fibre (TDF), textural properties and sensory features of extruded products after addition of by-products (BP) were determined. Dry matter, active acidity and sensory properties were analysed in fermented beverages. The obtained results showed a 12-55% increase in TDF of extruded cereals (11.8 g 100 g^-1) after addition of plant by-products. All extruded samples with BP showed lower hardness levels than control (35.55 ± 2.95 N); samples with PBF were the least hard (P < 0.05).
Samples with the lowest bulk density were obtained by the addition of 10% and 15% PBF, and 15% CBF, whereas addition of apple by-product flour in all tested concentrations gave the samples a higher bulk density compared to control. Highest taste and aftertaste scores using 5-point hedonic scale were given to samples with addition of 15% and 20% ABF, which also showed high consumer acceptance. With regards to fermented drinks, the highest dry matter content was found in PBF and ABF drink, 8.1 ± 0.1 and 7.0 ± 0.1, respectively. Sensory evaluation of fermented beverages showed that the intensity of flavour, acidity and aroma was most pronounced in sample with ABF, whereas colour was most pronounced in sample with PBF. In order to reduce production costs, it is possible to use production rejects of extruded cereals enriched with plant by-products to obtain new products.

Key words:

by–products, dietary fibre, extrusion, fermented beverage, sensory properties