Optimization of Hoagland solution macro-elements as a culture media, for increasing protein content of duckweeds (Lemna minor).

This study aimed to increase the protein content of duckweed, a promising alternative to animal proteins and a sustainable source of plant protein cultivated via soilless agriculture, by manipulating the culture medium conditions (Hoagland solution). The contribution percentages of KH2PO4 and Ca(NO3)2, pivotal macro-elements in Hoagland solution affecting duckweed protein content, were determined using Plackett-Burman factorial design as 33.06 % and 36.61 %, respectively. Additionally, optimization was conducted employing response surface methodology, incorporating pH alongside KH2PO4 and Ca(NO3)2. Under optimal conditions of 3.92 mM KH2PO4, 7.95 mM Ca(NO3)2, and 7.22 pH, the protein content of duckweed increased significantly, reaching 51.09 % from 39.81 %. The duckweed cultivated in modified Hoagland solution exhibited protein content of 41.74 %, while duckweed grown in commercial Hoagland solution displayed protein content of 33.01 %. This study showed protein content of duckweed could significantly increase according to the growth medium and showcasing its potential as a sustainable source of plant protein.

Determination of process parameters and precipitation methods for potential large-scale production of sugar beet leaf protein concentrate.

BACKGROUND: Sugar beet is one of the most produced industrial plants in the world, and during manufacturing it produces a large quantity of leaf waste. Because this waste is rich in protein, this study aimed to identify an efficient method for producing large-scale protein concentrate from sugar beet leaves. RESULTS: Results showed that protein extraction from fresh leaves was more effective than from dried leaves. Maximum protein extraction was achieved at pH 9, compared with pH 7 or 8. Blanching as a pretreatment reduced protein yield during isoelectric precipitation, with a yield of 2.31% compared to 20.20% without blanching. Consequently, blanching was excluded from the extraction process. After extraction, isoelectric precipitation, heat coagulation, and isoelectric-ammonium sulfate precipitation were compared. Although the latter resulted in the highest protein yield, Fourier transform infrared analysis revealed that excessive salt was not removed during dialysis, making it unsuitable for scale-up due to its additional cost and complexity. Therefore, isoelectric precipitation was selected as the appropriate method for protein precipitation from sugar beet leaves. To increase yield, extractions were assisted by ultrasound or enzyme addition. Ultrasound-assisted extraction resulted in an increased protein yield from 20.20% to 28.60%, while Pectinex Ultra SP-L-assisted extraction was the most effective, increasing protein yield from 20.20% to 38.09%. CONCLUSION: Proteins were extracted from fresh sugar beet leaves using optimum conditions (50 °C, 30 min, pH 9) and precipitated at isoelectric point, with enzymatic-assisted extraction yielding the maximum protein recovery. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Optimization of enzyme assisted extraction of protein from the sugar beet (Beta vulgaris L.) leaves for alternative plant protein concentrate production.

This research focused on the effect of temperature (25-75 °C), extraction time (40-120 min) and solvent/solid ratio (15-45 mL/g) and the enzyme assisted extraction on protein extraction efficiency from by-product of sugar beet. 3 different methods were applied in protein isolation and the highest protein yield (34.55%) was obtained by the isoelectric-ammonium sulfate precipitation method. At the optimized condition of temperature 54.25 °C, 81.35 min, and solvent/solid ratio of 27.65 mL/g, the protein yield was found 55.15%. The protein yield has reached 79.01% with an increase of 43.27% with the aid of the enzyme assisted extraction. The physicochemical properties were determined for revealing its potential use in food industry. It is promising that the isolated protein concentrates (SPC-IAP) show high protein content (69.08% d.b) as well as high solubility (98.71% at pH 7.5). SPC-IAP's high brightness (L* = 79.55), low redness (a* = 0.33) and low yellowness (b* = 13.27) values are encouraging for food industry.

Critical electric field strengths of onion tissues treated by pulsed electric fields.

The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (E(c)) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-µs pulses indicate that breakdown of the plasma membrane occurs above E(c)= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either E(c)= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.

Disintegration efficiency of pulsed electric field induced effects on onion (Allium cepa L.) tissues as a function of pulse protocol and determination of cell integrity by ¹H-NMR relaxometry.

The influence of electrical pulse protocol parameters on cell rupture of onion tissues was investigated in order to improve fundamental understanding and to enhance the processing of plant tissues with pulsed electric fields (PEFs). The impact of PEF parameters on cell integrity of 20 mm dia, 4-mm thick disks of Don Victor onions (Allium cepa L.) was determined by ion leakage measurements. Electric field strength, pulse width, total pulse duration, and frequency effects were determined in relation to their effects on cell damage as a function of pulse protocol. Electric field strengths up to 500 V/cm increased the damage efficiency but there was no significant difference in efficiency beyond this field strength. Larger pulse widths increased the degree of tissue disintegration at a constant pulse number. Higher PEF efficiency was achieved with shorter pulse widths and a larger number of pulses at a constant total treatment time. Lower frequencies caused a greater degree of disintegration at constant number of pulses. ¹H-NMR experiments were performed to determine the proton relaxation components of the PEF-treated onion samples and to obtain cell damage information nondestructively. Paramagnetic ion uptake by the onion sample was used to identify different proton relaxation components. Five different proton relaxation components were observed and changes in the 2 components representing different proton environments showed high correlations with ion leakage results (R²= 0.99), indicating that T(2) distributions can be used to obtain information about cell membrane integrity in PEF-treated samples. 1H-NMR proved to be an effective method for nondestructive quantification of cell membrane rupture in onions.