Physico-Chemical Characteristics and In Vitro Gastro-Small Intestinal Digestion of New Zealand Ryegrass Proteins

Abstract

Being widely abundant, grass proteins could be a novel source of plant proteins for human foods. In this study, ryegrass proteins extracted using two different approaches-chemical and enzymatic extraction, were characterised for their physico-chemical and in vitro digestion properties. A New Zealand perennial ryegrass cultivar Trojan was chosen based on its higher protein and lower dry matter contents. Grass protein concentrate (GPC) with protein contents of approximately 55 and 44% were prepared using the chemical and enzymatic approach, respectively. The thermal denaturation temperature of the GPC extracted via acid precipitation and enzymatic treatment was found to be 68.0 ± 0.05 °C and 66.15 ± 0.03 °C, respectively, showing significant differences in protein’s thermal profile according to the method of extraction. The solubility of the GPC was highly variable, depending on the temperature, pH and salt concentration of the dispersion. The solubility of the GPC extracted via enzymatic extraction was significantly lower than the proteins extracted via the chemical method. Digestion of raw GPC was also studied via a gastro-small intestinal in vitro digestion model and was found to be significantly lower, in terms of free amino N release, for the GPC prepared through acid precipitation. These results suggest that the physico-chemical and digestion characteristics of grass proteins are affected by the extraction method employed to extract the proteins. This implies that selection of an appropriate extraction method is of utmost importance for achieving optimum protein functionality during its use for food applications.

Valorization of green biomass Azolla pinnata fern: multi‐parameter evaluation of processing conditions on protein extractability and their influence on the physicochemical, structural, techno‐functional properties and protein quality

“…The protein content of AFPC significantly increased (P < 0.05), while fat, carbohydrate, moisture and ash contents significantly reduced (P < 0.05) compared to AFP due to the alkaline extraction process. Comparable results were reported for protein concentrates extracted from green biomass, 3,11 indicating that A. pinnata fern is rich in proteins, and a potential source for the production of protein concentrates.…”

“…1,2 Green plants, aquatic ferns and algae have immense potential for the production of plant-based protein concentrates to be utilized as value-added food ingredients. 3,4 To date, proteins have been extracted from a wide range of plant sources including green biomass such as aquatic weeds/ferns, 5,6 green leaves, 7,8 seaweeds, 9 microalgae, 10 and ryegrass, 11 seeds, 12 and legumes. 13 The nitrogen-fixing aquatic free-floating fern Azolla pinnata is the only genus from the Salviniaceae family that grows rapidly in tropical to temperate areas.…”

Current Status and Nutritional Value of Green Leaf Protein

“…The majority of luminal and cytosolic leaf proteins are highly soluble, while the proteins associated with thylakoid and plasma membranes show decreased solubility [ 86 ]. This can be partially improved by a successful pH-shift approach that solubilizes proteins at alkaline pH 11–12 with chemical additives such as NaOH and NH 4 OH before neutralizing the protein solution at pH 7 with HCl [ 97 ]. Protein solubility can be further improved with high pressure homogenization [ 98 ], glycation-induced structural modification [ 99 ], ultrasonic treatment [ 100 ], or enzymatic hydrolysis [ 101 ].…”

Biorefinery of Green Biomass─How to Extract and Evaluate High Quality Leaf Protein for Food?

“…Similarly, the solubility of leaf protein from perennial ryegrass was improved by solubilizing at alkaline pH before readjusting to neutral pH. 173 In addition to pH, the method used for protein extraction can also affect the solubility. For instance, alkaline extraction limits the solubility of protein from alfalfa leaves.…”

“…The solubility is slightly higher at pH 2 and increases from pH 5 to a maximum of ∼80% at pH 10. ,,,, Using a pH-shift method where the protein concentrate is solubilized at pH 11 or 12 prior to readjustment to pH 7 increases the protein solubility at pH 7, but the alkaline pH also induce formation of protein cross-linking products, lanthionine, and lysinoalanine, which lowers the content of the essential amino acids, cysteine, and lysine and lowers the protein digestibility and may as well change other functional properties. Similarly, the solubility of leaf protein from perennial ryegrass was improved by solubilizing at alkaline pH before readjusting to neutral pH …”