Enzymatic hydrolysis of extruded‐expelled soy flour and resulting functional properties

Abstract

Limited hydrolysis (4% degree of hydrolysis) of extruded-expelled soy flour protein (protein dispersibility index = 21) that was poor in solubility and other functional properties was evaluated at pilot-plant scale (5 kg of flour) with two endopeptidases and one exopeptidase. Some hydrolysates were merely spray-dried whereas others were jet-cooked at 104°C for 19 s before spray-drying. Solubility, emulsification capacity and stability, foaming capacity and stability, apparent viscosity, and sensory attributes were then characterized. The type of protease used and hydrothermal cooking affected functional and sensory properties. Protein solubility modestly increased with hydrolysis and jet cooking, but emulsification capacity decreased on hydrolysis and was not restored with hydrothermal cooking. Emulsion stability improved in the endopeptidase hydrolysates, but not in the exopeptidase hydrolysates. The foaming capacities of the hydrolysates for both types of enzymes were better than for the unhydrolyzed control. Highly stable foams were obtained after hydrolyzing with exopeptidase and hydrothermal cooking. Ten percent protein hydrolysate dispersions showed large losses in consistency coefficient and apparent viscosity, which increased significantly with hydrothermal cooking only for the unhydrolyzed control. Difference-from-control sensory evaluation indicated that both jet-cooked and non-jet-cooked enzyme hydrolysates were different from unhydrolyzed controls.Food proteins are critical components of foods owing to their important functional or physicochemical and nutritional contributions. Food protein ingredients are increasingly expected to perform functional roles that are critical to processing efficiency and consumer acceptance of foods. Functional properties of proteins govern their performance and behavior in food systems during processing, storage, and final food preparation as well as relate to sensory qualities. Factors affecting functional properties of food proteins can be classified as intrinsic, extrinsic, and process parameters, and those functional properties can be modified and improved (1). The tools available to modify the structure of proteins and hence alter their functional properties are chemical modifications, heat treatments, and enzymatic modifications. Particular attention has been devoted to enzymatic hydrolysis of proteins (2) because the resulting hydrolysates preserve and frequently enhance biological values, as well as achieve physicochemical properties superior to those of the original protein. Numerous reports on enzymatic modification of soy proteins to improve functional properties are available (3-7) and generally agree that soy protein can be modified to obtain improved functional properties that can be used in highly nutritional products such as beverages and infant formulas.Extruding-expelling (EE) is a relatively new process that combines extrusion and screw-pressing to recover oil from oilbearing seeds (8). A cooked semifluid extrudate is obtained in which the cell walls ...

Protein recovery from enzyme‐assisted aqueous extraction of soybean

“…Unhydrolyzed soy proteins extracted from soy flours 27,28 and extrudates 9 have very low solubility (\10%) between pH 4 and 5. The solubility-pH profiles of skim initially containing 26 and 50 mg/mL protein had minimum solubility between pH 4 and 4.5 (data not shown); however, the percentage of the protein that remained soluble was 70% at pH 4.…”

“…On the other hand, hydrolysis of soy extrudates has been linked to increased bitter, beany, and astringent off-flavors in soy. 9 Conventional methods of soy protein recovery and purification are based on solubility characteristics. SPCs are manufactured by washing defatted soymeal with ethanol, in which soy proteins have a low solubility, resulting in a cake that is 65% protein and is low in antinutritional oligosaccharides, with overall protein yields of 60%-70%.…”

Composition and properties of partially hydrolyzed sunflower protein isolates

“…In most cases limited protein hydrolysis can improve their emulsifying, foaming properties [3][4][5][6][7] and change sensory characteristics [8].…”

Mechanistic insights into solubilization of rice protein isolates by freeze–milling combined with alkali pretreatment

“…However, successful RPI preparation still poses difficulty in solubilizing RPIs under edible conditions; as a result, other functionalities, such as foaming and emulsification, may be substantially impeded. RPIs may lose commercial value when chemical or biochemical modifications likely generate undesirable substances, such as bitter hydrolysates (Lamsal, Reitmeier, Murphy, & Johnson, 2006), with uncertain effects on the human body. Various physical approaches, such as microfluidization (Xia, Wang, Gong, et al, 2012), hydrothermal cooking , freeze-thaw, sonication, high-speed blending, and high pressure (Tang, Hettiarachchy, & Shellhammer, 2002), have been investigated.…”