Browsing by Subject "Alternative proteins"

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    HybridMeat - products from animal and plant sources
    (2022) Ebert, Sandra Gabriele; Weiss, Jochen
    Consumer diversification and concerns about insufficient protein supply and global malnutrition demand for an exploitation of alternative protein sources such as plant proteins. While manufacturers have made substantial progress in industrially scaled extraction processes and structuring of plant proteins e.g. by extrusion, there is still a lack of information on their fundamental functional and organoleptic properties and interactions with other ingredients in traditional formulations. As a result, food product developers are facing a lot of challenges and are often forced to base their work on trial-and-error rather than mechanistically guided approaches. This is in particular the case for foods where complex raw material requirements and production processes make the manufacture of products with high acceptance and shelf stability not trivial. This includes the design of hybrid meat products that are composed of mixtures of meat and plant proteins. There, traditional meat products are often set as a benchmark, making the performance of such mixed products mostly unsatisfactory. Establishing composition material property functionality relationships may be a first step to overcome these obstacles. Therefore, a variety of plant proteins was assessed for their composition, physicochemical properties, and techno functionalities to gain an understanding of their suitability for the formulation of hybrid meat products. This included their dispersibility, the miscibility of select plant protein fractions with solubilized meat proteins at varying pH and mixing ratios, and the characterization of their odor-active compounds. The latter included powdered as well as extruded plant proteins due to their increasing relevance in the manufacture of hybrid meat and analogue products. Following this, plant proteins were screened in terms of their performance in hybrid meat formulations and during traditional manufacture with a special focus on dry cured products in order to define feasible protein sources and application thresholds. The first part of this thesis showed that aqueous solubility, native pH, and appearance of a variety of 26 plant protein powders from carbohydrate and vegetable oil production correlated with purity and the extraction process. Solubility ranged from as low as 4 % to as high as 100 % based on the protein concentration and prevalence of select protein fractions. For example, large amounts of prolamins (wheat) or glutelins (rice, pumpkin) resulted in low values, while high shares of albumins and globulins promoted moderate to high solubility in sunflower, pea, and potato proteins. A highly soluble (100 %) small molecular weight fraction (< 24 kDa) of the latter was subsequently screened for its particle size and electrostatic and hydrophobic properties as compared to solubilized water and salt soluble meat proteins and the miscibility of both proteins was assessed at pH 3.0 to 7.0 and at select mixing ratios. Phase behavior of mixtures started to change below the isoelectric point (pI) of salt soluble meat proteins (pH ~ 5.5), which was identified as a defining boundary value. Here, one-phase/co-soluble systems (pH > pI) transitioned to two-phased/aggregated ones mediated by interactions (pH ≤ pI) in between individual meat and meat and potato proteins. This resulted in dense, irregularly shaped meat-potato heteroprotein particles, that deviated from the characteristic assembly of pure meat proteins into regular, anisotropic aggregates. A perturbing effect of potato proteins on the structural, organized association of meat proteins below their pI was found. Protein-protein interactions were based on both electrostatics and hydrophobics as shown by variations in surface charge, hydrophobicity, and particle size if sole potato/meat and mixtures were compared. For example, particle size of solubilized meat proteins increased from 18.0 ± 2.9 µm (pH 3.0) to 26.8 ± 9.0 µm (pH 3.0) in 50:50 mixtures. FTIR results confirmed alterations as a function of mixing ratio and pH. Image analysis of microstructures revealed a shift from elongated regular networks towards more disorder and irregularity along with a lower degree of branching. Besides solubility, organoleptic properties influence the suitability of plant proteins as food ingredients. Therefore, odor active compounds of two pea isolates were analyzed by gas chromatography mass spectrometry-olfactometry (GC MS O) after direct immersion stir bar sorptive extraction (DI SBSE), and results were compared to those of their respective extrudates to define changes during dry and wet extrusion. Twenty-four odor-active compounds were found, whereof nine represented major (off-) flavor contributors in peas: hexanal, nonanal, 2 undecanone, (E)-2-octenal, (E, Z)-3,5-octadiene-2-one, (E, E) 2,4 decadienal, 2 pentyl furan, 2-pentyl-pyridine, and γ-nonalactone. The quantity of these nine volatiles was affected distinctively by extrusion. Hexanal was reduced from 3.29 ± 1.05 % (Isolate I) to 0.52 ± 0.02 % (Wet Extrudate I) and (E,Z)-3,5-Octadiene-2-one and (E,E)-2,4-decadienal decreased by 1.5- and 1.8-fold when powdered and dry texturized pea proteins were compared. As a result of the perturbing effect of soluble potato proteins and the higher amount of off flavors in pea isolates compared to their extrudates, use of plant powders as additives was rejected in favor of extruded ones for all subsequent studies. As the focus of this work was the development of dry cured hybrid meat products, the effect of various amounts of extrudates on the traditional formulation and manufacture of this product class was assessed. This included the susceptibility of extrudates towards acid-induced pH changes as compared to pork meat, as well as their behavior in a traditional acidification and drying processes. To that purpose, pork meat and six wet extrudates from peas, pumpkin, or sunflower seeds were analyzed in their proximate composition and subjected to titration starting from the same pH value and using the same acid concentrations. It was shown that wet texturized pumpkin and sunflower proteins had the highest buffering capacity (BC), especially between pH 7.0 and pH 4.5, while pea protein extrudates and pork meat were more prone to acidification and similar in buffering capacity with an average of 881 ± 5 mmol H+/(kg*ΔpH). The obtained data was then used to relate BC with the compositional elements of extrudates such as minerals, proteins, select amino acid, and non–protein nitrogen. These findings on varying susceptibility towards acids were extended by studies on a minced meat model systems containing pork meat, curing salt, and various amounts (0 to 100 wt%) of wet extrudates and the chemical acidifier Glucono delta-lactone (GDL). It was shown, that increasing concentrations of plant extrudates resulted in a linear increase of the initial (pH0h), intermediate (pH6h), and final (pH48h) pH of minced meat model systems. A sufficient acidification to common target pH values in dry cured meat products (pH ~ 5.0) could be achieved with acidifier amounts of 1.0 wt% up at no more than 15 wt% of extrudates. A mathematical model was proposed to correlate pH, time, acidifier, extrudate concentration, and plant protein origin to aid in the adjustments of formulations at higher extrudate contents, and to describe thresholds of feasible extrudate and acidifier concentrations. The calculated concentrations were then implemented to manufacture dry cured hybrid sausages where meat was partially replaced by 12.5, 25, 37.5, and 50 % of pumpkin seed extrudates. All recipes reached the target pH value with an accuracy of pH 5.0 ± 0.06 thereby validating the proposed mathematical correlations. Hybrid recipes with up to 25 % of extrudates were comparable to the traditional all-meat formulation in both the drying behavior and the distribution of moisture and free water. However, higher meat replacement levels promoted distinct changes in drying behavior and product texture where chewiness, hardness, and cohesiveness decreased by up to 70 %. In conclusion, plant protein functionality differs profoundly from the one of meat proteins, and this functionality also depends on the respective protein source as well as the applied extraction process. Their structuring by extrusion provides beneficial organoleptic changes and eases their incorporation in hybrid formulations. The fundamental characterization of plant proteins in terms of their proximate composition and (physico)chemical properties may be used to establish mathematical correlations to estimate the effect of these novel ingredients in hybrid meat products. Thus, the obtained results offer a valuable basis that manufacturers can draw upon not only to create new foods within this product class but also to broaden and facilitate the application of plant proteins on a large scale.