Aroma characterization and consumer acceptance of four cookie products enriched with insect (Ruspolia differens) meal.

This research aims to advance knowledge on the impact of four processing methods on volatile compounds from insect-based baked products (cookies) to provide insights on consumer acceptance. Samples were exposed to double step enzyme digestive test, volatiles characterized through headspace analysis, while semi-trained panelists were recruited for the sensory test. Blanched and boiled samples of R. differens had considerably higher digestibility (83.42% and 81.61%, respectively) (p < 0.05) than toasted and deep-fried samples. Insect-based cookie products integrated with blanched and boiled R. differens meal expressed higher digestibility (80.41% and 78.73%, respectively) that was comparable to that of commercial cookie products (control cookies-CTRC with 88.22%). Key volatile compounds common between the various cookie products included, nonanal, octanal, methyl-pyrazine, hexanal, tetradecane, 2-pentylfuran, 2-heptanone, 2E-octenal, 2E-heptenal and dodecane. Among the volatile compounds, pleasant aromas observed were 2E,4E-dodecadienal, pentanal, octanal, methyl pyrazine, furfurals, benzaldehyde, and 2-pentyl furan, which were more pronounced in cookies fortified with boiled, toasted and deep-fried R. differens meal. There was a greater resemblance of sensory characteristics between control cookies and those fortified with deep-fried R. differens. These findings underscore the significant influence of aroma compounds on consumer acceptability and preference for insect-based baked food products, which allows for future process-modification of innate aromas of insect-based meals to produce high-valued pleasant consumer driven market products.

Dynamics in nutrients, sterols and total flavonoid content during processing of the edible Long-Horned grasshopper (Ruspolia differens Serville) for food.

Long-horned grasshopper (Ruspolia differens Serville) is a tasty delicacy in over 20 African countries. This study evaluated the impact of diverse post-harvest thermal treatment (blanching, boiling, toasting, and deep-frying) on the nutrients, total flavonoid content and sterols preservation of R. differens products. Crude protein, ash, and fibre of R. differens was drastically reduced by deep-frying technique. There was increase in Omega-3 (α-linolenic acid), Omega-6 fatty acid (linoleic and arachidonic acids) and sterols [(22Z)-27-Norergosta-5,22-dien-3ß-ol, cholesterol, campesterol, cholest-4-ene-3-one and ß-sitosterol] and flavonoids (2-3 folds) during blanching compared to other techniques. The iron and zinc content increased significantly in blanched and boiled products of R. differens. Thus, losses of nutrients, total flavonoid content and sterols during processing of R. differens for food can be mitigated by employing blanching technique, which is cheaper and least time-consuming. The implications of these dietary and therapeutic compounds on human nutrition and health are discussed.

In vitro protein digestibility of finger millet complementary porridge as affected by compositing precooked cowpea with improved malted finger millet.

Protein-energy malnutrition is one of the leading causes of death for children under-five in developing countries and Kenya is no exception. These children rely on starchy weaning foods such as finger millet (Eleusine coracana), which have poor protein digestibility. Cowpea (Vigna unguiculata), a locally available nutritious legume, could be an excellent complement to lysine-deficient millet diets. The present study thus aimed at innovatively improving protein digestibility of a baby weaning food, by evaluating the effect of malting on improved finger millet genotypes (U15, P224, KNE741, KNE629 and Snapping green) to enable selection of the best varieties with superior nutritional credential post process. Blending of selected finger millet with precooked cowpea flour followed the WHO recommended level at 10.32%, 21.26%, and 32.75% with 0% as control. Extractable phenols, condensed tannins, phytic acid, protein content, and protein digestibility were determined using recommended methods. Extractable phenol, condensed tannin, and phytate notably decreased by 44%, 47%, and 29% respectively after malting. Additionally, compositing with precooked cowpea increased protein content and protein digestibility in flour by about 6-39%. Cooking resulted in a 10% increase in protein digestibility in the complementary porridge. Malting of finger millet and compositing it with precooked cowpea has the potential to address PEM as it results in reduced anti-nutritional content with a concomitant improvement in protein digestibility of the baby weaning food.

Comparison of formation of visco-elastic masses and their properties between zeins and kafirins.

Zeins of differing sub-class composition much more readily formed visco-elastic masses in water or acetic acid solutions than equivalent kafirin preparations. Visco-elastic masses could be formed from both zein and kafirin preparations by coacervation from glacial acetic acid. Dissolving the prolamins in glacial acetic acid apparently enabled protonation and complete solvation. Stress-relaxation analysis of coacervated zein and kafirin visco-elastic masses showed they were initially soft. With storage, they became much firmer. Zein masses exhibited predominantly viscous flow properties, whereas kafirin masses were more elastic. The γ-sub-class is apparently necessary for the retention of visco-elastic mass softness with kafirin and zein, and for elastic recovery of kafirin. Generally, regardless of water or acetic acid treatment, all the zein preparations had similar FTIR spectra, with greater α-helical conformation, than the kafirin preparations which were also similar to each other. Kafirin visco-elastic masses have a much higher elastic character than zein masses.

Biocompatibility and biodegradation of protein microparticle and film scaffolds made from kafirin (sorghum prolamin protein) subcutaneously implanted in rodent models.

Kafirin, the sorghum prolamin protein, like its maize homologue zein, can be made into microparticles and films and potentially used as a biomaterial. Zein has good bio- and cyto-compatibility. Kafirin could be advantageous as it is more hydrophobic, more crosslinked, more slowly digested by mammalian proteases than zein and is non-allergenic. The safety and biocompatibility of kafirin implants in two forms was determined in rodent models. One week post subcutaneous injection of kafirin microparticles (size 5-µm diameter) in mice, chronic inflammation, abnormal red blood cells, and gross fibrin formation were observed. This chronic inflammatory response was possibly caused by the release of hydrolysis products such as glutamate during the degradation of the kafirin microparticles. In contrast, films made from kafirin microparticles (50-µm thick, folded into 1 cm(3) ) implanted in rats showed no abnormal inflammatory reactions and were only partially degraded by day 28. The slower degradation of the kafirin films was probably due to their far smaller surface area when compared to kafirin microparticles. Thus, kafirin films appear to have potential as a biomaterial. This study also raises awareness that the form of prolamin based biomaterials, (kafirin and zein) should be considered when assessing the safety of such materials.

Role of γ-kafirin in the formation and organization of kafirin microstructures.

The possible importance of the cysteine-rich γ-prolamin in kafirin and zein functionality has been neglected. The role of γ-kafirin in organized microstructures was investigated in microparticles. Residual kafirin (total kafirin minus γ-kafirin) "microparticles" were non-discrete (amorphous mass of material), as viewed by electron microscopy and atomic force microscopy. Adding 15% γ-kafirin to residual kafirin resulted in the formation of a mixture of non-discrete material and nanosize discrete spherical structures. Adding 30% γ-kafirin to the residual kafirin resulted in discrete spherical nanosize particles. Fourier transform infrared spectroscopy indicated that γ-kafirin had a mixture of random-coil and ß-sheet conformations, in contrast to total kafirin, which is mainly α-helical conformation. γ-Kafirin also had a very high glass transition temperature (Tg) (≈270 °C). The conformation and high Tg of γ-kafirin probably confer structural stability to kafirin microstructures. Because of its ability to form disulfide cross-links, γ-kafirin appears to be essential to form and stabilize organized microstructures.

Physicochemical modification of kafirin microparticles and their ability to bind bone morphogenetic protein-2 (BMP-2), for application as a biomaterial.

Vacuolated spherical kafirin microparticles with a mean diameter of 5 µm can be formed from an acidic solution with water addition. Three-dimensional scaffolds for hard tissue repair require large structures with a high degree of interconnected porosity. Cross-linking the formed kafirin microparticles using wet heat or glutaraldehyde treatment resulted in larger structures (approximately 20 µm), which, while similar in size and external morphology, were apparently formed by further assisted assembly by two significantly different mechanisms. Heat treatment, which increased the vacuole size, involved kafirin polymerization by disulfide bonding with the microparticles being formed from round, coalesced nanostructures, as shown by atomic force microscopy (AFM). Kafirin polymerization of glutaraldehyde-treated microparticles was not by disulfide bonding, and the nanostructures, as revealed by AFM, were spindle shaped. Both treatments enhanced BMP-2 binding to the microparticles, probably due to their increased size. Thus, these modified kafirin microparticles have potential as natural, nonanimal protein bioactive scaffolds.

Improvement in water stability and other related functional properties of thin cast kafirin protein films.

Improvement in the water stability and other related functional properties of thin (<50 µm) kafirin protein films was investigated. Thin conventional kafirin films and kafirin microparticle films were prepared by casting in acetic acid solution. Thin kafirin films cast from microparticles were more stable in water than conventional cast kafirin films. Treatment of kafirin microparticles with heat and transglutaminase resulted in slightly thicker films with reduced tensile strength. In contrast, glutaraldehyde treatment resulted in up to a 43% increase in film tensile strength. The films prepared from microparticles treated with glutaraldehyde were quite stable in ambient temperature water, despite the loss of plasticizer. This was probably due to the formation of covalent cross-linking between free amino groups of the kafirin polypeptides and carbonyl groups of the aldehyde. Thus, such thin glutaraldehyde-treated kafirin microparticle films appear to have good potential for use as biomaterials in aqueous applications.