François Bera

Microbiological load of edible insects found in Belgium

Edible insects are gaining more and more attention as a sustainable source of animal protein for food and feed in the future. In Belgium, some insect products can be found on the market, and consumers are sourcing fresh insects from fishing stores or towards traditional markets to find exotic insects that are illegal and not sanitarily controlled. From this perspective, this study aims to characterize the microbial load of edible insects found in Belgium (i.e., fresh mealworms and house crickets from European farms and smoked termites and caterpillars from a traditional Congolese market) and to evaluate the efficiency of different processing methods (blanching for all species and freeze-drying and sterilization for European species) in reducing microorganism counts. All untreated insect samples had a total aerobic count higher than the limit for fresh minced meat (6.7 log cfu/g). Nevertheless, a species-dependent blanching step has led to a reduction of the total aerobic count under this limit, except for one caterpillar species. Freeze-drying and sterilization treatments on European species were also effective in reducing the total aerobic count. Yeast and mold counts for untreated insects were above the Good Manufacturing Practice limits for raw meat, but all treatments attained a reduction of these microorganisms under this limit. These results confirmed that fresh insects, but also smoked insects from non-European trades, need a cooking step (at least composed of a first blanching step) before consumption. Therefore, blanching timing for each studied insect species is proposed and discussed.

Survival rate analysis of freeze-dried lactic acid bacteria using the arrhenius and z-value models.

The survival rate of five freeze-dried bacteria species, Lactobacillus plantarum, Lactobacillus pentosus, Weisella paramesenteroides, Leuconostoc mesenteroides, and Lactobacillus fermentum, was described in terms of reaction rate constants (D or k) and temperature sensitivity of rate constants (z or Ea). The freeze-dried strains were stored under vacuum at 55, 37, and 4 degrees C for 168 h, 17 days, and 2 months, respectively. D-values decreased and k increased with an increase of the storage temperature. Neither the z-value nor the inactivation energy (Ea) of the reaction was significantly different (P > 0.05) for all the strains, suggesting that thermal inactivation of the freeze-dried lactic acid bacteria may occur by the same mechanism. Therefore, it was possible to compare rate constants of survival for the freeze-dried strains studied.

Chemical characterisation and in vitro assessment of the nutritive value of co-products yield from the corn wet-milling process

The chemical characteristics of co-products recovered during a laboratory-scale wet milling procedure as well as that of whole corn flour were characterised and their digestibility and fermentability value determined using a 2 steps in vitro digestibility and fermentation model of the pig digestive tract. Five co-products differing in their chemical composition were collected and analysed. These co-products differed in their in vitro dry matter Digestibility and in their kinetic of fermentation. High coefficients of digestibility were observed for starchy samples, while low coefficients of digestibility were observed for samples rich in lignocellulosic components. Fermentation patterns of samples analysed were different as well as the profile of volatile fatty acids produced during the fermentation. The production of straight-chain fatty acids produced was significantly correlated with the proportion of starch in the sample, while branched-chain fatty acids were correlated to proteins concentration of samples.

High pressure-induced gel formation of chicken meat patties

Abstract High pressure treatments produce gelified chicken meat patties with new properties (high water retention and cohesive texture) and without salt or fat addition. In comparison with heat-induced patties, the pressurised patties present an equivalent hardness with better water binding properties. Pressurisation causes an increase of the colour lightness parameter (L*) and a decrease of redness (a*) and yellowness (b*); but the meat discoloration provoked by the pressure treatments is less significant than the colour changes induced by heating. The pressure-gelation of chicken meat patties is affected by the intensity, the duration and the temperature of the process. The elevation of pressure from 400 to 600 MPa enhances the texture qualities and the water binding capacity of formed gels. A positive effect on texture quality is observed by prolonging the pressurisation time up to 30min. The pressurisation temperature (between 15 and 40°C) has no effect on product quality. Addition of salt (fat) prevents (reduces) the gelation ability of meat patties under pressure, whereas it improves the texture of heat-induced gels.

Structural and physicochemical characterization of Sphenostylis stenocarpa (Hochst. ex A. Rich.) Harms tuber starch

Several characteristics of African Yam Bean tuber starch (AYB) were studied and compared with that of a well-known native potato starch (P). The diameter of AYB granules ranged from 5.7μ to 49μ with a median at 19.5μ. During its pasting, AYB exhibited a low peak of viscosity in accordance with its low granules swelling and disintegration capacity. The gelatinization temperature of AYB was 75.2°C while that of P was 60.4°C. AYB was observed to be more stable during thermo-gravimetrical Analysis. Its degradation peak was observed at 308°C while that of P was 303°C. The X-ray diffraction analysis revealed that AYB belongs to the A-type crystalline group instead of C-type as claimed for several legumes starches. The stability of AYB and its capacity to structure starch-water systems make this resource an interesting ingredient for new food and non-food products.

In vitro and in vivo assessment of the effect of initial moisture content and drying temperature on the feeding value of maize grain

ABSTRACT 1. This study assessed the impact of drying temperature (54, 90, and 130°C) and maize grain moisture content at harvest (36% and 29%) on in vitro digestibility, the growth performance and ileal digestibility of broiler chickens. 2. In contrast to the results from the in vitro digestibility, apparent ileal digestibility of starch and energy decreased when the drying temperature was raised from 54 to 130°C, and this effect was more pronounced in maize grain harvested at high initial moisture content (36%). Ileal protein digestibility of maize grain decreased significantly when dried at the intermediate temperature (90°C) and with a high harvest moisture content (36%). Drying temperature and initial moisture content did not significantly affect AMEn. 3. When maize was dried at 130°C, the particle sizes of flour recovered after standard milling procedures decreased significantly, which would influence animal growth performance and in vivo digestibility through animal feed selection.

Morphological, structural and functional properties of starch granules extracted from the tubers and seeds of Sphenostylis stenocarpa

Sphenostylis stenocarpa (Hochst. ex A. Rich.) Harms, is a legume widely recognized in Africa for its edible starchy tuber and seeds. In the present morphological, structural and functional properties of starch extracted from the tubers and seeds of a same accession of this plant were characterized and compared. With smaller and more angular granules, tuber starch displayed higher resistance toward amylolysis and gelatinization than seed starch. The amylolysis of seed starch resulted in fragmented granules with typical layered structures of growth rings. During their hydrothermal treatments, both tuber and seed starches showed condensed ghosts even at 95°C. This high resistance toward hydrothermal degradation was considered as the basis of the typical pasting properties of these two materials. Both seed and tuber starch exhibited A-type crystalline pattern. Under non-oxidative combustion tuber starch presented a degradation peak at 310°C while seed starch was degraded around 302°C.