The influence of marula seedcake, mopane worm and mealworm on bread quality
Van Rooi, Charles Freddie
Van Rooi, Charles Freddie
Citations
Altmetric:
Abstract
The food industry faces a significant challenge with the surging demand for protein that minimizes environmental impact. Projections by the United Nations indicate that the global population, currently at 8.2 billion, could reach 8.6 billion by 2030. This growth is expected to intensify pressures on land use, greenhouse gas emissions, energy consumption, and food security. In this context, Africa's rich biodiversity and indigenous knowledge, particularly regarding wild flora and insects, offer promising solutions. The practice of entomophagy, or insect consumption, is increasingly recognized as a viable method to meet the rising protein needs associated with population growth, as insects have traditionally formed part of many African tribes' diets. The composition, safety, and functional properties of flour made from marula (Sclerocarya birrea) seed cake, mopane worm (Tenebrio molitor), and mealworm (Imbrasia belina) were evaluated, this assessment included their potential for breadmaking. The total viable count (TVC) was highest in mopane worm flour at 5.10×105 cfu/mL, followed by marula seed cake flour at 1.75×103 cfu/mL and mealworm flour at 2.70×102 cfu/mL. These counts exceed safety standards; in comparison to white wheat flour with a TVC of less than 25 cfu/mL. The total fungal count was also highest in mopane worm flour at 6.9×103 cfu/mL, followed by mealworm flour at 2.70 x 10² cfu/mL. Marula seed cake flour and white wheat flour both had TFC values <25 cfu/mL. No mycotoxins were detected on any of the flour samples.
The analysis of these flours revealed important nutritional values: ash content was measured at mopane worm (0.40%), mealworm (0.31%), and marula seed cake (0.18%); moisture levels were mopane worm (7.60%), mealworm (4.27%), and marula seed cake (3.79%); fat content was recorded at mopane worm (13.6%), mealworm (10.5%), and marula seed cake (6.7%); while protein was high for mopane worm (60.6%), mealworm (49.7%), and marula seed cake (38.0%). Dietary fiber was highest in marula seed cake at 15.1%, compared to mealworm 6.6% and mopane worm 3.9%. This suggests that incorporating these alternative flours into baked bread could enhance their protein content. The essential amino acid profile of white wheat was significantly lower than that of mealworms, mopane worms, and marula seed cake, revealing its limitations as a protein source. Amino acids such as isoleucine (0.42% vs 2.26% in mealworms), leucine (0.86% vs 3.95%), and lysine (0.28% vs 3.42%) were
v
notably deficient in wheat, with lysine being the first limiting amino acid. Other essential amino acids, including methionine (0.24%), phenylalanine (0.6%), and threonine (0.35%), showed lower levels compared to the alternative sources. The amino acid composition of white wheat was inadequate, particularly in essential amino acids like lysine and leucine, making it a less optimal choice for dietary protein needs. The total polyphenol index (TPI) varied among the flours, with white wheat flour showing a high value in water extract (441), while acetone extracts had lower values for all samples except for mopane worm which had a TPI of 770 indicating its superior antioxidant activity compared to others. In terms of baking performance, different percentages of alternative flours were incorporated into bread doughs (2.5%, 5%, 10%, 15%, and 20%). The rheological properties were characterized using Mixolab analysis; mopane worm flour exhibited the highest torque values across various concentrations, indicating stiffer dough. Baking trials indicated that bread made with white wheat flour had the brightest crust and crumb colours compared to those made with composite flours like mopane worm flour which produced darker colour at higher concentrations (20%). The increased levels of flour substitution led to a significant decrease in the height of all composite breads. The C-Cell analysis highlighted that the slice areas decreased as higher percentages of alternative flours were included. The texture analysis revealed that bread incorporating mealworm flour maintained a lower hardness compared to standard white wheat bread over 7 days. The inclusion of alternative flours, particularly mealworm flour and mopane worm flour, significantly affected the microbial quality of the bread over time. The high microbial counts observed, raise concerns regarding the safety and shelf life of products made with these flours. Although the absence of harmful microorganisms such as Staphylococcus aureus and Salmonella spp. in the samples is reassuring, careful monitoring and management of microbial loads are still essential in the processing of these alternative flours. A 15% replacement of wheat flour in bread with mealworm, mopane worm, or marula seed cake flour, resulted in protein contents (%) of 11.8, 12.9 and 10.7 compared to the 8.1 of standard white wheat bread. The estimated cost of ingredients (15% replacement) for the marula seed cake bread is R9.15 per loaf, which is lower than the mopane bread at R11.44 per loaf but higher than the standard bread at R7.68 and it is notably less than the mealworm bread at R30.18 per loaf. Thus,
vi
incorporating insects or marula seed cake into a staple item like bread could be a viable option to improve the nutritional status of the South African population.
Description
Submitted in partial fulfilment of the requirements for the degree, Master of Applied Sciences, Food Technology , in the Department of Biotechnology and Food Technology Faculty of Science at the Tshwane University of Technology
Date
2024
Journal Title
Journal ISSN
Volume Title
Publisher
Tshwane University of Technology
Research Projects
Organizational Units
Journal Issue
Keywords
marula seedcake, mopane worm, mealworm, bread quality