Comparative Fermentation Analysis of Wheat Shorts and Clear Flour to Produce Lactic Acid

The Canadian Society for Bioengineering La Société Canadienne de Génie The Canadian society for engineering in agricultural, food, Agroalimentaire et de Bioingénierie environmental, and biological systems. La société canadienne de génie agroalimentaire, de la bioingénierie et de l’environnement Paper No. CSBE18-217 Comparative Fermentation Analysis of Wheat Shorts and Clear Flour to Produce Lactic Acid Kjeld Meereboer1 and Ping Wu2 1. University of Guelph, Guelph, Canada 2. Ontario Ministry of Agriculture, Food and Rural Affairs Written for presentation at the CSBE/SCGAB 2018 Annual Conference University of Guelph, Guelph, ON 22-25 July 2018 ABSTRACT Wheat shorts and clear flour are by-products generated during flour milling that are either sold as animal feed or added back to certain types of bread products. The residual carbohydrates make them a suitable carbon source provided appropriate measures are taken to free the fermentable sugars. The objective of the study is to validate the effectiveness of extraction of carbohydrates originating from both wheat shorts and clear flour. The extraction process consists of thermal hydrolysis and enzymatic hydrolysis of wheat shorts and clear flour to free fermentable sugars and take 2 days. The fermentation process is completed at 37°C for 5 days, and in doing so the two by-products can be compared as a carbon source in terms of fermentable sugar and lactic acid yield. Keywords: wheat shorts, clear flour, lactic acid, fermentation, wheat middlings. Keywords: wheat shorts, clear flour, lactic acid, fermentation, wheat middlings. INTRODUCTION Wheat shorts Wheat shorts and clear flour both originate from milling of wheat, in Canada the most widely grown wheat is Canada Western Red Spring wheat due to its benefits in both milling and baking applications and thus can be a representative source of wheat shorts and clear flour by products in Canada (Canadian Grain Commission 2017). During the milling process shorts, bran and germ, of which consists of 25-30% the milling process output, is relegated to animal feed. The wheat shorts produced can be defined as a combination of fine particles of wheat bran, germ, and flour (Blasi et al. 1998), as well as residual offal or tailings Papers presented before CSBE/SCGAB meetings are considered the property of the Society. In general, the Society reserves the right of first publication of such papers, in complete form; however, CSBE/SCGAB has no objections to publication, in condensed form, with credit to the Society and the author, in other publications prior to use in Society publications. Permission to publish a paper in full may be requested from the CSBE/SCGAB Secretary: Department of Biosystems Engineering E2-376 EITC Bldg, 75A Chancellor Circle, University of Manitoba, Winnipeg, Manitoba, Canada R3T 5V6 or contact [email protected]. The Society is not responsible for statements or opinions advanced in papers or discussions at its meetings. (Bell 2003). Additionally, wheat shorts must not contain more than 7% fiber. The flour milling waste stream contains the majority of protein, minerals, and vitamins of the wheat kernel (Blasi et al. 1998), but wheat shorts by itself provides little in the way of nutrients, consisting of 17-18% protein, of which 70-75% is digestible and poses a poor degree of energy digestibility relative to other animal feed alternatives (Young and King 1981). Hence wheat shorts is usually combined with other flour milling by-products such as wheat germ and a significant portion of wheat bran to make animal feed or wheat middlings (Blasi et al. 1998). Despite wheat shorts having a poor degree of energy digestibility, it still remains a fact that shorts consist of 60% carbohydrates (Phillips Jr. and Balzer Jr. 1957). For experimental comparison, it is assumed wheat shorts is primarily made from wheat bran. The composition of wheat shorts is likely to vary depending on the type of flour produced, thus Table 1 indicates the approximate composition of the primary components that make up the waste stream from flour milling and bran is assumed to be of similar composition (Fraser and Holmes 1959). Furthermore, Tcachuk and Irvine reported wheat bran, endosperm, and germ all contain all amino acids (Tkachuk and Irvine 1969), and Fardet reported 2% of wheat bran consists of bioactive compounds, including vitamin B (Fardet 2010). Table 1: Wheat middling’s composition. Endosperm Germ Bran Moisture (%) 14.0 11.7 13.2 Protein (%) 9.6 28.5 14.4 Fat (%) 1.4 10.4 4.7 Ash (%) 0.7 4.5 6.3 Total Carbohydrates (%) 74.1 44.5 60.8 Starch (%) 71.0 14.0 8.6 Hemicellulose (%) 1.8 6.8 26.2 Sugars (%) 1.1 16.2 4.6 Cellulose (%) 0.2 7.5 21.4 Clear flour Clear flour is a co-product of patent flour milling and contains a higher ash content relative to it (Blasi et al. 1998). Clear flour can be further defined as first clear and second clear flour, indicating the degree of ash content, with the latter having the highest (FDA 2003). Similarly, the output of clear flour can vary. Flour can vary from 0.30 to 0.99% ash content during milling runs and largely depends on the type of wheat milled, the type of flour whether it be white or whole wheat, or the final type of flour (Canadian National Millers Association 2017). What’s left with higher ash content, is unsuitable for patent flours and, Posner and Deyoe considered these to be clear flour (Posner and Deyoe 1986). To a certain extent clear flour can be added back to wheat flour, but due to its higher ash content and discolouration, it may result in an undesirable final product (Lin et al. 2012). Regardless, it can improve the quality of some flours or be used to produce lower grade grain products such as pasta (Sissions et al. 2008). Table 2 indicates the clear flour composition of durum wheat, to approximate the composition of clear flour (Sayaslan et al. 2018). Table 2: Durum wheat flour composition. % Composition Moisture 12.5-14.1 Protein 14.4-14.9 Fat 2.1-3.7 2 Ash 1.28-1.72 Total Carbohydrates 79.8-82.2 Starch 66.7-70.5 Non-Starch 11.6-13.1 Damaged Starch 4.9-6.2 Lactic Acid Due to the high carbohydrate composition of clear flour and wheat shorts, both hold potential as carbon sources for fermentation in added value processing and lactic acid is a suitable product. 85% of the total lactic acid demand in manufacturing is from the food industry due to its desirable sensory properties over other food grade acids and the preservative functions it can fulfil (Datta et al. 1995). Two percent lactic acid has been reported to be effective as an antimicrobial agent in the meat industry against salmonella species (Killinger et al. 2010), as well as has potential use in industry as a disinfectant for carcasses and equipment (Datta et al. 1995). Additionally, lactic acid can be used as an antimicrobial, curing, pickling and flavouring agents in food (FDA 2017). Lactic acid is also heavily utilized in the development of polylactic acid, a biodegradable polymer, through polycondensation with minimal carbon foot print (Tsuji 2014). With varying processing techniques, desired functionality can be achieved for plastics, textiles and biomedical applications (Avérous 2008). Pre-fermentation Treatment The initial pre-treatment of grain based by products during extraction can be completed in varying manners. The documentation of the extraction of similar products to wheat shorts are more thoroughly covered and significantly more useful in interpreting the ideal method to extract and utilize the potential carbohydrates present in wheat shorts and clear flour. Wheat bran accounts for a considerable portion of milling byproducts. Pre-treatment of wheat bran is a common occurrence to supplement the extraction of carbohydrates upon which enzymes act. Favaro et al. reported heat treatment on wheat bran at 121°C for 30 minutes was effective in exposing carbohydrates to the subsequent enzymatic hydrolysis phases when used with minimal sulphuric acid. Lower temperatures proved ineffective in extracting carbohydrates (Favaro, Basaglia, and Casella 2012). Pre-treatment is likely to assist in enzyme hydrolysis following Manelius at al., who have reported increased enzymatic activity on small starch granules (Manelius et al. 1997). Although neglecting autoclaving procedures in repeated batch processing appears an ideal method to overcome limitations of autoclaving equipment while being less expensive and more desirable concept in industrial scaling and is something intended to be explored (Wang et al. 2017). Tirpanalan et al. utilized a ratio of 1:4, wheat bran to water, and enzymatic hydrolysis was directly implemented using amylase at 85C for 3 hours with a pH of 6.5 and amyloglucosidase at 55°C for 18 hours with a pH of 5.5 and indicate most if not all available starch was effectively hydrolysed into free glucose (Tirpanalan et al. 2015). Other approaches are founded in a similar manner, Favaro et al. utilized a two stage hydrolysis for cellulose, hemicellulose (Favaro, Basaglia, and Casella 2012). Alternative methods can entirely neglect enzymatic, acid and thermal hydrolysis among other methods and rely on the bacterial organism to directly produce lactic acid. Naveena et al. utilized solid state fermentation to directly produce lactic acid in a single step process, effectively reducing the subsequent cost of enzymes, acids and energy. In this case the addition of yeast extract among other additives were deemed necessary to increase production (Naveena et al. 2005). A significant detriment to solid state fermentation is the duration of fermentation was extended up to a week compared to Tirpanalan et al. which took 2 days with a liquid broth, though inoculum preparation of lactobacillus was required (Tirpanalan et al.

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