Bakery Shelf-life Extension

About

The challenge: Ambient baked goods (e.g. breads, cakes, yeast-raised sweet products) progressively deteriorate, losing their flavour, aroma, texture and are prone to degradation by microbes, particularly yeasts and moulds. Natural solutions are required to extend shelf-life to 3-6 months but they must maintain the company image of nutritious and healthy products.   The proposed solutions: Mould-free shelf life (MFSL) and staling control are the two mechanisms by which bakery goods deteriorate in ambient condition. Different solutions will be required for each. The project will focus on one bread product (e.g. soft rolls), one cake (e.g. low ratio plain cake) and one sweetened yeast-leavened product (e.g. croissant). Each product will present challenges for shelf life extension because of the different emphasis on gluten development, sugar content / water activity, and extent of starch gelatinisation. These products will be agreed with the client prior to starting work. Further products can be added to this list at additional cost. Mould-free shelf life (MFSL) The proposed solution for MFSL extension will involve technology transfer from sour dough bread using natural ingredients such as sour dough ferments. These can be in the form of powders, liquids or semi-solids. They contain naturally generated antimicrobial compounds from beneficial bacteria and yeast. The company has good working relationships with suppliers of ferments and will select appropriate ingredients to evaluate. Choice of sour ferment will be based on factors such as stability, ease of handling and likely changes to the product flavour. Powders and liquids are favoured. Flour without UK additives will be used to avoid pH buffering effects with calcium carbonate. Preservative action of the ferments tends to work optimally at acidic pH levels (pH 4-6) because most of the preservative action comes from organic acids. These dissociate into their salt and acid forms, with the acid form providing the preservation. Low pH in the final product forces the equilibrium towards the acid form and in doing so increases the preservative effect. This means less of the active compound is required to achieve an equivalent effect. MFSL will be tested by surface-inoculating baked products (after cooling) with raw flour to introduce microorganisms. Water activity (aw) for the cake product will be controlled using enzymically generated sugars and a small amount of natural humectants, should this be required. There are many factors that influence aw, including added sugars and water, baking loss, and humectants such as salt, glycerine and enzymically generated sugars. A balance of all the above factors is likely to be required so that taste and aroma are not compromised. It is assumed that the cake will be a chemically leavened product. Note that a yeast leavened cake would be easier to manage for MFSL control because the pH of added ferments will make the cake batters naturally acidic. With chemical leavening, any acids will react with alkaline leavening components and may require encapsulation of one component to control carbon dioxide release. Sugars, added in natural form or enzymically generated, will mask the acidic flavour to some extent. Staling control Staling control will require strategies that stop or slow down changes in the starch that lead to increased firmness and dryness of the product with time.  Typical strategies include changes in processing regime, the use of enzymes and emulsifiers, or a combination of all of these.  The staling process is not well understood but it is thought that enzymes (e.g. amylases) modify the amylopectin side chains which reduces the tendency of the molecule to retrograde and hence slows down the rate at which bread-like products firm during storage.  Other enzymes may also be important (e.g. lipases, lipoxygenase and even proteases) but these have not been researched as thoroughly as the amylases.  The bakery sector has used tailored enzymes for this purpose. Natural, enzyme-rich materials (only) will be considered in this project. These are likely to be enzyme-rich malted grains such as wheat or barley. Emulsifiers such as monoglycerides have also been used to slow down starch retrogradation.  It is well known that lipases can be used to generate emulsifiers in situ and hence perform in a similar way as synthetically used emulsifiers.  Other natural emulsifiers may also have similar functionality in baked systems. The moisture content of the final product, as well as the volume, should be considered in combination with the above strategies in order to optimise conditions to achieve longer shelf-life. Moisture content, textural properties, volume and crumb appearance will be tested using standard protocols appropriate to the products at various times over the 3-6 month period. Flavour and aroma will be evaluated using informal sensory assessment using non-inoculated samples.  Changes in starch over shelf-life will be measured at specific time points during storage trials.   Project timing The project will be carried out in four stages; review of suitable ingredients, develop the recipes and experimental protocols, the baking experiments and analysis of results (up to 6-months).