“Lipids & Fats  hold a crucial position in the realm of baked products. Their functional characteristics substantially enhance numerous quality traits desired by consumers in baked goods. Moreover, the physical and structural attributes of lipids markedly influence product characteristics. Hence, meticulous attention is essential pay attention when selecting  fats and oils, as the properties of these lipids dictate their functionality within a specific product framework.”

Dimitrios Argyriou
Food Scientist
Managing Director of Grainar

Introduction 

Fats and oils, like butter margarine , cocoa butter, oils, vegetable shortenings and lard are widely used for centuries in baking. Their primary role is organoleptic – they make the bread taste, texture and appearance better.

Figure 1: Butter

Shortening can defined as the capability of fat to modify the texture of baked goods by lubricating, weakening, or reducing the elasticity of the food components’ structure, thereby contributing to a desired textural outcome in the final food product.

The major functions of shortening include:

• imparting tenderness
• confer structure 
• lubricate during chewing
• improve flavor 
• giving a moister mouthfeel

Fats and oils also serve a functional purpose during the transformation of dough or batter into the final baked product, so they are used to:

• easier handling
• give structure to a dough or batter
• lubricate during forming
• incorpoarate air into batters
• transfer heat
• increase melting point
• extent shelf life

The oil component of shortening provides a moist mouthfeel, tender bite, and lubrication, while the solid component of shortening aids in structuring the dough.

The suitability of shortening for a given baking application is dependent on three main factors: 

• the ratio of the solid to liquid phase at a given temperature
• the crystal structure of the solid lipid 
• the oxidative stability of the shortening

Water and fat compete to occupy the surface of flour particle during dough mixing. In the absence of fat, flour proteins readily hydrate with the available water, leading to the formation of an extensible gluten network. However, when shortening is introduced, it envelops starch and protein particles, segregating them and thwarting their hydration and development. This obstruction in gluten network development typically leads to reduced dough elasticity, resulting in baked products with softer textures.

The function and importance of shortening differ based on its quantity in a product formula and the specific type of product. It has been noted that shortening helps to plasticize dough, especially the gluten polymers within the dough matrix. Without shortening, adjacent gas cell bubbles merge during baking, leading to a coarser crumb structure compared to formulas with shortening. As the levels of shortening increase, the dough needs less water to achieve a comparable dough consistency 

Dietary fat is an essential component of a balanced diet, having both positive and negative nutritional consequences. On the positive side, fats are crucial for energy production, absorption of fat-soluble vitamins like A, D, E, and K, and supporting cell growth. They also aid in hormone production, including hormones like insulin and stress hormones which are crucial for metabolic functions. Omega-3 and Omega-6 fatty acids, found in certain fats, are essential for brain health and inflammation control. However, on the downside, excessive consumption of fats, especially saturated and trans fats, can lead to weight gain, cholesterol elevation, and increased risk of heart diseases.

Generally, when the fat content in a traditional baked item is significantly reduced, for instance by 50%, the resulting product is often deemed to be much less desirable. A major challenge faced by bakery firms today is to minimize fat addition and explore alternative solutions without compromising the appeal of their products.

Chemical structure of fats

Fats, scientifically termed as triglycerides, are compounds composed of a glycerol molecule bonded to three fatty acid chains through ester linkages. Each fatty acid chain comprises a long hydrocarbon sequence with a carboxyl group (COOH) at one end. The nature of the bonds between carbon atoms in these chains categorizes them into:

• saturated -no double bonds,
• monounsaturated -one double bond 
• polyunsaturated fats -multiple double bonds. 

Saturated fats, typically solid at room temperature, are commonly found in animal products, while unsaturated fats, usually liquid at room temperature, are prevalent in plant oils. The precise arrangement and types of fatty acids significantly influence the chemical and physical properties of the fat. The double bonds in unsaturated fatty acids exhibit cis or trans configurations; the cis form leads to a bent molecular structure, representing natural unsaturated fats. In contrast, the trans form, often artificially created through hydrogenation, results in a straighter molecular structure and is associated with adverse health outcomes. 

Traditional Shortenings and Tailored Fats

Traditional shortenings

Traditionally, the shortenings utilized in bakery production are derived from animal products such as butter, lard, and tallow. These often impart a unique, cherished flavor appreciated by consumers. However, butter has a very narrow plastic range, becoming hard at refrigerated temperatures and almost liquid at warm room temperatures, making it challenging to handle, especially in large-scale roll-in bakery operations. On the other hand, tallow maintains a high solids content across most ordinary temperature ranges, often separating into liquid (oleo) and solid (stearine) fractions. Lard has a solid fat index profile more suitable for bread and related products, although it’s not ideal for cake making.

In addition to these technical challenges, growing consumer health consciousness has cast a spotlight on the negative health impacts associated with traditional shortenings, specifically their contribution to cholesterol levels and cardiovascular diseases. This awareness has diminished the attractiveness and, consequently, the usage of these fats in modern bakery production.

Tailored Fats

Margarine is manufactured through the emulsification of vegetable oils and water, and its solid consistency is attained through a process known as hydrogenation. In this process, hydrogen molecules are introduced to vegetable oil under high temperature and pressure, in the presence of a catalyst, usually nickel, to saturate the double bonds of the unsaturated fatty acids present in the oil. This hydrogenation alters the physical properties of the oil, turning it from a liquid to a semi-solid or solid state at room temperature, which is desirable for various culinary applications.

Figure 2: Lard

Historically, partial hydrogenation was utilized, which resulted in the formation of trans fats. These trans-isomeric fatty acids are associated with adverse health effects including an elevated risk of cardiovascular diseases due to their propensity to increase LDL (bad cholesterol) and decrease HDL (good cholesterol) levels.

Due to the health risks associated with trans fats, the production of margarine has evolved. Modern methods have moved towards complete hydrogenation to avoid trans fat formation or the use of alternative processes like interesterification. Interesterification rearranges the fatty acids on the glycerol backbone, either chemically or enzymatically, to achieve the desired physical properties without forming trans fats.

Additionally, margarines today are often fortified with essential vitamins such as vitamin A and D to enhance their nutritional value. They may also have plant sterols or stanols added, compounds known for their cholesterol-lowering properties.

Furthermore, the types of oils used in margarine production have diversified to include a range of healthier options like olive oil or canola oil, which are higher in monounsaturated and polyunsaturated fats, and lower in saturated fats

Margarine –Historical Trivia

Hippolyte Mege-Mouries
24 Ekim 1817 - 31 Mayıs 1880

The initial viable butter substitute was developed by French chemist Hippolyte Mege-Mouries in 1869, following a commission by the French government to create an economical alternative to butter. In his method, Mege-Mouries treated heated tallow with a warm solution of potassium carbonate, pepsin, and salt, which enhanced the fat’s flavor by eliminating non-fatty impurities. The extracted fat was then rinsed with water, allowed to crystallize in shallow trays, after which the softer fat fraction, termed ‘oleo,’ was separated from the harder fraction. This oleo fat exhibited a melting point akin to butter and somewhat similar consistency. This refined fat served as the foundational material for the first successful production of margarine.

Shortening Properties

Certain properties of shortening and especial the physical and chemical are of particular importance to bakers.

The Solid Fat Index

The Solid Fat Index (SFI) is an instrumental parameter used to characterize the crystalline state of fats and oils over a temperature range. It quantifies the percentage of fat that remains solid at specific temperatures. This measurement is pivotal in understanding the functionality and behavior of fats within food systems, particularly in the baking and confectionery sectors.

The SFI is often measured using techniques such as pulsed Nuclear Magnetic Resonance (p-NMR) or dilatometry. In p-NMR, the method distinguishes between the solid and liquid fractions of fat based on their different magnetic behaviors. On the other hand, dilatometry measures the volume changes of fat as it transitions between solid and liquid states with temperature alterations.

Figure 3: Margarine

Understanding the SFI is essential for food formulators as it directly impacts the texture, mouthfeel, and structural integrity of the end product. For instance, a fat with a higher SFI at room temperature will provide more structure to a baked good, leading to a different texture compared to a fat with a lower SFI.

Moreover, the SFI profile (i.e., the SFI values at different temperatures) gives insight into the melting behavior of fats, which is crucial for product development and quality control, ensuring the desired sensory attributes and functionality in final food products. It also aids in the selection and modification of fats to meet specific processing and product requirements, thus playing a significant role in the tailored formulation of fats for various food applications.

Plasticity and Crystal Structure

The plasticity of a fat is defined operationally; the shortening is smooth and when squeezed deforming readily but holding its shape. Plasticity is a function of 2 factors SFI and crystal structure.

The plasticity of a shortening is technically described by its rheological properties, which are the characteristics defining how a substance flows and deforms. Shortening’s flow behavior and deformation under stress are chiefly governed by its microstructure, which is determined by the balance of solid and liquid fat phases at the operational temperature.

Figure 4: Relatioship between SFI and Melting Point

A well-plasticized shortening demonstrates a balanced interplay of solid fat crystals dispersed within a liquid oil phase. This dispersion aids in maintaining a stable, consistent structure, ensuring the shortening remains pliable and manageable across varying temperatures. 

The plastic range refers to range of temperatures over which a shortening will exhibit the required properties mentioned above 

Various sorts of penetration tests give approximate results which are useful. One such test is the cone penetrometer method (AOCS Method Cc 16-60)

Oxidative Stability

Figure 5: Margarin plasticity

Oxidative stability is a critical aspect of fats and oils as it defines their resistance to oxidation, a process that can lead to rancidity, adversely affecting the flavor, aroma, and nutritional value. The fatty acid composition significantly impacts oxidative stability; saturated fats exhibit greater stability against oxidation due to the absence of double bonds, which could react with oxygen. Conversely, polyunsaturated and monounsaturated fats are more prone to oxidative reactions due to the presence of double bonds. The inclusion of antioxidants, either natural like Vitamin E or synthetic, can help enhance the oxidative stability by neutralizing the free radicals that accelerate oxidation. Various methods such as the Rancimat method or Peroxide Value measurement can assess oxidative stability, providing insights into the shelf-life and quality preservation of fats and oils.

Shortening Functionality and bakery products

Bread

Incorporating fat in bread yields several outcomes: it enhances the final volume, softens the crumb, renders the crust less crisp, and boosts the fresh-keeping quality. Typically, 3-4% of plastic fat or 2-3% of vegetable oil is used. The tenderizing effect of shortening derived from its liquid phase. Given that all-purpose shortening holds about 25% solid fat at room temperature, 3 kg of vegetable fat corresponds to 4 kg of plastic fat in softening bread crumb. 

The solid phase of shortening aids in improving volume, and when transitioning from plastic to fat oil, it’s essential to utilize dough strengtheners like SSL, DATEM, or Lipases. This is due to the ability of plastic shortening to allow dough to expand longer in the oven.

Figure 6: Puff pastry

It’s crucial to consider the oxidative stability of shortening, especially in products stored for extended periods, like croutons or toast bread, as rancidity could be imparted over time. To enhance resistance to oxidation, some vegetable oils are partially hydrogenated.

Danish and Puff Pastry

The role of fat in puff pastry is crucial in achieving the desired texture, volume, and flavor. Fat is laminated between layers of dough, contributing to the distinctive rise and layered texture of puff pastry. During baking, water in the dough evaporates, creating steam which lifts the layers apart, and the fat helps keep these layers separated, resulting in a flaky, airy structure.

The plastic range of the margarine should be sufficiently broad. The consistency of the margarine needs to match that of the dough across the temperature spectrum during which the dough is processed, including the temperature during dough retarding. If not, the fat may either not spread evenly or get absorbed by the dough, leading to a poorly layered product that will display a reduced final volume and irregular shape

The proper plasticity requires a relative flat SFI profile and stabilization in β’ crystal phase.  In case of Danish pastry and croissant, the melting point of fat must 5C higher than the temperature used in proofing.

Cakes

During the initial step of mixing the plastic shortening entraps air bubbles. The presence of monoglycerides typically at 3% , divide these bubbles  in numerous small air cells by the mixing action. The shortening should be exhibit good plasticity in order to envelop and retain air pocket. The most appropriate type for cake batter has the SFI profile of all-purpose shortening containing monoglyceride.

Cakes made with oil shortening are more tender than those made with a plastic shortening. Its crumb stays moist and soft for several weeks.

Bicuits

For wirecut biscuits where the the dough extruded the main role of plastic shortening is incorapration of finely distributed air bubbles. This will lead to finer  final grain.

In the rotary molded biscuits air incorporation is important but also the shortening plays a crucial structural role in the processing quality. A shortening with low SFI will result in soft and poor machinability. In case of high SFI the dough will be stiff and will not be molded properly. It is very important to find the right balance between solid and liquid phase.

In the production of sheeted biscuits, the primary role of fat is to provide a tender eating quality in the finished product. Hence, utilizing 75% oil in place of the amount of plastic fat in the formula would be a wise choice. It’s important to focus on the oxidative stability of the fat, as the finished product should remain acceptable to consumers for up to six months.

Crackers

Shortening is primarily utilized in cracker dough to tenderize the end product. For this scope a plastic all purpose shortening is used. It also enhances the oven spring, similar to its function in bread making. 

Figure 7: Cracker

Post-baking, snack crackers are coated with oil as they exit the oven, lending them a softer texture and a moist feel. Typically, the oil spray amounts to 10-12% of the cracker’s weight. If the snack manufacturer desires a dry look, an oil with a significant amount of solids is selected. On the other hand, if a shiny appearance is favored, an oil with the lowest Solid Fat Index (SFI) is chosen.

Donuts- Deep fried snacks

Fat serves as an effective medium for transferring heat while cooking foods. As the uncooked food releases water during the cooking process, the frying fat takes its place. Take a donut for example; its weight remains consistent before and after frying, with the loss of water being offset by the absorption of fat. This absorbed fat not only enhances the flavor but also tenderizes the finished snack.

Fat for frying is usually at a temperature of around  180-190C and a number of unwanted chemical reactions can occur.

Figure 8: Donus  during frying process

Water evaporation during frying causes fat hydrolysis, increasing Free Fatty Acid (FFA) levels. In commercial donut frying, fat with FFA greater than 1% is discarded. Higher FFA levels decrease the smoke point of fat by 5°C for every 0.1% increase and increase fat absorption in snacks, potentially altering the finished product’s composition. Fat oxidation rate doubles with every 10°C temperature increase, leading to hydroperoxides and epoxides formation. Oxidized fatty acids can cyclise and polymerise, showing as a dark coating on fryer walls. The level of polar material in frying fat is regulated, with above 25% being illegal in many countries. Oxidative stability is crucial when selecting fats or oils for deep frying. High stability oil with a 200-hour Active Oxygen Method (AOM) rating is preferred for commercial snack frying, while all-purpose shortening with a 75-hour AOM rating suits donut frying with rapid fat turnover.

Conclusion

 Lipids & Fats  hold a crucial position in the realm of baked products. Their functional characteristics substantially enhance numerous quality traits desired by consumers in baked goods. Moreover, the physical and structural attributes of lipids markedly influence product characteristics. Hence, meticulous attention is essential pay attention when selecting  fats and oils, as the properties of these lipids dictate their functionality within a specific product framework.