Functional characteristics of shortening:
(1) plasticity
Plasticity is the basic property of traditional shortening, which means that solid oil has the characteristics of plastic substance at a certain temperature, can maintain its shape under a certain external force, and will deform and flow plastically when the external force exceeds the range. Shortened oil has good plasticity and is convenient for coating and processing. The dough formed has good ductility, and the processed products are crisp.
The plasticity of fat can be roughly measured by consistency, and plastic fat with appropriate consistency has good plasticity. The temperature range that can keep fat plasticity is called plastic range. If the temperature changes little but the consistency of fat changes greatly, it means that its plasticity range is narrow. Conversely, if the temperature changes greatly, but the consistency changes little, the plastic range is wide.
(2) Brittleness
Brittleness refers to the ability to make baked cakes brittle, which is the main property to ensure that all kinds of biscuits, crackers and cake products have good edible characteristics. Shortening oil is distributed in the tissue of baked food in the form of film, which blocks the mutual adhesion of gluten and plays a lubricating role, making the product tissue crisp and delicious. Generally, shortening with proper consistency and good plasticity has good crispness. Excellent shortening is lumpy and unevenly distributed in dough, which makes the product brittle; Too soft shortening is distributed in the dough in the form of microspheres, which can not block the product and make it porous and rough.
(3) Tyrosination
The high-speed whipping of shortening can make air be sucked into the oil as fine bubbles, which increases the volume of shortening. This gas-bearing property of petroleum is called butter. Adding shortening to the mixed batter for high-speed beating will increase the volume of batter. Tyrosination can be expressed by tyrosination value (CV), that is, the volume of air contained in 100 g oil (ml).
(4) Emulsifiability
Oil and water are immiscible, but in food processing, the oil phase and the water phase containing milk, eggs and sugar are often mixed evenly. Cake dough is O/W emulsion, and the uniform distribution of shortening in the emulsion directly affects the lubrication effect of dough structure and the stability of products. Therefore, emulsifier is usually added to ghee to improve the dispersibility of oil droplets. Emulsifiability affects the foaming ability of eggs and sugar, and adding proper foaming agent can reduce the negative influence of emulsifier.
(5) Water absorption
Shortened oil can absorb and keep a certain amount of water even without emulsifier. The water absorption of shortening depends on its plasticity and the amount of emulsifier added. Hydrogenation of oils and fats can increase water absorption. For example, at about 22.5℃, the water absorption of several different types of shortening is: lard and mixed shortening are 25 ~ 50%; 75- 100% hydrogenated lard; 150 ~ 200% fully hydrogenated shortening; Shortened oil containing monoglycerides and diglycerides ≥400%.
Water absorption is of great functional significance for processing cream icing and baking cakes, which can compete for the water necessary for gluten formation, thus making the products crisp.
(6) Oxidation stability
In the process of baking, ordinary oils and fats do not contain natural antioxidants or are thermally decomposed by natural antioxidants, which leads to poor stability and short shelf life of baked products. Shortened base oil is modified by hydrogenation and transesterification to reduce unsaturation or add antioxidants, thus improving oxidation stability. The oxidative stability of shortening does not necessarily represent the storage stability of baked products, so when designing the oxidative stability of shortening, it needs to be different according to the purpose of shortening. For example, products such as salt and pepper biscuits are not protected by Maillard reaction products of amino acids and sugar when baking sugary cakes, so high-stability shortening with AOM value greater than 100 h is needed.
(7) solvency
The frying performance of shortening includes flavor characteristics and high temperature stability, and it should be resistant to oxidation, polymerization, hydrolysis and thermal decomposition at continuous high temperature to make the product have good flavor. The frying property of shortening is generally related to the saturation of base oil, the length of carbon chain of triglyceride fatty acid, defoamer and frying conditions (such as temperature, frying water content, oil residue cleaning and oil change rate).