1 OBJECTIVES 1. To understand terminology and classification of lipids;2. Important reactions of lipids; 3. Importance of lipids for food chemistry and food technology; 4. Hydrogenation of lipids.
2 ! Lipids 1 Classification – hydrolysable and non-hydrolysable lipidsType Subclass Description Hydrolysable (having ester bonds) Simple 1. Waxes Long chain alcohols and fatty acids 2. Acylglycerols Glycerol + fatty acids Complex 3. Phosphoacylglycerols Glycerol + fatty acids + phosphate + N-containing compound 4. Sphingomyelin Sphingosine + fatty acid + phosphate + choline 5. Cerebrosides Sphingosine + fatty acid + carbohydrate Non-hydrolysable (without ester bond) Other 6. Isoprenoids Polymers on the base of isoprene 7. Steroids Sterane structure Role of the lipids in the organisms
3 Lipids 2 Hydrolysable Simple: Waxes – esters of higher alcohols with higher carboxylic acids
4 ! Lipids 3 Hydrolysable Simple: Acylglycerols *fats *oils
5 Lipids 4 Hydrolysable Simple: Acylglycerols *fats *oils
6 ! Lipids 5 Simple: Acylglycerols – major carboxylic (fatty) acids
7 Lipids 6 Simple: Acylglycerols – influence of fatty acids composition on melting point
8 ! Lipids 7 Simple: Acylglycerols – major carboxylic (fatty) acidsHuman constitution (and some mammals) – lack the enzymes with which could be introduced double bond after the 9th C atom (linoleic, linolenic acids – essential fatty acids) Benefits of ω-fatty acids intake
9 Lipids 8 Simple: Acylglycerols – major carboxylic (fatty) acidsFat replacers Category Type and example Function Carbohydrate-based Cellulose (Avicel) Dextrins, modified starches (Stellar) Fruit-based fibre (WonderSlim) Grain-based fibre (Betatrim) Hydrocolloid gums (Kelgum) Maltodextrin (Maltrin) Pectin (Grinsted) Binder, body, bulk, flavor, moisture retention, mouth feel Protein-based Microparticulate protein (Simplesse) Modified whey protein concentrate (Dairy-Lo) Mouth feel, water-binding, reduce syneresis Fat-based Altered triglycerides (Caprenin) Sucrose polyesters (Olean) Emulsion, mouth feel Combination Carbohydrate and protein (Mimix) Carbohydrate and fat (Optamax) Flavour, texture, mouth feel, water retention
10 Lipids ! 9 Complex: Phospholipids Sphingolipids and GlycolipidsSphingosine
11 Lipids 10 Complex: Phospholipids – building the cell membranes
12 Lipids 11 Non-hydrolysable (isoprenoids) – without ester bondsTerpenes Isopren
13 Lipids 12 Gonane Non-hydrolysable (isoprenoids) – without ester bondsSteroids Squalene Cholic acid Cholesterol content of some food
14 Lipids 13 Non-hydrolysable (isoprenoids) – without ester bondsProstaglandins – inflammatory processes
15 ! Lipids 14 Hydrogenation of lipidsFormation of trans fatty acids; isomerization of double bonds (position)
16 Lipids 15 Hydrogenation of lipidsVaccenic acid – ω-7 – trans fatty acid (in the milk – human, cow; butter; animals’ fats) oxidative destruction 2-nonenal old people smell rumenic acid (anti cancer properties)
17 Transesterification (enzymatic)Lipids 16 Hydrogenation of lipids Transesterification (enzymatic)
18 Lipids – functional properties17 Lipids – functional properties Formation of ordered structures Arrangement of molecules of oleic acid Molecular arrangement of trilaurin lattice
19 Lipids – functional properties18 Lipids – functional properties Consistency and polymorphism of triacylglycerols Parameter α-form β'-form β-form Melting point Lowest Medium Highest IR absorption bands 720 cm-1 (singlet) 719 and 727 cm-1 (doublet) 717 cm-1 (singlet) Density Least dense Intermediate Most dense Packing Hexagonal orthorhombic triclinic Size of the molecule 0.415 nm 0.42, 0.38 nm 0.46, 0.39 and 0.37 nm
20 Lipids – functional properties18 Lipids – functional properties Consistency and polymorphism of cocoa butter
21 Lipids – functional properties20 Lipids – functional properties Fat consistency – melting and crystallization properties of fats Several factors have important influences on the consistency of commercial fats: Proportion of solids in the fat. In general, the greater the solids content, the firmer the fat. It has been estimated that plastic commercial fats, at workable temperatures, increase in either firmness or viscosity by about 10% with each increment of crystals. Number, size, and kind of crystals. At a given solids content, a large number of small crystals produces a harder fat than does a small number of large crystals. Larger, soft crystals are typically produced by slow cooling. Crystals composed of highmelting acylglycerols provide greater stiffening power than do those of lower melting acylglycerols.
22 Lipids – functional properties21 Lipids – functional properties Fat consistency Viscosity of the liquid. Oils differ in viscosity at a given temperature and this will influence viscosity of the melt, as well as consistency of a solid-liquid lipid mixture. Temperature treatment. If a fat tends to supercool excessively, this can be overcome by melting the crystalline fat at the lowest possible temperature, holding it for an extended period of time at a temperature just above its melting point, and then cooling it. This facilitates formation of numerous crystal nuclei, numerous small crystals, and a firm consistency. Mechanical working. Crystallized fats are generally thixotropic; that is, they become reversibly softer after vigorous agitation and only gradually regain their original firmness. If a melted fat is mechanically agitated during solidification, it will be much softer than if allowed to solidify in a static condition. In the static state the growing crystals form structures of relatively great strength. These structures can be deformed by mechanical working.
23 Lipids – functional properties19 Lipids – functional properties Fat consistency Plasticity of the fats – determined by the proportion of the solids and liquid phase; interval of melting; The cocoa butter has large amount of similar triacyl- glycerols – narrow range of melting;
24 Lipids – functional properties22 Lipids – functional properties Mesomorphic states – liquid crystals (b) and (c) - emulsions
25 Lipids – functional properties23 Lipids – functional properties Emulsions and emulsifiers Amylose – emulsifier complex; prevention of bread ageing and lost of softness
26 Lipids – functional properties24 Lipids – functional properties Emulsifiers - preparation Gerard L. Hasenhuettl, Chapter 2 - Synthesis and Commercial Preparation of Food Emulsifiers, In G.L. Hasenhuettl and R.W. Hartel (eds.), Food Emulsifiers and Their Applications. 11 © Springer Science + Business Media, LLC 2008
27 Lipids – functional properties25 Lipids – functional properties Emulsifiers - preparation Gerard L. Hasenhuettl, Chapter 2 - Synthesis and Commercial Preparation of Food Emulsifiers, In G.L. Hasenhuettl and R.W. Hartel (eds.), Food Emulsifiers and Their Applications. 11 © Springer Science + Business Media, LLC 2008