Editing Saffron (section)

===Phytochemistry and sensory properties===
[[File:Picrocrocin.svg|thumb|Structure of [[picrocrocin]]:{{Sfn|Deo|2003|p=4}}
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|{{Legend|#AEAEFF|[[Anomer|β]]–[[Monosaccharide#Isomerism|D]]-glucopyranose derivative}}
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|{{Legend|#F5D76C|safranal moiety}}
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[[File:Crocetin safranal esterification.png|thumb|[[Esterification]] reaction between [[crocetin]] and [[gentiobiose]]. Components of α–crocin:<ref name=dhar/>
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|{{Legend|#A6CAF0|[[Anomer|β]]–[[Monosaccharide#Isomerism|D]]-gentiobiose}}||{{Legend|#000000|crocetin}}
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Saffron contains some 28 [[Volatile organic compound|volatile and aroma-yielding compounds]], dominated by [[ketone]]s and [[aldehyde]]s.<ref name="Amanpour">{{cite journal | last1=Amanpour | first1=Asghar | last2=Sonmezdag | first2=A. Salih | last3=Kelebek | first3=Hasim | last4=Selli | first4=Serkan | title=GC–MS–olfactometric characterization of the most aroma-active components in a representative aromatic extract from Iranian saffron (''Crocus sativus'' L.) | journal=Food Chemistry | volume=182 | year=2015 | issn=0308-8146 | doi=10.1016/j.foodchem.2015.03.005 | pages=251–256|pmid=25842335}}</ref> Its main aroma-active compounds are [[safranal]] – the main compound responsible for saffron aroma – 4-ketoisophorone, and dihydrooxophorone.<ref name="dhar">{{cite journal | last1=Dhar | first1=Manoj K | last2=Sharma | first2=Munish | last3=Bhat | first3=Archana | last4=Chrungoo | first4=Nikhil K | last5=Kaul | first5=Sanjana | title=Functional genomics of apocarotenoids in saffron: insights from chemistry, molecular biology and therapeutic applications (Review)| journal=Briefings in Functional Genomics | volume=16 | issue=6 | date=28 March 2017 | issn=2041-2649 | doi=10.1093/bfgp/elx003 | pages=336–347|pmid=28369196}}</ref><ref name=Amanpour/> Saffron also contains nonvolatile [[phytochemical]]s,{{Sfn|Abdullaev|2002|p=1}} including the [[carotenoid]]s [[zeaxanthin]], [[lycopene]], various α- and β-[[carotene]]s, as well as [[crocetin]] and its [[glycoside]] crocein, which are the most biologically active components.<ref name=dhar/><ref name="pmid29134501">{{cite journal | vauthors=Hosseini A, Razavi BM, Hosseinzadeh H | title=Pharmacokinetic Properties of Saffron and its Active Components | journal=European Journal of Drug Metabolism and Pharmacokinetics | volume=43 | issue=4 | pages=383–390 | year=2018 | url=https://www.sciencedirect.com/science/article/pii/S0890623820302926 | doi=10.1007/s13318-017-0449-3 | pmid=29134501| s2cid=23836415 }}</ref> Because crocetin is smaller and more water-soluble than the other carotenoids, it is more rapidly absorbed.<ref name="pmid29134501" />

The yellow-orange colour of saffron is primarily the result of α-crocin.<ref name=dhar/> This [[crocin]] is trans-[[crocetin]] di-(β-D-[[gentiobiose|gentiobiosyl]]) [[ester]]; it bears the [[IUPAC nomenclature|systematic (IUPAC) name]] 8,8-diapo-8,8-carotenoic acid. This means that the crocin underlying saffron's aroma is a digentiobiose ester of the carotenoid crocetin.{{Sfn|Abdullaev|2002|p=1}} Crocins themselves are a series of [[hydrophile|hydrophilic]] carotenoids that are either [[glycosyl|monoglycosyl]] or diglycosyl [[polyene]] esters of crocetin.{{Sfn|Abdullaev|2002|p=1}} Crocetin is a [[conjugated system|conjugated]] polyene [[carboxylic acid|dicarboxylic acid]] that is [[Hydrophobe|hydrophobic]], and thus oil-soluble. When crocetin is [[esterification|esterified]] with two water-soluble gentiobioses, which are [[carbohydrate|sugars]], a product results that is itself water-soluble. The resultant α-crocin is a carotenoid pigment that may make up more than 10% of dry saffron's mass. The two esterified gentiobioses make α-crocin ideal for colouring water-based and non-fatty foods such as rice dishes.{{Sfn|McGee|2004|p=422}}

The bitter [[glucoside]] [[picrocrocin]] is responsible for saffron's [[pungency|pungent flavour]].<ref name=dhar/> Picrocrocin ([[chemical formula]]: {{Chem2|C16H26O7}}; systematic name: 4-(β-D-glucopyranosyloxy)-2,6,6-trimethylcyclohex-1-ene-1-carbaldehyde) is a union of an [[aldehyde]] sub-molecule known as [[safranal]] (systematic name: 2,6,6-trimethylcyclohexa-1,3-diene-1-carbaldehyde) and a carbohydrate. It has insecticidal and pesticidal properties, and may comprise up to 4% of dry saffron. Picrocrocin is a truncated version of the carotenoid [[zeaxanthin]] that is produced via [[redox|oxidative]] cleavage, and is the [[glycoside]] of the [[terpene]] [[aldehyde]] safranal.{{Sfn|Leffingwell}}

When saffron is dried after its harvest, the heat, combined with enzymatic action, splits picrocrocin to yield [[Monosaccharide#Isomerism|D]]–[[glucose]] and a free safranal molecule.{{Sfn|Deo|2003|p=4}} Safranal, a [[essential oil|volatile]] oil, gives saffron much of its distinctive aroma.{{Sfn|McGee|2004|p=423}}{{Sfn|Dharmananda|2005}} Safranal is less bitter than picrocrocin and may comprise up to 70% of dry saffron's volatile fraction in some samples.{{Sfn|Leffingwell}} A second molecule underlying saffron's aroma is [[Lanierone|2-hydroxy-4,4,6-trimethyl-2,5-cyclohexadien-1-one]], which produces a scent described as saffron, dried hay-like.{{Sfn|Leffingwell}} Chemists find this is the most powerful contributor to saffron's fragrance, despite its presence in a lesser quantity than safranal.{{Sfn|Leffingwell}} Dry saffron is highly sensitive to fluctuating [[pH]] levels, and rapidly breaks down chemically in the presence of light and [[redox|oxidising]] agents. It must, therefore, be stored in air-tight containers to minimise contact with atmospheric oxygen. Saffron is somewhat more resistant to heat.