maturity and ripening

Post harv est Biolo gy and Techn ology 71 (201 2) 41–5 0 Con tents lis ts ava ilable at SciV erse ScienceDirect Postharvest BiologyandTechnology j ourna l h ome p a g e : www.elsevier.com/locate/postharvbio Influenceof maturityandripeningonaromavolatilesandflavorin‘Hass’avocado DavidObenland a,∗ , SueCollin b , JamesSievert b ,FayekNegm b ,MaryLuArpaia b a San Joa qui n Val ley Agr icultural Sci enc es Center, USDA-A RS,Parlie r, CA 936 48,United Sta tes b Depart ment of Bot any and Pla nt Sci enc es, Universit y of Cal ifornia, Rivers ide , CA92521,United Sta tes articleinfo Article history: Rece ived 30 Sept embe r 2011 Acce pted 26 Mar ch 201 2 Keywords: Dry weight Minimum maturity Sensory Grassy Carbohydrates abstract Changesinaromavolatilesweredeterminedusingsolidphasemicroextraction(SPME)andgaschro- matography/mass spectrometryinripeavocados(PerseaamericanaMill.,cv.Hass)throughout an eight-monthmaturationperiodandrelatedtothesensorypropertiesof thefruit.As matura tionpro- gressedsensorypanelistsfoundthelikeabilityof thefruittoincrease,coincidingwiththefruitbecoming creamierandlesswateryintexture,andtheflavorricherandlessgrassy. Duringthismaturationtimethe concentrationof hexanal, (E)-2-hexenal and2,4-hexadienal, threeof themostabundantvolatiles, greatly declinedinamount. Thesevolatilesallhavea gra ss-l ike aroma,anditis lik ely thatthelossinamount wasresponsibleforthedeclineingrassyflavorduringmaturation. Acetaldehyde, methylacetate,pen- tanal, and-myrcenewereathigherconcentrations inmaturethannon-maturefruitandmayalsohave contributedtotheoverallflavor. Avocadosof anintermediatematuritywereripenedat20 ◦ C an d fr u it of differentripenesslevels(firmnesses)measuredforethyleneproduction, rateof respirationandaroma volatilecontent.Asharpincreaseintheratesof respirationandethyleneproductionmarkedarapid increaseinsofteningand thebeginningof the climacteric. Twenty-fivevolatileswereidentifiedin th e ripeningavocadosof whichthree(pentanol, hexanol, and2-nonenal)werenotdetectableinfully-ripe fruit.Of particularinterestwasan85%declineintheamountof hexanal inacomparisonof firmtofully ripe(4N firmnes s)fruit.Aromavolatileshaveinthepastbeenlittle-studiedinavocadosbutappearto ha ve a roleindeterminingtheflavorof thefruit. Publishedby Elsev ier B.V. 1. Intr oduc ti on Avoc ados (Persea ameri can a,Mi ll .) pi cked pr emat u re l y at an imma tur e s ta ge c an ha ve an ea ti ng qual it y that ha s be en as soci - at ed wi th a gr ee n or gr as sy af t er ta st e, l ac k of fla vor and a ru bber y or w at er y t e xt ure (Har ding, 1954 ). As anearly response to this problem, Cali fornia growers in 1925 establ ished a state maturi ty st andard that re quired a mini mum oil conte nt of 8% before avocados coul d be ha rvested in Cali fornia (Ano n., 1925 ). This wasbased on the fa ct that o il a cc um ul a te s in av oc ad os in la rge amo un ts as they mature and wa s tho ught to provide a reasonable estimat e of ma tur ity (Church and Chance, 1920–1921 ). Al tho ugh oi l conte nt wa s shown t o r el a te to flav or a nd ea ti ng qual it y (Hodgki n, 1939 ), fr ui t-to-f ruit va ri abil ity in oi l conte nt and vari et al dif fe rences in ac cumulation rate (H at t on et al. , 1957a; Stah l, 1 93 3 ) ma ke pe r- cent oil an imperf ect thr eshold for maturity. An exten sive study in Ca li fornia on the rela tionship of maturi ty, eating qual it y and dry wei ght accumulat ion (Lee et al. , 1 98 3 ) le d to the ado pt ion of dr y ma tte r in conj unct ion wi th release dates as the basi s for mi ni mum ∗ Corre spond ing autho r. Tel .: +1 559 596 2801; fax : +1 559 596 2803. E-mail addres s: [email protected](D. Obe nlan d). ma t ur it y i n 1 98 3, r ep la ci ng o il con te nt. Dr y m at te r and o il a cc u- mulation are closel y rela ted , but measureme nt of dry matt er is far simpler to per form and isnowthe standardmaturitymeasuremen t used throughout most of the worl d. Nonethe less, it is recognize d in the avocado indust ry that neith er dry matte r nor percent oil ar e ade quatein the mselvesto ful ly explain thediffer ence s in theeating qualit y of avocados and that additional means of assessing eati ng qua lit y would be desirable. Volati les ha ve a well -esta bl ished role in helping to det ermi ne fla vo r in a wi de va ri et y o f f ru it s, b ut h a ve not be en s tu di ed e xt en - si ve ly in a vo ca do. T hi s m ayh av e b ee n l ar ge ly du e to the stron g emp hasis that ot her fla vor influencing factors in avocado, such as oi l content and texture, have received. Also, the hi gh li pi d content maymake some types of flav or vol ati le ana lys is mor e pro ble mat ic. In an earl y s tu dy, Ya maguchi et al. (19 83) utilized vacuum distil- lation and solvent extraction to identi fy 96 compounds, the ma jor constituents bein g n-hexa nol , cis -3- hexano l and trans- 2-he xenol wh ic h made up ove r 8 0% of t he e xt ract on a pe ak ar ea ba s is . Si m- il ar extracti on techni ques were later used to identif y a numbe r of compo unds in avoca do extracts,with terpen es and aldehy des being some of the most pr edomin ant comp ounds p re se nt (Pin o et al ., 2000, 2004; Si nyi nd a a nd G ra ms haw, 1998 ). Extr a ct s that we re st o re d r at he r t han being pr o ce ss ed imm ed ia t el y were fo und to have a greater number of compou nds , some bei ng pro duc ts of lip id 092 5-52 14/ $ – see fron t matt er. Pub lishe d by Elsev ier B.V. http://dx.doi.org/10.1016/j.postharvbio.2012.03.006

maturity and ripening

Documents