Ispitivanje sadržaja i antioksidativne aktivnosti fenolnih kiselina u toku proizvodnje slada i piva

Abstract

Cilj istraživanja doktorske disertacije je bio da se u konitnuitetu ispita sadržaj ukupnih fenola, fenolnih kiselina i anitoksidativna aktivnost (antiradikalska aktivnost na DPPH i hidroksil radikale) u toku proizvodnje slada i piva (u ječmu, namočenom ječmu, zelenom sladu, sladu, sladovini, ohmeljenoj sladovini, sladovini tokom fermentacija, mladom pivu i pivu) proizvedenih od tri priznate sorte pivskog ječma: NS 525, NS 565 i NS 583. Sadržaj ukupnih fenola u uzorcima ječma je bio: NS 525 - 0,76; NS 565 - 0,75 i NS 583 - 0,70 mg GAE/g suve materije. Sadržaj ukupnih fenola u svim proizvednim sladovima (0,96; 0,94 i 0,91 mg GAE/g suve materije za NS 525; NS 565 i NS 583) je bio viši od sadržaja u ječmu. Sorta NS 525 je imala najviši sadržaj ukupnih fenola tokom svih faza sladovanja, dok su sorte NS 565 i NS 583 imale niže sadržaje ukupnih fenola. Najniži sadržaj ukupnih fenola imala je sorta NS 583. U svim ispitivanim sortama ječma ferulna, p-kumarinska i vanilinska kiselina su bile dominantne u uzorcima ječma, tokom sladovanja i u proizvedenom sladu. Sadržaj ukupnih fenolnih kiselina u ječmu je iznosio za sortu NS 525 - 200,98; NS 565 - 184,10 i za NS 583 – 177,27 μg/g suve materije. Sadržaj ukupnih fenolnih kiselina je rastao kod svih ispitivanih sorti tokom močenja i dostigao maksimum u toku prvog dana klijanja za NS 525 – 548,31; NS 565 – 518,65 i NS 583 – 517,17 μg/g suve materije. Dobijeni rezultati su pokazali da je proces sladovanja imao značajan uticaj na sadržaj pojedinačnih i ukupnih fenolnih kiselina. Sorta NS 525 je imala najvišu antiradikalsku aktivnost na DPPH radikale (EC50 za NS 525 - 0,658; NS 565 - 0,667 i NS 583 - 0,758 mg/ml) što pokazuje da sorta ječma ima uticaja na antiradikalsku aktivnost na DPPH radikale. Za ispitivane sorte ječma, antiradikalska aktivnost na DPPH radikale se povisila značajno tokom močenja. U proizvedenim sladovima antiradikalska aktivnost na DPPH radikale bila je viša nego u ječmu. Trend porasta i smanjenja antiradikalske aktivnosti na DPPH radikale tokom sladovanja je bio isti za sve ispitivane sorte ječma. Antiradikalska aktivnost na hidroksil radikale, izražena kao EC50 vrednost, u ispitivanim sortama ječma je iznosila: NS 525 – 0,352; NS 565 – 0,385 i NS 583 – 0,455 mg/ml. Može se zaključiti da je sorta NS 525 imala najvišu antiradikalsku aktivnost na hidroksil radikale. Antiradikalska aktivnost na hidroksil radikale se znatno povisila tokom močenja. U proizvedenom sladu je antiradikalska aktivnost na hidroksil radikale bila viša nego u ječmu. Trend porasta i smanjenja antiradikalske aktivnosti na hidroksil radikale tokom sladovanja je bio isti za sve ispitivane sorte ječma. Sorta NS 525 je imala najviši sadržaj ukupnih fenola kao i najvišu antioksidativnu aktivnost tj. DPPH i hidroksil antiradikalsku aktivnost. Ovi rezultati pokazuju da sorta ječma može da utiče na antiradikalske osobine slada. Sorta NS 525 je imala najviši sadržaj ukupnih fenola, ukupnih fenolnih kiselina i najvišu antiradikalsku aktivnost na DPPH i hidroksil radikale u toku sladovanja. U svim proizvedenim sladovinama, ohmeljenim sladovinama i pivima, ferulna, p-kumarinska, vanilinska i sinapinska kiselina su imale najviše sadržaje. Sadržaj svih ispitivanih fenolnih kiselina je povišen nakon hmeljenja. Najviši ukupni sadržaj fenolnih kiselina je odreñen u ohmeljenim sladovinama (NS 525 - 461,41, NS 565 - 426,22 i NS 583 - 423,56 μg/100ml). Sadržaj ukupnih fenolnih kiselina je u svim proizvedenim pivima bio niži u odnosu na odgovarajuće ohmeljene sladovine. U sladovini proizvedenoj iz slada NS 525 je odreñena najviša antiradikalska aktivnost na DPPH i hidroksil radikale što ukazuje da antiradikalska aktivnosti komponenti slada ima uticaja na antiradikalsku aktivnost proizvedene sladovine. U ispitivanim sladovinama, nakon hmeljenja se znatno povisila antiradikalska aktivnost na DPPH i hidroksil radikale. Antiradikalska aktivnost na DPPH i hidroksil radikale se smanjila tokom glavne i naknadne fermentacije. U sladovini proizvedenoj od slada NS 525 sa najvišim sadržajem ukupnih fenola i ukupnih fenolnih kiselina odreñena je najviša antiradikalska aktivnost na DPPH i hidroksil radikale. Tokom proizvodnje piva sadržaj ukupnih fenola se blago smanjio, što ukazuje da je proces proizvodnje imao uticaja na njihov sadržaj. Trend smanjenja antiradikalske aktivnosti na DPPH i hidroksil radikale odgovara smanjenju sadržaja ukupnih fenola i ukupnih fenolnih kiselina tokom procesa proizvodnje piva. Primenjena GC-MS metoda za odreñivanje sadržaja fenolnih kiselina tokom procesa proizvodnje slada i piva se pokazala kao osetljiva, specifična i dobre ponovljivosti. Može se primeniti za odreñivanje sadržaja fenolnih kiselina u ječmu, namočenom ječmu, zelenom sladu, sladu, sladovini, ohmeljenoj sladovini, tokom fermentacije i u pivu. Sadržaj ukupnih fenola, fenolnih kiselina i antioksidativna aktivnost slada, koji se koristi za proizvodnju piva, imaju značajan uticaj na antioksidativnu aktivnost piva. Razumevanje promena sadržaja fenolnih kiselina i antioksidativne aktivnosti tokom proizvodnje slada i piva može nam pružiti vredne informacije o zaštiti endogenih antioksidanata u proizvodnji piva. Na taj način mogu se proizvoditi piva sa višom antioksidativnom aktivnošću i prema tome i povišenom otpornošću prema lipidnoj oksidaciji i starenju piva.

Studies carried out in the frame of the doctorial thesis aimed at continuous determination of the content of total phenolics, phenolic acids and antioxidant activity (antiradical activity on DPPH and hydroxyl radicals) during malt and beer production (in barley, steeped barley, green malt, malt, wort, hopped wort, fermenting wort, green beer, and beer) produced from three accepted brewer’s barley varieties: NS 525, NS 565, and NS 583. The total phenolics content in the barley samples was 0.76 for NS 525, 0.75 for NS 565 and 0.70 mg GAE/g dry matter (d.m.) for NS 583. Higher content of total phenolics was determined in the malt samples in comparison with the barley samples: (0.96, 0.94, and 0.91 mg GAE/g d.m. for NS 525, NS 565, and NS 583, respectively). Variety NS 525 was the highest in total phenolics content during all stages of malting when compared to the other varieties. The lowest content of total phenolics was found in the variety NS 583. In all examined samples, ferulic, p-coumaric and vanillic acid dominated in the barley samples, during malting and in the produced malts. Content of total phenolic acids in the barley samples was 200.98 for NS 525, 184.10 for NS 565 and 177.27 mg/g d.m. for NS 583. During steeping, the content of total phenolic acids increased for all samples reaching the maximum at the first day of germination (NS 525 – 548.31; NS 565 – 518.65, and NS 583 – 517.17 μg/g d.m.). The obtained results revealed that the malting process had significant impact on the content of total and individual phenolic acids. Variety NS 525 showed the highest antiradical activity on DPPH radicals (EC50 for NS 525 was 0.658, for NS 565 0.667, and for NS 583 0.758 mg/ml) indicating that barley variety influences the antiradical activity on DPPH radicals. Antiradical activity on DPPH radicals significantly increased during steeping for all investigated barley varieties. Higher antiradical activity on DPPH radicals was determined in produced malts when compared to corresponding barley varieties. Similar increasing and decreasing trends in the antiradical activity on DPPH radicals during malting were observed in all investigated barley varieties. The antiradical activity on hydroxyl radicals, expressed as EC50 value, in investigated barley varieties, was: 0.325 for NS 525, 0.385 for NS 565, and 0.455 mg/ml for NS 583. It can be concluded that barley variety NS 525 showed the highest antiradical activity on hydroxyl radicals. The antiradical activity on hydroxyl radicals significantly increased during steeping. Higher antiradical activity on hydroxyl radicals was determined in produced malts when compared to corresponding barley varieties. Similar increasing and decreasing trends in the antiradical activity on hydroxyl radicals during malting were observed in all investigated samples. Variety NS 525 had the highest content of total phenolics and exhibited the highest antioxidant activity that is antiradical activity on DPPH and hydroxyl radicals. These results suggest that variety can influence the malt antiradical properties. Variety NS 525 was the highest in total phenolics content, total phenolic acids content and antiradical activity on DPPH and hydroxyl radicals during malting. The highest contents of ferulic, p-coumaric, vanillic, and sinapic acids were determined in all wort, hopped wort and beer samples. Increased contents of all phenolic acids were observed after hopping. The highest content of total phenolic acids was determined in the hopped worts (461.41 for NS 525, 426.22 for NS 565, and 423.56 μg/100 ml for NS 583. The beers contained less total phenolic acids when compared to the corresponding hopped worts. Wort produced from NS 525 malt showed the highest antiradical activity on DPPH and hydroxyl radicals which indicates that the antiradical activity of malt components affects the antiradical activity in produced wort. After hopping, antiradical activity on DPPH and hydroxyl radicals significantly increased in all worts. The antiradical activity on DPPH and hydroxyl radicals decreased during primary and secondary fermentation. Wort produced from NS 525 malt contained the highest total phenolic content, total phenolic acids content and showed the highest antiradical activity on DPPH and hydroxyl radicals. During beer production, content of total phenolic compounds slightly decreased which indicates that production process had an influence on their content. Similar decreasing trends between the antiradical activity on DPPH and hydroxyl radicals and the contents of total phenolics and total phenolic acids during beer production were observed. The applied GC-MS method for determination of phenolic acids contents during malt and beer production was sensitive, specific and had good repeatability. It can be used for determination of phenolic acids content in barley, steeped barley, green malt, malt, wort, hopped wort, during fermentation and in beer. The content of total phenolics, phenolic acids and antioxidant activity of malt used for beer production have significant influence on the beer antioxidant activity. Understanding how the phenolic acids and antioxidant activity change during malt and beer production can provide valuable information about the protection of endogenous antioxidants in beer production. In this way, the production of beer with enhanced antioxidant activity is possible and therefore higher resistance to lipid oxidation and longer shelflife could be introduced.