Uticaj dodatka cvekle na fizičko-hemijska i nutritivna svojstva čajnog peciva

Abstract

Predmet ove doktorske disertacije je ispitivanje uticaja dodatka praha od cvekle (BP, engl. beetroot powder) na fizička svojstva, hemijski sastav, teksturu i senzorne karakteristike obogaćenog čajnog peciva, kao i praćenje promena relevantnih parametara tokom skladištenja u trajanju od šest meseci. Za pripremu čajnog peciva korišćen je prah egipatske pljosnate cvekle sorte Detroit. Speltinom brašnu (SF, engl. spelled flour), koje je bilo osnova za čajno pecivo i praha cvekle (BP), koji je korišćen kao funkcionalni dodatak, određena su sledeća svojstva: nasipna gustina, kapacitet vezivanja vode i ulja, kapacitet bubrenja i hidriranja. Utvrđene su visoke vrednosti kapaciteta vezivanja vode (7,2 g za BP i 2,0 g za SF), kao i kapaciteta vezivanja ulja (3,6 g za BP i 3,4 g za SF). Ovi nalazi se mogu povezati sa količinom dijetnih vlakana prisutnih u speltinom brašnu i prahu cvekle. Prah cvekle je sadržao znatno veći udeo dijetnih vlakana (19,9%) i pepela (3,8%) od brašna spelte (4,03% i 1,4%, redom). Takođe, brašno od spelte je imalo oko 20% veći sadržaj proteina od cvekle u prahu. Sadržaj pepela u prahu cvekle ukazuje da je cvekla dobar izvor minerala. Sa druge strane, prah cvekle je imao sadržaj vlage od 6,8%, što ukazuje na dobar kapacitet skladištenja. Zbog svega navedenog, BP se može preporučiti umesto sintetičkih aditiva u prehrambenim proizvodima, npr. za povećanje viskoziteta, zgušnjavanje proizvoda i produženje njegove svežine. Termalne osobine praha od cvekle određene su metodama diferencijalne skenirajuće kalorimetrije (DSC) i termogravimetrijske analize (TGA). Temperatura ostakljivanja (Tg) praha cvekle iznosila je 41,0 °C na početku skladištenja i 37,4 °C nakon godinu dana skladištenja, što su vrednosti značajno iznad uobičajenih temperatura skladištenja. Ovakva vrednost Tg obezbeđuje produženu stabilnost praha cvekle, što je u saglasnosti sa vrednostima za aktivnost vode (aw), koje su iznosile 0,38 na početku skladištenja i 0,36 nakon godinu dana skladištenja na sobnoj temperaturi. Termalna stabilnost praha od cvekle ispitana je termogravimetrijskom analizom. Glavna oblast degradacije praha cvekle je u opsegu temperatura od 170 do 270 °C, gde uzorak gubi oko 40% početne mase. Čajno pecivo je pripremljeno tako što je 30-50% speltinog brašna zamenjeno prahom cvekle, tako da udeo cvekle u zamesu iznosi 15-25%. Od speltinog brašna i cvekle u prahu napravljene su dve serije uzoraka, koje su pečene na 150 i 170 °C. U okviru svake serije je pripremljena i slepa proba, bez cvekle u prahu. Sve analize su rađene neposredno nakon pečenja, kao i nakon 3 i 6 meseci skladištenja. Poređenje uzoraka čajnog peciva pokazuje da je najveći sadržaj dijetnih vlakana imao uzorak sa najvećim udelom praha od cvekle (7,6%). Konzumiranjem ovakvog čajnog peciva može se nadoknaditi nedovoljni dnevni unos dijetnih vlakana koji u modernoj ishrani retko dostiže preporučenu vrednost od 28 do 35 g dnevno. Čajno pecivo sa dodatkom praha od cvekle ima znatno veće količine kalijuma i kalcijuma od uzorka koji je napravljen samo od speltinog brašna, što je još jedan od parametara koji opravdava upotrebu praha od cvekle kao funkcionalnog dodatka ishrani. Rezultati ispitivanja antioksidativne aktivnosti (AO), primenom DPPH i FRAP metode, pokazali su povećanu AO čajnog peciva sa prahom cvekle u poređenju sa slepom probom. Temperatura pečenja nije znatno uticala na AO uzoraka, ali je sa vremenom skladištenja AO opadala...

The subject of this doctoral dissertation is the investigation of the addition of beetroot powder (BP, engl. beetroot powder) on the physical properties, chemical composition, texture and sensory characteristics of the enriched biscuits, as well as the monitoring of changes during storage for six months. The powder of the Egyptian flat (elliptical) beetroot of the Detroit variety was used for the preparation of the biscuits. The following properties were determined for spelled flour (SF), which was the basis for biscuits, and beetroot powder (BP), which was used as a functional additive: bulk density, water and oil binding capacity, swelling and hydration capacity. High values of water binding capacity (7.2 g for BP and 2.0 g for SF) and oil binding capacity (3.6 g for BP and 3.4 g for SF) were determined. These findings can be linked to the dietary fiber content present in both spelled flour and beetroot powder. Beetroot powder contained a significantly higher proportion of dietary fiber (19.9%) and ash (3.80%) than spelled flour (4.03% and 1.4%, respectively). Also, spelled flour had about 20% more protein than beetroot powder. The ash content of beetroot powder indicates that beetroot is a good source of minerals. On the other hand, beetroot powder had a moisture content of 6.8%, indicating a good storage capacity. Therefore, BP can be recommended for use instead of synthetic additives in food products, e.g. to increase the viscosity, thicken the product and prolong its freshness. The thermal properties of beetroot powder were determined by thedifferential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The glass transition temperature (Tg) of beetroot powder was 41.0 °C at the beginning of storage and 37.4 °C after one year of storage, values that are significantly above the usual storage temperatures. Value of Tg ensures prolonged stability of beetroot powder, which is in agreement with the water activity (aw) values, which were 0.38 at the beginning of storage and 0.36, after one year of storage at room temperature. The thermal stability of beetroot powder was tested by thermogravimetric analysis. The main area of beetroot powder degradation is in the temperature range from 170 to 270 °C, where the sample loses about 40% of its initial mass. Biscuit was prepared by replacing 30-50% of spelled flour with beetroot powder, so that the share of beetroot in the dough was 15-25%. Two series of samples were made from spelled flour and beetroot powder, which were baked at 150 and 170 °C. Within each batch, a blank test was prepared, without beetroot powder. All analyzes were performed at the initial point (after baking), as well as after 3 and 6 months of storage. A comparison of the biscuits samples shows that the sample with the highest proportion of beetroot powder had the highest dietary fiber content (7.6%). By consuming this type of biscuit, the insufficient daily intake of dietary fiber can be compensated, which in a modern diet does not reach the recommended value of 28 to 35 g per day. Biscuit with the addition of beetroot powder has significantly higher amounts of potassium and calcium than the sample made only from spelled flour, which is another parameter that justifies the use of beetroot powder as a functional food supplement. The results of the antioxidant activity (AO) test, using the DPPH and FRAP method, showed an increased AO of biscuits with beetroot powder compared to the blank sample. The baking temperature did not significantly affect AO of the samples, but the AO decreased with the storage time...