Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation

Erten, Edibe Seda

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Description

Title

Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation

Author(s)

Erten, Edibe Seda

Issue Date

2016-07-15

Director of Research (if dissertation) or Advisor (if thesis)

Cadwallader, Keith R.

Doctoral Committee Chair(s)

Engeseth, Nicki J.

Committee Member(s)

• Lee, Soo-Yeun
• Lee, Youngsoo

Department of Study

Food Science & Human Nutrition

Discipline

Food Science & Human Nutrition

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• raw almonds
• roasted almonds
• aroma-active compounds
• storage
• lipid oxidation
• solvent-assisted flavor evaporation (SAFE)
• gas chromatography-olfactometry (GCO)
• aroma extract dilution analysis (AEDA)

Abstract

Almond is the most produced tree nut in the US. Along with potential health related studies, popularity of almonds has been rising among consumers in the last few decades. Furthermore, consumer liking the flavor of both raw and roasted almonds plays a role in its increasing popularity. However, because of its high unsaturated fat content almond is prone to lipid oxidation during storage that leads to flavor and quality changes. Predominant aroma-active compounds in almonds were identified and the effect of oxidative state of raw almonds on roasted aroma was observed in this study. Volatile components of raw, dry roasted and oil roasted almonds were isolated by solvent extraction-solvent-assisted flavor evaporation and the predominant aroma-active compounds were identified by gas chromatography-olfactometry (GCO) and aroma extract dilutions analysis (AEDA), and by GC-mass spectrometry determination of odor-activity values (OAVs). Results demonstrated the importance of lipid-derived volatile compounds such as ketones and aldehydes in raw almond aroma. Meanwhile, volatile compounds derived via the Maillard reaction, lipid degradation/oxidation and sugar degradation were predominant aroma compounds in dry and oil roasted almonds. These compounds were mainly pyrazines, pyridines, pyrrolines, aldehydes and furanones. Aroma changes of stored raw (SR) and stored raw-then-roasted (SRTR) almonds were investigated by gas chromatography-olfactometry (GCO) and aroma extract dilutions analysis (AEDA) and GC-mass spectrometry (GC-MS). Raw almonds were stored at either room temperature (24±1°C), 37°C or 4°C for 18, 9 or 12 months, respectively. Based on their relatively high flavor dilution (FD) factors and OAVs, the predominant aroma compounds in stored raw almonds were identified as 1-octen-3-one, hexanal and acetic acid. Aldehydes and acids were found in highest abundance in raw almonds. Storage of raw almonds resulted in an increase in the total concentration of aroma compounds at all storage temperatures. In SRTR almonds, methional, Furaneol, 3-methylbutanal and 2-acetyl-3,4,5,6 (& 1,4,5,6)-tetrahydropyridine were the predominant aroma compounds, while aldehydes, nitrogen-containing compounds and acids were found in highest overall abundance. Total concentration of aroma compounds increased in SRTR almonds stored at RT and 37°C, whereas they decreased in almonds stored at 4°C. Concentrations of nitrogen-containing aroma compounds, responsible for roasted notes, increased in the SRTR almonds throughout the storage period. Results of this study indicate that storing raw almonds prior to roasting affects the levels of thermally generated aroma compounds formed during roasting.

Graduation Semester

2016-08

Type of Resource

text

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Copyright 2016 Edibe Erten

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