Abstract SCHIRACK, ANDRIANA VAIS. The Effect of Microwave ...

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contamination, microorganisms or enzymatic activity (Ory and others 1992; Sanders and others 1993). Hydroperoxides formed during lipid oxidation subsequently break down into alcohols, alkanes, ketones and aldehydes which can be the source of off- flavors in the peanut. Exposure to high temperatures, such as during the curing process, has also been correlated to the development of off-flavors (Whitaker and others 1974). High concentrations of certain compounds such as ethanol, ethyl acetate, and acetaldehyde were found in high temperature cured peanuts (Pattee and others 1965). In addition, fruity fermented off-flavor has been shown to occur predominantly in immature peanuts undergoing high temperature curing (Sanders and others 1989; Didzbalis and others 2004). Most previous studies examining the effects of processing techniques on peanut flavor have concentrated on high temperature curing. However, new processing technologies have been developed which can improve production efficiency but can also impact flavor quality. For example, microwave technology has been investigated as an alternative method for the drying (Delwiche 1986) and roasting of peanuts (Megahed 2001; Yoshida and others 2005). Although microwave roasting led to formation of undesirable lipid oxidation products, the use of microwaves for blanching has potential as an alternative to traditional blanching methods due to the speed of operation, energy savings, and efficiency of process control. However, during high temperature microwave treatments, an off-flavor has been observed which was related to other off-flavors such as cardboardy, ashy, and bitter, and was related inversely to positive attributes such as roast peanutty and sweet aromatic (Schirack and others 2006). 144
The objective of this study was to investigate the off-flavor formed in peanuts during the high temperature heating step of microwave blanching through instrumental volatile analysis and model systems. The identification of the compounds responsible for the off-flavor could enable better quality control and may ultimately aid in the adoption of alternative blanching methods in peanut processing. Peanuts Materials and Methods Medium-grade size, runner-type peanuts (Arachis hypogaea L., variety Georgia Green) at an average moisture content of 7 % (wet basis) were obtained from a single harvested lot from USDA, ARS, National Peanut Research Laboratory (Dawson, Georgia). The peanuts were harvested, cured, shelled, sized, and stored according to normal practices prior to delivery to Raleigh, NC. Peanuts were heated as part of the blanching process using a 5 kW, 915 MHz microwave unit (Industrial Microwave Systems, Morrisville, NC) using the equipment and methods detailed previously in Schirack and others (2006). A filled conveyor of peanuts (approximately 6 kg) was exposed to the microwave field for 11 minutes in a continuous process, in which internal peanut temperatures were as high as 128 °C. Immediately after heating, peanuts were cooled to room temperature using forced ambient air. The control sample was peanuts undergoing the same preparation and storage procedures but which were not treated with microwave energy. The peanuts were roasted before descriptive sensory and instrumental analysis, in order to approximate the impact of the off-flavor on commercial products, such as 145
Page 1 and 2:
Abstract SCHIRACK, ANDRIANA VAIS. T
Page 3 and 4:
THE EFFEGT OF MICROWAVE BLANCHING O
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BIOGRAPHY Andriana Schirack is orig
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TABLE OF CONTENTS v Page List of Ta
Page 9 and 10:
Materials and Methods..............
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Table 3 High Impact Aroma-Active Co
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CHAPTER 1: INTRODUCTION 1
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The processing parameters used duri
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educed from 35-40% moisture to 8-10
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REFERENCES Adelsberg GD, Sanders TH
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Interdependency and underlying dime
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Composition of Peanuts The structur
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and Burma. The peanut prices in the
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(w.b.) within 3 days, large quality
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cdry = Specific heat of dry seeds (
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there is no direct correlation publ
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Peanuts are commonly stored in flat
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lanching has been imitated using a
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(1999), no detrimental effects of b
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when the air is distributed from ab
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y-product (Giese, 1992). Drying is
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the material to absorb electromagne
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ε' = Relative real permittivity (d
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oils, both ε' and ε" are low and
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1969). The flavor characteristics o
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et al., 1980). Likewise, sugars pre
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n-methylpyrrole. Walradt et al. (19
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fact, Ory et al. (1992) suggested t
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Flavor Research in Other Nuts Sever
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changed with time of roasting and i
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polyunsaturated acids that have a c
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hexanal are intensified to the high
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The results of temperature stress i
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Brown et al. (1977) found that the
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exhibited the fruity fermented off-
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(Pawliszyn, 2000). Also, the elevat
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compounds eluting from microwave-he
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Table 1: Peanut Volatile Analysis b
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the identification of volatile comp
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the detector. The compounds can the
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GC-O Applications High vacuum disti
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each half was allocated into one of
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Woody/Hulls/Skins Cardboard Table 2
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Givaudan-Roure developed Quantitati
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during high temperature microwave b
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OVM Organic volatiles meter Pa Pasc
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References Abegaz EG, Kerr WL, Koeh
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odorants in high temperature cured
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17(4): 728-732. Mason ME, Waller GR
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partitioning constants and release
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Vercellotti JR, Crippen KL, Lovegre
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ABSTRACT Peanut blanching consists
Page 105 and 106: peanut moisture content from 5.5 to
Page 107 and 108: The computer monitored power output
Page 109 and 110: RESULTS AND DISCUSSION Energy Absor
Page 111 and 112: All treatments using the fan (F) ha
Page 113 and 114: Treatments 11NF, 8NF, and 5NF also
Page 115 and 116: lanchabilities as well as a longer
Page 117 and 118: microwave attain much higher temper
Page 119 and 120: REFERENCES ADELSBERG, G.D. and SAND
Page 121 and 122: TABLES AND FIGURES Table 1: Process
Page 123 and 124: Energy absorbed (kJ) 3000 2500 2000
Page 125 and 126: Temperature of peanuts (°C) 160 14
Page 127 and 128: Percent blanchability 100 90 80 70
Page 129 and 130: Maximum internal temperature (°C)
Page 131 and 132: ABSTRACT Microwave blanching of pea
Page 133 and 134: Several methods are used for blanch
Page 135 and 136: Peanuts MATERIALS AND METHODS Mediu
Page 137 and 138: Canada) on a laptop computer (Dell
Page 139 and 140: Sensory Analysis RESULTS AND DISCUS
Page 141 and 142: significantly lower final moisture
Page 143 and 144: ACKNOWLEDGMENTS Funded in part by t
Page 145 and 146: Foods and Beverages, Vol. 29, (G. C
Page 147 and 148: TABLE LEGENDS Table 1. Microwave ap
Page 149 and 150: TABLE 2. LEXICON OF PEANUT FLAVOR D
Page 151 and 152: Sweet Aromatic TABLE 4. CORRELATION
Page 153 and 154: CHAPTER 5: CHARACTERIZATION OF AROM
Page 155: Introduction The most common use of
Page 159 and 160: attributes which were different fro
Page 161 and 162: Volatile compounds from the solvent
Page 163 and 164: 0.25 μm df; J & W Scientific, Fols
Page 165 and 166: adjusted with the same concentratio
Page 167 and 168: characterized by the attributes of
Page 169 and 170: (E,E)-2,4-decadienal (fried/oxidize
Page 171 and 172: flavor dilution factors, nor did th
Page 173 and 174: that of the control, but only in th
Page 175 and 176: e high enough for pyrazine formatio
Page 177 and 178: sensory panelists analyzing process
Page 179 and 180: References (ASTM) American Society
Page 181 and 182: Megahed MG. 2001. Microwave roastin
Page 183 and 184: Vercellotti JR, Mills OE, Bett KL,
Page 185 and 186: Table 2- Model system concentration
Page 187 and 188: 28 4-acetoxy-2,5-dimethyl- 3(2H)-fu
Page 189 and 190: Table 5 - Quantification, sensory o
Page 191 and 192: Conclusions This research investiga
Page 193 and 194: microwave technology may provide ma
Page 195 and 196: protect against colon, prostate, an
Page 197 and 198: APPENDICES 185
Page 199 and 200: SAFE (3 SAFE's can be done in 1 day
Page 201 and 202: 2. Turn off waterbath. 3. Turn off
Page 203 and 204: 5. Filter through a third sodium su
Page 205 and 206: contamination, and run a blank on t
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AC nutty/burnt 975 1.5 NB cabbage/g
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AC oxidized 1289 1.5 NB dusty/nutty
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NB brothy 1612 3.5 NB honey/hay 161
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Table 2: Aroma-Active Compounds in
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AC cedar 1081 3.0 AC burnt sugar/nu
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AC brothy 1350 2.0 NB garlic 1352 5
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NB fruity/floral 1670 3.0 NB rosy 1
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