Commercial Frying Stability of LowLinolenate, HighOleate, and Typical Soybean Oils

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Commercial Frying Stability of Low-Linolenate,
High-Oleate, and Typical Soybean Oils

• Pamela J. White1, Caiping Su1 and
• Monoj Gupta2
• 1 Food Science and Human Nutrition Dept and
  Center for Crops Utilization Research, Iowa State
  University, Ames
• 2 MG Edible Oils, Consulting, Plano, TX

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Introduction

• Common frying oils are stabilized by
  hydrogenating to reduce PUFA
• Hydrogenation introduces trans fatty acids, which
  creates health concerns
• Nutrition labeling of trans fatty acids in foods

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Objectives

• Evaluate new soybean oils with altered fatty acid
  composition for their stability during frying of
  commercially prepared French fries
• Underlying objective Create trans-free soybean
  oils that are stable to commercial frying
  conditions

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Materials

• Soybeans grown in Iowa, Summer 2000
• Beans crushed and hexane-extracted, Montana Power
  Group, Culverston, MT
• RBD at POS plant, Saskatoon, Canada
• 50 ppm citric acid TBHQ (100 ppm)

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Soybean (SBO) Oil Treatments

• Low linolenate (LL)
• High oleate (HO)
• LL and HO processed into pourable shortenings by
  blending with fully hydrogenated typical SBO (AC
  Humko, Champaign, IL)
• Control
• Typical hydrogenated SBO, designed for commercial
  frying

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French Fries

• Commercially prepared fries, Simplot, Caldwell,
  Idaho
• Pretreated with
• Highly hydrogenated SBO for control
• LL shortening for frying in LL oil
• HO shortening for frying in HO oil

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Experimental Design

• Phase I
• Fries fried continuously (1kg/hr, 8 hr/day, 10
  days) in commercial 6.8-kg fryers
• At days end
• fries removed for sensory evaluation and testing
• Oils sampled, cooled, filtered, returned to fryer
• At days start
• fryer replenished with fresh oil to fill line

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Experimental Design, cont.

• Phase II
• Packaged French fries, sealed fresh oils
• Stored at -20o C for 3 months
• Entire 10-day frying operation and testing
  repeated

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Methods for Oil Evaluation

• Fatty acid methyl esters by GC (AOCS, Ce 1c-89)
• PV of fresh oil (Stamm test by Hamm et al. JAOCS,
  1965)
• Free fatty acids (modified AOCS by Rukunudin et
  al., JAOCS, 1998)
• Polar compounds (AOCS, Cd 20-91)
• Polymers by HPLC (AOCS, Cd 22-91)

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Methods for French Fry Evaluation

• Hexanal and total volatiles with SPME (Jelen et
  al., J Ag Food Chem, 2000)
• Fatty acid methyl esters by GC (AOCS, Ce 1c-89)
  of oil extracted from fries
• Oil content (AOCS Ba 3-38)
• Moisture content (AOCS, Ba 2a-38)
• Sensory evaluations, daily, fresh after frying

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Method for Sensory Evaluation

• 12-member, descriptive, trained panel
• Intensity of individual flavors
• 15-cm line scale, 0 no flavor, 15 intense
  flavor

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Sensory Training for Flavors

• Potato baked potatoes
• Sweet potatoes soaked in sugar solutions
• Buttery potatoes in butter, marg, or oil
• Grassy fries in parsley-infused oil soln
• Rancid and Painty fries in oxidized oil
• Astringent potatoes soaked in alum
• Burnt fries in overheated oil, then diluted

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Fatty acid methyl esters () in Oils
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Peroxide Values and Free Fatty Acids of Oils
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Oil Extr. from Fries during Frying
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Moist. extr. from Fries during Frying

• Uncooked fries set 1, avg 62.6
• Uncooked fries set 2, avg 63.9
• Fries after 16 hr, set 1, avg 39.7
• Fries after 16 hr, set 2, avg 39.4
• Fries after 80 hr, set 1, avg 39.6
• Fries after 80 hr, set 2, avg 39.7

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Sensory Evaluations-Summary

• Sets 1 and 2
• Fries from HO had more intense rancid, painty and
  astringent flavors slightly more grassy flavor,
  slightly less potato and buttery flavors
• Fries from Control and LL oils were similar to
  each other

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Overall Summary, best to worst

• FFA Sets 12, LLgtHOgtControl
• Polar cmpds Set 1, HOgtControlgtLL
• Set 2, ControlgtHOgtLL
• polymers Sets 12, HOControlgtLL
• Hexanal Sets 12, HOgtControlgtLL

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Conclusions

• Lack of oil breakdown in HO fries was reflected
  in a poorer flavor profile
• More stable oils do not necessarily create better
  quality fried foods, but depends upon length of
  heating time
• All oils in study had excellent initial quality
  and were not heavily abused during frying

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Acknowledgments

• MG Edible Oils Consulting Intl
• Christina Blair
• Jennifer Kuesar
• Jose Gerde
• Trust Beta
• Amalia Tziotis