アマランス種子の膨化加工の最適化 : 体積増加率向上のための気流温度と種子含水率の操作 [in Japanese] Optimization for Popping Treatment of Amaranth Seeds : Flow Temperature and Conditioning of Seed's Moisture Content for Improved Expansion Ratio [in Japanese]
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Abstract
アマランスの種子は栄養価が高く，また適切な条件下で加熱すると急激な水分蒸発と共に膨化（ポッピング）する性質を有しており，膨化は消化性が改善されるなど有用な加工法の一つである．本研究では，膨化に大きな影響を与える種子含水率に注目し，その調整と測定方法，ならびに機械的強度に与える影響について検討した．さらに，種子の初期含水率と気流温度が膨化による体積増加ならびに膨化後の性状に与える影響について，熱風として高温空気と過熱水蒸気を用いて流動床型の膨化装置により調べた．その結果，種子の初期含水率が約0.15，気流温度が約260°Cの高温空気中で，体積増加率は約8.7倍と最も大きくなった．また，気流温度が高いほど種子の変色が激しいことがわかった．一方，過熱水蒸気中では，体積増加率が最大となる初期含水率は，空気の場合よりもわずかに低くなる傾向がみられ，最大の体積増加率も空気中に比べてやや小さくなった．その原因は水蒸気の初期凝縮により，アマランス種皮の機械的強度が低下したためと考えられる．また，アマランス種子の水分吸着等温線より，体積増加率が最大となる含水率は，相対湿度の増加に対して，平衡含水率が急増し始める直前の含水率付近であり，それ以上の含水率では，体積増加率が減少するとともに，弾性率低下が顕著となることがわかった．また，これらの結果から最適な含水率に調整するための指針を示した．
Amaranth seeds have a high nutritional value, and predisposition for popping when heated under proper conditions, accompanied by evaporation of contained water. Popping can be an effective and beneficial method for food processing. In this study, regulation and measurement of moisture content and its relationship to the mechanical properties of the amaranth seed were investigated. The effect of initial moisture content and gas temperature on expansion ratio, seed shape and browning, using hot air and superheated steam as heating media with a special fluidized bed for popping, was also studied. As a result, the maximum volume of the samples after popping was 8.7 times higher than the raw samples' volume, provided that the initial moisture content of the raw samples was 0.15 kg/kg, using hot air at 260°C for 15 seconds. In the case of superheated steam, the optimum moisture content was slightly lower than that of hot air, and the expansion ratio was measurably lower because the seed coat was softened by initial steam condensation. The optimum condition for regulation of seed moisture content for popping was determined from the water sorption isotherm, with the optimum moisture content located just before the moisture content started to increase at a faster rate, with increasing relative humidity. The results of rheometer measurements showed that the degree of elasticity decreased and yield load was nearly constant when the moisture content was higher than the optimum value of 0.15.
Journal
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- KAGAKU KOGAKU RONBUNSHU
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KAGAKU KOGAKU RONBUNSHU 32(2), 167-172, 2006-03-20
The Society of Chemical Engineers, Japan