Progressive freeze-concentration (PFC) by a tubular ice system was successfully applied to concentrate apple juice from 13.7 to 25.5 o Brix under a program controlled operation for the coolant temperature and the circulation pumping speed. The organic acid distribution and the flavor profile analysis revealed that no substantial differences were observed for the juice before and after concentration both in organic acids and flavor components showing the high quality concentration by PFC. This was also confirmed by electronic taste and flavor analyzers. The PFC-concentrated apple juice was fermented to obtain a new type apple wine with alcohol content as high as 13.7 vol-% without chaptalization. The organic acid distribution was slightly changed before and after fermentation while the flavor profile changed drastically. The present technique will be applicable to produce new type of wine from many other fruits.

Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, Tt , was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From Tt and the melting enthalpy, ΔHsol , the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the sol-to-gel ratio as a function of water activity, was successfully applied to obtain a good linear relationship. From this analysis, the role of water activity on the sol-gel transition of gelatin was clearly explained and the contributions of hydration and solute binding to gelatin molecules were separately discussed in sol-gel transition. The general solution for the free energy for gel-stabilization in various solutions was obtained as a simple function of solute concentration.

Water activity (a w ) was measured for various two component aqueous solutions at various intersolute interactions and the obser ved a w was compared with the theoretical prediction by Ross equation assuming no inter-solute interactions. For solutions with neutral components including electrolytes, sugars, and neutral amino acid, solute-solute interaction was weak so that no substantial deviation was observed for observed a w from that predicted by Ross equation. When acid and base were involved, the deviation between the two was large because of the neutralization. For a solution containing macromolecule, bovine serum albumin (BSA) and sucrose mixture showed a strong cooperative effect between solutes to reduce a w much smaller than the theoretical expectation. In a case with an amino-carbonyl reaction between glycine and ribose kept at 60℃, a drastic increase in optical absorbance at 327 nm was observed with time and a w increased accordingly because of the water liberation at the initial stage of the Schiff-base formation and the following complex Maillard reaction process to reduce the number of solute molecules in the system.

Progressive freeze-concentration (PFC) of blueberr y juice was carried out by a tubular ice system and the original juice at 11.2 Brix was concentrated up to 27.2 Brix. The PFC-concentration was proved to give a high quality concentrate with no substantial change both in organic acid distribution and flavor profile. The PFC-concentrated blueberr y juice was fermented to produce a blueberry wine with 11.1 vol-% alcohol content, showing that a high alcohol content can be obtained without chaptalization in the present method. After the fermentation, some changes were observed both in the organic acid distribution and the flavor profile. As a whole, however, the blueberry wine retained enough amount of original blueberr y flavors. The present results suggest a possibility to produce a new-type blueberry wine with rich ingredients and flavors. 緒 言これまでにブドウ以外にも種々の果実を原料とする ワイン(果実酒)が製造されてきている [1] が，糖度が 低いため，十分なアルコール濃度を得るためには補糖 が必要である [2,3]．ブルーベリーについてもこれまで にブルーベリーワイン製造の試みが報告 [4-6] されて いるが，いずれも補糖を必要としている． 果汁糖度を補糖することなく上げる方法として濃縮法 があり，このためには，蒸発法，膜濃縮法，凍結濃縮法 があるが，蒸発法は香気成分がほとんど散逸してしまい， 膜濃縮法も果汁濃縮においてはフレーバーバランスが濃 縮前後でかなり変化するため，このような目的のための 濃縮法としては凍結濃縮法が最適である [7]．しかしな がら，従来法の凍結濃縮法は多数の微細氷結晶を成長 させることにより濃縮を行う懸濁結晶法 [8] に基づいて おり，これは大規模で複雑なシステムを必要とし，平 均滞留時間の極めて長い連続操作方式に限られるため， このような比較的規模の小さい濃縮操作には適してい ない． これに対して，われわれは界面前進凍結濃縮(PFC) を提案しており，これは，系に唯一個の巨大氷結晶を 成長させて凍結濃縮を行う方法 [9] で，従来法の懸濁結 晶法と比較して，システム単純化によるコスト低下が 期待される．さらにこの方法は，100 mL 規模の小規模 試験装置から，100 L 規模の循環流壁面冷却方式のス ケールアップ装置 [10] まで，幅広いラインアップを揃 えることができる回分操作方式で，フレキシビリティ が高く，これまでに凍結濃縮を適用することのできな 「日本食品工学会誌」

Pineapple juice was concentrated from 13. 0 to 22.3 Brix by progressive freeze-concentration (PFC). The distributions of organic acids and flavors were measured and no substantial changes were observed in the component profiles before and after PFC concentration. The PFC-concentrated pineapple juice was fermented to produce pineapple wine with an ethanol concentration as high as 12.7 vol-%, indicating that a sufficient alcohol level can be obtained using PFC concentration without chaptalisation. After fermentation, acetic acid and succinic acid increased in the organic acid distribution. In terms of flavors, several of the esters in the original juice disappeared, while fermentation products, such as ethanol, 3-methyl-1-butanol, ethyl octanoate, ethyl decanoate, methyl 3acetoxyhexanoate and benzene ethanol, appeared after fermentation. Generally, the pineapple wine retained enough amount of flavors present in the original juice. These findings suggest that a new-type pineapple wine, presently not available on the market, can be produced by PFC.