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VACUUM‐PUFF FREEZE DRYING OF TROPICAL FRUIT JUICES
Author(s) -
MOY JAMES H.
Publication year - 1971
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1971.tb15557.x
Subject(s) - tropical fruit , freeze drying , food science , fruit juice , vacuum drying , environmental science , chemistry , biology , horticulture , chromatography
SUMMARY— A study was made to develop high Quality juice powders from four tropical fruits. Guava and mango puree, passion fruit and pineapple juice were dehydrated in a vacuum‐puff freeze‐drying process. Sucrose in amount (25–40%) approximating nectar formulations was mixed with single‐strength juice or puree samples, blended 2 min, and frozen. Freezing temperatures of various samples were measured in a constant temperature bath of −21.6°F. Samples initially frozen in blast freezers at −40°F or 0°F with 0.25–1.0 lb/ft 2 were vacuum‐puffed and freeze dried on aluminum trays at 50μ Hg and 120–130°F shell temperature for 6–9 hr to 1–2% moisture. Puffing was affected by (1) rapid freezing of the juice‐sucrose mixture; (2) artificially entrapping some gas in the mixture before freezing; (3) changing the pressure or temperature in the chamber to effect gas expansion; and (4) increasing the mixture viscosity to limit bubble sizes. Results of drying over 160 different samples showed that: (1) added sucrose to give a 40° 5° Brix in the mixture resulted in a stable ‘puffed’ structure; (2) several permissible calcium salts and silica at 0.1–0.5% (w/w) added to the mixture before drying, improve the free‐flowing properties of the dried product. Process variables are discussed and typical sample compositions given.