Teknologi Pengolahan Hasil Hortikultura : Penyimpanan Beku

Teknologi Pengolahan Hasil Hortikultura : Penyimpanan Beku

Dewi Cakrawati, S.TP.,M.Si

Agroindustri-UPI

Freezing is one of the best methods for long-term storage of fruits.

Freezing preserves the original color, flavor, and nutritive value of most fruits.

Fresh fruits, when harvested, continue to undergo chemical, biochemical, and physical changes, which can cause deterioration reactions such as senescence, enzymatic decay, chemical decay, and microbial growth.

The freezing process reduces the rate of these degradation reactions and inhibits the microbiological activity.

FREEZING PRINCIPLES

The freezing process reduces food temperature until its thermal center (food location with the highest temperature at the end of freezing) reaches 18C, with the consequent crystallization ofwater, the main component of plant tissues.

Crystallization of water during freezing reduces water activity (aw) in these tissues and consequently produces a decline in chemical and biochemical reactions and microbial growth.

Freezing Rate

solute-induced damage

osmotic damage

structural damage.

Freezin rate :

Slow, 1 cm/h

Semiquick, 15 cm/h

Quick, 510 cm/h

Very quick, 10 cm/h.

Preparing, Pretreatments, and Packaging

Preparing : Washing, rinsing, sorting,

peeling, and cutting

Seleksi produk untuk pembekuan

Fruits are best when frozen fully ripe but still firm and at the peak of quality, with a pleasing color, texture, flavor, and maximum nutritional value.

The suitability of varieties or cultivars for freezing can be studied on the basis of physical (texture and color), physicalchemical (pH, acidity, and soluble solids), chemical (volatile, pigments, and polyphenol compounds), nutritional (vitamins and dietary fiber content), and sensorial aspect (firmness, color, and taste).

Pretreatments

Enzymes, namely polyphenoloxidase (PPO), peroxidase (POD), lipoxygenase (LOX), catalase (CAT), and pectinmethylesterase (PME) are involved in the fast deterioration of fruit during postharvest handling and processing.

Enzymes not inactivated before freezing can produce off-flavors, off-odors, color changes, development of brown color, and loss of vitamin C and softness during frozen storage and thawing.

Water blanching is the most common method for inactivating vegetable enzymes (Fellows, 2000). It causes denaturation and therefore, inactivation of the enzymes that also causes destruction of thermosensitive nutrients and losses of water-soluble compounds such as sugar, minerals, and water-soluble vitamins.

Addition of Chemical Compounds

They are mainly antibrowning additives such as sulfiting agents (sulfur dioxideor inorganic sulfites salts) and ascorbic acid, which are applied by dipping or soaking the fruit in different solutions before freezing

Dipping fruits in dry sugar or syrups is a traditional pretreatment to preserve color, flavor, texture, and vitamin C content and to prevent the browning of freezingthawing fruits. Sugar or syrups are used as cryoprotectants by taking out the fruit cell water by osmosis and excluding oxygen from the tissues.

The proposed mechanisms of antibrowning additives that inhibit enzymatic browning are

(1) direct inhibition of the enzyme;

(2) interaction with intermediates in the browning process to prevent the reaction leading to the formation of brown pigments;

(3) to act as reducing agents promoting the reverse reaction of the quinone back to the original phenols

Faktor yang mempengaruhi kualitas buah beku

Two principles dominate the control of quality and safety in frozen foods: product-process-package factors (PPP) and time-temperature-tolerance factors (TTT).

Product: High-quality frozen food requires high-quality raw materials and ingredients.

Process: The speed and effectiveness of the freezing operations and the use of additional processes (blanching, etc.).

Package: Packaging offering physical and chemical barriers

TTT factors maintain the quality and safety during storage.

TTT concepts refer to the relationship between storage temperature and storage life.

TTT relationships predict the effects of changing or fluctuating temperatures on quality shelf life

pengemasan

Pengemasan produk beku sangat penting untuk melindungi produk dari udara dan oksigen yang menyebabkan reaksi oksidasi, mikroorganisme dari lingkungan luar serta dari kerusakan selama distribusi

Kemasan yang digunakan dapat berupa plastik, logam, cardboard, polietilen, laminasi.