'Laba' garlic processed by dense phase carbon dioxide: the relation between green colour generation and cellular structure, alliin consumption and alliinase activity.

BACKGROUND: 'Laba' garlic is usually processed by soaking garlic in vinegar for more than 1 week during winter. It is popular for its unique green colour and tasty flavour. Greening is desirable and required for this product as its characteristic. Dense phase carbon dioxide (DPCD) had a significant effect on the greening of intact garlic (Allium sativum L.) cloves. The relation between green colour generation and alliin consumption, alliinase activity and the cellular structure of garlic, respectively, were investigated in this work. The effects of treatment time, pressure and temperature of DPCD were also analysed and discussed. RESULTS: DPCD had a significant effect on the cellular structure of garlic cells. Garlic protoplast underwent greater morphological change after DPCD treatments at higher temperatures while the amount of precipitate increased with greater treatment time and temperature. Common trends on garlic greening and alliin consumption were observed except for DPCD treatment at 10 MPa and 65 °C. The alliinase activity decreased with increasing treatment time, pressure and temperature. It reached the lowest level at 13 MPa and 55 °C. CONCLUSION: The formation of the green colour was a comprehensive result of DPCD on changing cellular structure, alliin consumption and alliinase activity. DPCD treatment at 10 MPa and 55 °C was the optimum condition for the greening of 'Laba' garlic. This work further facilitated the application of DPCD in the industrial production of 'Laba' garlic. © 2015 Society of Chemical Industry.

Increase in the permeability of tonoplast of garlic (Allium sativum) by monocarboxylic acids.

Immersion of intact aged garlic (Allium sativum) cloves in a series of 5% weak organic monocarboxylate solutions (pH 2.0) resulted in green color formation. No color was formed upon treatment with other weak organic acids, such as citric and malic acids, and the inorganic hydrochloric acid under the same conditions. To understand the significance of monocarboxylic acids and their differing function from that of other acids, acetic acid was compared with organic acids citric and malic and the inorganic hydrochloric acid. The effects of these acids on the permeability of plasma and intracellular membrane of garlic cells were measured by conductivity, light microscopy, and transmission electron microscopy. Except for hydrochloric acid, treatment of garlic with all three organic acids greatly increased the relative conductivity of their respective pickling solutions, indicating that all tested organic acids increased the permeability of plasma membrane. Moreover, a pickling solution containing acetic acid exhibited 1.5-fold higher relative conductivity (approximately 90%) as compared to those (approximately 60%) of both citric and malic acids, implying that exposure of garlic cloves to acetic acid not only changed the permeability of the plasma membrane but also increased the permeability of intracellular membrane. Exposure of garlic to acetic acid led to the production of precipitate along the tonoplast, but no precipitate was formed by citric and malic acids. This indicates that the structure of the tonoplast was damaged by this treatment. Further support for this conclusion comes from results showing that the concentration of thiosulfinates [which are produced only by catalytic conversion of S-alk(en)yl-l-cysteine sulfoxides in cytosol by alliinase located in the vacuole] in the acetic acid pickling solution is 1.3 mg/mL, but almost no thiosulfinates were detected in the pickling solution of citric and malic acids. Thus, all present results suggest that damage of tonoplast by treatment with monocarboxylates such as acetic acid may be the main reason for the greening of garlic.

[Ultracytochemical localization of enzymes and DNA analysis during the development of garlic].

It is believed that during storage, the parenchyma cells of garlic (Allium sativum L.) bulb would wither and fade gradually, and nutrients released inside the cells become available for the germination and growth of the young bud. In this study, The distributions of acid phosphatase (APase) and Adenosine Triphosphatase (ATPase) during germination were analyzed based on the method of lead precipitation at the electron microscopic level. It was found that their activities presenting in plasma membrane, cell wall and plasmodesma increased along the different developmental periods during storage. The fact that the most intensive enzymatic activity of APase and ATPase appeared at germination indicates that degradation, transformation and exportation of cell matrix are helpful in complete translocation of nutrient to new bud. The DNA in the degrading parenchyma cells was analyzed using the agarose electrophoresis. Results clearly showed a typical DNA ladder on the gel, indicating that gene-controlled, programmed cell death may contribute to the degradation of garlic parenchyma cells.

Light and electron microscopic immunocytochemical localization of two major proteins in garlic bulb.

Garlic is known as a potent spice and a medicine with broad therapeutic properties ranging from antibacterial to anticancer, antidiabetic, and anticoagulant. Two major proteins of 40 KD and 14 KD constituting approximately 96% of total garlic proteins have been recently purified at our Institute. This immunocytochemical and ultrastructural study revealed that the 40 KD protein was localized in the parenchyma sheath cells (PSC) of garlic bulbs, whereas the 14 KD protein was present in the cortical cells (CC). Immunogold electron microscopy study indicated that the 40 KD protein was specifically localized in the globular granules of the cytoplasmic area of PSC. Each globular granule was amorphous and homogenous with membrane limiting its outermost layer. The yellowish color of PSC in freshly cut slices of garlic bulb suggested that PSC may have sulfur-containing compounds such as allicin, the primary contributor of the pungency and medicinal properties of garlic. Ellman's reagent test quantitatively revealed that there were 17.8 n moles sulfhydryl (SH)/ml of 40 KD garlic protein. Microtubule tubulin in mitotic figures from PHA-stimulated human short-term whole blood cultures reacted strongly with antitubulin antibody but reacted negatively with anti-40 KD garlic protein antibodies and therefore was not related to the 40 KD garlic protein immunocytochemically.