Food Science

The effect of hot-air drying namely drying time (3-15 h), drying temperature (40-80°C) and loading capacity (0.5-2.0 kg/m2 ) on the physicochemical characteristics of kaffir lime leaves was optimized using Response Surface Methodology. Twenty treatments were assigned based on the second- order CCD including 6 center points, 6 axial points and 8 factorial points. The quality of dried kaffir lime leaves was evaluated by determining moisture content, water activity, texture (brittleness) and Hunter L, a, b values. The results indicated that the most significant (p<0.05) hot-air drying conditions that affect the physicochemical properties of dried kaffir lime leaves were the main effect of drying time and drying temperature as well as the quadratic effects of the independent variables. The overall optimum conditions that resulted in desirable dried kaffir lime leaves, were achieved when the drying time was 4.9 h, the drying temperature, 60°C and loading capacity 1.4 kg/m2.

Crude latex of Carica papaya L. has been known to offer a lot of benefits and potentials especially in the agricultural industry and human health. This study focuses on the latex coming from its fruits of Papaya CX variety. Seven to eight longitudinal incisions were made in order to allow latex to appear and drain in the collecting devices. 439.5 g dried la- tex was stored in plastic containers and freezed. Results showed that dried latex contained higher amount of crude pro- tein (57.24 ± 0.69%), followed by moisture (17.76 ± 0.09%), ash (7.00 ± 0.01%), crude fat (5.21 ± 0.13%) and crude fiber (0.67 ± 0.09%) based on the complete proximate analysis. In the enzyme analysis, papain had protease activity of 2655 units·g−1 at pH 5.5 and 285 units·g−1 at pH 9.0. These results provided evidence that papain as a protease enzyme is found in the crude latex of papaya which is a major constituent in various proteolytic activities. Crude latex from C. papaya L. can be utilized to address the issues in agricultural farms to accelerate production and reduce environmental hazards.

"Reduction of water activity aw can extend the shelf life and improve the quality of foods. After the optimal water activity has been selected, based on Karel’s aw-spoilage graphs, a simple decision scheme in this document helps to choose the best equation (“Law”) to calculate or adjust the water activity: for an aqueous one component  solution: Raoult’s and Norrish’ laws; spreadsheet “aw-Raoult-Norrish.xls”; or in case of an aqueous multi-component solution: Norrish’ and Ross’ laws; spreadsheet “Norrish-Ross.xls: aw calculations of a multi-component solution”. Both Excel spreadsheets, present in this document, simplify the tedious exponential aw calculations.
The water activity of a mixture of 2 to 5 solids can be predicted either by constructing the solids mixture sorption isotherm, or by using the Salwin equation. When applying the 3rd spreadsheet in this document, “Calculation Water Activity aw Solids Mixture.xls”, the  2 to 5 separate solids isotherms are converted into one new solids mixture sorption isotherm. Because the total water content of the solids mixture is known, the water activity of the solids mixture can be found from that new mixture isotherm. The calculations by the “aw Solid Mixture” spreadsheet are compared with aw findings from Salwin’s equation. Both aw values are in good agreement.
Several worked examples, for each of the 3 spreadsheets present, illustrate step-by-step the aw calculation of solutions and of solid mixtures.
Annex 1 lists the lowest water activity for growth and/or toxin production of many micro-
organisms in foods. Annex 2 shows the minimal aw for activity of the main food spoiling enzymes.
"