EXTRUSION PROCESSING OF TRITICALE

Whole triticale kernels were extruded using a Brabender Plasti-corder extruder with 3/4-in. rifled barrel and 1:1 flight depth ratio screw. Samples were extruded at initial moisture contents of 15% and 20% using barrel temperatures of 350 °F, 400 °F and 450 °F through nozzle openings of 1/8 in. and 1/16 in. The products were measured for pH, final moisture content, color, trypsin hydrolysis, torque during extrusion, and texture and flavor as evaluated by a taste panel. From the results it was concluded that an acceptable product could be produced at 20% initial moisture using either the small nozzle and operating at 350 °F or the larger nozzle and operating at 400 °F.     

STUDIES ON MECHANISMS OF RETENTION OF VOLATILE IN FREEZE-DRIED FOOD MODELS: THE SYSTEM PVP-n-PROPANOL

Retention of C¹⁴-labeled n-propanol was studied in a freeze-dried system containing polyvinylpyrrolidone (PVP). Variables affecting retention during freeze drying were: initial concentrations of PVP and n-propanol, rate of freezing and sample thickness. Rehumidification above the BET monolayer value resulted in losses of propanol which increased with increasing water content. Behavior of the model system based on PVP is consistent with the "microregion volatile entrapment theory." The PVP system (and perhaps polymeric carbohydrates) differ from low molecular weight carbohydrates: water sorption below the BET monolayer is reduced by entrapped volatile, and absolute level of retention is lower     

RETENTION OF SPARINGLY SOLUBLE VOLATILE COMPOUNDS DURING THE FREEZE DRYING OF MODEL SOLUTIONS

The retentions of terpenic essential oil components (carvone, pulegone and piperitone) and non-terpenic essential oil components (eugenol and m-anisaldehyde) were measured during the freeze drying of model aqueous solutions. Model solutions contained sucrose, glucose, sodium chloride or gum arabic which are all common food components. The percent retentions of these slightly soluble flavoring compounds were found to increase with increased initial solids concentration, decreased initial volatile content, increased sample thickness, increased freezing rate and the absence of an additional sparingly soluble volatile.     

SOLUBILIZATION OF APPLE POMACE BY EXTRUSION

Apple pomace (AP), a fibrous by-product of apple juice processing, was solubilized by a twin-screw extruder. AP was extruded under 14 different operating conditions, where the process variables are controlled in the following ranges: screw speed, 250–350 rpm; feed rate, 30–40 kg/h; moisture, 20–30%. Water soluble index (WSI) increased linearly with specific mechanical energy (SME). Soluble dietary fiber of extruded AP also increased with SME, which in turn decreased the content of insoluble dietary fiber (IDF). As a result, total dietary fiber (TDF) remained nearly unchanged. Water holding capacity (WHC) remained nearly constant at low SME, but markedly deceased at high SME due to disintegration of cell wall. Gel filtration of WSP exhibited the structural fragmentation of cell wall by extrusion: the higher SME, the higher fragmentation of SME. Ion exchange chromatography of WSP demonstrated that increasing SME resulted in increasing the extractability of free neutral polysaccharides from the cell wall of AP. It was also found that the degradation of AP cell wall by extrusion preferentially occurred at the arabinogalactan sidechains of pectins.     

HEATING BEHAVIOR AND QUALITY FACTOR RETENTION IN A CANNED MODEL FOOD AS INFLUENCED BY THERMAL PROCESSING IN A ROTARY RETORT

Heat penetration data were obtained for a canned model food (gelatinized starch) during processing in a rotary retort under various conditions (retort temperature, 110–130C; rotation speed, 10–20 rpm, can headspace 6.4–12.8 mm and starch concentration, 3–4%) to establish thermal processes with an equivalent lethality (F₀ value) of 10 min. Apparent viscosity and Hunter L, a and b values were experimentally evaluated both before and after each run. The percentage of selected quality factors (nutrients, color) retained at each processing condition was estimated using the heat penetration data and documented kinetic parameters for each quality factor. The study indicated that the heating behavior was influenced (p < 0.05) by all factors except can headspace. Higher temperatures and higher rotation speeds favored better retention of quality factors and reduction in process times.     

ENERGY CONSUMPTION IN SINGLE-SCREW EXTRUSION PROCESSING OF FULL FAT AFRICAN BREADFRUIT (TRECULIA AFRICANA) BLENDS

Full fat African breadfruit, corn and defatted soy blends with moisture content range of 6.20–7.50% (wet basis) were extruded in a single‐screw Brabender laboratory extruder (DCE 330, Brabender Instruments Inc., South Hackensack, NJ) at varying independent process variables of feed composition (fc), feed moisture (fm) and screw speed. A central composite design was employed to study the effects of these variables and extrusion cooking on several quality characteristics of the center point blend, and energy input as torque and specific mechanical energy (SME). SME is relevant in that the more the energy applied, the greater the degradation of starch while torque is directly correlated with power usage. Extrusion cooking significantly (P ≤ 0.05) affected bulk density, water absorption, water solubility and nitrogen solubility indices. Torque and SME ranged from 4.00 to 8.50 N·m and 216 to 376 kJ/kg, respectively. Regression analysis of data generated of experimental data showed that fc had significant (P ≤ 0.05) quadratic effect on both energy measurements. Screw speed and fm showed significant (P ≤ 0.05) linear effects on SME while screw speed alone showed significant (P ≤ 0.05) linear effect on torque. At 160‐rpm screw speed and 85% fc, the torque value was maximum (8.50 N·m). Maximum SME value of 376.72 kJ/kg was obtained at 85% fc, 24% fm and 120‐rpm screw speed. Economically, therefore, extruded products made from blends of breadfruit, corn and soy flours will require lower extruder power usage given the fat and fm levels. Findings of this research might be useful to processors for better process control and optimal energy utilization when extruding these or related blends in a single‐screw extruder.     

RETENTION OF VITAMINS IN FRESH AND FROZEN BROCCOLI PREPARED BY DIFFERENT COOKING METHODS

Fresh and frozen broccoli were analyzed for retention of ascorbic acid, riboflavin and thiamine by semi-automated fluorometry before and after steaming, boiling or microwave cooking for 5 min. Retention of vitamins in general was higher for fresh than for frozen broccoli. Steamed fresh broccoli retained most ascorbic acid, riboflavin, and thiamine. Boiled fresh samples retained least riboflavin and ascorbic acid and microwaved samples, the least thiamine. In frozen broccoli, microwaved samples retained most ascorbic acid and riboflavin, and steamed samples retained most thiamine.     

P＆T—GC分析酒中的挥发性醛酮

挥发性羰基化合物是酒中重要的有害物质,为此建立了吹扫捕集-气相色谱法(P&T-GC)测定白酒和啤酒中的乙醛、丙醛、正丁醛、丁酮和丙酮.结果表明:此方法有较好的重复性,相对标准偏差在5.39%以下;检出限为1.27 ng/mL～6.55 ng/mL;5种物质的回收率在91.90%～98.24%之间.