DURIAN LEATHER: DEVELOPMENT, PROPERTIES AND STORAGE STABILITY

Three formulations of durian leather were developed and evaluated for their physicochemical, microbiological, sensory properties and storage stability. Proximate composition is reported. Vitamin C contents of the leather were relatively high and ranged between 21.6–26.6 mg/100 g. Water activity (Aw) of all formulations ranged between 0.57–0.62 and caloric content, 431–473 Kcal/100 g. After 12 weeks’ storage, all durian leather formulations were stable and showed low mold counts. The results from sensory evaluation revealed that the three formulations were acceptable in all attributes studied.     

QUALITY OF SWEETPOTATO FLOUR DURING PROCESSING AND STORAGE

Sweetpotato flour can easily be promoted as a substitute for wheat flour in sweet baked products and can also be used for its high carotenoid content. However, the price of the sweetpotato flour must be competitive with wheat flour and be of good quality. This article defines and describes the different quality characteristics of sweetpotato flour. After an overview of the different steps and equipment used in the small-scale processing of sweetpotato flour, the influence of the different processing steps and storage on the quality characteristics are reviewed.     

RETENTION OF VOLATILE FLAVORS IN CONFECTIONS BY EXTRUSION PROCESSING

Cold extrusion has been used for many years to form gums, licorice, and other confectionery products. The cooking extrusion of confectionery products is relatively new and is currently being pursued by many manufacturers. The technology of cooking extrusion offers the industry the opportunity to modernize processes, shorten processing time, and ultimately achieve significant cost savings for their production. However, stabilizing volatile flavors during extrusion has been a difficult problem to resolve because of the heat, pressure, and mechanical shear applied. Several different approaches have been made in recent years to solve the problem. One recent approach is the use of encapsulated flavors in extruded confectionery products. Encapsulation makes volatile flavors more stable under the rigid conditions of cooking extrusion and helps retain them better in a food matrix. However, maintaining the quality of volatile flavors in products will continue to be a challenge for the confectionery industry.     

RETENTION OF IODINE IN FORTIFIED PARBOILED RICE AND ITS PASTING CHARACTERISTICS DURING STORAGE

Iodine fortification, as potassium iodide (KI) or potassium iodate (KIO₃), in parboiled milled rice was investigated. The fortified parboiled milled rice (9–10% moisture content) contained 11.6 × 10^?2 mol KI per 100‐g salt or 9 × 10^?2 mol KIO₃ per 100‐g salt. The iodine‐fortified parboiled milled rice after dialysis retained 80.50–84.87% iodine, while the milled rice retained 97–100% iodine in the samples. Test on in vitro starch digestion showed that most iodine was released within 15 min of starch digestion. The iodine‐fortified and nonfortified parboiled milled rice showed significant higher pasting temperature, peak time and setback viscosity than normal milled rice. After storage for 5 months, iodine content in fortified parboiled milled rice decreased significantly (P ≤ 0.01), while iodine content in milled rice did not change during storage. For the rice stored at ambient temperature, the rapid visco‐analyzer amylograph viscosity (peak viscosity, trough viscosity and final viscosity) increased during the first 2 months and decreased during storage. Iodine did not affect these attributes of parboiled milled rice.     

EFFECT OF DIFFERENT DRYERS AND DRYING CONDITIONS ON ACCEPTABILITY AND PHYSICO-CHEMICAL CHARACTERISTICS OF DURIAN LEATHER

Optimization study on drying condition ofdurian leather was carried out using Response Surface Methodology (RSM). The optimization was conducted for two different dryers, oven dryer and forced-air cabinet dryer, with temperature and time of drying as independent variables. It was shown that both variables significantly affected most of the sensory properties. For both dryers, the optimum points for 5 sensory attributes evaluated including taste, aroma, texture, appearance and overall acceptability, were at temperatures ranged from 47–55 C for 10–14 h. Based on the overall acceptability, the optimum condition for oven-dried leather was achieved at temperature 50C for 12.6 h, while for cabinet-dried leather at 52.5C for 10 h. Results showed that panelist preferred product dried with low temperature-long time compared with high temperature-short time. Except for Hunter color b value of cabinet-dried product, results also indicated that drying condition was significantly influencing the physico-chemical properties such as moisture, A_w, nonenzymatic browning, texture, vitamin C and color of durian leather.     

CHANGES IN TOTAL PHENOLIC AND FLAVONOID CONTENTS OF ROWANBERRY FRUIT DURING POSTHARVEST STORAGE

ABSTRACT

Postharvest storage conditions of rowanberry (Sorbus aucuparia) fruits were investigated. The influences of temperature and storage time on total phenolic content were observed. Both variables affected phenolic content of rowanberries, and their total phenolic contents significantly reduced during the 20‐day storage at 4 and 22C. The loss of total phenolic was found to be almost 50% of its initial amount (3,619.8 mg/kg fresh weight [fw]) at 22C, which was higher than occurred loss (30%) at 4C. An investigation of rowanberry flavonoids showed the presence of rutin, quercetin‐3‐glucoside and quercetin‐3‐D‐galactoside (Q3DG). Quantitative analysis of berry flavonoids showed Q3DG as a major compound, being 24.55 mg/kg fw. The highest reduction (86% of its initial amount) was also seen in that compound level compared with other ones. Degradation kinetics of flavonoids was studied at 22C over 16 days of storage. Checking of model adequacies indicated that their reductions followed a first‐order kinetic.

PRACTICAL APPLICATIONS

Postharvest storage has been taken, increasing the interest of scientists because of various reasons, one of which is explained next. The presented results indicated the direct and/or indirect influence of storage conditions on the quality of berries, implying that whoever is planning to store plant and/or plant origin food products in a refrigerator or at room temperature should consider the conditions and their possible effects on the quality parameters from the aspects of economics and nutritional properties of products. In the present study, the stability of an important bioactive group, phenolics, in rowanberries and the influences of environmental conditions were examined, and additionally, degradation kinetics of major phenolic group, flavonoids, was analyzed. The results are valuable and helpful for the evaluation of the postharvest storage and its effect on rowanberries. Introduced model may be helpful for the prediction of storage time required for the degradation of phenolics up to the acceptable limit.     

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.     

VARIOUS ANTIBROWNING AGENTS AND GREEN TEA EXTRACT DURING PROCESSING AND STORAGE

The production of bottled green tea beverage has encountered a browning problem mainly caused by the autoxidation of flavanols (catechins). Five antibrowning agents, ascorbic acid, kojic acid, citric acid, L-cysteine, and glutathione, were tested for their effectiveness on preventing the color changes of green tea extract during processing and storage. One-tenth percent of the antibrowning agents were individually added to the freshly prepared green tea extracts, heat processed at 121C for 1 min, and then stored in a 50C oven for up to 12 days. Samples of fresh, processed, and stored tea extracts were measured for their color maintenance and (-)-epigallocatechin gallate (EGCG) content to compare the antibrowning and antioxidant effects of these agents, respectively. Results indicated that the antibrowning activity and antioxidant effect of individual agents often did not correlate with each other, but citric acid showed both significant antibrowning and antioxidant effects on green tea extract.     

老挝咖啡的挥发和半挥发性成分提取分析

采用超声波提取(UE)和同时蒸馏萃取(SDE)两种前处理方法提取老挝咖啡中的挥发性成分,利用气相色谱-质谱(GC-MS)联用仪进行定性检测,并加入乙酸苯乙酯作为内标进行定量分析.实验结果表明:两种萃取方法共鉴定出挥发性成分77种,共同组分26种.其中超声级萃取以正己烷为溶剂鉴定出18种,以二氯甲烷为溶剂鉴定出28种,以甲醇为溶剂鉴定出41种,同时蒸馏萃取鉴定出54种.咖啡的主要挥发性成分有咖啡因、棕榈酸、亚油酸-2-氯乙酯、油酸、硬脂酸、醋酸孕烯醇酮等.超声波提取适用于主要成分和高沸点物质的提取,而同时蒸馏萃取更适合于低分子量、低沸点致香物质的萃取.两者各有所长,可根据需要来选择.