Effect of Calcium Lactate, 4-Hexyl Resorcinol and Vacuum Packing on Physico-chemical, Sensory and Microbiological Qualities of Minimally Processed Litchi (Litchi chinensis Sonn.)

Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D₆ Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.     

弱酸性电解水用于提升鲜切马铃薯安全品质的研究

目的 探究弱酸性电解水和自来水处理的鲜切马铃薯在室温贮藏条件下不同时间段内品质的变化。方法 模拟现代厨房贮存模式,经弱酸性电解水和自来水处理的鲜切马铃薯在室温(25±0.5)℃贮藏环境下,贮藏0、7、14、21、28、35h时,检测其感官、色度、质构、淀粉、蛋白质、钾、维生素C、菌落总数、大肠杆菌、沙门氏菌、金黄色葡萄球菌、霉菌、酵母菌。结果 经弱酸性电解水处理的鲜切马铃薯在室温贮藏21 h内,经自来水处理的鲜切马铃薯在室温贮藏14 h内,感官正常,其营养成分淀粉、蛋白质、维生素C、钾元素下降较少,金黄色葡萄球菌、沙门氏菌、菌落总数、大肠杆菌、霉菌、酵母菌的含量均在国家标准和团体标准许可的安全范围内,可安全食用。结论 弱酸性电解水可显著提升鲜切马铃薯的贮藏品质,抑制其金黄色葡萄球菌、沙门氏菌、菌落总数、大肠杆菌、霉菌、酵母菌繁殖,延长室温贮藏期。     

Thaumatin-like protein in kiwifruit

A 21-kDa protein extracted from woody tissue underlying the pedicel of kiwifruit (Actinidia deliciosa var deliciosa [A Chev] Liang and Ferguson) was purified to homogeneity by cation exchange, gel filtration, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) on a 15% gel and electro-transfer onto a polyvinylidene difluoride (PVDF) membrane, followed by excision of the band of interest. Amino terminal sequence analysis of this band revealed a high degree of homology with basic endochitinase (EC 3.2.1.14) in orange and thaumatin-like proteins in tobacco, barley, maize and tomato. This is the first record of a thaumatin-like protein in a subtropical berryfruit. Potential implications of this finding and the need for future research are discussed. © 1999 Society of Chemical Industry     

Kiwifruit Juice Clarification using a Fungal Proteolytic Enzyme

A commercial fungal proteolytic enzyme from Aspergillus niger was used in kiwifruit juice as a replacement for conventional fining agents to produce a stable clarified juice. Reductions in detectable protein levels of 73% and 82% were achieved using 500 mg/kg of enzyme and incubating at 60°C for 20 and 60 min respectively. Concentrates prepared from proteolytic enzyme-treated juice had reduced browning and haze formation compared to a control, without affecting ascorbic acid level. When stored at 20°C, proteolytic enzyme treated concentrates (60 min) remained clear up to 90 days and had minimal haze (A_{650 nm}= 0.047) and browning (A_{420 nm}= 0.93) after 6 mo storage. The molecular size of the protein as well as protein concentration are important factors in haze formation.     

Shelf Life of Minimally Processed Honeydew, Kiwifruit, Papaya, Pineapple and Cantaloupe

This study was to determine the shelf life of minimally processed honeydew melon, kiwifruit, papaya, pineapple, and cantaloupe stored at 4°C. Sensory assessments were carried out at 3-day intervals by highly trained panels until the end of shelf life. Microbiological counts were made immediately after dicing fruit and at the end of shelf life. Results indicated that both the length of shelf life and type of spoilage were related to fruit species. Minimally processed fruit had longer shelf life at 4°than at temperatures recommended for whole fruit when these were greater than 4°C. Spoilage of 4°C-stored kiwifruit, papaya and pineapple pieces was not a consequence of microbial growth.     

Growth of Escherichia coli,Salmonella enterica and Listeria spp., and their inactivation using ultraviolet energy and electrolyzed water,on ‘Rocha’ fresh-cut pears

The present study aimed at evaluating the growth of Escherichia coli, Salmonella enterica, and Listeria spp. and studying the efficacy of Ultraviolet-C (UV-C) irradiation, acidic electrolyzed (AEW) and neutral electrolyzed (NEW) waters in the reduction of these bacteria on ‘Rocha’ pear. Fresh-cut pieces were inoculated and incubated at 4–20 °C for 8 days. Inoculated pears were treated with UV-C (2.5–10 kJ/m²), AEW, NEW and sodium hypochlorite (SH) and microbiological and quality parameters were evaluated. The three bacteria, inoculated at 6.1–6.2 log cfu/g, grew on the pear at high growth rates at 12 and 20 °C reaching populations of 8.1–8.6 log cfu/g, in 24 h. At 8 °C the microorganisms increased their populations by at least 1 log cfu/g in three days. At 4 °C adaptation phases of less than 24 h for Listeria spp. were measured before exponential growth occurred and the enterobacteria did not grow despite having survived for 8 days. AEW and NEW caused microbial reductions similar to SH, of approximately 1 log cfu/g, while the best UV-C dose (7.5 kJ/m²) of at least 2.4 log cfu/g. Fresh-cut pears were a good substrate for foodborne bacteria emphasizing the importance of preventing contaminations and cross contaminations. The UV-C was more effective than the chemical decontaminations, as it provided superior microbial reductions without greatly affecting the quality of pears.     

Postharvest CO2 and Ethylene Production and Quality Maintenance of Fresh-Cut Kiwifruit Slices

The quality attributes and gas production of fresh-cut kiwifruit slices (Actinidia deliciosa cv. Hayward) were studied to identify the optimum ranges of storage temperature, relative humidity, and atmospheric composition. Also the effects of wounding, C₂H₄ addition or removal, and chemical treatments (calcium, ascorbic acid, citric acid) on deterioration rate were investigated. Flesh softening was the major quality loss of stored fresh-cut kiwifruit slices. Fresh-cut kiwifruit slices had a shelf-life of 9–12 days if treated with 1% CaCl₂ or 2% Ca lactate, and stored atO-2°C and >90% relative humidity in an C₂H₄-free atmosphere of 2 to 4 kPa O₂ and/or 5to10kPaCO₂.