Microbial population, physicochemical quality, and allergenicity of molluscs and shrimp treated with cobalt-60 gamma radiation

Frozen molluscs (squid, octopuses, and cuttlefish) and crustaceans (shrimp) were irradiated using a cobalt-60 gamma source, at different doses, in order to investigate the effects of gamma radiation on their microbial population, organoleptic characteristics, lipid profile, and tropomyosin content. Irradiation of shrimp and squid with either 2.5 or 4.7 kGy reduced mesophilic bacteria contamination to low or nondetectable levels, respectively, whereas irradiation of octopus and cuttlefish with the same doses reduced the bacterial population. Irradiation treatment had no significant (P > 0.05) effect on the total lipid content and the major detected classes of polar and neutral lipids, whereas it significantly (P < 0.05) increased the contents of neutral lipids in octopus mantle and in shrimp muscle and cephalothorax samples. The total fatty acid content and the omega-3: omega-6 fatty acid ration was not affected. A dose-dependent significant (P < 0.05) decrease in the ratio of polyunsaturated fatty acids:saturated fatty acids was observed. With the increase in radiation dose, redness (a) and yellowness (b) values showed a variation, whereas the lightness (L) value was significantly (P < 0.05) decreased in mollusc mantles and shrimp muscle and increased in shrimp cephalothorax. The total of color changes ( delta E) increased (P < 0.05) as the dose increased. Significant (P < 0.05) changes in textural properties were observed with radiation treatment in octopus tentacles and in squid and cuttlefish mantle. The amount of tropomyosin, which is the major mollusc and crustacean allergen in the irradiated organisms, was reduced by gamma radiation, depending on the dose.     

Mass transfer evaluation of ultrasonic osmotic dehydration of cherry tomatoes in sucrose and salt solutions

In order to elaborate dehydration and osmotic equilibrium characteristics of cherry tomatoes and to analyse the applicability of Peleg model in prediction of equilibrium moisture content and the methodology of Crank’s solution to Fick’s diffusion law in calculation of effective diffusivity, cherry tomatoes were osmotically treated in ternary solution (water, sucrose and NaCl) with or without ultrasound at 30 °C. Results indicated that, a time cumulative effect of ultrasound occurred about 30 min for water loss (WL), while for sugar gain it happened after 45 min, which made the dehydration efficiency index best at the ultrasonic power of 150 W for 40 min. As a function of salt content, the equilibrium WL followed well the first order exponential decay model, and the equilibrium salt content followed well the second order polynomial. A great relative error (29.13%) between the practical determination and the predicted value indicated that Peleg model was not suitable for prediction of equilibrium moisture content. A great truncation error (865%) occurred when moisture effective diffusivity (6.66 × 10^?9 m² s^?1) was calculated with Crank’s solution to Fick’s diffusion law by letting n = 1 as compared to that (0.77 × 10^?9 m² s^?1) by letting n = 100.     

超高压灭菌法生产圣女果罐头的研究

将超高压技术应用于圣女果罐头杀菌,探讨了处理压力、时间和温度对微生物菌落总数以及霉菌酵母菌教的影响,利用正交实验对影响超高压灭菌的关键因子压力、温度、时间及相互作用进行了深入的探讨,并结合圣女果色值的变化.得出最佳灭菌工艺.结果表明:处理压力600MPa,处理温度20℃,处理时间为15min圣女果可达到商业无菌的要求,得到色味俱佳的产品.     

樱桃番茄渗透预处理热风干燥特性研究

为了提高干制品的营养保留率和品质,进行了渗透预处理联合热风干燥的工艺路线的实验研究。以樱桃番茄为例,分别对不同浓度(50%,70%)蔗糖溶液常压渗透以及真空渗透处理后热风干燥的干燥时间、干燥速率、样品体积比、Vc保留率、硬度、颜色等参数分别进行测定和比较。结果表明:渗透预处理可以除去新鲜樱桃番茄中的大部分自由水,从而减少其热风干燥时间,使产品在高温中的暴露时间减少,从而缩短整体干制时间、提高干制效率及营养品质。经渗透预处理的樱桃番茄干制产品的体积比和Vc保留率要比直接热风干燥的产品增加,而硬度大大下降;其中经浓度为50蔗糖溶液真空渗透预处理后干燥产品的体积比、Vc保留率以及硬度是直接70℃热风干燥的1.72、2.26和0.12倍;而且产品的色泽更加接近新鲜原料,使产品的口感和感官品质更好。研究表明,渗透预处理联合热风干燥是1种很有发展前景的制干工艺。     

Identification of cherry tomatoes growth origin by means of magnetic resonance imaging

Magnetic resonance imaging (MRI) spectroscopy is a promising non‐invasive and non‐destructive analytical technique in food science, since it offers the opportunity of studying vegetables and fruits in their wholeness without any manipulation. The aim of this preliminary study was to demonstrate the possibility of assessing unambiguously the place of origin of fresh cherry tomatoes by means of MRI experiments. The innovative approach has been successfully used to distinguish PGI (Protected Geographical Indication) cherry tomatoes from non‐PGI ones, as well as cv. Naomi from cv. Shiren samples. The method determines informative physical and morphological parameters, transverse relaxation times and thicknesses, respectively, which can be combined into four empirical equations; two of them are used to determine the cultivated variety and the other two to assess the place of origin. This approach has successfully recognize the cultivated variety of c. 90% of the analyzed samples and the geographical origin of c. 80% of the investigated cherry tomatoes. Copyright © 2006 Society of Chemical Industry     

On the evolution of key physiological and physicochemical parameters throughout the maturation of Burlat cherry

We have studied the ripening process of Burlat sweet cherry during two consecutive growing seasons in order to identify its main specific characteristics. An increase in ethylene production is consistently observed when the fruit reaches an acceptable degree of ripeness. This ethylene peak clearly divides the ripening process into two distinct phases with markedly different behaviour of all of the parameters measured in this study: respiration rate, titratable acidity, soluble solids content, firmness, colour, pectolytic and oxidation enzymes and anthocyanin content. Copyright © 2005 Society of Chemical Industry     

Phenolic profiles of cherry tomatoes as influenced by hydric stress and rootstock technique

The aim of the present work was to evaluate the influence of genetic and technological factors (cultivar and grafting) combined with the abiotic stress (water stress) on the content of phenolic compounds (flavonoids and phenolic acids classes and total phenolics) in cherry tomato. The identification and contents of phenolic compounds and flavonoids were determined by HPLC-MS in fruits on reciprocal grafting between a drought-tolerant cultivar (Zarina) and drought-sensible cultivar (Josefina), compared with both self-grafted and non-grafted plants. The results show how pre-harvest factors, such as grafting and water stress, can influence the phenolic content of tomato fruits. Phenolic compounds, including rutin that belongs to the group of flavonoids, display a remarkable array of biological and pharmacological activities. So, the richness of ZarxJos under water stress conditions with these compounds confirms its nutritional value and it can be used as a potential source of phenols. The results suggest that grafting on specific rootstocks more adapted to water stress conditions may be a tool to improve crop quality under artificially imposed mild water stress.     

1-甲基环丙烯处理对樱桃番茄果实低温贮藏品质的影响

为了探讨低温贮藏条件下1-甲基环丙烯(1-methylcyclopropene,1-MCP)处理对樱桃番茄果实采后品质的影响,该研究以'粉娇'樱桃番茄为试材,测定了经1-MCP(0.14μL/L)处理的樱桃番茄在低温[(8±1)℃]贮藏期间果实腐烂率、呼吸强度、果实硬度、可溶性固形物、维生素C、有机酸和类胡萝卜素含量的...     

Pectin methylesterase,polyphenol oxidase and physicochemical properties of typical long‐storage cherry tomatoes cultivated under water stress regime

BACKGROUND: The selection of cherry tomato genotypes with extended shelf‐life and resistant to water stress is an important aspect of Sicilian agriculture. The aim of the present study was to evaluate the effects of watering regime on the expression of enzymatic activities (pectin methylesterase (PME, EC 3.1.1.11) and polyphenol oxidase (PPO, EC 1.14.18.1)) and the physicochemical properties of typical long‐storage cherry tomatoes in order to propose a solution strategy suitable for Sicilian cultivation. RESULTS: PPO activity seemed to be related to the watering regime employed, showing a maximum under normal watering conditions. PME activity also decreased greatly with increasing water stress (loss of activity ranging from 22.31 to 82.01%). Water stress induced an increase in titratable acidity (up to 68.7% in cultivar ‘Giallo piccolo a punta’) and, above all, in dry matter and total soluble solids (increases ranging from 24.08 to 91.68% and from 5.93 to 40.90% respectively). Possible solution strategies for cultivation of tomato genotypes with extended shelf‐life are (a) selecting the local type that presents the lowest levels of PME and PPO (‘Pizzutello’) or (b) modifying the watering regime in order to induce commercial cultivars employed in intensive cultivation (e.g. ‘Naomi’) to better protect themselves from degradative enzymatic activities. CONCLUSION: It appears that the adoption of high watering levels, leading to a more marked expression of degradative enzymatic activities, could result in cherry tomatoes with a high susceptibility to undesirable browning and softening reactions. Copyright © 2007 Society of Chemical Industry     

油茶饼提取物对圣女果保鲜作用的研究

油茶饼提取物中含有大量具有功能性的物质,如单宁、茶皂素、黄酮类物质。本研究分别以水和95%乙醇作为溶剂对油茶饼进行萃取分离,得到油茶饼提取物。然后研究提取物对常见微生物的抑菌作用和对圣女果的保鲜作用。结果表明,提取液对圣女果保鲜有促进作用。采用浓度为50mg/mL的乙醇提取物配制涂膜液,对圣女果进行涂膜处理,能有效保证圣女果15d不腐烂。在抑菌实验中发现,提取液明显抑制大肠杆菌和金黄色葡萄球菌的生长,而对霉菌抑制作用较弱。      

Production and evaluation of some physicochemical parameters of peanut milk yoghurt

The peanut milk for yoghurt production was prepared by fortifying peanut milk (∼12 g/100 g total solids) with 4 g/100 g skimmed milk powder. The final product was subjected to physicochemical analysis using cow milk yoghurt (CMY) as a control throughout the study. Peanut milk yoghurt (PMY) had higher protein content, fat, water holding capacity and lower susceptibility to Syneresis than CMY. PMY had lower lactose level (1.73 g/100 ml) compared to CMY (4.93 g/100 ml). Generally both PMY and CMY had high mineral composition and contained high amounts of essential amino acids. PMY also contained a higher proportion of unsaturated fatty acids than saturated fatty acids as compared to CMY. Therefore, in terms of fatty acid composition, PMY could be considered to be more health promoting than CMY. Sensory evaluation revealed that though PMY had better sensory texture scores than CMY, its sensory appearance, flavor and overall acceptability scores were lower than those of CMY.     

Microbial decontamination of medicinally important herbals using gamma radiation and their biochemical characterisation

A comprehensive study was carried out to assess the microbiological and biochemical characteristics of four herbals, namely, rose (Rosa centifolia), guggul (Commiphora mukul), chirata (Swertia chirayita), gulvel (Tinospora cordifolia) and four herbal formulations rasayan, shatpatryadi, scrub and kashayam. Total aerobic plate count (TAPC) was in the range of 3–7 log cfu/g, whereas, presumptive coliform count in many of these samples was in the range 2–6 log cfu/g. The IMViC (indole, methyl red, Voges-Proskauer, citrate) analysis and molecular characterisation (16S rDNA sequencing) ascertained the presence of Escherichia coli in some of the samples. A gamma radiation dose of up to 10 kGy was found to be sufficient for complete microbial decontamination without affecting the bioactive properties of herbal formulations, including antioxidant potential, which was high in rasayan, shatpatryadi, scrub, rose, and guggul. The antioxidant property of these herbals could be attributed to components such as phenolics, flavonoids and colour pigments.     

Effects of gamma radiation on microbial,physicochemical, and structural properties of whey protein model system

Gamma radiation has been used in food processing for many years, though it has certain effects on food components. Whey protein solutions (10%/30%, wt/vol) were treated with gamma radiation at various dosages (10–25 kGy) and evaluated for microbial changes in the solutions and physicochemical and structural changes of whey proteins. Whey protein solutions after gamma radiation showed substantially lower populations of all viable microorganisms than those of controls. The 10% whey protein solution treated at radiation of 20 or 25 kGy remained sterile for up to 4 wk at room temperature. Gamma radiation increased viscosity and turbidity and decreased soluble nitrogen of whey protein solutions compared to nonradiated control samples regardless of radiation dosage. Nonreducing sodium dodecyl sulfate-PAGE suggested that whey proteins under gamma radiation treatment formed aggregates with high molecular weights. Reducing sodium dodecyl sulfate-PAGE showed that disulfide bonds played a role in gamma radiation-induced whey protein cross-linking. Scanning and transmission electron microscopy micrographs exhibited large aggregates of whey proteins after gamma radiation treatment. Results suggested that gamma radiation could be applied to whey protein solution for purposes of reducing microbial counts and cross-linking protein molecules.     

Pasteurization of tender coconut water by pulsed light treatment: Microbial safety,enzymatic inactivation,and impact on physicochemical properties

The study investigated the potential of pulsed light (PL) in the pasteurization of tender coconut water (TCW). The initial counts of E. coli, B. cereus and L. monocytogenes in the inoculated TCW were 7.00, 9.14 and 7.8 log₁₀ cfu mL⁻¹, respectively. For a PL fluence of 465 J cm⁻², E. coli, B.cereus and L. monocytogenes exhibited a log reduction of 5.12, 2.97 and 3.40, respectively. Bacillus cereus and Listeria monocytogenes exhibited greater resistance than Escherichia coli in the TCW. Peroxidase (POD) was more sensitive to PL treatments than polyphenoloxidase (PPO) in TCW. Weibull model and n^th order model exhibited excellent fit for microbial inactivation (R² > 0.96) and enzyme inactivation (R² > 0.97) kinetics, respectively. While 5-log₁₀ reduction of B. cereus and L. monocytogenes was achieved at 2.5 kV|2.5 min (1073 J cm⁻²), PPO was inactivated by greater than 99% at 2.9 kV| 5 min (2988 J cm⁻²). While the total reducing sugars increased, the changes in color (0.49 < ΔE* < 1.51), pH, total soluble solids, and acidity were insignificant after the PL pasteurization. The PL condition of 2.9 kV|5 min preserved 21 and 24% more phenolics and ascorbic acid in TCW, along with greater sensory scores than the thermal treatment (90 °C|3 min).Industrial significanceThe outcome of this study determined the intensity (fluence of 2988 J/cm²) and penetration depth (4–5 mm) required for the pasteurization of tender coconut water (TCW). On an industrial scale of large processing volumes, continuous pulsed light (PL) pasteurization of TCW can be undertaken in an annular flow reactor or thin film flat bed chamber. The thickness of the film can be mimicked from this study to ensure adequate penetration of PL in the sample to achieve adequate lethality.