The effect of sulphur-containing fungicides on the corrosion of plain cans of fruit

The addition of 2–5 ppm of TMTDS (tetramethylthiuramdisulphide) or ziram markedly decreased the shelf life of canned pears, but 1 ppm of these materials had little effect. The addition of trace levels of sulphur or captan to canned pears appeared to increase the shelf life; addition of sodium sulphide appeared to have a negligible effect on shelf life. The shelf life of canned peaches, apricots, pineapple, apples, and citrate solution was also decreased by the addition of 5 ppm TMTDS or ziram. TMTDS and ziram caused pitting of the base steel of the tinplate with little attack on the tin coating. Pitting was not seen in cans containing added sulphur, sulphide, or captan and the rate of corrosion of the tin coating was less than in cans containing no added chemicals. Formation of passive films and reduction of the hydrogen overpotential were considered to be important factors influencing corrosion of cans containing the added agricultural chemicals.     

黑芝麻复合蜜丸货架期预测及包装方式对其贮藏品质的影响

以黑芝麻复合蜜丸为研究对象,以酸价和过氧化值为评价指标,考察不同储藏温度对其品质的影响;在此基础上,通过构建Arrhenius模型对裸包装条件下的黑芝麻复合蜜丸的货架期进行预测。为进一步延长货架期,设置4种不同包装形式对黑芝麻复合蜜丸进行包装,同时考察不同包装方式对其水分、质构、理化特性等贮藏品质的影响。结果表明：与对照组相比,充氮、包壳、蜡封对阻止黑芝麻复合蜜丸水分下降、硬度和酸价上升均有一定的作用,其中以蜡纸+药丸壳+蜡封+锡箔纸+聚乙烯塑料袋这种包装形式效果最佳。该研究结果为蜜丸类产品的储存提供参考。     

Shelf life of modified atmosphere packed cooked meat products: a predictive model

The effect of temperature, concentration of dissolved CO2 and water activity on the growth of Lactobacillus sake was investigated by developing predictive models for the lag phase and the maximum specific growth rate of this specific spoilage organism for gas-packed cooked meat products. Two types of predictive model were compared: an extended Ratkowsky model and a response surface model. In general, response surface models showed a slightly better correlation, but the response surface model for the maximum specific growth rate showed illogical predictions at low water activities. The concentration of dissolved CO2 proved to be a significant independent variable for the maximum specific growth rate as well as for the lag phase of L. sake. Synergistic actions on the shelf life-extending effect were noticed between temperature and dissolved CO2, as well as between water activity and dissolved CO2. The developed models were validated by comparison with the existing model of Kant-Muermans et al. (1997) and by means of experiments in gas-packed cooked meat products. Both developed models proved to be useful in the prediction of the microbial shelf life of gas-packed cooked meat products.     

Shelf life of modified atmosphere packed cooked meat products: addition of Na-lactate as a fourth shelf life determinative factor in a model and product validation

Cooked meat products are often post-contaminated because of a packaging and/or slicing step after the pasteurisation process. The shelf life is therefore limited and can be extended by adding Na-lactate. A previously developed model for the spoilage of gas packed cooked meat products, including temperature, water activity and dissolved CO2 as independent variables, was extended with a fourth factor: the Na-lactate concentration in the aqueous phase of the meat product. Models were developed for the maximum specific growth rate mu(max) and the lag phase lambda of the specific spoilage organism Lactobacillus sake subsp. carnosum. Quadratic response surface equations were compared with extended Ratkowsky models. In general, response surface equations fitted the experimental data best but in the case of mu(max) the response surface model predicted illogical growth behaviour at low water activities and high Na-lactate concentrations. A extensive product validation of the mathematical models was performed by means of inoculated as well as naturally contaminated industrially prepared cooked meat products. The deviations of the experimentally determined versus predicted growth parameters in inoculated cooked meat products were in general small. Both types of models were also able to predict the shelf life of naturally contaminated cooked meat products, except for paté where an under-estimation of the shelf life was predicted by the response surface equations. The validation studies revealed higher accuracy of the extended Ratkowsky models in comparison to the response surface equations. A significant shelf life extending effect of Na-lactate was predicted, which was more pronounced at low refrigerated temperatures. A synergistic effect has also been noticed between Na-lactate and carbon dioxide which, at least partly, could be explained by the pH-decreasing effect of CO2.     

蓝柑风味糖浆货架期预测模型的建立与评价

本文主要阐述了蓝柑风味糖浆货架期预测模型的研究过程及方法,对蓝柑风味糖浆储存过程中多维度品质变化、保藏期限等进行评估预测。在4、27、37 ℃的贮藏条件下,通过对感官指标、可溶性固形物含量、pH、还原糖含量、羟甲基糠醛（5-hydroxymethyl-furfural,HMF）等多项指标变化的逐一分析,结合动力学模型和Arrhenius方程,完成了货架期预测模型的构建。结果表明,以感官得分为80分、可溶性固形物含量为85%、pH为2、还原糖含量为100%、羟甲基糠醛含量为35 mg/kg作为蓝柑风味糖浆货架期的终点,在4 ℃冷藏条件下,蓝柑风味糖浆的理论货架期约为48个月;20 ℃室温条件下,蓝柑风味糖浆的理论货架期约为24个月,货架期终点蓝柑风味糖浆的品质出现不可接受的损失。蓝柑风味糖浆货架期预测模型的建立,为糖浆类产品货架期预测建模提供了新思路。     

不同制油方法对青海亚麻籽油品质及货架期的影响

为研究不同制油方法对青海亚麻籽油品质及货架期的影响,对青海亚麻籽分别进行焙炒、烘烤、高压高温湿热、脱胶、真空冷冻干燥前处理,再分别采用螺旋压榨法和液态静压法制油,测定亚麻籽油出油率、过氧化值、酸价、水分及挥发物质量分数、脂肪酸含量、挥发性组分相对含量、总酚含量,并利用Schaal烘箱法建立亚麻籽油氧化动力学模型预测货架期。结果表明,焙炒螺旋压榨法制得的亚麻籽油出油率、总酚含量明显高于其他处理组,过氧化值、酸价、水分及挥发物质量分数均低于其他处理组,模拟预测货架期最长,为353 d。焙炒螺旋压榨法制得的亚麻籽油挥发性组分种类最多,为72 种,其他制油方法制得的亚麻籽油挥发性组分为40～60 种,不同制油方法对亚麻籽油挥发性组分影响明显。此外,亚麻籽油5 种主要脂肪酸中亚麻酸含量最高,为54.71～61.03 g/100 g,不同制油方法对亚麻籽油脂肪酸含量影响不明显。综上,与其他方法相比,焙炒螺旋压榨法制得的亚麻籽油品质较好。     

Recent advances in shelf life prediction models for monitoring food quality

Each year, 1.3 billion tons of food is lost due to spoilage or loss in the supply chain, accounting for approximately one third of global food production. This requires a manufacturer to provide accurate information on the shelf life of the food in each stage. Various models for monitoring food quality have been developed and applied to predict food shelf life. This review classified shelf life models and detailed the application background and characteristics of commonly used models to better understand the different uses and aspects of the commonly used models. In particular, the structural framework, application mechanisms, and numerical relationships of commonly used models were elaborated. In addition, the study focused on the application of commonly used models in the food field. Besides predicting the freshness index and remaining shelf life of food, the study addressed aspects such as food classification (maturity and damage) and content prediction. Finally, further promotion of shelf life models in the food field, use of multivariate analysis methods, and development of new models were foreseen. More reliable transportation, processing, and packaging methods could be screened out based on real-time food quality monitoring.     

Tin and Iron Content of Canned and Bottled Foods

The tin and iron content of 14 different types of canned foods and of 5 different types of bottled foods were determined. No tin was detected in most bottled foods, but tin was detected in all canned foods. Storage of foods on the shelf for 4 months or in open cans in the refrigerator for 1 wk resulted in increased amounts of tin and iron in some of the canned foods. Those foods which were packed in totally lacquered cans accumulated little tin or iron during storage; those foods which were packed in unlacquered or partially lacquered cans generally accumulated significant amounts of iron and tin during storage. The tin content of the canned foods was not statistically correlated to the pH of the foods.     

Internal corrosion and shelf‐life of food cans and methods of evaluation

Internal corrosion in food cans is characterized by metallic dissolution which is an electrochemical reaction. In lacquered cans, corrosion may also cause disruption in the continuity of the lacquer film. These reactions may cause organoleptic changes in the product, loss of vacuum, swelling, and leaking in extreme cases. In some instances the metal dissolution (i.e., lead) may give rise to toxicological problems. Therefore, these phenomena are often the limiting factor in the shelf life of canned products. Changes in color, texture, and sensoric properties of the foods, which take place simultaneously, affect the aesthetic and nutritional value of the product and thus its shelf life. These changes are often related to interactions with the container. For example, tin dissolution prevents browning and loss of ascorbic acid. Shelf life of canned foods is governed by the quality of the raw materials, the processing technology, quality of the container and storage conditions which will be reviewed in this paper. Can manufacturing technologies, mechanisms of electrochemical corrosion, methods of their measurement and prediction of shelf life will be discussed.     

Effect of Intermittent Curing on Mandarin Quality

ABSTRACT: The effect of an intermittent curing treatment (IC), 2 cycles of 18 h at 38 °C, to control decay during shelf life of mandarins was studied. The effectiveness of IC to control blue mold development in artificially inoculated Clemenules fruits ( Citrus reticulata Blanco cv. Nules) was complete with 0% decay after 1 wk storage at 20 °C. Nonsignificant differences were found in soluble solids, color, and firmness. By the end of shelf life, a significantly lower acidity and a higher weight loss (4.75%) was observed in IC-treated fruits. Ascorbic acid levels decreased in all stored fruits along shelf life, with slightly lower values in IC-treated mandarins than in control fruits. Sugars and organic acids content were not affected by curing. Though slight increases in ethanol and some detrimental terpene oxidized compounds were found, not off-flavor development was observed. This, intermittent curing treatment seems to be a feasible treatment to control blue mold development during shelf life of Clemenules mandarin fruits, without impairing quality parameters such as color, firmness, sugars, and organic acids contents, vitamin C content, and aroma.     

包装材料结合活性包装对荞麦半干面常温货架期及品质的影响

为了延长荞麦半干面的常温货架期,以聚偏二氯乙烯(PVDC)和聚乙烯(PE)为包装材料,采用不同活性包装方式(脱氧包装和脱氧结合酒精缓释包装)对其进行包装处理。考察脱氧剂、酒精缓释剂和不同包装材料对荞麦半干面货架期和储藏期间品质的影响。测定荞麦半干面在储藏期间菌落总数、酸度值、p H值、质构特性、感官品质和包装袋内顶空氧气含量、顶空酒精浓度的变化。结果表明:储藏期间菌落总数整体呈现上升趋势,脱氧结合酒精缓释包装协同抑制微生物生长。储藏9 d后,脱氧结合酒精缓释包装的面条菌落总数均未超过106cfu/g,同时显著抑制了理化品质的劣变(P0.05);脱氧剂的吸氧量越大,24 h内除氧速率越快,抑菌效果越显著;相同活性包装方式下,与PE包装材料相比,PVDC包装材料能增强其延长荞麦半干面常温货架期的作用效果。与其他包装方式相比,脱氧(200 m L)结合酒精缓释PVDC包装将荞麦半干面货架期延长至16 d,并且维持了面条储藏期间的品质。     

杜仲籽精炼油的氧化稳定性及货架期预测

本文以杜仲籽毛油为原料,经过精炼后以过氧化值、酸价和脂肪酸含量为评判指标,采用Schaal烘箱法探究了5种抗氧化剂在不同浓度和温度下对杜仲籽精炼油氧化稳定性的影响,建立了杜仲籽精炼油货架期模型,预测其货架期。结果表明,添加丁基羟基茴香醚（butyl hydroxyanisole,BHA）、叔丁基对苯二酚（tert-butyl hydroquinone,TBHQ）、维生素E（vitamin E,V_E）、鼠尾草酸（carnosic acid,CA）和L-抗坏血酸棕榈酸酯（L-ascorbyl palmitate,L-AP）的抗氧化效果从大到小依次为TBHQ>CA>L-AP>BHA>V_E,CA、TBHQ、V_E、BHA、L-AP的最佳添加量分别为0.05%、0.02%、0.01%、0.02%、0.02%;随着储藏温度的升高和储藏时间的延长,过氧化值和酸价升高,氧化速度加快,饱和脂肪酸和单不饱和脂肪酸含量增加,不饱和脂肪酸含量减少;杜仲籽精炼油的氧化符合一级氧化动力学反应,通过构建的杜仲籽精炼油货架期模型,预测出在25、40、50和60 ℃的温度下,杜仲籽精炼油的货架期分别为10.70、8.76、7.74和6.89 d,添加抗氧化剂能延缓不饱和脂肪酸的氧化,其中TBHQ的抗氧化效果最好,添加0.02% TBHQ的杜仲籽精炼油的货架期可以延长至41.41、19.71、12.48和8.13 d,说明添加抗氧化剂可以有效延长杜仲籽精炼油的货架期。     

基于模糊数学的天然保鲜剂对冷鲜肉保鲜效果评价

为研究天然保鲜剂对冷鲜肉的保鲜效果,应用模糊数学综合感官评价法对不同天然保鲜剂处理过的冷鲜肉进行综合感官评价,并通过测定冷鲜肉的总挥发性盐基氮（total volatile base nitrogen,TVB-N）含量、pH值和菌落总数变化情况,验证冷鲜肉模糊数学综合感官评价方法的科学性和合理性。结果表明：天然保鲜剂茶多酚、乳酸链球菌素（Nisin）、壳聚糖、纳他霉素及海藻糖均能有效延长冷鲜肉的保质期,其中海藻糖效果最好,能使冷鲜肉保质期达到8 d左右,其次为茶多酚、Nisin及纳他霉素,冷鲜肉保质期能达7 d左右,壳聚糖效果稍差,冷鲜肉保质期约6 d;通过分析腐败指标和感官得分的相关性发现,TVB-N含量和菌落总数与感官得分之间具有显著负相关性,相关系数绝对值均大于0.9,说明该模糊数学综合感官评价法具有较好的科学性和合理性。     

不同温度和包装方式对荔枝保鲜品质的影响

为掌握温度和包装对荔枝货架期的影响,本试验以“淮枝”荔枝为试验材料,以裸露的荔枝和由开孔袋包装的荔枝,分别处于常温货架和低温货架,研究不同因素对荔枝质量损失率、褐变指数、好果率、色差、可溶性固形物含量和可滴定酸含量的影响。试验表明：低温货架和包装都能延长荔枝货架期,各品质指标整体衰变速度从快到慢依次为：常温裸露、常温包装、低温裸露、低温包装。对荔枝货架期影响因素中,温度占主要影响作用,低温货架有效的降低了荔枝各指标的变质速度;开孔聚乙烯薄膜包装也能降低荔枝品质的衰变,该影响小于货架温度的影响。常温货架无包装的荔枝好果率在30 h变为0,低温包装荔枝的好果率在60 h仍保有9.20%。与常温货架荔枝裸露的销售方式对比,采用低温货架并由开孔聚乙烯薄膜包装可以使荔枝货架期延长一倍以上。该文为荔枝货架期保鲜研究提供了参考。     

大蒜提取液对新鲜树莓保鲜效果的影响

为保持树莓果实贮藏品质,延长保鲜期,本文以树莓品种‘Festival’为试材,研究不同浓度大蒜提取液对树莓果实的保鲜效果。试验采用浓度为60、90、120、150 mg/mL的大蒜提取液对树莓进行浸泡处理,并模拟超市售卖时的环境条件贮藏于温度为4 ℃,相对湿度为90%的恒温恒湿箱中,分析贮藏期间果实的菌落总数、腐烂率、硬度、营养品质、感官品质、丙二醛（MDA）含量、货架期等指标的变化。结果表明:大蒜提取液具有显著的保鲜效果,能较好抑制微生物的生长繁殖,降低腐烂率,维持较高硬度,减少营养物质损失,降低MDA的生成量,提高感官品质,延长保鲜期;综合比较分析可知,4种处理浓度中,120 mg/mL的大蒜提取液保鲜效果最好,无异味残留,处理后使货架期延长了6.4 d。因此,120 mg/mL的大蒜提取液能很好地保持树莓果实的贮藏品质,在树莓绿色生成中具有一定的应用潜力。     

EFFECT OF VARIOUS ANTIBIOTIC APPLICATIONS ON SOME CHEMICAL, MICROBIAL AND PHYSICAL PROPERTIES OF LAMB

This study was carried out to investigate the effect of various application methods for a chlortetracycline (CTC) and oxytetracycline (OTC) combination (0.9 mg of each per kg of meat) on the shelf‐life of lamb during storage. Twelve‐fat, tail type Akkaraman male lambs were divided into four groups by a “block assignment method”. The first group was kept as the control (C), while the others were subjected to applications as “injection antemortem (A)”, “immersion (I)” and “spraying (S)”. Meat samples were stored at 4C for 12 days. The specimens from loin and leg were tested for microbial, chemical and physical criteria. The results indicated that a CTC and OTC combination extended the shelf‐life of lamb at 4C in an increasing order from A to S to 1. The last one may be used to extend the shelf‐life of lamb during refrigerated storage.     

温度对金针菇贮藏品质的影响及货架期的预测模型

为了研究采后流通贮藏销售过程中金针菇子实体品质的变化以及快速预测金针菇子实体的货架期,本实验模拟了金针菇子实体的3种货架贮藏流通温度(4、15、25 ℃),并定期对其感官品质和理化品质进行测定.采用一级动力学模型结合Arrhenius方程建立基于金针菇子实体品质指标的货架期预测模型,并对模型的预测精确度进行验证及评价....     

SHELF-LIFE SIMULATION OF PACKAGED RICE CRACKERS

ABSTRACT

Two varieties of rice crackers (RC‐1 and RC‐2) were packaged in two types of packaging materials, polyethylene and polypropylene pouches, and stored at 30C/75% RH and 30C/85% RH to simulate actual storage conditions and determine shelf‐life. The main composition differences in the samples were in their fat content (1.87% for RC‐1 and 21.09% for RC‐2) and initial moisture content (4.12% for RC‐1 and 2.28% for RC‐2). The shelf‐life of this product is mainly affected by moisture adsorption as evidenced by sensory evaluation. Guggenheim‐Anderson‐de Boer (GAB) model was used to fit the moisture sorption isotherm. Good precision of fit was found as measured by a determination coefficient (R²) close to 1. The shelf‐life was then predicted based on the relationship between permeability coefficient of the packaging materials and moisture adsorbed by the rice crackers determined by the GAB equation. The validation of the simulations against the experimental shelf‐life gave R² of 0.90 and 0.51, and root mean square error of 2.93 and 5.20 for RC‐1 and RC‐2, respectively. The simulation model was found to be applicable for a rapid and accurate shelf‐life prediction of RC‐1. However, a large difference between experimental and simulated shelf‐life of RC‐2 was probably because the moisture content may not be the only parameter influencing the shelf‐life of the RC‐2 samples. Other factors may also significantly affect the shelf‐life characteristics of the packaged rice crackers.

PRACTICAL APPLICATIONS

For a low‐moisture food product, actual storage testing by a long‐term stability study involves storing a packaged product under typical storage conditions and examining the product at regular time intervals. The testing is costly and time consuming, since most low‐moisture food products have a shelf‐life of several weeks or even months. This paper describes the shelf‐life prediction of two varieties of rice crackers having different compositions using a simulation model based on the relationship between barrier property of the packaging materials and moisture adsorbed by the rice crackers determined by the Guggenheim‐Anderson‐de Boer (GAB) model. The shelf‐life simulation provides a powerful support tool for shelf‐life estimation and packaging development.

     

Blanching, Freezing and Frozen Storage Influence Texture of White Asparagus

We studied effects of three methods of blanching in conjunction with freezing, on texture of white asparagus as defined by three measures: maximum shear force, cutting energy, and total fiber content. We also assessed shelf life of asparagus kept in frozen storage at -22°C. Methods of blanching were total immersion in hot water, progressive immersion in hot water and steam. An increase in total fiber content was found throughout frozen storage. This increase correlated with lignification of vascular bundles in the basal segment of spears, even during frozen storage. This was reflected in an increase in maximum shear force and cutting energy required. The shelf life of frozen asparagus was 12 mo using total fiber content as a criterion.     

Assessment of the long-term stability of retort pouch foods to support extended duration spaceflight

To determine the suitability of retort processed foods to support long-duration spaceflight, a series of 36-mo accelerated shelf life studies were performed on 13 representative retort pouch products. Combined sensory evaluations, physical properties assessments, and nutritional analyses were employed to determine shelf life endpoints for these foods, which were either observed during the analysis or extrapolated via mathematical projection. Data obtained through analysis of these 13 products were later used to estimate the shelf life values of all retort-processed spaceflight foods. In general, the major determinants of shelf life appear to be the development of off-flavor and off-color in products over time. These changes were assumed to be the result of Maillard and oxidation reactions, which can be initiated or accelerated as a result of the retort process and product formulation. Meat products and other vegetable entrées are projected to maintain their quality the longest, between 2 and 8 y, without refrigeration. Fruit and dessert products (1.5 to 5 y), dairy products (2.5 to 3.25 y), and starches, vegetable, and soup products (1 to 4 y) follow. Aside from considerable losses in B and C vitamin content, nutritional value of most products was maintained throughout shelf life. Fortification of storage-labile vitamins was proposed as a countermeasure to ensure long-term nutritive value of these products. The use of nonthermal sterilization technologies was also recommended, as a means to improve initial quality of these products and extend their shelf life for use in long-duration missions. Data obtained also emphasize the importance of low temperature storage in maintaining product quality. PRACTICAL APPLICATION: Retort sterilized pouch products are garnering increased commercial acceptance, largely due to their improved convenience and quality over metal-canned products. Assessment of the long-term stability of these products with ambient storage can identify potential areas for improvement, and ultimately increase consumer satisfaction with these technologies.