不同阻隔包装猪肉光照下品质变化

室温25℃,用高阻隔、低阻隔包装材料,真空包装、普通包装方式包装新鲜猪肉,研究光对阻隔包装猪肉过氧化值(POV)、p H值、挥发性盐基氮(TVB-N)含量的影响。结果表明:光照下阻隔包装猪肉的过氧化值、p H值、挥发性盐基氮含量均随着贮藏时间的延长而增加;过氧化值先升后降,整体呈现出不规则上升变化趋势;光照条件下贮存的包装猪肉p H值增加量均高于避光贮存;挥发性盐基氮值在贮存后期变化速度比前期大,光照对挥发性盐基氮值影响较小。     

壳聚糖复合茶粉对广式豆沙月饼的保鲜研究

本文采用壳聚糖和茶粉为保鲜剂,以菌落总数、酸价(AV值)、过氧化值(POV值)作为月饼保鲜评价指标,研究月饼在常温保存时的品质变化规律。结果表明,经过壳聚糖涂膜和茶粉添加处理的广式豆沙月饼菌落总数、AV值、POV值均明显低于对照实验组。壳聚糖和茶粉对广式豆沙月饼的保鲜有协同增效作用,最佳保鲜效果的复配组合为:浓度为1. 5%相对分子质量为4 k Da的壳聚糖与浓度为2. 0%相对分子质量为200 kDa壳聚糖的混合配比分别为45%、55%,茶粉添加量为3. 5%。     

油脂的提取方法对酸价和过氧化值测定的影响

酸价和过氧化值是判定油脂品质好坏的重要指标,食用酸价或过氧化值超标的食品对人体会造成伤害,因此多类食品都将酸价和过氧化值作为重要的卫生指标来进行检测控制。除食用油以外其他食品的检测,需要先进行油脂提取,提取过程会对油脂质量造成影响。用已知食用油模拟食品产品中油脂的提取过程,通过对提取过程中脱溶时间的长短,温度高低的设定,样品水分含量的多少对酸价、过氧化值检测结果的影响,从而总结出最佳的提取方法。     

油茶籽贮藏方法对油脂品质的影响

以小果油茶的油茶籽为研究对象,分析了7种贮藏方法对其及相应的油脂品质的影响。研究了油茶籽鲜果的含水率、出仁率,不同贮藏条件下的鲜果和风干籽的含油率,油脂的酸值、过氧化值、不皂化物含量。结果表明：12个月贮藏期后,不同的贮藏条件对油茶籽的含油率和油菜籽油不皂化物含量没有显著影响;对油菜籽油酸值和过氧化值的影响较为显著。综合考虑油茶籽油酸值、过氧化值两个指标的变化规律,干籽玻璃瓶包装冷冻（-18℃）贮藏法是最适宜贮藏油茶籽的方法,经12个月的贮藏,其油茶籽含油率和茶油不皂化物含量稳定,茶油的酸值和过氧化值均处于较低水平分别为1.46 mg/g和16.60 mmol/kg。     

光解花生油中黄曲霉毒素B_1对油品质影响研究

为研究紫外光解食用花生油黄曲霉毒素B_1(AFB_1)对油品质的影响,通过测定食用花生油的酸价、过氧化值及黄曲霉毒素B_1三项主要指标来评价。结果表明,紫外光解能有效降解AFB_1,但长期而言光解对食用花生油的酸价、过氧化值有影响,会导致食用花生油的酸价和过氧化值升高,光照后的食用花生油不利于长期保存。研究结果可为紫外光解食用花生油中AFB_1的应用提供理论参考。     

人造奶油酸价和过氧化值影响因素研究

人造奶油酸价和过氧化值的准确测定一直是研究热点。本文基于最新的标准,采用先进的自动电位滴定仪,研究存储条件对人造奶油酸价和过氧化值的影响。结果表明,存放时间、温度、光线、容器材质对样品的酸价和过氧化值的影响较大。随着存放时间的延长、温度的升高,酸价和过氧化值变大;光线强度和存储容器对结果有相应的影响。     

常温条件下真空包装对酱卤猪蹄保鲜度影响的研究

以菌落总数、TVB-N值和pH值为主要指标,并结合感官评价,在常温条件下研究真空包装对酱卤猪蹄保鲜度的影响。结果表明：真空包装具有明显的保鲜效果并能延长其货架期。在常温条件下,使用真空包装酱卤猪蹄的货架期延长9 d。     

MAP处理对草莓采后生理的影响

本研究对采后草莓利用0.035 mm厚的PE保鲜袋进行包装并贮藏于0℃条件下,研究了不同体积分数的O_2、CO_2、和N_2的MAP包装方式对草莓贮藏效果的影响,结果表明,与其他MAP包装方式相比,F2处理(将草莓装入0.035 mm厚的PE保鲜袋中,抽真空,充入5%O_2+10%CO_2+85%N_2,封口)可以明显抑制草莓的呼吸作用,减缓了超氧化物歧化酶(SOD)活性的下降,维持了较高的过氧化物酶(POD)活性,抑制了丙二醛(MDA)含量的积累,降低了膜脂过氧化程度,保持了草莓的原有品质。     

PE/EVA/分子筛复合保鲜膜对菠菜的保鲜作用研究

以聚乙烯(PE)/乙烯-醋酸乙烯共聚物(EVA)为基体树脂,分别添加2.5 %、5 %、7.5 %、10 %分子筛,自行吹制PE/EVA/分子筛复合气调包装膜,并对新鲜采摘菠菜进行常温保鲜包装研究。测定了保鲜膜的拉伸强度、断裂伸长率和撕裂强度,对菠菜包装的保鲜效果进行感官评价。研究了随着分子筛含量的增加,菠菜失重率、可溶性固形物和呼吸强度的变化。结果表明：室温下添加EVA和分子筛可增大PE保鲜膜的气体透过性,有效抑制菠菜的呼吸作用。当分子筛含量为7.5 %时,薄膜的保鲜性能最好。气调保鲜包装的平衡气体浓度为O2含量8.7 %~9.3 %、CO2含量7.2 %~7.7 %。PE/EVA/分子筛复合保鲜膜比纯PE膜更适于菠菜的保鲜。     

不同膜的真空包装对澄海猪头粽的保鲜性研究

通过涂膜法制备得到壳聚糖/PE复合膜和壳聚糖/纳米ZnO/PE复合膜,并分别对澄海猪头粽进行真空包装,在储存期第0、2、4、6天,通过测量感官特性、色度、TBARS值,比较膜的保鲜效果。结果发现,随着储存时间的增加,每组猪肉粽都出现了不同程度的腐变。与普通PE膜的真空包装相比,壳聚糖/PE复合膜和壳聚糖/纳米ZnO/PE复合膜对猪头粽都有一定的保鲜效果,其中壳聚糖/纳米ZnO/PE复合膜的保鲜效果略好。     

Effect of argan kernel storage conditions on argan oil quality

In the present study, we investigated the relationships between storage conditions of argan kernels and argan oil quality over a 1‐year period. Argan kernels were packaged in black or white bags. Kernels in black bags were stored at room temperature (RT) while kernels in white bags were stored either at RT or at 4°C. Quality parameters periodically monitored over the 12 months were peroxide and acid value, oil yield, moisture content, UV absorption, and fatty acid composition. Whereas light had no impact on argan oil quality, only argan kernel storage at 4°C allowed a perfect preservation of argan oil quality after 1 year. Practical applications: In the present study we have established that solar light does not damage argan kernels in such a way that it could alter argan oil quality, and that argan kernels can be stored for up to 1 year at 4°C without alteration of argan oil quality. If stored at RT, argan kernels should be used within 10 months to prepare edible argan oil.     

The effect of coatings formed by low temperature tetramethoxysilane plasma treatment on water-vapor permeability of poly(L-lactic acid) film

One of the most promising applications of poly(L-lactic acid) (PLLA) is food packaging. However, PLLA has a poorer gas barrier property than ordinary food packaging polymers. An improvement of the water-vapor barrier property is therefore required. In this study, low temperature plasma treatment on a stretched PLLA film in the presence of tetramethoxysilane (TMOS) was carried out in order to improve its water-vapor barrier property. The flux of water-vapor permeation through a stretched PLLA film treated with low temperature plasma in the presence of TMOS was decreased to 60% of an untreated stretched PLLA. The effects of plasma treatment parameters on the water-vapor permeability were investigated.     

Effect of water activity on autoxidation of raw peanut oil

The effect of water activity (a_w) on rate of autoxidation of raw peanut oil at 37 C was studied. Up to 3 weeks of storage, no marked effect of a_w on the rate of peroxide formation was noticeable. However, with prolonged storage, the rate of peroxide formation decreased rapidly at a_w of 0.67 and higher as compared to a_w of 0.50 and lower. At the end of 9 weeks’ storage, the peroxide value at a_w=0.02-0.50 was in the range of 31–35, while it was only ca. 10 at 0.79 and 0.92 a_w. There was no noticeable influence of a_w on the rate of free fatty acid formation. The oil stored for 7 weeks at 0.02 and 0.11 a_w had fresh flavor, although the peroxide values were high; whereas the oils at 0.79 and 0.92 a_w were stale, although the peroxide values were less than 10. The anisidine value at 0.02 a_w (348) was higher than at 0.92 a_w (62). The carbonyl values at 0.02 and 0.11 a_w were also higher (1090, 1021) than at 0.79 and 0.92 a_w (573, 780). The results indicate that the protective effect on the oil against peroxide formation at high a_w may be due to certain components present in raw peanut oil.     

Chemical and nutritional studies onTerminalia bellirica Roxb. Kernel and its oil

Terminalia bellirica Roxb. is a valuable tree of Indian forests. The seeds are valued medicinally and also industrially, for tanning purposes. The kernels, which are not currently used for edible purposes, have 40% oil and 35% protein. The oil extracted from the kernels is sweet-smelling and has palmitic (35%), oleic (24%) and linoleic (31%) acids as major fatty acids. The proximate principles, antinutritional factors and amino acid composition of the protein of the kernel are analyzed. Short term feeding of the oil at 10% level in a 10% casein protein diet to rats for 4 weeks resulted in growth comparable to that observed with animals fed a similar diet containing 10% groundnut oil. The protein utilization of casein used in the diet, as judged by the protein efficiency ratio (PER) and net protein utilization (NPU), was not adversely affected by theT. bellirica oil in the diet. The liver and heart lipid profiles of both the groups as reflected by the parameters, total lipids, total cholesterol and triglycerides content were comparable except for the heart triglycerides of the TBO-fed group, which were elevated. The absorption of nutrients like calcium, phosphorus and nitrogen was not adversely affected by the intake ofT. bellirica oil.T. bellirica oil is absorbed to the same extent as groundnut oil. The results of this preliminary study indicate thatT. bellirica kernel oil may be used for edible purposes because it is a good source of linoleic acid. However, long term toxicological studies are necessary to establish its safety before it can be recommended as an edible oil for human consumption. Feeding a diet containing 10%T. bellirica kernel protein as a raw diet as well as a cooked diet to rats, mice and chicks resulted in low food intake and death in all three species, probably due to heat stable antinutritional factors in the kernel.     

The rate of development of acidity in stored tung seeds and kernels

Summary Whole tung seeds, whole kernels, and chopped kernels of high, medium, and low moisture contents were sealed in tin cans and stored in incubators maintained at 25°, 31°, and 38°C. At intervals samples were removed and the acid value of the oil determined. The different temperatures used had slight effect on the rate of development of free fatty acids in the oil of the whole seeds and kernels, but the higher temperatures greatly increased the rate of development of free acid in the chopped kernels. Whole seeds containing 7% and 12% moisture were stored for 4 weeks and seeds containing 17% moisture were stored for 2 weeks, during which periods the oils developed free fatty acids equivalent to acid values of 2.0 or less. Under none of the conditions used did the acid values of the oils exceed 8.0 after storage for 13 weeks. Whole kernels developed even less free fatty acids than seeds stored under similar conditions. Kernels containing 4% and 6% moisture were stored for 12 weeks during which period the acid value of the oil never exceeded 1.5. Even in kernels containing 12% moisture the acid value of the oil did not exceed 6.0 at the end of 12 weeks. Chopped kernels with moisture contents of 5% and 7% could be stored for 12 days without developing an acid value in the oil of more than 8.0. However chopped-kernels with a moisture content of 12% developed an acid value in the oil in excess of 8.0 in less than a week. Whole seeds with as much as 15% moisture could probably be stored for several weeks without developing an objectionable amount of free fatty acids. Since commercial hulled “nuts” practically always contain some broken kernels, to avoid development of free fatty acids in storage they should be dried to 10% or less moisture before storage. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Effect of roasting on oxidative and tocopherol stability of walnut oil during storage in the dark

The effect of roasting on the oxidative stability of oil from walnut (Juglans sinensis Dode) was investigated by observing changes in the characteristics of oils from unroasted and roasted kernels during storage in the dark at 60°C. Walnut kernels were roasted at 160°C for 15 min prior to oil extraction with the solvent, hexane. Roasting of kernels increased the peroxide value (POV) and conjugated dienoic acid (CDA) value of the oil. The rate of increase in the POV was significantly lower in roasted than in the unroasted walnut oil during storage at 60°C (1.90 vs. 1.06 and 4.45 vs. 3.55 meq/kg/day during induction period (IP) and post‐IP, respectively). Roasting of kernels significantly increased the IP of walnut oil from 0.89 to 3.39 days during storage. The total tocopherol content in roasted walnut oil was lower as compared to that in unroasted one (277.77 vs. 314.88 µg/g). However, the rate of degradation of total tocopherol during storage was lower in roasted walnut oil compared to unroasted one (1.18 vs. 2.17%/day), which showed that the tocopherol retention was higher in roasted walnut oil. These results indicate that roasting of kernels increased the oxidative and tocopherol stability of oil during storage in the dark.     

Effect of Storage Conditions on the Oil Quality of Chinese Tallow Tree Seeds

The Chinese tallow tree (TT) has been widely considered to be an invasive species in the US without potential benefits. However, the literature on TT seeds is scarce and the effect of storage conditions on seed oil quality in particular has not been published to our knowledge. Prior research revealed that TT has a very high yield of seeds containing large percentages of long and short chain fatty acids (mainly palmitic fatty acid, along with some oleic, linoleic and linolenic fatty acids), which can be base transesterified into biodiesel. This study aims to address the issue of the quality of the kernel oil of TT seeds stored at different temperatures (4 °C and room temperature) and under controlled atmosphere storage conditions (3% CO₂, 6% CO₂, vacuum, normal headspace). The total storage time was 3 months with the oil quality being analyzed weekly. Extracted oil was analyzed by titratable acidity, peroxide value, oxidative stability index and fatty acid composition. These experiments provided evidence that, after 12 weeks of storage, a controlled atmosphere did not produce any remarkable advantage over low cost air storage. The results validate the belief that no elaborate storage conditions are required to store this economically promising high oil content biofuel feedstock.     

Increased oilseed shelf life using peanut flour biopackages

This study analyzed the ability of defatted peanut flour packaging to preserve chemical quality stability of sunflower seeds throughout storage. Sunflower seed samples packaged in defatted peanut flour pouches (RS-DPFP), high-barrier plastic pouches made of ethylene vinyl alcohol (RS-EVOH) and plastic pouches made of polyethylene (RS-PE) were stored for 30 days at room temperature. Peroxide values and conjugated dienes showed a lower increase in RS-DPFP and RS-EVOH than in RS-PE samples during storage. The samples packaged in DPFP pouches exhibited similar changes in oleic/linoleic acid ratio and iodine value with respect to EVOH pouches during storage. A higher decrease in α-tocopherol was observed in RS-PE compared to RS-DPFP and RS-EVOH. After 30 days, RS-PE presented the highest hexanal, 2-octenal (E), hexanoic acid, and 1-pentanol contents. DPFP delayed sunflower seeds deterioration, improving their shelf life during storage.     

Lipid Composition and State of Oxidation of Fortified Infant Flours in Low‐Income Countries Are Not Optimal and Strongly Affected by the Time of Storage

Food fortification is widely used to address the public health problem of nutrient deficiencies. This study's purpose is to assess the lipid profile and nutritional quality of 13 fortified infant flours (FI) collected “in the field” in Africa and Asia after different periods of storage. The lipid content, fatty acid profiles, lipophilic vitamin content, and lipid oxidation state (peroxide values, secondary oxidation products) are determined. Mycotoxins and packaging materials are also characterized. The lipid content averages 9.1 ± 3.5 g/100 g. Fatty acid profiles are dominated by linoleic (43.3 ± 8.8%), oleic (29.5 ± 7.4%), and palmitic acid (17.8 ± 6.7%) and result in an average ω6/ω3 ratio of 12.2 ± 5.9 but with high values for some FI. Very high overages in vitamins A, D, and E are observed in products stored for short periods (1–6 months), whereas FI stored for more than 12 months has insufficient vitamin content. Lipid oxidation is acceptable but for six products presenting excessive peroxide values. Most products are contaminated by low amounts of mycotoxins but only two FI do not abide by the regulation. A strong correlation between peroxide values, hexanal content, and time of storage is observed. Practical Applications: The expiration dates for FI commercialized in low‐income countries should be shortened from 36 to 12 months so as to guarantee their nutritional quality of these functional foods and to abide by the fortified infant flour legislation. Indeed, FI quality significantly decreases over time of storage. The use of high barrier packaging materials must be generalized, although it is a necessary criterion but not sufficient to ensure the long‐term stability of FI. Special attention should be given to reduce lipophilic vitamin overages and to improve their lipid profile, especially the ω6/ω3 ratio, which has to be lower than 15.     

Limiting temperature and relative humidity for aflatoxin production byAspergillus flavus in stored peanuts

Sound mature kernels, broken mature kernels, immature kernels and unshelled cured Early Runner peanuts were inoculated with spores ofAspergillus flavus and incubated up to 84 days in controlled environment cabinets. In a series of experiments temperatures ranged from 8 to 49 C in combination with 98±1% relative humidity (RH); in others RH was varied from 70% to 99% at 30±1/2 C and from 83% to 99% at 20±1/2 C. Samples were removed after 7, 21, 42 and 84 days of incubation and assayed for aflatoxin, free fatty acids and peanut kernel moisture. Aflatoxin was formed in sound mature kernels at 40 C and 14 C and in broken mature kernels at 13 C, but none was formed at 41 C after 21 days or at 12 C after 84 days in 98±1% RH. The limiting temperatures for aflatoxin formation in peanut kernels with intact shells were 41 C for 21 days and 16 C for 84 days of incubation. The limiting RH at 30 C for aflatoxin production in sound mature kernels was 84%, whereas in broken mature and immature kernels it was 83% and in kernels from unshelled peanuts the limiting RH was 86% for 84 days of incubation. The limiting RH at 20 C for sound and broken mature kernels was 83%, whereas it was 86% RH for immature kernels and 92% for kernels from unshelled peanuts. Free fatty acid formation was correlated with visible growth of fungi rather than with aflatoxin production. Aflatoxin formation was generally correlated with kernel moisture contents of 10% or higher.