天然食品防腐剂的应用进展

阐述了近年来食品生产过程中实际应用的微生物源、动物源和植物源食品天然防腐剂。防腐剂，保证食品安全，保护消费者切身利益提供指导。     

PRESERVATION OF NATURAL STABILITY OF FRUIT "BROMELAIN" FROM ANANAS COMOSUS (PINEAPPLE)

Pineapple extract, "bromelain," is a rich source of proteases having therapeutic benefits. The processed fruit does not show proteolytic activity probably due to harsh conditions of sterilization. Storage of fresh fruit at − 4C without preservatives retained 75  ±  5% proteolytic activity after 180 days (with or without eight cycles of freeze–thawing in between) and was devoid of microbial contamination. Peroxidase, acid phosphatase and amylase activities were also retained by 75  ±  5%. Immunomodulatory activity of the fresh and the stored fruit was comparable. For industrial scale, γ irradiation of 1–2 kGray is proposed to ensure sterility that does not affect enzyme activities. Under these conditions, no signs of freeze burning are observed. The ultraviolet-visible spectra of the fresh and stored fruit extracts are also indistinguishable. The process is commercially viable and amply improves the quality of processed pineapple in terms of active "bromelain."

PRACTICAL APPLICATIONS

Bromelain, the fruit extract of pineapple, is a rich source of beneficial enzymes primarily because of its medicinal properties. Because the fruit grows in abundance in a short time, it requires preservation to prevent wastage. This work reports the absence of enzymatic activities in preserved pineapples commercially available in the global market because of harsh conditions of sterilization. Alternately, exposing to low dose of irradiation followed by preservation under frozen condition at −4C retains enzymatic and immunomodulatory activities of the fruit. Being free from adverse effects of freeze burning, it offers a cost-effective way of proper preservation of pineapples retaining its medicinal properties. Promotion of pineapple in dietary consumption can prove to be beneficial to the society and businesses at large.     

百香果加工适性的测定及提高其出汁率的研究

测定了百香果的加工适性,并针对百香果汁加工企业现有工艺出汁率较低、果渣中果肉成分含量较高的生产实际,研究酶法二次浸提技术,以提高百香果出汁率.结果表明:百香果是一种优质的果汁加工原料,其果汁可溶性固形物高达16.5%,对热具有相当的化学稳定性;对果渣进行酶法浸提,可提高百香果出汁率12%左右.     

THERMAL PROPERTIES OF PASSION FRUIT JUICE AS AFFECTED BY TEMPERATURE AND WATER CONTENT

The specific heat, thermal conductivity and density of passion fruit juice were experimentally determined from 0.506 to 0.902 (wet basis) water content and temperatures from 0.4 to 68.8C. The experimental results were compared with existing and widely used models for the thermal properties. In addition, based on empiric equations from literature, new simple models were parameterized with a subset of the total experimental data. The specific heat and thermal conductivity showed linear dependency on water content and temperature, while the density was nonlinearly related to water content. The generalized predictive models were considerably good for this product but the empiric, product‐specific models developed in the present work yield better predictions. Even though the existing models showed a moderate accuracy, the new simple ones would be preferred, because they constitute an easier and direct way of evaluating the thermal properties of passion fruit juice, requiring no information about the chemical composition of the product, and a reduced time of the estimation procedure, as the new empiric models are described in terms of only two physical parameters, the water content and the temperature.     

生物防腐剂和气调保鲜在食品中的应用

随着社会的发展和生活水平的提高,食品保鲜技术越来越受到关注,采用先进的保鲜设备、将安全无毒的天然防腐剂应用到食品中已得到了较好的效果.概述生物防腐剂的种类、气调保鲜的原理和应用,并介绍生物防腐和气调保鲜协同作用在食品中的应用.     

PRODUCTION AND USE OF YEAST PECTOLYTIC ENZYMES TO AID PINEAPPLE JUICE EXTRACTION

A crude preparation of pectolytic enzyme was obtained by culturing Saccharomyces cerevisiae (ATCC512712) in pineapple juice. Maximum cell growth was obtained on the 6th day after inoculation. Correspondingly, optimum protein concentration and enzyme activity were also observed on the 6th day old culture. Although not purified, the addition of this crude enzyme extract to crushed pineapple mash at 0.02% resulted in a significant increase in juice yield (P≥0.05). The overall processing time was also significantly reduced (P≤0.05) with the enzyme treatment compared to controls. A combination of 0.02% enzyme treatment of mash for 30 min, was found to be the most effective dosage in reducing the processing time significantly.     

果胶酶和纤维素酶对菠萝汁澄清效果的研究

本文研究比较了果胶酶和纤维素酶对菠萝汁的澄清效果,确定了各自的最佳工艺参数,并在单因素试验的基础上,通过复合酶的多因素正交试验,获得澄清菠萝汁的最适工艺条件为：果胶酶用量为8.48 U/100mL、纤维素酶42.13 U/100g、时间45min、温度30℃,此时菠萝汁的透光率能达到了87%以上.     

果汁非酶褐变的机制及控制措施

本文阐述了果汁非酶褐变的机制：焦糖化反应、美拉德反应、抗坏血酸氧化分解和多元酚氧化缩合,并对目前常用的抑制果汁非酶褐变的方法进行了综述.     

欧李果芳香油的成分研究

欧李果实香气浓郁、愉悦,本文应用水蒸气蒸馏方法提取其挥发性油脂并利用气相色谱及色谱-质谱联用(GS/MS)技术进行了定性和定量分析,结果表明,欧李果香气主要由2,2'-丙基联二[2-甲基-5-甲氧基-4-氢-4-吡喃酮]、环丁基二羧酸二乙酯、2,2-二甲基-丙酸-庚酯、己烯二酸二乙酯、2[1-硝基-2[四氢吡喃基-2-氧]-环己醇、3,7,7-三甲基-1,3,5-环庚三烯、2,4-二甲氧基-苯酚组成,其它重要成分有:邻甲基-苯乙酮,环丁基二羧酸二乙酯等,是一种极具开发潜力的天然资源,可广泛应用于食品强化和医药领域。     

天然复合果蔬汁饮料的研制

以色彩一致，营养丰富的苹果、草莓、胡萝卜、番茄为原料制成复合果蔬汁饮料，经正交试验法得出最佳工艺参数，为天然复合果蔬汁饮料的进一步开发与研究提供了科学的依据。     

OPTIMAL GRINDING CHARACTERISTICS OF BLACK PEPPER FOR ESSENTIAL OIL YIELD

Black pepper (Piper nigrum L) was ground to different particle sizes at ambient conditions, and the ground material temperatures at the mills’outlet were recorded. The surface mean diameter (d_s) and geometric mean diameter (d_ga) of the pepper grits were determined by sieve analysis. Energy for size reduction was computed using Bond's equation. The quantity of essential oil distilled, using Clevenger's method, was recorded at 30 minutes interval for each particle size. Effective diffusion coefficient (D) determined using Fick's second law, was constant (1.38 × 10^?11 m²s^?1) for higher oil concentrations and it was very less in lower oil concentrations. The essential oil yield was evaluated in terms of four major compounds using gas chromatographic analysis. The particle size (d_go) of about 0.7 mm was found to be optimal for distillation of essential oil.