OCCURRENCE OF CHILLING INJURY IN GOLDEN APPLE (Spondias dulcis, Sonn.) FRUITS

The effects of modified atmosphere packaging, waxing, storage temperature (5C) and duration (3, 7, 11, 15, 19 and 23 days) on the keeping quality and chilling-tolerance of golden apple fruits were evaluated. The extreme susceptibility of golden apple fruits to chilling injury (CI) at 5C was evidenced by extensive pitting and fungal decay. Symptoms appeared after 11 days storage at 5C or after holding at 30C for 1 day after storage for 3 days at 5C. Waxing delayed the appearance of pitting in the above situations to 23 days and 15 days, respectively. Skin pitting developed in low density polyethylene (LDPE) packaged fruits after 19 days at 5C and became more pronounced after holding at 30C for one day. Despite the symptoms observed, measurements of bioelectrical resistance and electrolyte leakage indicated that severe membrane damage had occurred by 7 days storage at 5C for all treatments. Therefore, bioelectrical resistance and electrolyte leakage provided a measure of the onset of chilling injury prior to the appearance of CI symptoms. Changes in fresh weight losses, a reliable indicator of CI in some commodities, did not prove to be so in this case.     

PHYSIOLOGICAL CONSEQUENCES OF MINIMALLY PROCESSED FRUITS AND VEGETABLES

The physiological consequences of minimal processing are dire. Mechanical injury sets off a complex series of events which result in loss of quality (i.e. color, texture and flavor). Control of this wounding response is a major obstacle that must be overcome. To prolong postharvest life, respiration must be reduced while producing enough energy to maintain the “energized state”. The central roles of membranes and calcium in maintaining quality are discussed.     

粥化酶及其在果蔬加工中的应用研究

研究了粥化酶的粗酶特性及其在果蔬加工中的应用，并比较了粥化酶与其它果蔬加工用酶在苹果加工中的应用效果。研究结果表明粥化酶作用的最佳条件符合果蔬加工的要求，它能够不同程度的提高果蔬的出汁率及其澄清度；与其它果蔬加工用酶相比粥化酶具有作用效果好，价格便宜的优点     

几种树莓果实在加工过程中的理化指标变化初探

对9个品种树莓果实在加工过程中的理化指标变化进行研究,结果表明,9个品种中,Tulameen的糖度高,糖酸比合适,VC含量较高,既可鲜食,也适合作加工品种.在树莓果汁的加工过程中,加酶处理比热榨的出汁率平均增加9.89%,可溶性固形物平均增加5.93%,是果汁加工必不可少的措施.提汁后比提汁前,树莓果汁总糖、总酸变化不明显,VC含量明显减少,这表明温度对VC的影响比较大.     

CHILLING INJURY. A REVIEW OF POSSIBLE MECHANISMS

Chilling injury (CI) is a physiological defect of plants and their products that results in reduced quality and loss of product utilization following exposure to low but nonfreezing temperatures. To design more effective control strategies and maximize shelf-life, it is necessary to develop an understanding of the biochemical mechanism(s) responsible for the initiation of CI. Despite considerable efforts in this field of study, there is no general agreement on the cause or nature of CI, or even the primary event(s) triggering low temperature damage.
The first unified theory to explain CI was founded on low temperature induced membrane lipid phase transitions leading to a loss of membrane integrity and physiological dysfunction. This was modified to account for the observation that the level of certain high melting phospholipids appears to be related to the chill sensitivity of many plant tissues. Membranes and changes in their physical characteristics are further implicated as having a role in CI by the discovery that chilling stress evokes an elaborate membrane retailoring response that leads to increased fluidity at reduced temperatures.
Others have postulated that CI results from the direct effect of reduced temperatures on enzymes or the indirect effect of membrane perturbations on intrinsic enzymes. The redistribution of cellular calcium has most recently been advanced as the primary transducer of CI. The weight of this theory rests on the role of calcium as a secondary messenger for many cellular functions. In this review it is also speculated that lipid peroxidation may have a role in the development of irreversible injury during low temperature stress. Its effect would be similar to the senescent processes of free radical damage to tissue and progressive membrane rigidification.     

CHILLING INJURY. A REVIEW OF QUALITY ASPECTS

The various quality aspects of chilling injury (CI) serve as the focus of this review in which symptoms, occurrence and its alleviation are discussed. CI is a term used to describe the physiological damage that occurs in many plants and plant products, particularly those of tropical and subtropical origin, as a result of their exposure to low but nonfreezing temperatures. The substantial economic consequences of CI have provided the impetus for studying/developing effective means of alleviating symptoms which manifest this disorder. A diversity in plant responses to low temperature stress exists, including alterations in ethylene biosynthesis, increased respiration rates, cessation of protoplasmic streaming, increased solute leakage, and uncoupling of oxidative phosphorylation. These various responses ultimately give rise to an array of visual symptoms (e.g., surface pitting, water rot, poor color development, general loss of structural integrity) which can render severe losses in product quality both pre- and postharvest. A number of different methods are available by which to alleviate symptom development, including manipulation of storage conditions (e.g., temperature cycling, hypobaric and modified atmosphere storage), exogenous chemical treatments (e.g., application of phospholipids, antioxidants, calcium) and genetic modification of chill sensitive species. These are discussed with respect to their effectiveness and possible control mechanisms.     

罗汉果的化学成分与应用研究

罗汉果是广西特产罗汉果属植物[Siraitia grosvenorii（Swingle）]的果实。本文综述罗汉果的化学成分和药理研究，为罗汉果的进一步开发利用提供依据。     

MECHANICS OF FAILURE IN FRUITS AND VEGETABLES

An understanding of mechanical failure in fruits and vegetables is essential to the reduction of damage in processing, handling and transport operations and to the evaluation of textural characteristics of foods. This paper proposes a theory of failure for solid horticultural materials based on the classification of failure as cleavage, slip or bruising. For each of these three modes of failure, the role of intensity of loading or stress in initiating failure is described. It is shown that cleavage is a normal stress phenomenon and that slip and bruising are shear stress phenomena. The mechanical properties of horticultural produce are described in terms of cleavage strength, slip strength and bruising strength; properties which may vary with ripening and loading conditions.
A failure diagram is constructed by superimposing strength boundaries on the normal and shear stress axes of the Mohr's circles representation of the applied stress state. This novel diagram is shown to apply to selected fruits and vegetables. The model can be extended to include buckling. It is shown that horticultural materials do not fail according to one failure criterion alone, but fail, on a rising load, according to the current strength boundary first encountered by an expanding stress state. Potatoes, for example, may fail by cleavage, slip or bruising, depending on the loading conditions.     

葵花籽烘烤前后化学成分的分析及对比

对烘烤前后葵花籽中的化学成分进行分析并对比.采用同时蒸馏萃取装置萃取葵花籽中的挥发性成分,采取超临界CO2流体萃取技术萃取葵花籽油脂,并将其分为酸、碱、中性三个部分,用气相色谱--质谱联用方法分析其中的化学成分并对烘烤前后的葵花籽中主要化学成分进行对比.结果表明,葵花籽挥发性成分中舍有多种醛类和酯类化合物,烘烤后的葵花籽中产生了大量的吡嗪类化合物,其在碱性部分中的相对含量比烘烤前提高23.37%,不饱和醛类化合物含量也有所提高;葵花籽油脂中的主要化学成分是油酸、亚油酸及其酯类;另外还含有生物活性功能性成分如VE、植物甾醇和角鲨烯等.烘烤后除角鲨烯含量有所降低,维生素E、植物甾醇、亚麻酸等含量均有提高.     

THE CHEMISTRY OF TEXTURE IN FRUITS AND VEGETABLES

This review is concerned with the chemistry of the major primary cell wall components, pectins, hemicelluloses and cellulose, under conditions found during the normal handling of fruits and vegetables. These polymeric components are considered separately, then their combined changes during maturation, storage and processing are covered. The effects of tissue conditions, pH, enzymes and salt concentrations on the rate and degree of change are discussed. A large part of the review deals with the important texture-affecting reactions of pectic materials including glycosidic hydrolysis, β-elimination type depolymerization, demethoxylation, and complex formation.     

NUTRITIONAL AND CHEMICAL STUDIES OF THREE PROCESSED SOYBEAN FOODS

Three different processing methods were used to prepare foods based on whole soybean. Product A was prepared by soaking the beans overnight, blanching at 210° for 20 min, blending and drum drying at 40 psig steam. Product B was water-packed canned soybeans, blanched at 210°F for 20 min and thermally processed in cans at 250° F for 60 min, then blended, frozen and freeze dried. Product C, a mixture of soy and banana (1:1 solid basis), was prepared by the same method as Product A. The amino acid composition of the three products determined by gas chromatography was compared. The thermally processed product (B) showed a considerable decrease in methionine compared to Product A (from 23.4 to 11.3 mg Met/g protein). Product A showed superior quality (PER = 2.43; NPU = 46.3), but as a result of methionine supplementation (0.5%) the PER of the thermally processed product (B) was increased from 1.61 to 2.94 and the NPU from 33.2 to 49.3. The effect of the different processing procedures on the quality of the end products, such as browning, nitrogen solubility index (NSI) and amino acid partition between the soluble and the nonsoluble fractions was compared. Product (A) was superior to the thermally processed product (B) considering browning (A₄₂₀= 0.072 compared to 0.156), but was inferior considering NSI (14.92% compared to 23.89%). Amino acid analysis of the soluble fraction indicated a relatively high amount of soluble lysine (114.5 mg/g protein). Cost analysis of the three products shows their economic advantage compared to casein as a protein source.     

EFFECTS OF SHRINK FILM WRAP ON INTERNAL GAS CONCENTRATIONS, CHILLING INJURY, AND RIPENING OF HONEYDEW MELONS

Honeydew muskmelons (Cucumis melo L.) were individually wrapped with polyvinyl chloride (PVC) shrink film and stored at 2.5° or 7.5 °C for 21 days and examined, then held an additional 2 or 3 days at 20°C and examined again. Nonwrapped melons were the control. The concentration of CO₂ in the cavity of wrapped melons stored 21 days was 5.6% at 2.5°C, 9.1% at 7.5°C, but only 1.1% and 1.5% in the nonwrapped held at 2.5°C or 7.5°C, respectively. Wrapped fruit ripened slower than nonwrapped fruit during storage and subsequent holding at 20°C, after which time 70% of the wrapped melons were rated eating ripe, but 62% of the controls were overripe. Wrapped melons exhibited 30% less chilling injury (CI) symptoms than nonwrapped fruit stored at 2.5°C. The CI symptoms ranged from reddish-brown to dark-brown surface discolorations and sometimes included dry sunken areas of skin. Fresh weight loss was about 1 % in wrapped melons, but 5% in nonwrapped fruit, regardless of storage temperature. Decay incidence was about equal in wrapped and nonwrapped melons after storage at 2.5°C, but was greater for wrapped than nonwrapped melons after storage at 7.5°C. Soluble solids content was about 12.5% in wrapped and nonwrapped melons stored at either temperature.     

PHYSICAL, PHYSIOLOGICAL AND CHEMICAL CHANGES IN POTATO AS INFLUENCED BY ERWINIA CAROTOVORA INFECTION

Bacterial soft rot, caused by Erwinia carotovora ssp. carotovora (Ecc), is a major disease in stored potatoes. The pathogen causes different physical, physiological and chemical changes in potatoes, which may affect the acceptability of raw and processed products. This study was carried out to evaluate the effect of disease severity on different physico-chemical and physiological properties of raw and cooked potatoes and to select the parameters most responsive to disease severity. Potatoes were inoculated with bacteria and incubated at 20C for different lengths of time to produce different levels of disease. As incubation time increased the volume of disease (VDS) increased, which in turn influenced the respiration rate (RR). In both raw and cooked potatoes, the physical changes (texture and color) associated with the progress of disease were reduced hardness, firmness and L value, and increased a and b values and total color difference (ΔE). The chemical changes were reduced ascorbic acid and pH, and increased reducing sugars, total sugars and titrable acidity along with the activities of peroxidase and polyphenol oxidase. The changes in physical and chemical parameters of raw and cooked potatoes during storage were described by fractional conversion equation models. All parameters were quite sensitive to disease except reducing sugars, peroxidase and PPO activity. The correlation matrix indicated that several of the quality parameters were related and thus most of them could be successfully used to predict tuber quality from disease.     

THE USE OF CHEMICAL MARKERS AND MODEL STUDIES TO ASSESS THE IN VITRO PRO- AND ANTIOXIDATIVE PROPERTIES OF METHYLXANTHINE-RICH BEVERAGES

Chemical markers and model studies are useful in predicting the stability and shelf life of foods and beverages in food technology and chemistry. Chemical modification induced by food processing has an impact on the reactivity and chemical properties of the food constituents, frequently giving rise to new molecules with enhanced antioxidative activity and potential health benefit. In the case of coffee, tea, and cocoa, these positive characteristics are often associated with dietary polyphenols. In particular, the often referred to “paradox” behavior of endogenous polyphenols to act as anti- and/or prooxidants is demonstrated with the aid of in vitro model studies. Furthermore, in-situ chemical markers such as 8-oxocaffeine are described in methylxanthine-rich beverages that reflect oxidative reactions. Such chemicals can be employed to help assess the impact of processing conditions on food quality as well as to predict the stability of the final product.