EXTENDING SHELF LIFE OF FRESH-CUT PERSIMMON BY HONEY SOLUTION DIPS

Ripe persimmon fruit ( Diospyros kaki L) cv. "Hachiya" were diced, then treated with 10–20% w/v diluted honey solution or water as the control, followed by cold storage at 4C until loss of acceptable quality. The persimmon cubes were subject to assessments during the storage of organoleptic and visual quality, softness and exuding juice, soluble solids content (SSC), and absorbance at 436, 440, 675 and 760 nm, respectively. Honey treatments prevented off-aroma development and delayed jelling. Softness and exuding juice of the fresh-cut persimmon cubes increased with time, with the increase in both parameters being significantly suppressed by honey solution dips. Changes in SSC, pH and the absorbance at 436, 440, 675 and 760 nm, respectively, during storage were minor and there was little effect of the honey treatments on these parameters. Overall, the shelf life of fresh-cut persimmon cubes was extended by honey solution dips, which delayed off-aroma development, firmness loss and jelling.

PRACTICAL APPLICATIONS

New products and changing trends make today's food marketplace alive, and fresh-cut fruits and vegetables seem to be on top of list of these products. Although fresh-cut produce has been on the market for a long time, preserving their quality attributes has not been completely successful especially in the case of fruit. This study focuses on a new alternative fresh-cut produce, fresh-cut persimmon, with adapting a potentially safe organic method, use of honey dips. The present study demonstrated that honey solution dip treatments could preserve the fresh-like quality of typical flavor or aroma of persimmon fruit by causing no changes in aroma and taste attributes and extending shelf life. Therefore, honey dip treatment may be used, depending on commodity, to preserve and extend shelf life of fresh-cut produce in fresh-cut processing industry.     

IMPROVED SHELF LIFE ESTIMATION OF UHT MILK BY PREDICTION OF PROTEOLYSIS

ABSTRACT

During growth in raw milk, many psychrotrophic bacteria produce proteases that can retain activity following ultra‐high temperature (UHT) treatment. In this study, casein and skim milk powder assays for detecting very low levels of protease in UHT milk were optimized, and the suitability of azocasein and fluorescein isothiocyanate‐casein (FITC‐casein) as substrates was investigated. The strongest correlations of protease activity with proteolysis in stored UHT milk were observed when FITC‐casein was used as substrate in the assays. Assays using casein and FITC‐casein as substrates yielded the highest activities. To determine sensitivity, crude protease was added at low concentrations to UHT milk, and the milk was assayed for progress of proteolysis over 12 months and for protease activity using the casein and FITC‐casein assays. With long assay incubation times, the FITC‐casein assay was more sensitive than the casein assay and may be suitable for detecting very low levels of protease activity and predicting progress of proteolysis in stored UHT whole milk.

PRACTICAL APPLICATIONS

This study contributes to the development and evaluation of practical assays for the detection of protease activity in the industry to identify potential premature spoilage of contaminated UHT milk before it is distributed for sale. The developed assays are also useful for assessing the quality of milk powder as active protease can persist in milk powder to cause spoilage in reconstituted milk. Although the assays require up to 14 days to complete, this is not an excessive time, compared with the time required for microbiological clearance and total shelf life of the product. High protease activity can be identified with less incubation time. The cost of protease detection assays developed during this work is quite low and, although 20 min analysis time is required per sample, the tests can be very cost efficient when run in batches, as would be expected in a commercial testing facility.

     

IMPROVEMENT OF SHELF LIFE STABILITY OF CAKES

ABSTRACT

The effects of new ingredient strategies to slow down starch retrogradation rate in cakes were investigated. In this study, devil's fudge cakes were formulated using gum, modified starch and enzyme technology. Cake samples that were prepared with combinations of gums, bacterial amylases and pregelatinized starch were found to have slower starch retrogradation rates. An accelerated shelf life protocol was followed to observe the effect of predescribed ingredients on slowing the starch retrogradation rate. The samples were evaluated for moisture content, water activity, texture and thermal properties, as well as morphological characteristics. The staling rate was found to be accelerated by the fluctuations in temperature from high to low temperatures. Modified starches, enzymes and gums were found to decrease the rate of staling and improve product quality. The formulated cakes were found to have 25% lower toughness and hardness values as compared with the control product. It was found that for all the cake formulations, there was a significant decrease in both hardness and toughness values, whereas springiness values did not change much. The basic differences within formulations were created by incorporation of gums, enzymes, soluble fibers, emulsifiers and modified flours in the cake.

PRACTICAL APPLICATIONS

Nutritional balance is quite important for each individual. For certain groups of people, based on their activity levels, high energy supplies are required to help them to achieve their optimal performance. Cakes, waffles and pancakes are in the group of breakfast bakery items that provide high energy for these groups of people. In bakery food products, staling reactions start before microbial deteriorations; as a result, they are the major factor in determining shelf life. Cakes that are acceptable to the consumers should be moist and soft in texture. Starch retrogradation is the primary mechanism determining the shelf life of the product. Although the product is microbiologically safe, the adverse affects of starch crystals on textural properties is the main cause of product rejection by the consumer, which leads to huge economical losses. The current methods of controlling starch retrogradation lean on technologies of the 1980s. Despite several studies on bread staling, there is hardly any study on the staling mechanism of cakes and other bakery food items. This study provides information on how to retard staling in cakes by the use of an in‐house developed accelerated shelf life protocol.     

EXTENDING SHELF LIFE OF UHT CREAMS

The effect of additives and changes of composition on the shelf life of UHT creams was examined. All changes investigated with the exception of added lecithin, showed some improvement in cream feathering properties. Marked improvement with shelf life extended to at least six months was, however, only found with addition of sodium caseinate (30 g/l) and reduction of calcium activity, the latter being achieved either by removal with ion exchange resins or by immobilization with citrate and carbonate.     

EUROPEAN BREWERY CONVENTION: HAZE AND FOAM GROUP. TOWARDS THE CHEMICAL PREDICTION OF SHELF LIFE

Rapid chemical methods are described for assesssing in beer the levels of “oxidizable polyphenols” and “sensitive proteins,” both of which influence non-biological shelf life. The method for oxidizable polyphenols depends on the formation of an insoluble complex with cinchonine sulphate. Freshly processed beers form only a slight haze on the addition of cinchonine sulphate, but the haze produced is greatly increased if the beers are previously oxidized. For beers stabilized by a process involving reduction of the polyphenol content, it is found that the rate of haze formation is then directly related to shelf life and is inversely proportional to it.     

EXTENDING THE SHELF LIFE OF SET FISH BALL

Set fish ball is an extruded surimi‐based product that is popular in Singapore and other Southeast Asian countries. Oversetting of set fish ball occurs at chilled temperature during storage. Shelf‐life extension of set fish ball by reducing oversetting conditions and microbial counts were examined. Encapsulated citric acid (CT) and glucono‐delta‐lactone (GDL) were used to reduce oversetting. Acetic acid, GDL and chitosan were used to inhibit the growth of microorganisms. Shelf life was measured for a period of 21 days at 4C. At day 21, a reduction of 46, 56 and 26% in breaking force compared with the control (without additives) was observed for 0.5% GDL, 1.0% GDL and CT, respectively. GDL at 1.0% was shown to be the most effective in controlling the oversetting of set gel. Chitosan (1%) dissolved in acetic acid maintained both aerobic plate and yeast counts at <1 log cfu/g throughout 21 days of storage.     

ACCELERATED STORAGE, SHELF LIFE AND COLOR OF MANGO POWDER

Vacuum‐dried mango powder was produced from mango pulp through the addition of glycerol monostearate and tricalcium phosphate at 0.015 kg each per kg mango solids and maltodextrin at 0.62 kg per kg dry mango solids. The mango powder was packed in aluminum foil‐laminated pouches and stored in an accelerated storage environment maintained at 90% relative humidity (RH) and 38 ± 2C. The sticky‐point moisture content at 38 ± 2C was considered as the maximum moisture content to which the mango powder would remain stable. The shelf life of the powder predicted from this consideration and the Guggenheim‐Anderson‐de Boer (GAB) model for the water activity moisture content relationship was 114.68 days, whereas the actual shelf life was 105 days. The color change of the powder during storage followed first‐order reaction kinetics with a rate constant of 0.038 per day.     

STRATEGIES FOR PROLONGING THE SHELF LIFE OF MINCED BEEF PATTIES

The study of different strategies for prolonging the shelf life of fresh minced beef patties was addressed in this work. Fresh minced beef was supplemented with thymol (THY) at levels of 250, 500 and 750 mg per kg of ground beef. Treated samples were packed using a high barrier film and stored in refrigerated conditions (4C) under ordinary atmosphere packaging and modified atmosphere packaging (MAP) conditions for 16 days. The microbiological quality decay kinetic was determined by monitoring the following microorganisms: Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria, Brochothrix thermosphacta, coliforms and total psychrotrophic viable count. Results show that THY, working alone, was effective on coliforms and Enterobacteriaceae, whereas it does not seem to inhibit to a great extent the growth of the other microbial populations. On the other hand, an increased amount of THY, under MAP conditions, had better effects on the product quality, with a consequent prolongation of the shelf life.

PRACTICAL APPLICATIONS

Great interest is developing in food bio-preservation, because of the ever-increasing needs to protect consumers' health and to valorize the naturalness and safety of food products. However, very few works have been carried out on the applications of bio-preservatives to extend the shelf life of fresh meat products. This study, therefore, was mainly initiated to evaluate the possibility of extending the shelf life of packed fresh meat patties by a combination of thymol (THY) to other extrinsic factors such as storage temperatures and modified atmosphere during packaging. Interesting results were obtained suggesting that THY can perform an efficient synergy with modified atmosphere conditions and could be advantageously utilized by the meat industry.     

不同包装处理对切分芋头货架期的影响

与对照(普通塑料薄膜包装)、聚乙烯塑料薄膜(PE)包装相比,4℃贮藏的前12天,真空包装(VP)能较好地保持鲜切芋头的可溶性固形物含量(TSS)和淀粉含量,褐变度、丙二醛(MDA)含量和多酚氧化酶的活性较低,而超氧化物歧化酶活性较高.随着贮藏时间延长,聚氯乙烯塑料薄膜(PVC)包装的鲜切芋头,酚类物质含量及丙二醛(MDA)含量低于其他包装,超氧化物歧化酶(S0D)活性最高,TSS和淀粉含量、多酚氧化酶(PP0)活性与VP处理的接近.结论:VP处理适合鲜切芋头的短期低温贮藏,PVC包装适合鲜切芋头的较长期贮藏.