SHELF-LIFE of SPRAY-DRIED INFANT FORMULA SUPPLEMENTED WITH LACTULOSE

Storage studies were carried out to assess the stability of a lactulose-containing infant food formula (II) in comparison with a control formula (I) at, 5, 27 and 38C up to 20 weeks. Products were packed in tinned containers and sealed in nitrogen. No changes were observed in moisture and solubility of formulas I or II at any temperature-time combination. Lactulose levels increased during storage, while available lysine decreased to a similar extent in both formulas. Hydroxymethyl furfural content increased during storage, while the whiteness of both formulas remained unaffected. Addition of lactulose did not influence the acceptability of the product, but there was a correlation between the increase in free fatty acid levels and the decrease in acceptability scores. the study indicated that addition of lactulose did not alter any storage characteristic of the product and that the product with added lactulose was acceptable up to 16 weeks of storage at all temperatures.     

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.

     

STRUCTURED LIPIDS: ACIDOLYSIS OF GAMMA-LINOLENIC ACID-RICH OILS WITH n-3 POLYUNSATURATED FATTY ACIDS

Structured lipids were synthesized by acidolysis of γ-linolenic acid-rich oils and n-3 polyunsaturated fatty acids (PUFA), namely eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), using different lipases. Lipase PS-30 from Pseudomonas sp. was chosen over the other enzymes to catalyze the acidolysis reaction owing to higher incorporation of n-3 PUFA. Effects of mole ratio, reaction time, incubation temperature, enzyme load, and solvent type on acidolysis reactions were studied. At 250 enzyme activity units, incorporation of n-3 PUFA reached optimal values of 29.9 and 30.7% for the reactions with borage and evening primrose oils, respectively. For the time course reaction, incorporation of n-3 PUFA increased up to 34.1 and 31.5% (in 30 h), in borage and evening primrose oils, respectively. After 24 h incubation in hexane, n-3 PUFA (EPA+DHA) incorporated into borage and evening primrose oils was 31.8 and 32.7%, respectively. The highest n-3 PUFA incorporation in both oils occurred at a mole ratio of 1:2:2 (oil/EPA/DHA). Among the solvents tested, n-hexane was found to be highly effective; total n-3 PUFA incorporation of 33.3 and 27.8% in borage and evening primrose oils, respectively, was achieved in hexane. However, the solvent-free reaction afforded products with a total of 23.4–28.8% n-3 fatty acids (EPA and DHA).     

PREDICTION OF HONEY SHELF LIFE

Fourteen commercial honey samples of different botanical origin (acacia, chestnut, citrus, eucalyptus, multifloral) were stored for up to 18 months at room temperature. Both 5-hydroxymethylfurfural (HMF) and diastase were evaluated and kinetics carried out. The highest HMF increase was in citrus and eucalyptus honeys at 3 mg/kg/month; the lowest in chestnut at 0.256 mg/kg/month. The highest diastase deactivation was in eucalyptus honey at 0.485 DU/kg/month; the lowest was in chestnut at 0.258 DU/kg/month. Honey shelf life was estimated for both indices, HMF and diastase, using a Bayesian approach. The results show that commercial honey shelf life depends on botanical origin as well as processing. Except chestnut, all other honeys showed shorter shelf lives than the declared one (usually 36 months). The shortest values, 15 months, were for citrus and eucalyptus honeys. The longest, 20 months, was for acacia and multifloral honeys.

PRACTICAL APPLICATIONS

Both kinetic equations and results of simulations can be used to estimate, for quality control purposes as well as regulation requirements, the most probable value of shelf life for a specific honey.     

栅栏技术延长牦牛腱子制品货架期的应用研究

通过对牦牛腱子加工过程中原料、辅料、各加工工序及用具中微生物消长情况的研究,在危害分析关键控制点（HACCP）的基础上,应用栅栏技术（HT）控制微生物,提高成品率,延长产品的货架期.     

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.     

COMPOSITION PROPERTIES, PHYSICOCHEMICAL CHARACTERISTICS AND SHELF LIFE OF WHOLE MILK AFTER THERMAL AND THERMO-SONICATION TREATMENTS

Raw whole milk (RM) was pasteurized with heat-pasteurized milk (TT) and thermo-sonication (US) treatments. Batch pasteurization was used for TT and 36, 72, 108 and 120 µm of the ultrasound wave intensity (24 kHz, 400 W); in addition, the heat conditions were applied together for US. Apparent protein content of US milk decreased; butter fat content was increased by US treatment. Proximal analysis showed the presence of added water in US milk and a decrease of nonfat solids, whereas pH was decreased for US milk, lactic acid was increased and density was decreased from RM to US; also, the color of US milk was whiter. The tested parameters for the TT samples were often intermediate between RM and US samples. Statistical analysis showed a significant difference ( P <  0.05) among all treatments. After 16 days, US samples (4C) did not show mesophilic growth higher than 2 log; pH, acidity and color remained constant.

PRACTICAL APPLICATIONS

Thermo-sonication (US) is an available method that can improve some sensorial and quality milk characteristics such as color and appearance, while at the same time, ultrasound pasteurizes the product. Minor changes in nutritional properties of milk (i.e., protein content) have been reported after US, with the advantage of extending the shelf life of the product for more than 16 days at 4C without the use of intensive heat treatments. This is a potential technology for use in research and development of new and current products in the dairy industry.     

PHYSICOCHEMICAL PROPERTIES OF EUROPEAN BAKERY MARGARINES WITH AND WITHOUT TRANS FATTY ACIDS

Physicochemical properties of commercially available European bakery margarines (cream margarines, cake margarines [CM] and puff pastry margarines [PPM]) containing and devoid of trans fatty acids (TFAs) were investigated. Studied physical properties were the solid fat content (SFC), dropping points (DPs), polymorphism, texture (hardness), plasticity and the melting profile by differential scanning calorimetry. Experimental results confirm that physical properties of the margarines corresponded with their application area. For example, SFC and DPs of PPM were higher than cream margarines and CM; they were also harder at 15C. Moreover, all the investigated physical properties were affected by the suppression of TFA in bakery margarines .

PRACTICAL APPLICATIONS

This study has shown that margarines present different physical properties with respect to their purposed application but also highlight changes that appear due to the absence of trans-fatty acids in the formulations. These changes can really affect the bakery abilities and will, finally, influence the quality of the bakery products.     

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.     

EFFECTS OF ANTIOXIDANTS AND PROCESSING ON STABILITY OF MUSCLE FROM HYBRID STRIPED BASS WITH OMEGA-3 FATTY ACIDS

Hybrid striped bass were fed four diets containing 0, 4, 8, and 12% menhaden fish oil (MFO) for 18 weeks during final growth to determine (1) omega-3 (n-3) fatty acid uptake and its effect on fish and postharvest quality, and (2) the effects of selected antioxidants on oxidation and sensory quality of fish enhanced with n-3 fatty acids. Lipid content was significantly higher in the two highest MFO treatments: 3.2, 3.5, 3.9 and 4.4% in the 0, 4, 8 and 12% MFO treatments, respectively. During this study EPA(eicosapentaenoic acid) significantly increased with increasing dietary MFO: 5.4 ± 0.93, 6.9 ± 0.15, 8.0 ± 0.45 and 8.1 ± 0.35 for the 0, 4, 8 and 12% MFO diets, respectively. The following fatty acids in muscle increased 1% or more in fish fed 12% MFO compared to fish fed 0% MFO: 14:0, 16:1n-7, 22:6n-3, and total polyunsaturates, total n-3, and the n-3/n-6 ratio. Changes in individual fatty acids in fish muscle reflected the concentrations of fatty acids in the diet. Hybrid striped bass fed 8 and 12% MFO had twice as much n-3 fatty acids (1.0 g/100 g tissue) as fish cultured on diets without MFO     

DIETARY FATTY ACIDS AND AMINO ACIDS OF CAMELINA SATIVA SEED

Abstract Camelina sativa ( L. ) Crantz is an ancient oilseed crop. Camelina seed can be used as a food ingredient and raw material for the production of oil. The by-product from the production of oil by pressing (oil cakes) was traditionally used as fodder ingredient.
Camelina seed samples for analyses were collected from geographically remote localities in Europe and in Scandinavia (6° W - 25° E, 48 - 61° N). The seed was analyzed for the content of oil, fatty acids, total nitrogen and amino acids.
The mean content of oil in the seed was 43.3 ± 0.22%/DM. The predominating acid, α-linolenic (18:3 n-3), was 37.8 ± 0.17%; and others were oleic acid (18:1 n-6) 13.4 ± 0.13%; linoleic acid (18:2 n-6) 14.8 ± 0.12%; gondoic acid (20: 1 n-9) 15.4 ± 0.16% and erucic acid (22: 1 n-9) was 2.76 ± 0.07%/total FA.
Crude protein was 42.5 ± 0.46%/fat free DM. Considerable amounts of essential amino acids were present, such as arginine 8.15 ± 0.06%; glycine 5.44 ± 0.04%; isoleucine 3.96 ± 0.02%; leucine 6.63 ± 0.04%; lysine 4.95 ± 0.04%; phenylalanine 4.19 ± 0.04%; proline 5.09 ± 0.03%; threonine 4.25 ± 0.03% and valine 5.42 ± 0.04%. The methionine content was 1.72 ± 0.04% and cystine, 2.12 ± 0.05% (A.A. g/16 g N).