EFFECT OF BLANCHING AND SULFITE TREATMENT ON THE QUALITY OF FROZEN CAULIFLOWER

The influence of blanching time and post-blanching sulfite treatment on the sensory quality and texture of frozen cauliflower were assessed after storage at -18°C for up to one year. The treated cauliflower florets, sealed in polyethylene bags, were placed in waxed paperboard cartons and frozen in a contact plate freezer at -35°C. Samples blanched for 3 min and dipped in a solution containing 1000ppm of SO₂ for 5 min gave a significantly (p<0.05) superior product even when stored for one year. The residual SO₂ content of 50 ppm found in these stored samples disappeared after a 3 min cooking in boiling water. Cauliflower texture was influenced by blanching time but the textural differences of blanched samples diminished following freezing and storage. After a 3 min cooking, the texture of all thawed samples were comparable to that of fresh cauliflower cooked for 10–12 min.     

Effect of Microwave Blanching on the Yield and Quality of Canned Mushrooms

Shrinkage of mushrooms during blanching and retorting processes was studied using microwave and boiling water blanching treatments. A microwave blanching treatment of 4 min 40 sec at the high setting in a microwave oven was compared to a 7 min, boiling water, conventional blanching treatment. Data showed that the microwave blanching process was superior with respect to yield, allowing for a significant (p < 0.01) increase in net yield (3.41%) for three trials. Color and sensory analyses of the canned mushrooms showed that the two treatments were not significantly different (p<0.05) with respect to flavor, texture, color and overall acceptability.     

PHYSICAL, CHEMICAL AND SENSORY QUALITY OF MICROWAVE-BLANCHED SNOW PEAS

Snow peas were blanched using four methods [conventional boiling water (BW); steam (ST); microwave (MW); and microwave blanched in heat sealable bags (MWB)], then held frozen at (～18C) for four weeks. Immediately after blanching, MWB‐blanched snow peas retained more reduced ascorbic acid (RAA; 72%), than other treatments. Blanching treatment had no effect on lightness [L* value). With the exception of BW‐blanched peas, blanching significantly altered color. After frozen storage, MWB‐ and MW‐blanched samples both contained about 26 mg/100 g RAA, significantly more RAA than other treatments. MWB‐blanched peas generally had as high or higher sensory appearance, aroma, flavor, texture and general acceptability scores than other treatments. These results imply that blanching snow peas in a heat‐sealable microwave bag, prior to frozen storage, produces a product of equivalent sensory quality and superior nutritional quality compared with more conventional blanching methods.     

The effect of preliminary processing and period of storage on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms

This paper investigates the effect on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms of blanching or soaking and blanching in aqueous solutions containing combinations of added substances safe for human consumption, or period of frozen storage. During 12 months of storage, sensory evaluations, instrumental colour measurements and chemical analyses of the frozen products were carried out every four months. Based on the results of the sensory evaluation, a maximum storage period of four months was set for the frozen product obtained from unblanched mushrooms. Frozen products having undergone preliminary processing retained good sensory quality for up to 12 months. Soaking, blanching and freezing resulted in the appearance of colours, such as yellow, honey and pink–violet. As a result of freezing, decreases in the contents of thiamine, riboflavin and vitamin C were noted. Blanching in water, as a method of pre-processing, was sufficient for maintaining acceptable sensory quality.     

CHEMICAL, NUTRITIVE AND SENSORY CHARACTERISTICS OF TOMATOES BEFORE AND AFTER CONVENTIONAL AND MICROWAVE BLANCHING AND DURING FROZEN STORAGE

The objective of this study was to evaluate the effects of microwave blanching on chemical, physical and sensory characteristics of tomatoes prior to and after frozen storage. Tomatoes were blanched (4 min) using four treatments: conventional boiling water (BW), steam (ST), microwaved in a glass container (MW), and microwaved in boilable bags (MWB). The lowest moisture content occurred in MW‐blanched tomatoes before (92%) and after (86%) frozen storage. These tomatoes had the highest reduced ascorbic acid (RAA) content and the highest RAA retention (> 23 mg/100 g, >91%) after blanching and after frozen storage. After blanching, MWB‐blanched tomatoes were the lightest, while after frozen storage, ST‐blanched tomatoes were the lightest. BW‐blanched tomatoes had generally higher flavor, texture and appearance scores. This study demonstrated that though visual color and sensory attributes were highest for BW‐blanched tomatoes, MW‐blanched tomatoes retained more nutritive value in the finished product.     

Quality attributes of vegetable soybean as a function of boiling time and condition

Vegetable soybeans are marketed fresh or frozen, either shelled or in pods. The objective of this research was to characterise the change in quality attributes of vegetable soybean with boiling time (0–20 min), and presence/absence of pods, using an electrical-resistance stove or a steam-jacketed kettle. Trypsin inhibitor activity (TIA), texture, colour, soluble sugars, nitrogen, calcium and iron content were analysed. Blanching using a steam-jacketed kettle for approximately 2 min rendered 80% inactivation of TIA, and resulted in high colour, texture and sucrose. There were no differences between blanching in pods or shelled for TIA, colour and texture; however, blanching in pods prevented losses of sucrose. Blanching did not affect iron, mono- and oligosaccharide levels, but increased nitrogen and calcium content. Additionally, we observed that all traits decreased linearly with cooking time when using an electrical-resistance stove, except for calcium and nitrogen that increased, and oligosaccharides that remained constant.     

MICROWAVE BLANCHING EFFECTS ON CHEMICAL, SENSORY AND COLOR CHARACTERISTICS OF FROZEN GREEN BEANS

Green beans (cv. Mustang) obtained from the University of Illinois at Urbana-Campaign Horticulture plots were assayed within 3 h of harvest. Beans were blanched in covered containers: conventional boiling water (1900 ml, 3 min) (BW), steam (300 ml water, 3 min) (ST), microwave heated in 1 L glass containers (60 ml water, 3 or 5 min, 700 W) (MW-3, MW-5), and microwave heated in 1 L Seal-a-Meal^TM bags (45 ml water, 3 min) (MW-Bag). Baseline data were collected immediately after blanching. Aliquots were frozen at – 18C for 4 weeks. Unblanched beans had 82 units of peroxidase activity/min; activity was zero immediately after all blanching treatments. Reduced ascorbic acid (RAA) content was highest for unblanched, ST and MW-5 beans and lowest for BW and MW-Bag beans immediately after blanching. ST beans retained 100% of original RAA. Instron shear force (kg) was highest for unblanched beans and lowest for BW and MW-Bag beans immediately after blanching. After frozen storage, ST and BW beans had the lowest shear values. Visual color was poorest for MW-5; other treatments were not different. Microwave blanching green beans for 3 min in a covered container or bag prior to 4 weeks frozen storage resulted in a product that was not different in RAA content, retention or color from BW blanched beans; however, these samples differed in tenderness and crispness from boiling water blanched beans.     

EFFECT OF DIFFERENT TREATMENT PROCESSES AND PRESERVATION METHODS ON THE QUALITY OF TRUFFLES: I. CONVENTIONAL METHODS (DRYING/FREEZING)

Truffles are one of the major food ingredients of many favorite traditional dishes in the Middle East. Because of their short shelf life, truffles are considered a perishable commodity. Two varieties of local truffles were blanched in 2 or 4% boiling salt (NaCl) solutions for 2 or 4 min or by dry salting and or spraying with 5% vinegar. The treated samples were dried in an oven at 110C or were immediately frozen at ?18C and were stored for 1 year. In conclusion, color, texture and flavor were best preserved by blanching in 4% boiling NaCl solution for 4 min. Freezing was superior to dehydration as a preservation method.     

INFLUENCE OF PLATE TEMPERATURE AND MODE OF REHYDRATION ON TEXTURAL PARAMETERS OF PRECOOKED FREEZE-DRIED BEEF

The effects of various plate temperatures and rehydration procedures in texture of precooked freeze-dried beef, were evaluated. Frozen precooked commercial beef was freeze-dried at 20, 40, 60 and 80C during 24 h. The rehydration procedure involved two main variables: distilled water at room-temperature and at 80C, for 30 min. The texture profile analysis was performed with a TA-XT2 Texture Analyzer (SMS) for freeze-dried rehydrated samples and compared to frozen precooked beef. The results showed that with a same drying period, the 60C plate temperature and rehydrated in distilled water at room-temperature resulted in a better product texture, in regards to texture parameters hardness and chewiness.     

EFFECTS OF BLANCHING METHOD ON THE QUALITY CHARACTERISTICS OF FROZEN PEAS

This study evaluated the effects of microwave blanching prior to freezing as an alternative pretreatment for frozen peas. Peas were blanched (steam‐, boiling water immersion‐, microwave‐ or microwave‐blanched in a bag), frozen and evaluated after 0, 6 and 12 weeks for moisture and ascorbic acid content, peroxidase activity, visual appearance and instrumental color, and after 6 and 12 weeks for aroma, flavor and texture. All blanch treatments reduced peroxidase activity by 97% compared with controls (unblanched); blanching methods did not differ. Steam blanching resulted in significantly better ascorbic acid retention than all other treatments; microwave blanch treatments were either equivalent to or better than boiling water immersion. Both microwave treatments darkened (L* value) peas. Microwave‐blanched peas were visually greener than other treatments, but their appearance was less intact. Aroma and flavor were similar among blanch treatments. Texture of boiling water immersed peas was similar to the two microwave treatments.     

Influence of Pre-drying Treatments on Quality and Safety of Sun-dried Tomatoes. Part I: Use of Steam Blanching, Boiling Brine Blanching, and Dips in Salt or Sodium Metabisulfite

ABSTRACT The effect of various pre‐drying treatments on the subsequent quality of sun‐dried tomatoes was evaluated by determining moisture, color, rehydration ratio, mold, yeast, sulfur dioxide, and/or salt content. The 4 pre‐drying treatments under investigation were (1) steam blanching or (2) boiling brine blanching, followed by gas sulfuring and (3) dipping in either salt (0%, 10%, 15%, 20%) or (4) sodium metabisulfite (0%, 4%, 6%, 8%) for 0, 2.5, 5.0, and 7.5 min. Neither blanching pretreatment improved the quality of the dried product. Salt dipping resulted in significant differences in rehydration ratio, yeast, and salt. The most effective salt pretreatment conditions were a 10% or 15% salt dip for 5 min. Sodium metabisulfite dipping caused significant differences in rehydration ratio, yeast, color, and sulfur dioxide. Dipping tomatoes in 6% or 8% sodium metabisulfite for 5 min before drying established the best color. The 9 pretreatments studied were also evaluated for storage stability at 25 °C and 30% to 34% relative humidity for 3 mo.     

MICROWAVE AND CONVENTIONAL BLANCHING EFFECTS ON CHEMICAL, SENSORY, AND COLOR CHARACTERISTICS OF FROZEN BROCCOLI

Broccoli (cv. Empress) obtained from a local supplier was blanched within 15 h of harvest. It was blanched by four methods in covered containers: conventional boiling water (1900 mL, 4 min) (BW), steam (300 mL water, 4 min) (ST), microwave heated in 1 L glass containers (60 ml water, 4 min, 700 W) (MW), and microwave heated in 1 L Seal-a-Meal^TM bags (45 ml water, 4 min) (MWB). Aliquots were frozen at -18C for 4 weeks. Fresh unblanched broccoli peroxidase activity ranged from 389 to 829 units/min; activity was essentially zero immediately after all blanching treatments. The highest reduced ascorbic acid (RAA) content occurred in fresh unblanched broccoli. Some peroxidase regeneration occurred during frozen storage. Immediately after blanching, all blanched broccoli had lower RAA content than control broccoli. MW-blanched broccoli retained the greatest amount of RAA and had appearance, visual color, texture scores, and chroma of florets and stems equivalent to ST-blanched broccoli. MW-blanched broccoli had flavor and general acceptability scores similar to BW-blanched broccoli. After 4 weeks in frozen storage, MW-blanched broccoli had the highest RAA content.     

提高冻干山药片品质的工艺优化

为改善冻干山药片的复原率、质构、色泽以及口感,对加工过程中的烫漂、浸泡液处理方案和冻干工艺进行研究。结果表明：山药片在95℃条件下烫漂60s可防褐变,并有利于后续的浸泡和冻干;用含有5% NaCl、10%葡萄糖和10%麦芽糊精的浸泡液,在30℃条件下浸泡30min,可提高复原率;较优的冻干工艺为使用带有强对流鼓风的速冻生产线在－30℃条件下对山药片冻结,采用5℃保持7h,35℃保持2h程序冻干。该工艺生产出的山药片具有较好的复原率和感官品质。     

漂烫对速冻苹果质地的影响

采用质地多面分析（TPA）试验方法,研究了速冻苹果不同漂烫过程中的漂烫时间、漂烫温度、料液比对质地的影响,并对其过氧化物酶（POD）活性、感官品质的变化以及其硬度、内聚性、回复性、弹性和咀嚼性等相关性进行了研究。结果表明,漂烫对速冻苹果质地有显著影响,适度漂烫在其速冻加工中至关重要,最佳漂烫工艺为漂烫时间4～5 min、漂烫温度87～92 ℃,料液比为1∶10～1∶12（g∶mL）。     

Canning of vegetable soybean: procedures and quality evaluations

Some aspects of the preservation process of vegetable soybean are discussed in this paper. Factors, like the effects of blanching duration, and brine composition, were discussed in relation with the quality attributes of the product including enzyme activity, texture and colour. It was observed that the concentration of CaCl₂ influenced the texture and luminosity (L), while the pH affected luminosity (L) and green colour (– a / b ) of the processed product. Furthermore, blanching for 90 s before heat-processing was effective to inactivate 99% of the initial lipoxygenase activity. It was found that a brine containing 150 g L⁻¹ NaCl and 2.9 g L⁻¹ CaCl₂, at pH 6.5 that was thermally treated for 9 min generated a lethality of 4 min that is enough to produce a 12-log reduction required for low acid foods and at the same time retaining desirable colour and texture.     

LOW TEMPERATURE BLANCHING OF FROZEN CARROTS WITH CALCIUM CHLORIDE SOLUTIONS AT DIFFERENT HOLDING TIMES ON TEXTURE OF FROZEN CARROTS

The objective of this study was to evaluate the effect of low temperature blanching in calcium chloride solutions to increase firmness retention of frozen carrot slices and to determine optimum conditions to provide a final product with maximum firmness. Low temperature (65 C) blanching in CaCl² solutions (0.05–0.6 molar) for holding times (5–90 min) was performed on carrots 'Apache' cultivar. Calcium absorption was affected (P≤0.05) by the CaCl² concentration. Behavior of this variable was adequately fitted by a second order model (R²=0.99). Firmness was affected (P≤0.05) by the CaCl² solutions and holding times. Optimum conditions gave extrusion forces of 1693–2095 N and calcium levels of 69–144 mg/100 g. These were verified experimentally and agreed closely with predicted calcium absorption and firmness values.     

前处理对真空冷冻干燥香菇脆品质的影响

目的 研究前处理对真空冷冻干燥香菇脆品质的影响。方法 对真空冷冻干燥香菇脆进行冻融处理、糖渍处理、酶解处理,对香菇脆的质构、感官性质、微结构进行测定。结果 冻融处理有利于香菇脆微观结构的破坏,香菇脆品质随冻融处理次数的增加而逐渐改善。以麦芽糖浆为糖渍液时,3次冻融处理的香菇脆硬度从35.97 N降至23.43 N,组织纤维网孔破坏,糖渍液固形物含量从40%降至15.45%,糖渍效率大幅提高。麦芽糖浆糖渍液中添加麦芽糊精导致了香菇脆品质的劣化,香菇脆硬度高达39.48 N,糖渍效率和产品口感均明显下降。漂烫前对香菇进行蛋白酶酶解可促进组织结构的破坏,香菇脆硬度降至17.59 N,且酶解过程释放的鲜味肽加强了产品的特征风味,感官评分为89.49分,远高于漂烫后酶解和纤维素酶酶解所得样品。结论 多次冻融处理、麦芽糖浆糖渍处理和漂烫前蛋白酶酶解处理有利于提高真空冷冻干燥香菇脆的品质。本研究可为香菇的精深加工提供理论基础。     

QUALITY OF CABBAGE PART I: EFFECTS OF BLANCHING,FREEZING, AND FREEZE-DEHYDRATION ON THE ACCEPTABILITY AND NUTRIENT RETENTION OF CABBAGE (BRASSICA OLERACEA L.)1

Cabbage was blanched with steam, and chemical solutions. Blanching in solution involved boiling of cabbage with a chemical solution (or water) for 3 mm at 96°C. In steam blanching, cabbage was vacuum impregnated in a chemical solution for 5 mm under a 25 in. vacuum and then exposed to steam for 3 mm. Blanching (without chemical treatment) was achieved within 3 mm as judged by the inactivation of peroxidase. Among solution- and steam-blanched (without chemical treatment) products, the former had better organoleptic qualities, whereas the latter had higher ascorbic acid retention. Cabbage blanched in the presence of 0.5% malic acid, 0.05% NaHCO₃, and 1.2% NaCl was preferred for texture, color, and overall quality, respectively. The results from chemical (vitamin C and chlorophyll contents), physical (firmness), and sensory evaluations of processed and stored (at -19°C up to 24 months) cabbage indicate blanching in the presence of 1.2% NaCl solution to be the most generally preferred treatment.     

Amino Acid Content of Frozen Agaricus bisporus and Boletus edulis Mushrooms: Effects of Pretreatments

The effect of blanching or soaking and blanching on the amino acid content of frozen A. bisporus and B. edulis mushrooms was determined. Frozen mushrooms contained lower amounts of most amino acids compared to fresh mushrooms. In A. bisporus, the greatest changes were observed in mushrooms soaked and blanched in citric and L-ascorbic acid solution in A. bisporus, while in the case of B. edulis, mushrooms soaked and blanched in solution containing pectin showed the maximum change. Blanched-only products were significantly higher in asparagine, glutamine, isoleucine, and lysine than those that were soaked and blanched.